DEMERSAL FISH RESOURCES
In 1981 the total reported landings of demersal fish was 135 000 tonnes. Gulland estimates that on top of this some 500 000 tonnes of demersal fish, mostly Sciaenids, are discarded as by-catch by the shrimp and other trawl fisheries. However, in its Review of the State of Exploitation of Resources Other Than Crustaceans (1980), the Western Central Atlantic Fishery Commission (1980) put the figure for discards as high as between 800 000 and 1.5 million tonnes. They estimate another 80 000 tonnes are taken by sport fishermen, chiefly from the U.S.A. Of the reported demersal landings, no one species forms a predominant part of the catch, but groupers, snappers, croakers, grunts, drums, weakfish and slipmouths are all taken in reasonable quantities. The diversity of the fish fauna in the area makes assessments of particular species difficult if not impossible. Some stocks are probably still lightly fished, but many others, of high market value, or concentrated on the shrimp grounds are probably moderately to heavily.
SERRANIDAE
More than 20 000 tonnes of numerous species, particularly groupers (Epinephalus spp.) were landed in 1981. These are almost all from hard bottomed areas, reefs, where most fishing is done with traps, and deepwater areas on the shelf edge where they are taken principally by handline and snapper reel. Such fisheries are unlikely to involve interactions with marine mammals.
LUTJANIUAE
More than 10 000 tonnes were landed in 1981, again, from a number of species. Snappers are found in similar places to groupers, but are often smaller in size. They are taken in the same ways on reefs and on the shelf edge where they are most concentrated at around 200 metres in the Caribbean, and around 100 metres in the gulf of Mexico and Atlantic.
SCIAENIDAE
More than 30 000 tonnes were landed in 1981. These species are mostly soft bottomed species, found in the shallower waters of the shelf, particularly on the northern and eastern coasts of South America and in the gulf of Mexico. The croaker Micropogon undulatus is the species most commonly caught as a by-catch in the shrimp fisheries of the area, which are also carried out on soft bottoms. There are, however, a number of directed fisheries for sciaenids also. A small industrial fleet operates in the northern Gulf of Mexico, and other, artisanal, fisheries fish the Mexican and Central American waters. There are also some local trawl fisheries along the Caribbean coast of South America, especially the Gulf of Venezuala which is overfished already.
SPARIDAE
At present only about 2 000 tonnes of a handful of species are taken. The stocks are said to be underexploited along the shelf edge of the U.S. Atlantic coast.
Other demersal fish caught in the area include surmullets, wrasses, triggerfishes and puffers, reefs providing the highest diversities.
PELAGIC FISH RESOURCES
Pelagic catches in this area are again characterised by a great diversity of species. Only inadequate resource surveys have been made, but the potential may exceed 2 000 000 tonnes. Menhaden accounts for the main part of the total pelagic catch, together with around 100 000 tonnes of all other species. Again, catch statistics are not reliable and actual catches may be considerably higher than this.
CLUPEIDAE
Brevoortia tyrannus and Brevoortia patronus Menhaden
The former is caught in the Atlantic off the southern United States, the latter in the Gulf of Mexico. Between them they account for a total catch of around 7–800 000 tonnes per year. The Gulf stock is thought to be at or around MSY, the Atlantic stock is overexploited, but seems to have recovered somewhat since the 1960's. These species represent much the largest single finfish fishery in the area, and are taken by purse seiners, almost all from the United States. There has been some reported by-catch of Tursiops, and a number of other species may be feeding on these stocks, but there is no evidence yet of any conflict.
Sardinella anchovia
32 000 tonnes were taken in 1981 by the purse seine fishery off Venezuela, and this species is apparently fully exploited at present.
The FAO Atlas of Living Marine Resources maintains that there are between 1 and 2 million tonnes potential yield of other clupeids in the area, but these remain largely unexploited, perhaps because of the small size of schools of many of them. These species include the thread herring, Opisthonema oglimum, for which a small fishery exists already off Brazil, as well as scaled herring, dwarf herring and anchovy. Many of these are presumably food species of delphinids and possibly of Bryde's whales too.
CARANGIDAE
Over 12 000 tonnes of a number of species are taken. According to the FAO Atlas, largest concentrations are found in the Gulf of Mexico, along the Yucatan Peninsular and off the coast of Florida, and also along the coast of Venezuala. Lowe-McConnell (1962) reports that Carangids off northern South America are most often found in clear water, away from the muddier bottomed areas near estuaries.
MUGILIDAE
Several species of mullet yielded over 28 000 tonnes in 1981. These are chiefly coastal species found in shallow waters. There is no indication of their potential, nor of the state of the stocks. Local concentrations are found in the Gulf of Mexico and on the coast of Venezuala, and in both areas they may be presumed to be important food fishes for Tursiops.
SCOMROIDET
A great number of species, they include 9 or more tunas, spanish mackerels, marlins and other high value fish, the catch for all species in 1981 was 71 000 tonnes. Longlining and other hook and line fisheries, including the U.S. sport fishery, are important in the capture of these fish, but there is no indication as to the state of the stocks in the region. Catches by foreign vessels are small, amounting to only a few thousand tonnes per year, mostly Japanese and Korean catches of tuna. Catches of all species have remained stable since 1976, with the exception of the blackfin tuna (Thunnus atlanticus), the catches of which have increased from 90 to 845 tonnes during the last 6 years, and the white marlin (Tetrapturus albidus), the catches of which declined from 369 tonnes in 1976 to 15 tonnes in 1981. Caldwell and Caldwell (1971) have pointed out that the same species of dolphin (Stenella spp.) and of tunas exist in area 31 as in the eastern central Pacific, and that the possibility may exist for the development in area 31 of a similar fishery to that of the dolphin associated tuna fishery of the eastern central Pacific.
ELASMOBRANCHS
Elasmobranchs predominate in the fauna of the shallow inshore muddy waters of the continental shelf regions of area 31. WECAFC (1980) estimate that 54% of the biomass in water less than 55 metres deep off the United states Atlantic coast is made up of sharks and rays. Lowe-McConnell (1962) also reports them as predomiant off the coast of the Guianas in shallow waters. Current catches total around 20 000 tonnes. Mexico and Cuba are the only countries with directed fisheries, but the true catch may be a lot higher than those given in the FAO yearbook, due to sport fisheries and discards. Total potential yield has been estimated around 45 000 tonnes (WECAFC 1980), but it is unclear how closely actual catches approach this figure already.
INVERTEBRATE RESOURCES
CRUSTACEANS
The most important fishery in the region, economically, is for shrimp. At least 6 species of shrimp are taken from soft bottomed areas of the continental shelf by trawlers, chiefly from the USA, but also from Mexico, Venezuala, Surinam and Guyana. Catches exceeded 170 000 tonnes in 1981, and appear to be relatively stable over the past 6 or 7 years. This fishery is also notable for the large amount of fish discarded, anything up to 1.5 million tonnes of demersal fish per year. Some other species are also taken, including the blue crab Callinectes sapidus on the Atlantic seaboard of the U.S. and a number of lobster species from reef areas.
MOLLUSCS
Between 150 and 200 000 tonnes of molluscs are taken in the waters of area 31 every year. Most of this is in the form of bivalves, particularly the oyster Crassostrea virginica which is taken from U.S. Atlantic waters. A number of other species are taken from reefs throughout the area, largely by hand. The catch of these amounts to only a few thousand tonnes per year, but is nevertheless important to island economies.
CEPHALOPODA
The amount of cephalopods taken is very small, being less than 10 000 tonnes in any year, most of this being common squids, Sepia spp., and octopuses. There appear to be no surveys which estimate the potential size of the squid resource, but considering the location of large sperm whale feeding grounds within the area, and also the number of mammalian species in the area which appear to be largely or wholly teuthophagous, the potential may be enormous. Voss (1973) states: “there can be little doubt that vast potential stocks of octopus and squid occur in the Caribbean Sea and adjacent regions, but documentation is not available. Gulland (1971) has suggested that the potential is more than 100 000 tonnes, possibly as much as 0.5 to 1 million tonnes, and probably not as much as 2 million tonnes.”
The United States is the largest fishing nation in this area, with in 1981 total recorded landings of around 1.26 million tonnes (or 66% of the total landings from the area). As has been noted its catches of menhaden dominate the statistics on fish landings. The menhaden fishery is pursued by purse seiners, and despite its size (ca. 800 000 tonnes p.a.), there appears to be little conflict with marine mammals, this being possibly due to the fact that icthyophagous mammals in the area do not appear to be very numerous, the species in the genus Stenella together with Delphinus delphis and Tursiops truncatus being perhaps the only other likely candidates for possible by-catch in this fishery.
The United States also takes large amounts of shrimp by trawlers, which again do not appear to affect marine mammals in any noticeable manner, unless the by-catch of demersal fish were to affect the feeding habits of Tursiops truncatus, which is about the only mammalian species which preys on this group of organisms to any great extent. WECAFC (1980) reports that in the northern Gulf of Mexico there are already signs of groundfish over-exploitation. Similarly the fisheries for oyster and for crab do not affect marine mammals.
One of the very few records of interactions between marine mammals in this area comes from the small scale fisheries of Florida. A number of species are taken there by hooks and lines as well as by gill nets in the creeks and channels around the coast. The sport fishery is also economically very important. Leatherwood (1979) reports some conflict between these fishermen and Tursiops truncatus, one of the few mammalian species regularly found inshore in the entire region. The manatee, Trichechus manatus is also thought to be threatened in the same waters by accidental killings by fishermen, amongst others, especially from the propellors of small boats.
Mexico is the next largest fishing nation in area 31. 1981 landings were around 270 000 tonnes, or 14% of the total. Mexican catches are distributed fairly evenly amongst a great number of species. Mullets, from inshore and largely small scale fisheries are one of the more important groups landed, accounting for more than 10 000 tonnes. Groupers, snappers, slipmouths, sharks and rays are also important. Most Mexican fisheries in the Gulf of Mexico appear to be artisanal. In view of this, one might expect some conflict between fishermen and at least one species, Tursiops truncatus, which is apparently common all around the coastal areas of the Gulf of Mexico. No such conflict has yet become apparent however.
Venezuela landed 167 000 tonnes in 1981, or about 9% of the area total. Of this 27 000 was from the purse seine fishery for sardines. No conflict is apparent in this fishery. Longliners also take some tuna and related fish. Most of the rest of the catch is from artisanal fisheries along the coast, for mullets, sciaenids, groupers, grunts, sharks and other shelf fish. Caldwell and Caldwell (1971) report that the beach seine nets along the coast here, and on offshore islands do take some by-catch of marine mamals, which, as one might expect, appear chiefly to be Tursiops, although around certain river mouths Sotalia fluviatilis is also taken in gill nets.
Most of the other nations around the area have only small catches, Cuba and Guyana take about 3% and 1.5% of the total area catch respectively, and the remainder is split amongst more than 40 other nations. Although there have been developments in the fishing industries of some of these, such as Cuba, small scale fisheries still predominate throughout the area. These fisheries are pursued by a number of methods; traps are used mostly on reef areas, and hooks and lines along some of the rough-bottomed shelf areas. Beach seines and other nets are also evidently used in soft-bottomed areas. There are remarkably few reports of interactions with marine mammals, possibly due to the under-exploited nature of the area as well as the type of gear used. Gulland (1983) considers the area the least heavily fished in the world after the southwest Pacific, although some areas are over-exploited locally.
Operational interactions
There are very few reports of interaction between fisheries and marine mammals in this area, and these are limited to 4 species, all freshwater or coastal, with a few more as possible future conflicts.
Tursiops truncatus, described by Shane (1980) as one of the 3 commonest species in the Gulf of Mexico, is evidently involved in gear conflicts throughout the area.
Inia would also seem likely to be caught accidentally in this area, although records of this area scarce. There are also reports of it helping fishermen in the Amazon (Lamb 1954), and it may well do the same therefore in parts of Venezuela or Colombia.
Sotalia is also liable to incidental capture in gill nets.
The Manatee is seriously overexploited and continues to suffer through accidental drownings in nets and collisions with boats throughout the region (FAO 1978).
Other instances of interaction have not been recorded. However there are at least two areas where the potential for such may exist. One is in the development of the tuna fishery, which, according to Caldwell and Caldwell (1971) could develop means of catching tuna and dolphins in the same manner as in the eastern central Pacific. They suggest this could be useful supplement to the diet of protein-poor islanders in the Caribbean, some of whom are already accustomed to eating dolphin meat. The species involved here would be those of the genus Stenella and possibly Delphinus delphis.
A second potential interaction may be considered possible due to the reported presence of a number of feral Californian sea lions on the Atlantic coast of the U.S.A. (Caldwell et al 1971). A breeding colony of these animals could cause some nuisance to fishermen in the area, particularly to the sport fishery of the Florida and adjacent waters, as is known in Californian waters (see area 77). As yet no breeding is reported.
Biological interactions
Considering the generally underexploited state of the marine resources of the area, it would seem that any significant competition for food between fisheries and marine mammals in this area is unlikely. This is particularly so as, in common with most warmer areas of the world, there appears to be a relatively low biomass of marine mammals.
Most of the species present also appear either not to eat in the area, (the baleen whales), or else to feed primarily on squid, a greatly undeveloped resource by the fisheries of the area. Those species which are either fully or partly ichthyophagous, such as D. delphis, the Stenella species and a few others tend to be oceanic and so rarely come into contact with the primarily small scale fisheries. Only coastal species have so far been implicated in interactions.
Should any of the large squid resources become exploited to any great extent, the possibility of interactions with marine mammals should be considered far more likely than at present.
Eubalaena glacialis Right whale
Tomilin (1967) describes the right whale from the north west coast of Africa, Madeira and the Azores. This represents the southern limit of the North Atlantic population which may now number no more than a few hundred. No feeding is recorded in this area.
Balaenoptera physalus Fin whale
Jonsgaard (1966a) states that this species is found as far south as 20°N off the African coast. The numbers of animals which migrate into this region are unknown, but the entire North Atlantic stocks may number no more than 12 000.
Balaenoptera musculus Blue whale
Jonsgaard (1966a) reports that the blue whale has been seen as far south as Cape Verde. There is no information on how many blue whales migrate to this region, and feeding is unlikely.
Balaenoptera acutorostrata Minke whale
Minke whales are known to be found infrequently in tropical regions. There is no information on the numbers present in this area; feeding is unlikely.
Balaenoptera borealis Sei whale
Jonsgaard (1966a) describes the southern limit of the distribution of the sei whale as Cape Blanco off the West African coast. There is no indication of numbers in this area. The total population in the North Atlantic may be only a few thousand, but is unknown.
Balaenoptera edeni Bryde's whale
Ivashin (1980) describes the distribution of this species and states that it has been hunted off Spanish Morocco and Dakar. There are no population estimates for this or any other area. Feeding is known to occur in the tropics and includes pilchards and anchovies in other areas, as well as a large proportion of pelagic crustacea. (Best 1967).
Megaptera novaeangliae Humpback whale
Tomilin (1967) describes the migration route of the north east Atlantic stock of the humpback whale as from the Baerents Sea to northwest Africa and Cape Verde. This stock has been severely reduced and is not thought to feed in southerly areas.
Mesoplodon densirostris Blainville's beaked whale
Moore (1966) suggests that this species may inhabit a mid ocean area of the southern North Atlantic. It is only recorded rarely, and is of unknown population size, presumably no more than a few tens of thousands at most. All beaked whales feed on squid.
Ziphius cavirostris Cuvier's beaked whale
There is little information on this species in this area. The population size is unknown, but the diet is known to consist, generally, of squid.
Physeter macrocephalus Sperm whale
Sperm whales have been hunted extensively in this area in the past as the whaling maps of Townsend (1935) demonstrate. The existence of two winter hunting grounds at about 5° and 15°N indicate probable feeding grounds for sperm whales in those areas, presumably on concentrations of squid. There are little data on sperm whales in this area at present, but the Atlantic population has been estimated at a few tens of thousands 22 000, which suggests that, judging from the apparent distribution of whales on Townsend's maps, a few thousand may be in this area in the winter, and far fewer in the summer.
Kogia breviceps Pygmy sperm whale
Very little information exists for this species in this area, as there as few records of it in Africa (Handley 1966). Cadanet (1959) reports two unconfirmed records. There is no information on population size. Food is thought, in other areas at least, to include squids, crabs and shrimps.
Steno bredanensis Rough-toothed dolphin
No population estimates are available and there are very little data on feeding. Hershkovitz (1966) states that it occurs as far south as Senegal and the Ivory Coast, where Cadenet (1959) examined the stomachs of 3 individuals and found cephalopods in all 3 and some indeterminable fish in 2 of them.
Sousa teuszii Atlantic hump-backed dolphin
Hershkovitz (1966) describes the distribution of this species as along the West African coast from Senegal to the Cameroons, in the mouths of rivers and in shallow waters. Cadanet (1956, 1957, 1959) records a number of individuals from the coasts of Senegal and the Ivory Coast. At least 7 of these were caught in shark nets and one in a sardinella net. The stomachs of four animals which Cadanet (1959) examined contained Ethmalosa dorsalis, three of them also containing Mugil remains. Cadanet (1959) suggests that although once thought rare, this may be a common species locally. Busnel (1973) describes how fishermen in Mauritania co-operate with dolphins of this species. The fishermen beat the surface of the sea when, during the period December to February, there are schools of mullet running along the coast. The dolphins are then said to corral the fish in to the shore while fishermen on the one side and dolphins on the other catch them. This is one of the few examples of interaction between man and marine mammals where both parties benefit.
Peponocephala electra Melon-headed whale
There appears to be only one record of this species in this area, that of Goodwin (1945). There is therefore no information on population size nor on feeding.
Feresa attenuata Pygmy killer whale
Caldwell and Caldwell (1971a) summarize the information on the distribution of this species at that time, with only one record from the tropical east Atlantic although Cadanet (1959) reports two possible records from Senegal and the Ivory Coast. There is therefore no information on population size nor on feeding in this area. Captive specimens have eaten fish and squid in Japan.
Pseudorca crassidens False killer whale
There are no obvious records of this species in this area, but Tomilin (1967) amongst others describes its disribution from the North Sea to the Cape in South Africa. Tomilin describes the diet as predominantly squid, but also including some fish.)
Orcinus orca Killer whale
A cosmopolitan species which is more common in higher latitudes, there is very little information on this species in area 34. Bourne (1965 cited in Mitchell 1975) states that the killer whale is shot on sight on the Atlantic seaboard of Morocco where it is believed to scare tuna fish (Thynnus thynnus) away from the fishing grounds, Cadanet (1959) also records its presence further south. The population size and diet are unknown in this area.
Globicephala macrorhynchus Short-finned pilot whale
Mitchell (1975a) affirms the presence of this species as far north as Mauritania and Madeira, and Cadanet (1959) examined 2 specimens further south, one with fish and squid remains in its stomach, the other with only squid remains. There is very little or no other information on the diet or the abundance of this species.
Tursiops truncatus Bottlenose dolphin
Busnel (1973) records this species in Mauritania and Cadanet (1957, 1959) records it on the West African coast too. In his description of cooperation between fishermen and dolphins Busnel states that two species were involved, one of which was not able to be identified, but which was “probably Tursiops truncatus”. The diet of the bottlenose dolphin is elsewhere known to include mullet (Mugil spp.) and so it would seem safe to conclude that as mullet are abundant in this region they are likely to form part of the diet of Tursiops here also. Cadanet (1957) refers to a troupe of bottlenose dolphins attacking a trawl net, which had to be frightened off with explosive charges. Another is recorded in an unspecified net. There is no indication of abundance in area 34.
Grampus griseus Risso's dolphin
Widely stated to exist in warm waters worldwide, as with other species in this area there is little or no information pertaining to this species in this area. Risso's dolphin is known to prefer deeper water and to feed on squid, and is generally uncommon.
Stenella longirostris Spinner dolphin
Cadanet (1959) records this species from Senegal and the Ivory Coast. There are reports of dolphins being caught in tuna seines off the coast of West Africa. Maigret for example is quoted in the report of the Sub-Committee on Small Centaceans (IWC 1982) as stating that 7 French seiner captains made on average 12 sets on dolphins annually, killing about 14 per set. By extrapolation Maigret suggests that 3 300 dolphins are killed in this manner each year. There is no indication of the species involved, but by analogy with other areas they may be presumed to be largely Stenelia species. The spinner dolphin is thought to eat mesopelagic fish and mesopelagic and epipelagic squids, though there is no data for this area. There are no population estimates for this area either, although by analogy with the eastern tropical Pacific, a population of more than a million would not seem unreasonable.
Stenella coeruleoalba Striped dolphin
Little information is available on this species, and although it may be involved in the tuna seine fishery as described for S. longirostris, in other areas the main species involved in tuna seining operations are spinner and spotted species.
Stenella spp. Spotted dolphins The taxonomy of these species is still confused. At least 4 species have current acceptance in the Atlantic. The comments concerning the incidental capture of dolphins in tuna nets under Stenella longirostris almost certainly apply to spotted dolphins also, as it is they which are chiefly involved in the eastern tropical Pacific tuna fishery. By analogy with the eastern tropical Pacific a population of the order of a million would not seem unreasonable in this area. Mitchell (1975) states that as spotted dolphins are involved in the eastern tropical Atlantic tuna fishery, a high priority should be given to the solution of taxonomic problems in that area.
Stenella clymene Clymene dolphin
There is very little information on this species which is not common, and has only recently been accepted as a species. Cadanet (1959) refers to it in this area though.
Delphinus delphis Common dolphin
This is one of the species which Cadanet (1957, 1959) records for the West African coast. There is no indication of population size, but the Report of the Small Cetacean Sub-Committee (IWC 1982 pp 113–126) states that common dolphins are killed in surface trawling for sardines and mackerel in this region. One trawler was said to have caught 6–22 dophins per haul at night, in an area where 12 trawlers were fishing. Cadanet (1957) refers to this species being taken in beach seines on the West African coast where he states that it is common. Cadanet (1959) found sardinellas, anchovies, mullet and strongylura in stomachs which were examined.
Phocoena phocoena Harbour porpoise
Another of the species found by Cadenet (1959) in this region; Gaskin (1983) summarizes other reports of its presence in the area. There is little recent information however and none on the size of population. Cadanet (1959) mentions that one was found to have 3 Mugil in its stomach, and Cadanet (1957) refers to 3 cought in beach seines in this area.
Monachus monachus Mediterranean monk seal
This species still survives in discrete and very small populations on the Mauritanian coast and the Desertas Islands. Food from the stomachs of specimens in this region indicate a diet including horse mackerel, sparids and rays. The two populations are thought to total around 100 animals (Sergeant et al 1978).
Trichechus senegalensis West African manatee
Husar (1978) provides a comprehensive review of this species, giving its distribution as from Senegal to Angola, in river estuaries and coastal regions. The manatee is said to prefer shallow weedy estuaries, and feeds on vascular plant material. There are no population estimates, but although the species is protected throughout most of its range, hunting still continues illegally. Husar states that the population is severely reduced at present and attributes this not just to hunting, but also to incidental captures of this species in shark netting. Sikes (1974) also states that new monofilament meshes have contributed to the decline of this species in Nigeria.
There is overall an extreme paucity of information on marine mammals in area 34. Very little is known on the distribution of marine mammals within this area, and even less on their diets. At least 26 species are thought to inhabit these waters for at least part of the year. 7 of these are baleen whales, which presumably do not feed to any great extent at these latitudes, and anyway are mostly confined to the northern part of area 34 for a limited part of the year. The exception is the Bryde's whale, the distribution of which is more tropical than other species; this may consume some unknown quantity of small pelagic shoaling fish.
Of the remaining 19 species, at least 6 are known to feed predominantly on squid. Of these, only the sperm whale has been known to inhabit this area in large numbers. Another 4 species have been recorded so infrequently worldwide that their diets remain obscure; these are the rough-toothed dolphin, melon-headed whale, pygmy killer whale, and the short-finned pilot whale. Of the remaining 8 cetacean species 4 may have their diets guessed at in this region. The killer whale is known to frighten tuna fish off Morocco and may therefore prey on this species in part. The Atlantic hump-backed dolphin and the bottlenose dolphin may both be presumed to consume mullet as a part of their diet. It is also possible, but by no means sure, that as common dolphins are caught in surface trawl nets for sardines and mackerel they may consume these species of fish.
The last 4 cetacean species are a nominal 3 Stenella species and the harbour porpoise. The diets of the former are known to consist in other areas of small shoaling fish and squids including myctophids. The latter species consumes a variety of species including commercial ones such as gadoids and clupeids; its diet in this area however cannot be surmised.
DEMERSAL FISH RESOURCES
The northern part of this region, in the upwelling zone, is among the richer fishing grounds of the world, though the demersal stocks are somewhat less productive than the pelagic ones (Belveza and Bravo de Laguna 1980). The southern, tropical part is less productive, (Troadec and Garcia 1979). Total demersal catches in 1981 were a little under half a million tonnes, with most stocks, according to CECAF studies, being fully exploited. Over the years there have been large changes in the species composition.
There are no specific records of any of these being consumed by marine mammals in this area, but one might expect at least 3 marine mammal species, the hump-backed dolphin, the bottlenose dolphin, and the harbour porpoise to be capable of some interaction with fisheries for these species, as they are all found in coastal waters, and may feed on demersal fish.
BALISTIDAE
Balistes spp. Triggerfish
Catches in 1981 rose to 102 000 tonnes from 10 000 tonnes in 1978. Gulland (1983) says of this group of fish that “tough skin and strong spine render a commercial use difficult - even for fish meal Balistes is unattractive.” There are no records of interactions between these species and marine mammals in this area.
GADIDAE
Merluccius spp.
There are several stocks of these species, which include Merluccius and M. senegalensis. Total catches in 1981 exceeded 38 000 tonnes, these stocks are particularly important in the north of the area, and seem to be fully exploited at present. No interactions are known with marine mammals.
Other demersal species include a few flatfish species (about 30 000 tonnes taken in 1981) and sea breams, which are more important in the north of the area. Further South the main groups are croakers, grunts and threadfins, particularly on muddy bottoms, and also sea breams, grunts, snappers and groupers and goatfish on harder bottams. In the tropical zone offshore, that is in waters of depth more than 70 metres, sea breams, cusk eels and black croakers are important (FAO 1981). Porgies have been reported in the stomach of one monk seal, but this seems unlikely to represent a significant interaction between the monk seal and local fisheries.
PELAGIC FISH RESOURCES
The pelagic catches in 1981 were around 2 million tonnes. Most of the major stocks are heavily exploited but some others particularly in the south could produce higher yields with harder fishing. Gulland (1983) states that Balistes species are becoming dominant in the pelagic community in some places. This region seems to have a number of species such as horse mackerels, mackerels, and sardinellas, which occur near the bottom, over the shelf edge, and are taken by trawlers, mostly from foreign nations.
CLUPEIDAE
This family is represented in the catch statistics most prominently by a number of Sardinella species and the pilchard, Sardina pilchardus. The pilchard (sardine) stocks are probably currently under exploited with catches of around 500 000 tonnes and estimated potentials of 800 000 tonnes (FAO 1981a). The sardinella stock off Ghana and the Ivory coast, however, has collapsed (Gulland 1983), whereas elsewhere higher catches could still be achieved (FAO 1981a). The known involvement of marine mammals with these stocks is limited to the example quoted above, in which common dolphins (D. delphis) are caught in surface trawl nets, possibly in fairly large numbers. Nevertheless it is possible that other interactions have so far gone unnoticed. It would seem reasonable that common dolphins may be consuming pilchards here as they do in the Mediterranean; the effects of a significant catch of dolphins and a possible future increase in fishing effort on pilchards in this area can only be surmised.
It should also be noted that there are an unknown number of Brydes whales in this region which may be assumed to feed locally. This species of baleen whale has been known to consume pilchards in other areas, and therefore such an interaction cannot be ruled out in this area.
ENGRAULIDAE
About 90 000 tonnes of various anchovy species were taken in this region in 1981, and comments concerning D. delphis and B. edeni and their predation on pilchards may apply in part to anchovy stocks also.
MUGILIDAE
Mugil spp.
Two species, M. cephalus and M. auratus are reported by Busnel (1973) in his account of the interactions between Sousa and the fishermen of Mauritania. Mullet are largely a coastal species and so presumably are taken along the coast of this area by artisanal fisheries, as most of the purse seiners, trawlers and other large fishing vessels work further offshore. Catches are around 20 000 tonnes per annum, and it may be assumed that both Sousa and Tursiops prey on these species.
SCOMBRIDAE
Scomber japonicus
This species is taken largely in trawl nets and is currently probably over-exploited (Gulland 1983). As has been noted already, common dolphins are known to be taken as a by-catch, and may well feed on this species too. The extent of this interaction remains unclear at present, but possibly a large number of dolphins are killed in this fishery.
Tuna species
A number of tuna species are taken in this area, and two interactions with marine mammals have already been noted. An estimated 3 300 dolphins of unknown species, but possibly of the genus Stenella, may be caught in tuna seining operations every year in this area in (IWC 1982). There is also the record of Bourne (1965 cited in Mitcell 1975) of killer whales being shot at by tuna fishermen in Morocco, but no more recent information is available on this particular conflict.
OTHER SPECIES
Horse mackerel (Trachurus spp.) stocks in this region could possibly produce higher yields if fished harder, but they are fairly fully exploited already (Gulland 1983) with a catch in 1981 of 360 000 tonnes. There are no reported conflicts with marine mammals. Other important pelagic stocks include a number of Caranx species.
INVERTEBRATE RESOURCES
CEPHALOPOOA
Voss (1973) describes the northwest coast of Africa as having one of the richest cephalopod fisheries in the world. Gulland (1983) suggests that the cephalopod stocks in this area may now be overexploited. The main species caught include Sepia officianalis, Loligo vulgaris, and Octopus vulgaris.
Gulland (1983) summarizes the fisheries of this area. After a period when the fisheries were dominated by foreign vessels, local boats have started to take a larger share of the catch since the late 1970's. In the north of the area there are large local fleets purse seining for sardines, and to a lesser extent, trawling for hake and a variety of other demersal species. The Mauritanian coast includes large areas of desert land with a very low human population density, and almost no local fishing. Further south, Senegal has a large traditional fleet employing small seines and gill nets for pelagic species, as well as a smaller fleet of modern trawlers and purse seiners, which take shrimp and other demersal species, and tuna and sardinella.
Further south still, most of the West African countries have well developed artisanal fisheries, commonly using gill nets, hand lines and various types of seines. A number of these countries, including the Ivory Coast, Ghana, Nigeria and Togo, have modern industrial fleets of trawlers and some seiners.
A number of foreign fleets still operate in the waters of area 34, particularly off the West Saharan coast. Purse serners and trawlers are both employed to catch a wide variety of fish such as tuna, sardinella, mackerel, horse mackerel, hake, sea bream and shrimp.
Throughout the region, artisanal fisheries are important, and although by-catch statistics are not recorded, it would seem probable that a number of species, such as Tursiops, Sousa,Trichechus, and possibly Delphinus and Phocoena are taken in appreciable numbers, particularly in gill nets.
The recorded information on this subject is very sparse, with only a few recorded interactions. Operational interactions are almost certainly far more widespread than the available information suggests.
Operational interactions
By-catches have been recorded in 3 situations. Common dolphins are known to be taken by midwater trawl, possibly in quite large numbers, and in beach seines; Phocoena, Tursiops and Sousa have all also been recorded in gill and seine nets: Manatees are known to become caught in gill nets throughout their range, and some unspecified species, presumably Stenella, are taken in tuna purse seining operations, again possibly in large numbers.
Atlantic hump-backed dolphins and probably bottlenose dolphins are known to co-operate with fishermen in herding shoals of mullet off the Mauritanian coast.
Killer whales are reportedly shot on sight off Morocco where they are said to scare tuna schools away from the fishing areas. Tursiops is also reported to harass trawlers.
Biological interactions
No biological interactions are reported, but a number of marine mammal species are presumed to eat commercial fish species.
Bryde's whales and common dolphins may be presumed to feed on some shoaling commercial species such as sardinella, pilchard, anchovy and possibly mackerel and horse mackerel also. Of these only the sardinella is thought to be over-exploited by commercial fisheries, but the implications of this type of interaction are unclear.
Other possible biological interactions involve the 6 species of marine mammal which are known to feed on squid. The cephalopod resources of the area are heavily fished and possibly overexploited. The extent to which the commercial fishery overlaps with the marine mammals in terms of prey species is not known, and again, the implications of the interaction are unclear.
Eubalaena glacialis Right whale
Tomilin (1967) states that this whale is found in the Mediterranean, but such occurences are presumably very rare as only a few hundred individuals are thought to survive from the North Atlantic population (Berzin and Vladimirov 1981).
Balaenoptera physalus Fin whale
Tomilin (1967) states that this species is also found in the Mediterranean where a few individuals migrate in the winter, there are no estimates of the numbers involved, but Viale (1981) indicates that this number should be in the hundreds at least. This species has also been reported in incidental captures in the western end of the Mediterranean (Duguy et al 1983).
Balaenoptera acutorostrata Mainke whale
Hershkovitz (1966) states that this species is present in the Mediterranean and the Black Sea, and Di Natale (1983a) records the incidental capture of 4 individuals in surface drift nets between 1978 and 1982. No estimates are available for the population size, nor are any feeding data available for this area.
Mesoplodon bidens Sowerby's beaked whale
This species is recorded as being present in the Mediterranean (Hershkovitz 1966), but is apparently rare in this area.
Ziphius cavirostris Cuvier's beaked whale
A relatively uncommon species, Duguy et al (1983) record the capture of a total of 14 individuals between 1972 and 1982, 11 in French and 3 in Spanish waters, 14 of them were shot and 1 harpooned. Preferring deeper waters this species feeds on squid; the population size in the Mediterranean is unknown.
Hyperoodon ampullatus Northern bottlenose whale
Not recorded in fishing nets or strandings in recent years, Tomilin (1967) records it as present in the Mediterranean; preferring water deeper than 1 000 metres, this species feeds mostly on squid.
Physeter macrocephalus Sperm whale
Di Natale and Mangano (1983) give details of records of 448 individuals in the central Mediterranean between 1978 and 1982. Of these 20 specimens were captured in drift nets, 3 in trawls, 1 in gill netting, and one by a drifting longline. They suggest that human activity may therefore play an important part in the mortality of sperm whales in the seas around Italy. Viale (1981) suggests that sperm whales are now much rarer in the western Mediterranean than they have been in the past, but no population estimates are available.
Steno bredanensis Rough-toothed dolphin
Another apparently rare species, not recorded in nets or as having stranded recently, although Mitchell (1975) states that it seems to occur “in small numbers”. Preferring deeper water there is little data on feeding.
Pseudorca crassidens False killer whale
Not recorded in any nets recently, this species is apparently uncommon in this area. It prefers deeper water, but in other areas at least is found inshore also, feeding on squid and fish, including commercial species (Carangids).
Orcinus orca Killer whale
Another uncommon species, Duguy et al (1983) report just one capture known to them, in Italy, in the period 1978–1982. There is no information on population size, which is presumed to be small. Feeding is on a wide range of food items and elsewhere is known to include a wide range of commercial species.
Globicephala melaena Long-finned pilot whale
A number of individuals are known to become caught in fishing and other gear. Duguy et al (1983) report 26 individuals in the western Mediterranean between 1978 and 1982, at least 3 of which were caught in tuna nets. The population size is unknown, as is the diet in this area, although presumably the latter consists mostly of squid.
Lagenorhynchus acutus Atlantic white-sided dolphin
Apparently uncommon, with no recent records of incidental capture, Marcuzzi and Pilleri (1971) state that this dolphin has been seen in the Adriatic, but Leatherwood and Reeves (1983) suggest it does not occur further South than the British Isles. Diet and population size in this area are unknown.
Tursiops truncatus Bottlenose dolphin
One of the more frequently caught species in fishing nets, there has also been a live capture fishery in the Adriatic (Mitchell 1975) and a directed fishery in the Black Sea which was stopped in 1983. The Black Sea population may have been dramatically affected by the fishery (Smith 1976); there are no estimates of the current population size, but catches in recent years were probably in the tens of thousands, as since 1967 between 56 000 and 222 000 animals of 3 species were being taken per annum (IWC 1983: Rep of the Sub-Committee on Small Cetaceans). In the western Mediterranean Duguy and Hussenot (1982) record 3 individuals caught in trawl nets, and Duguy et al (1983) report a number of other incidental captures. This species is one of the commonest in this area, but no population estimates are available. The food in the Black Sea is said to consist of mullet and herring, and a number of other commercial fish species (Tomilin 1967). Tomilin also quotes Police stating that this species used to cause damage to the sturgeon fishery in the Danube, in pursuit of food species, and that it also caused damage to nets and catch in the Mediterranean, particularly of the species Smarus vulgaris and S. alcedo.
Grampus griseus Risso's dolphin
An uncommon species throughout its range, nevertheless Duguy et at (1983) report 11 incidental captures in 4 years in the western Mediterranean, in a number of different types of net. This species feeds mostly on cephalopods.
Stenella coeruleoalba Striped dolphin
One of the more commonly caught species in nets in this area, Duguy et al (1983) report a total of 23 individuals in a variety of nets. Collet (1983) suggests that around 100–200 small cetaceans, mainly this species and the common dolphin are taken every year in French Mediterranean waters, both directly (for food and to scare them away from tuna trolling lines) and indirectly in nets. Di Natale (1983) describe this species as one of the most common in the central Mediterranean, preferring offshore waters. He also states that this species is caught in tuna seine nets in the Ligurian Sea, but not necessarily with any great loss of life. The food is said to consist mainly of sardines and anchovies (Di Natale 1983).
Delphinus delphis Common dolphin
This is another frequently caught species (see comments for preceding species), and is also one of the three species which was caught in the Black Sea until recently. There are no recent population estimates, except Viale's (1981) suggestion that around 8000 are present in the northwest Mediterranean, presumably the population in the Black Sea at least is depleted. Duguy et al (1983) report a total of 8 individuals as incidental captures in a variety of nets. This species is known to annoy Greek fishermen (IWC Small Cestacean sub-committee 1977). Tomilin (1967) relates that it is also known to help Mediterranean sardine fishermen, who follow the dolphins which are responsible for frightening the fish to the surface. He continues that the population of 500 000 animals in the Black Sea destroys 2 500 tonnes of fish per day, and that on the coast of Anatolia were “the population of dolphins totals about one million” they consume 1 million tonnes of fish in 100 days. The food of this species in this area is known to include chiefly sprats and anchovies and also pelagic pipefish, as well as a variety of other species including horse mackerel and mullet (Tomilin 1967).
Phocoena phocoena Harbour porpoise
The third of the three species caught in the Black Sea fishery, it is nevertheless thought to be absent from the western Mediteranean (Gaskin 1983). In the Black Sea they are known to eat anchovy, silverside and especially gobies, and a number of other species in smaller quantities. There is no recent information on incidental captures of this species in area 37, nor on its status outside the Black Sea where it is presumably severely depleted after heavy exploitation for decades (see T. truncatus).
Monachus monachus Monk seal
The only pinniped found in this area, the numbers of this species are severely reduced, and may now number only about 500 (Ronald and Healey 1976). Sergeant et al (1978) indicate that the population is threatened by human activity including that of fishermen who, in some areas, are known to club seals and to shoot them, as they damage nets. They also state that incidental captures are known from tuna nets, in trammel gill nets, on baited hooks and possibly in trawls. The food is known to include a large number of species including Mullus surmuletus, Mugil cephalus, Boops boops, Dentex sp., and octopus.
Of the 18 species of marine mammal thought to inhabit the Mediterranean, 6 are known to feed either exclusively or partly on squid. The diet of the 3 species of baleen, whales which are found in these waters remains uncertain, and they may not feed at all as baleen whales in general do not feed in the winter in the south of their range. It is possible that minke or fin whales do consume some fish, such as sardines or sprats, but his must be of minor importance.
Of the remaining 9 species, 4 feed on unknown species, of which the killer whale, the false killer whale, and the Atlantic white sided dolphin are all known to feed on commercial species elsewhere in the world. 5 species are known to consume commercial fish species in this area.
The 5 species of marine mammal are the harbour porpoise, the bottlenose dolphin, the common dolphin, the striped dolphin, and the monk seal. The food items include mullets, red mullets, herring, anchovies, sprats, pipefish, silverside, gobies, sardines, horse mackerel, bogue, dentex and octopus.
DEMERSAL FISH RESOURCES
The total demersal catch is around 500 000 tonnes (FAO 1981a). The Review of the State of World Fish Resources (FAO 1981a), on the basis of studies by the General Fisheries Council for the Mediterranean suggests that stocks on the northern and western shores of the Mediterranean are over-exploited, whilst those on the African and Asian shores are ‘moderately to fully exploited’. Few demersal species are involved with interactions with marine mammals, and Tursiops and Monachus are probably the only species which feed to any great extent on demersal fish in this area.
SPARIDAE
Boops boops Bogue Bogue is a one of the main catches of the area particularly in the Aegean and in the western end of the Mediterranean. This species is one of the known food items of the monk seal. The state of the stocks of bogue are unknown, but the low numbers of monk seals are unlikely to seriously alter their condition. Over 25 000 tonnes were reported caught in 1981, and the catch has been stable for a number of years.
MULLIDAE
Mullus spp. Red mullets These species accounted for more than 25 000 tonnes in 1981, and catches have fluctuated between 20 000 tonnes and 25 000 tonnes since 1976. The state of the stocks is unknown, but presumably stable. The demersal stocks of the western Mediterranean are in general heavily fished and suffer from growth overfishing, but catches remain stable (GFCM, 1978). Red mullets are known to be eaten by D. delphis and M. monachus, but is unlikely to form the major part of the diet of either of these species.
Other species
In terms of weight of catch the only other demersal species which figure prominently in the catch statistics are Micromesistius poutassou, the blue whiting, which has sustained a yield of between 9 and 19 thousand tonnes between 1976 and 1981, Merluccious merluccius, the Euorpean hake (28 000 tonnes in 1981) and picarels (Maena spp., 13 000 tonnes). None of these species are reported as food items of marine mammals in this area.
PELAGIC FISH RESOURCES
The pelagic catch in 1981 totalled over 1 110 000 tonnes. FAO's Review of the State of World Fishery Resources (FAO 1981a) states that some stocks are already over exploited, whilst others (e.g. anchovy) could be more heavily fished. The pelagic fish of the area seem to be more important to marine mammals then demersal ones. The common dolphin is described by Tomilin (1967) as mainly feeding on pelagic fish far from shore, and Stenella coeruleoalba has been similarly described by Di Natale (1983).
CLUPEIDAE
Engraulis encrasicolus European anchovy This species supports the single largest fishery of any species in the area by a large margin. Nearly 600 000 tonnes were taken in 1981, most of which was taken from the Black Sea. Turkish catches of anchovy have increased from 80 000 tonnes in 1976 to 273 000 tonnes in 1981. FAO's (1981a) Review of the State of World Fishery Resources indicates that concern has been expressed over the state of this stock.
All 4 species of small cetacean whose feeding habits have been studied are known to eat this species. Tomilin (1967) states that it may form 99% of the diet of D. delphis in some parts of the Black Sea in spring. Although not a major part of the diet of Tursiops, it has also been recorded (Tomilin 1967), whilst the other species in the Black Sea, P. phocoena is also known to feed on the anchovy heavily. In the central Mediterranean, anchovy is also the main food of the pelagic dolphin Stenella coeruleoalba. It can be seen that anchovy is an important food source for at least 3 species of small cetacean. In past years common dolphins have been accredited with consuming vast quantities of anchovies in the eastern end of this area (see above), but the presumed reduction in the numbers of dolphins in the Black Sea must have also reduced the amount of anchovy and other fish eaten. The current high level of exploitation of anchovy stocks coupled with the fact that the severely reduced populations of both P. phocoena and D. delphis in the Black Sea have recently been relieved of exploitation, must present the possibility of future conflict if the dolphins are to increase in numbers. Conflict could also arise in the Mediterranean where the anchovy stocks are also heavily exploited, though small cetacean populations may not be so severely reduced as in the Black Sea.
Sardina pilchardus Pilchard/Sardine There is some suggestion that stocks of this species are over-exploited off France and Morocco (FAO 1981a), with catches in 1981 reaching 233 000 tonnes. Known to be eaten by the pelagic species Stenella coeruleoalba, and also, according to Tomilin (1967) by D. delphis. The fact that this species is concentrated in the western end of the Mediterranean, where the harbour porpoise P. phocoena is apparently absent suggests that for these 2 species at least there is not likely to be any considerable interaction.
Sprattus sprattus Sprat Sprats yielded 100 000 tonnes in 1981 in this area, their area of greatest concentration being the Black Sea. The common dolphin is known to feed on them and many of the comments on anchovy may therefore apply to this species also.
MUGILIDAE
Mugil cephalus Striped mullet This species is thought to be the main food of the bottlenose dolphin in the Black Sea at least (Tomilin 1967), and is presumable important elsewhere also. The total catches in area 37 in 1981 were only 3 000 tonnes, so it may not be considered to be an important commercial species. Catches of other Mugil species however totalled nearly 15 000 tonnes; the importance of other species in the diet of marine mammals is not known. Monachus monachus is also known to eat the striped mullet.
CARANGIDAE
Trachurus spp. Horse mackerels The horse mackerel is known to be eaten to some extent by the common dolphin. Catches in 1981 totalled 90 000 tonnes (all species), but it has been suggested (FAO 1981a) that the fishery could be expanded in a number of places. It is not possible to predict the effects of such an expansion on any interaction with marine mammals.
SCOMBRIDAE
Tuna species
Although by no means important as food species for marine mammals, these species are important commercially, and their capture is known to affect some species of marine mammal (see below).
INVERTEBRATE RESOURCES
CEPHALOPODA
Squids and octopuses are relatively important in this area, with total catches for all species in 1981 exceeding 50 000 tonnes. The fisheries are pursued with a number of gear types including trawls, trolled jigs and lights, dipnets, trammel setnets, and other types of nets and traps (Voss 1973). Voss doubts that the potential in this region exceeds 100 000 tonnes, but there is a considerable biomass of cetaceans (at least 7 species) in this area which feed either entirely or partly on squid.
Whereas a number of commercial species of fish and cephalopod are known to be important in the diet of some marine mammals, it should be noted that a number of other species are also important in marine mammal diets which are not commercially important. The harbour porpoise is said to feed mostly on gobies in the Black Sea, whilst pelagic pipefish are important in the diet of the common dolphin. It should also be noted that for at least 5 species of marine mammal present in area 37 there are no data on feeding. None of these species is thought to be present in very large numbers, but some of them are known to consume commercial species elsewhere.
Trawling with boats ranging up to 200-300 tons is very important in the region, for both demersal and pelagic species. Purse seines and similar surrounding nets (ring nets, lamparas) are also important for small pelagic species (sardines, mackerels etc.) and for tunas.
A number of traditional and artisanal fishing methods are retained in this region. Large traps are used to catch tuna in a number of places in the Mediterranean. Beach seines, particularly in the eastern end of the Mediterranean are used to catch mullet, bogues and other inshore fish. Gill nets and trammel nets are used for the capture of fish in shallow waters also, such as species of Sparidae and Serranidae, whilst drift nets are used for sardines and other pelagic fish, including some scombrids. A number of other artisanal gears are also employed.
The incidental capture of marine mammals has been recorded in a great number of gear types. The capture of minke whales in drift nets should be noted: whilst Di Natale (1983a) does not record the species of fish being sought here, it is interesting to speculate that minke whales thus caught may be feeding on that same species, possibly sardines or anchovies. Sperm whales have also been caught in drift nets and trawls, gill nets and even on a drifting longline. Pilot whales have been caught in tuna nets (type unspecified) and tuna seine nets have also caught a number of Stenella coeruleoalba.
The incidence of shooting of marine mammals should be noted. The total value of the Mediterranean catch is one of the highest among the regions of the world, despite the relatively low volume (FAO 1981a). This is because of the high market values fish may attract in Europe and the Mediterranean. The large number of artisanal fisheries and the predominance of small boats indicates that a large number of fishermen are employed throughout the area. These two facts may help explain the large numbers of cetaceans, and the numbers of monk seals, which are shot or otherwise killed by fishermen who doubtless regard them as unfavourable competitors for a relatively scarce and expensive resource. Duguy and Hussenot (1982) claim that several thousand dolphins, mostly Stenella coeruleoalba and Delphinus delphis are killed every year in this way by French fishermen.
In a relatively small intensively fished area where fish fetches a relatively high price, it would perhaps be surprising if marine mammal fishery interactions were not a prominent feature. Despite this the available information on the subject is comparitively sparse. Tomilin's (1967) account of marine mammals in the USSR contains much information on the feeding habits of a number of species in this area and also details a number of (now) dated examples of interactions with fishermen.
Operational interactions
As regards incidental captures, with so many small scale fisheries operating in the area it would be surprising if these were not widespread, and yet only a few papers by Duguy, Di Natale and others provide any information on the subject. It would appear nevertheless that many of the species occurring in this area are also subject to incidental capture.
Bottlenose, striped and common dolphins are the 3 species most frequently caught incidental to fishing operations, using a variety of gear.
Fin whales, minke whales, Cuvier's beaked whales, sperm whales, pilot whales and Risso's dolphin are also caught or killed in a variety of fishing operations in small numbers.
Monk seals are known to damage nets and annoy fishermen.
Biological interactions
Competitive interactions are even less clear, but it would seem that a number of marine mammal species are currently depleted, notably the common dolphin, harbour porpoise and bottlenose dolphin in the Black Sea. The recovery of these stocks must bring into question the possible future conflict with anchovy and other fisheries in the area.
Eubalaena glacialis Right whale
Mermoz (1980) reports on the status of this species in area 41. At least 120 individuals are thought to migrate to the coastal waters of Argentina, Uruguay and possibly Brazil, to places where they have not been seen for a number of years. No fish are eaten and no conflicts would seem likely, although there is one record of an individual being killed by fishermen in Brazil in 1972 (IWC 1977). The world's first marine nature reserve was set up off the Chubut Peninsula in Argentina in order to protect a valuable breeding site of this species in that region (Goodall and Cameron 1980).
Caperea marginata Pygmy right whale
Recorded from the Falklands/Malvinas (Ross et al 1975), this species is uncommon, and apparently does not feed on fish. No interactions with fisheries are recorded or likely.
Balaenoptera physalus Fin whale
An unknown number of fin whales, presumably in the low tens of thousands, winters in the waters of area 41. Feeding is unlikely, and no other interactions with fisheries have been recorded.
Balaenoptera musculus Blue whale
Unknown numbers migrate into this area during the winter, possibly thousands rather than hundreds, but the fact that they are thought to fast in the winter (MacKintosh 1965) and the low population levels make interactions with fisheries unlikely.
Balaenoptera acutorostrata Minke whale
There is a breeding population off the coast of Brazil which is subjected to some whaling, although this is due to be phased out by 1985. Williamson (1975) describes the fishery, which occurs off the north east tip of Brazil (7°S). Minke whales congregate over the continental slope 50 km offshore; around 1 000 were taken per year. The stomachs were almost always empty. The size of the breeding population in this area is unknown, but presumably in the tens of thousands at least. No interactions between this stock and fisheries is envisaged.
Balaenoptera borealis Sei whale
An unknown number of sei whales spend the winter in area 41, possibly tens of thousands; there is known to be some mixing between the west and east South Atlantic stocks (Antarctic areas II and III) (Gambell 1977). Williamson (1975) records the capture of a few sei whales in the Brazilian minke whale fishery in the 1950's. There are no interactions with fisheries, and these do not seem likely as most feeding is on krill in the Antarctic (Nemoto 1959).
Balaenoptera edeni Bryde's whale
Gambell (1977) suggests that there may be an inshore and an offshore stock of this species off Brazil. Bryde's whales tends to stay in warmer waters, but very little is known of this species in this area. The diet is known to include fish in other areas, so some commercial fish may be eaten here, however, no conflict is evident at present. The population size is unknown, but could be in the thousands.
Megaptera novaeangliae Humpback whale
A breeding ground occurs off north eastern Brazil (Mackintosh 1965); the total population in area 41 probably does not exceed 1 000 at any time. Feeding is mostly confined to the swarming crustacea of the lower latitudes, and as yet no interaction with the fisheries of area 41 have been recorded.
Tasmacetus shepherdi Shepherd's beaked whale
This species has only been recorded once in area 41 (Mead and Payne 1975), and is very rare worldwide. The stomach contents included hake, serranids and brotulids, all of which groups contain commercial species. The implications of such an apparently rare species eating commercial fish are unclear. On the one hand, there would seem to be little threat to commercial fisheries from such a mammal, but the effects of overfishing a particular food fish for that mammal on the other hand are unpredictable.
Berardius arnuxii Arnoux's beaked whale
Another relatively rarely seen species, a few individuals have turned up in the Falklands /Malvinas and in Argentina. Stomach contents indicate a diet consisting largely of cephalopods. No interactions with fisheries are reported or likely at present, (Goodall 1977, McCann 1975).
(Mesoplodon densirostris Blainville's beaked whale
This species has not yet been recorded in area 41, but strandings in most other temperate seas of the world indicate that it may occur here. No interactions with fisheries can be envisaged at present.)
Mesoplodon layardii Straptooth beaked whale
Although fairly frequently stranded in New Zealand, this species is only recorded from the Falklands/Malvinas, Uruguay and Tierra del Fuego in area 41 (Goodall 1977, Leatherwood and Reeves 1983). No interactions with fisheries are likely.
Mesoplodon hectori Hector's whale
One of the least known of all cetacean species, this animal has been identified on the basis of very few individuals, one of which was found in Tierra del Fuego (Goodall 1977). It has also been found in the Falkland/Malvinas Islands, and may be circumpolar in all southern hemisphere temperate waters (Leatherwood and Reeves 1983). Nothing is known of its natural history and the most that can be done is to compare it with other beaked whales; interactions with fisheries are unlikely.
Mesoplodon grayi Gray's beaked whale
Although relatively frequently stranded in the southern hemisphere, this species is recorded from only one location in area 41, in Argentina (Goodall 1977). No interactions with fisheries are likely.
Ziphius cavirostris Cuvier's beaked whale
This whale is known in area 41 from strandings in Brazil and Argentina (Watson 1981, Goodall 1977). Although not uncommon throughout the world, interactions with fisheries seem unlikely, partly due to its deepwater habitat.
Hyperoodon planifrons Southern bottlenose whale
This whale has turned up in the La Plata estuary in Argentina, in the Falklands/Malvinas (Watson 1981) and in Tierra del Fuego (Goodall 1977). A diet of squid, coupled with apparent rarity, make this an unlikely species to interact with fisheries.
Physter macrocephalus Sperm whale
Townsend's (1935) maps demonstrate large concentrations of this species on the edge of the shelf in summer months from 10°S to about 50°S. The state of the population in area 41 is unknown but is presumably depleted. A figure of less than, or around, 100 000 individuals may not be unreasonable. No direct interactions with fisheries have been recorded, and would seem unlikely unless oceanic deep sea squid resources become more intensively fished.
(Kogia breviceps Pygmy sperm whale
No strandings have yet been recorded in the South Atlantic, but it seems probable that this species may occur there also; it is at any rate uncommon throughout the world. No interaction with fisheries is likely at present.)
(Kogia simus Dwarf sperm whale
Once again this species has not yet been recorded in the South Atlantic, yet its otherwise worldwide distribution in warmer waters indicates that this is probably merely because of its general scarcity. Interactions with fisheries are improbable at present).
Steno bredanensis Rough-toothed dolphin
Stranding are known from locations in Argentina and Brazil (Leatherwood and Reeves 1983). Nothing is known of the size of the population, nor of any trends in abundance, but the general scarcity of recorded sightings indicates that it is probably a relatively uncommon species. No interaction with fisheries is known in area 41, though it has rarely been reported in the eastern tropical Pacific tuna fishery as a by-catch (Alverson et al 1972 cited in Mitchell 1975a), so presumably the possibility of interaction with pelagic fisheries exists.
Sotalia fluviatilis Tucuxi Although commonly seen throughout the range, there is some suggestion that the species is becoming rarer. No estimates are available on the size of the population. Best and da Silva (1984 in press) record about 30 specimens which they collected in two years from fishermen's nets in the central Amazon region, but the effect of this incidental catch on the population is unknown. The diet includes catfish and crustaceans (Mitchell 1975).
(Peponocephala electra Melonhead whale
Although recorded in the mid-Atlantic (Perrin 1976), it has apparently not yet turned up in area 41. This species is presumed rare, and is unlikely to interact with fisheries now or in the future.)
Pseudorca crassidens False killer whale
Hershkovitz (1966) records the distribution of this species from the Caribbean to Buenos Aires. There are neither any hunts nor any interaction with fisheries recorded in area 41, and there is no indication of population size either.
Orcinus orca Killer whale
One recent IWC estimate (Hammond 1983) of the size of the southern hemisphere stock put this as high as about 160 000, but there is no indication as to the distribution of these within area 41. There are no records of any interactions with fisheries in area 41, but these cannot be discounted, as this is predominantly a coastal species, and as conflicts have already arisen in the North Atlantic (see area 27). Indeed in 1978, Goodall and Cameron (1980) report that killer whales were numerous in the Beagle Channel, and were shot at. Presumably fishermen and others in the area regard this species disfavourably already.
Globicephala melaena Long-finned pilot whale
Goodall & Cameron (1980) record the depth charging and killing of 27 adult and 12 young pilot whales at Tierra del Fuego in 1972 by the Argentinian Navy, in the belief that they were killer whales. Although strandings are common, there appear to be no records of gear entanglements or other interactions with fisheries in this area. There are no estimates of abundance for any of the stocks in the southern hemisphere either.
Globicephala macrorhynchus Short-finned pilot whale
No estimates of abundance are available and there are no records of interactions with fisheries in area 41, and again, for such a pelagic species, none are likely at present.
Lagenorhynchus obscurus Dusky dolphin
Goodall and Cameron (1980) report that this species is caught in the north of Argentina in the fine meshed surface nets of the anchovy and mackerel fishery in that area in October and November. As an inshore species, feeding primarily on anchovies (Leatherwood and Reeves 1983) other interactions might be expected but there are no data. There is no estimate of abundance either.
Lagenorhynchus cruciger Hourglass dolphin
Watson (1981) reports seeing these dolphins feeding at the surface on fairly large fish, but nothing more is known of their feeding habits. As yet there are no records of any interaction with fisheries, but this cannot be discounted if fisheries are developed in the more southerly waters of the South Atlantic.
Lagenorhynchus australis Peale's dolphin
Limited to cold coastal waters around the Falklands/Malvinas and from the southern tip of South America to the Gulf of San Matias in Argentina, in parts of which range it is common (Leatherwood and Reeves 1983). Some individuals of this species are evidently caught in the net fishery for ‘robalo’ (Eleginops maclovinus) in Tierra del Fuego as a by-catch (Goodall and Cameron 1980). The local nature of the population of this species, coupled with its coastal habitat, makes it vulnerable to any expansion in the fisheries of this area. There is no population estimate, and little is known of its ecology, but Leatherwood and Reeves (1983) report individuals swimming and diving in kelp beds, and found octopus in the stomach of one.
Tursiops truncatus Bottlenose dolphin
Preferring inshore waters, this species is distributed throughout the area as far south as Patagonia. There are reports of this species being caught in small numbers in fishing nets, such as the gill net fishery for Micropogon (croaker) along the central Argentine coast, (Goodall and Cameron 1980). The effect of such by-catch is unknown. Other interactions are not recorded as yet but may yet become more evident.
Grampus griseus Risso's dolphin
There are no estimates of abundance of Risso's dolphin in area 41, and it is apparently not involved in any interaction with fisheries in this area at the moment. Any offshore development of a squid fishery could perhaps alter this situation.
Stenella longirostris Spinner dolphin
Reported by Perrin et al (1981) from southern Brazil, there are no estimates of the population size in area 41. This species tends to inhabit deeper waters, but may also be found closer to the shore. There is no known interaction with fisheries in this area.
Stenella coeruleoalba Striped dolphin
There is no information on population size or feeding of this species in this area, and no interaction with fisheries has been recorded.
Stenella spp. Spotted dolphin
Again there is a relative paucity of observations on this species in this area, and as yet no interaction with fisheries in this area has been recorded; S. attenuata is the species apparently most affected by incidental catches in the fishery for yellowfin tuna in the Pacific, and like the other species of Stenella could conceivably come into conflict with any development of large scale pelagic fisheries in area 41.
Delphinus delphis Common dolphin
A common species in all warm water areas of the world, no population size estimate is available for this area and there do not appear to be any feeding data for area 41 either. As yet there are no interactions with fisheries in this area.
Lissodelphis peronii Southern rightwhale dolphin
Very little is known of this species which is found primarily in cold offshore waters. There would seem to be little likelihood of any important interactions with fisheries.
Cephalorhynchus eutropia Black dolphin
A relatively rare species whose main area of distribution is along the Chilean coast but which is nevertheless also found (by Goodall 1977) in area 41 around Tierra del Fuego. Leatherwood and Reeves (1983) state that the diet is unknown. A number are known to get caught in fish nets and are used to bait crab traps (Goodall and Cameron 1980), which could have some effect on the population. No data are available on either the size of the population nor on the size of the by-catch.
Cephalorhynchus commersonii Commerson's dolphin
This species is known to be caught in Argentinian waters, incidentally in gill nets, and tangle nets in the fisheries for Eleginops (blenny) and Lithodes (king crab) and also deliberately for crab bait and for human consumption; up to 200 may be taken in these ways each year (Goodall and Cameron 1980). The effect that this has on the population is unknown but could be significant. Leatherwood and Reeves (1983) add that the diet may include squid, cuttlefish, krill, crabs, shrimps and small fish such as sardines, silversides and anchovies.
Phocoena spinipinnis Burmeister's porpoise
Brownell and Praderi (1982) give an acount of this species. Nothing is known about the population size or status, but it is apparently quite often caught in fishermen's nets throughout its range. Brownell and Praderi report 4 as having been caught in the shark gill net fishery in Uruguay over a one year period, and Goodall and Cameron (1980) record another in the tangle nets for southern king crabs in Argentinian Tierra del Fuego before these were made illegal. Brownell and Praderi found Merluccius hubbsi and Pagrus sedecim in the stomach of one specimen; they also state that this is one of the most abundant coastal small cetaceans in the area. The effect of the by-catch and the fact that this species feeds on commercial fish remains unclear, but Brownell and Praderi suggest that this species is heavily over exploited in area 87 at least.
Phocoena dioptrica Spectacled porpoise
Nothing is known of diet or the size of the population, but fewer than 20 specimens have been recorded (Brownell 1975a, 1976,). It has, however, also been caught in Argentinian tangle nets (Goodall and Cameron 1980), and like P. spinipinnis, may be more common than would at first appear.
Inia geoffrensis Boutu This species is relatively common in the Amazon river, and until recently was afforded some protection by the superstitions of the local people. Watson (1981) suggests that in some areas in the Amazon this species may help fishermen by responding to their calls and herding fish from deeper waters into their seine nets. Ribeiro (1943 cited in Mitchell 1975a) indicates that in some areas some of these animals were captured for processing into oil. More recently a live capture fishery has developed, and increasing numbers are shot by settlers. There is also a small incidental catch of this species associated with gill net and seine fisheries for catfish (IWC 1977); few data are available on this yet, but Best and da Silva (1984 in press) collected more than 20 specimens from fishermens nets in the central Amazon in a year and a half. The effect of this capture on the population is unknown.
Pontoporia blainvillei Franciscana The size of the population is unknown, but the species is thought to be fairly common. Stomach samples have yielded about 19 species, mainly fish, of which the majority were a few species including Engraulis anchoita, Cynoscion striatus, Trachurus lathami, and Polyclemus brasiliensis. Incidental catches in shark nets have been common, with between 600 and 2 000 taken per year. This may have had an impact on the size of the population, although more recently this type of shark fishery has been in decline (Brownell 1975, Fitch & Brownell 1971). The proximity of this species to coastal fishing operations is likely to mean that some form of interaction between the dolphin and fishermen is inevitable.
Otaria flavescens South American sea lion The population size in area 41 is thought to be around 230 000, breeding on the Atlantic coast being confined to islands offshore. Contact with land is thought to be maintained throughout the year, feeding in shallow water often less than 5 miles from the shore. Individuals have been recorded very much further out to sea however. Stomach contents vary from area to area, but include Sebastodes oculatus, Clupea bentinckii, Merluccius gayii, various crustacea, molluscs, and birds, notably penguins. Europeans have exploited the population since around 1520, and commercial exploitation is still carried out by Uruguay and Chile (see area 87), several thousand individuals being killed every year. In addition clandestine exploitation and killing by fishermen impose further mortalities. This species is also known to drown in nets and to cause damage to fishing gear, particularly shore based trammel nets. No quantification of this damage to nets or sea lions is available. Sea lions have also learned to follow boats where they interfere with nets, particularly seine nets, and to take fish from hook and line fisheries. This species is thought to occupy a more inshore habitat than the fur seal (Vaz-Ferreira 1979, 1981, 1982).
Arctocephalus australis South American fur seal
The population is distributed in area 41 south of Sao Paulo in Brazil, breeding on offshore islands including the Falklands/Malvinas; it is thought to be stable or declining at present, although the population in Uruguay has increased in this century, after some heavy exploitation, to a more stable size. These seals feed further out to sea than the sea lions and are therefore less conspicuous near the coast outside of the breeding season. Food items include Engraulis anchoita, Trachurus lathami, Cynoscion striatus Pneumatophorus japonicus, Peprilus sp. amongst the fish, as well as cephalopods, bivalves and gastropods. Exploitation is both regulated commercially and clandestine. Uruguay has one of the oldest regulated seal hunts in the world dating back to the early 16th century, and currently takes around 10 000 skins annually. Seals are also killed incidentally in fishing gear, particularly seine nets, and although these seals do not follow fishing boats as their South African relatives do, they still get into both trawl and seine nets at sea. No quantitative data are available on this. No population estimates are available for the whole stock, but the Uruguayan population is estimated at 252 000 in 1972, and the populations in Argentina and the Falklands may total 20 000. (Vaz-Ferreira 1979a, 1982a).
Mirounga leonina Southern Elephant seal
Several small breeding sites exist on the coast of Argentina and in the Falklands/ Malvinas; fish and squid have been identified in stomach samples (Laws 1979) but as yet no conflicts are reported.
Leptonychotes weddelli Weddell seal
This is an Antarctic species which is occasionally recorded having wandered northward into area 41 (DeMaster 1979). No interactions with fisheries are likely.
Trichechus inunguis Apparently confined to the Amazon basin, this species feeds only on plants but has been dramatically reduced in numbers by hunting throughout its range even though this is now illegal in Brazil at least. There may also be a significant number taken as a by-catch in gill nets in the river system (FAO 1978, IUCN 1981).
Of the 47 or so species of marine mammal, quite a high number seem to have the potential to interact, or actually do interact with fisheries, and yet, as regards this particular problem, this is one of the least well documented areas in the world. Seven of the species of baleen whale probably do not feed much in these waters, and at least 13 other species probably feed almost entirely on squid. Leaving aside the potential problems of a squid fishery, there are a further 17 species that are either known to feed on commercial species, or could be likely to include some in their diet. There are a particularly large number of small neritic cetaceans in this area, such as the dusky dolphin, Peale's, Commerson's, and the black and bottlenose dolphins, the spectacled and Burmeister's porpoise and the franciscana, boutu and tucuxi. Many of these are probably caught very frequently throughout the area, which could already be having serious affects on the population dynamics of a number of species, but there are very few data. The paper of Goodall and Cameron (1980) is the only one which addresses this particular problem.
At present few of the fish stocks are over exploited, and it may be that there is little biological interaction; this situation, however, remains unclear.
DEMERSAL FISH RESOURCES
The FAO Atlas of the Living Resources of the Sea (FAO 1981) estimates the total potential yield of demersal stocks in this area to be about 2.5 million tonnes. In 1980 the total demersal catch in area 41 was less than 750 000 tonnes. Most of this was made up from about 4 or 5 species, with one species, Merluccius hubbsi, accounting for about half of the total yield.
MERLUCCIDAE
Merluccius hubbsi Argentine hake
This is the most abundant commercial species between latitudes 34° and 44°S. Averaging 38 and 45 cm in length. It is distributed below 100m on the slope of the continental shelf. South of 47°S, this species becomes replaced by Merluccius polylepis. In 1980 only 370 000 tonnes were taken, mostly by Argentinian, Uruguayan and Brazilian benthic trawlers; this nevertheless represents the largest yield of any species in the area. This species is known to be eaten by a number of marine mammal species.
GADIDAE
Micromesistius australis Southern blue whiting
This species, together with Macruronus magellanicus, from the dominant group numerically between 45° and 55°S. M. australis has an average length of 48–56 cms, and is found in major concentrations between 44 and 52°S. It tends to stay on the slope of the continental shelf between 150 and 500 metres in depth. M. magellanicus tends to shallower water and has major concentrations between 46 and 54°S. CARPAS estimated in 1971 that the potential yield of these two species was about 1.3 million tonnes, M. australis forming 60–70% of this. In 1971 catches of the two species were negligible, but by 1980 78 000 tonnes of M. australis and 7 000 tonnes of M. magellanicus were being taken, almost all by the USSR and Poland. There is little or no reported by-catch in the offshore fisheries.
SCIAENIDAE
Drums and croakers of which at least 6 species are commercially important. These species are found in shallower more coastal waters than the previous species, down to a depth of only about 50 metres, preferring muddy bottoms.
Micropogon spp. Croakers
Caught along all three coasts of area 41, these species are thought to have a potential yield of around 80 000 tonnes, and are probably fully exploited already.
Cynoscion striatus Striped weakfish
This species is found along the South American coast from central Brazil to 42°S, but is only exploited south of 30°, mainly by Uruguay and Argentina. The catch levels are much lower now than they were in the late 1960's, the stock apparently having been overfished. In 1980 the total catch of this species was 25 000 tonnes. Other species of the same genus are fished in Brazil which took 42 000 tonnes in 1980. This species has also been identified in the stomach of Arctocephalus australis.
Micropogonias undulatus Atlantic croaker
There appears to be no estimate of either the initial abundance nor of the potential yield of this stock, but nevertheless in 1980 113 000 tonnes were taken, which makes this species one of the 3 or 4 largest in terms of yields in area 41. The stock is thought to be moderately to fully exploited. Together with the previous species and the sea bass A. brasilianus, this forms the major part of the Uruguayan catch.
Macrodon anycylodon King weakfish
Concentrated mostly on the southern coast of Brazil and along the oceanic coast of Uruguay, this species is thought to have an annual potential yield of about 80 000 tonnes, but currently the catch is around 1 200.
SERRANIDAE
Acanthistus brasilianus Sea bass
One of the most important species to the Uruguayan fishing industry in terms of weight landed. In 1980 a total of 12 690 tonnes of this species were caught. Another 5 000 tonnes of grouper were also landed.
SPARIDAE
Pagrus pagrus Red porgy
This species is distributed mainly between 35° and 41°S, at depths of less than 50 m, or not further than about 60 miles offshore. It would seem to prefer hard-bottomed areas. There is no indication of the potential yield, but currently about 15 000 tones are taken per year.
LUTJANIDAE
Lutjanus purpureus Red snapper
Distributed mostly along the north east continental shelf of Brazil, this stock is largely under-exploited; potential yield is estimated at about 5 000 tonnes and the current catch is about 1 200 tonnes.
ARIIDAE
Marine catfish are usually all considered as one group in the catch statistics. They form one of the major landed catches in terms of biomass, 14 000 tonnes being landed in 1980, all of which was taken by Brazil. They appear to be particularly abundant in the muddybottomed Amazon estuary area, but no estimate of potential yield has been made.
OPHIDIIDAE
Genypterus spp. Cusk eels
With a similar distribution to the hakes, these species are found below 100m south of 35°S and below 200m to the south of 41°. There is no indication of potential yield, but in 1980 a total catch of 6 722 tonnes was landed, mostly by Argentina.
CHAELODACTYLIDAE
Chaelodactylus bergi Hawkfish/castaneta
Found on the middle slope of the continental shelf, especially in the south, this species yields around 2 000 tonnes per year, mostly to Argentina. There is no indication of potential yield.
PERCOPHIDIDAE
Percophis brasiliensis Brazilian flathead
Distributed between 50 and 100 m around southern Brazil, Uruguay, and northern Argentina, this stock yields around 2 500 tonnes per year, but once again there is no indication of its potential.
NOTOTHENIDAE
There is no indication as to the potential size of this resource which is distributed in the south of area 41, but foreign fleets, particularly Polish ships, take around 7000 tonnes per year at present.
ELASMOBRANCHS
These include sharks, dogfish, chimaeras and rays, and account for around 20 000 tonnes of landed catch per year. The total potential is unknown. At least two of these fisheries which are coastal are responsible for some incidental catches of marine mammals.
‘Miscellaneous marine fish’:
This group makes up the 4th largest category of catch. 111 000 tonnes were recorded in 1980, and almost all of this was from Brazil. There is no indication as to the nature of this catch, nor the nature of the fishery.
PELAGIC FISH RESOURCES
The total potential pelagic resources of area 41 are unknown, but may be considerably in excess of 2 million tonnes per year if squid stocks are considered. The anchovy in this area alone should yield 1 million tonnes, yet the total pelagic yield in 1980 was just over 300 000 tonnes.
CLUPEIDAE
Sardinella brasiliensis Brazilian sardine
Distributed inshore along the Brazilian coast between about 23 and 27°S this stock has seen a steadily increasing catch since the 1960's. In 1971 the catch totalled 110 000 tonnes, in 1977 165 000 tonnes and in 1980 it had reached 210 000 tonnes. This stock has probably now become fully exploited.
Sprattus fuegensis Patagonian sprat
A large stock distributed on the continental shelf off Patagonia and around the Falklands /Malvinas, this remains unexploited at the present. No estimates of the potential yield of this stock have been made, but it is expected to have a potential of several hundred thousand tonnes per year at least.
ENGRAULIDAE
Engraulis anchoita Anchovy
Distributed on the continental shelf from about 33°S to about 45°S and confined to the top 50 metres of water, there are major concentrations of this stock from 35 to 41°S. The virgin stock size has been estimated by CARPAS at around 3 million tonnes and the total mortality rate (Z) at about 0.85; the fishing mortality is very low so this may also be a good approximation to the natural mortality rate (M). The potential yield is estimated in the FAO Atlas of Living Marine Resources (FAO 1981) at 1 million tonnes. Almost all the current catch of between 10 and 20 thousand tonnes is taken by the Argentine fishmeal industry. This species has been found in the stomachs of Arctocephalus australis.
POMATOMIDAE
Pomatomus saltatrix Bluefish
Distributed in the coastal waters of Brazil and Uruguay from the mouth of the Rio Plata to northern Brazil (about 8°N), this voracious predatory fish yields around 10 000 tonnes per year. There is no indication of the potential nor the degree of current exploitation.
MUGILIDAE
Mullets are important locally in Brazil and an annual catch of around 17 – 35 000 tonnes is taken. They are not caught elsewhere in any great numbers and there is no indication of their potential yield.
SCOMBRIDAE
Sarda sarda Bonito
Distributed in two main areas to the south and to the north of the Rio Plata estuary, the latter a breeding area and the former the feeding area. The catch is mostly on the feeding grounds in the summer. In 1980 2 600 tonnes were taken all by Argentina. In the early 1970's Brazil used to take around 1 000 tonnes also but this seems to have stopped. There are no stock size estimates nor estimates of potential yield. Goodall and Cameron (1980) suggest that some dolphins or porpoises may get caught in purse seine nets set for bonito in Argentina.
Scomber japonicus Chubb mackerel
About 9 000 tonnes of mackerel are taken per year, mostly by Brazil. There is no indication as to the potential of this stock, nor the fishing method in Brazil. Goodall and Cameron (1980) however mention the incidental capture of an undetermined number of dolphins, probably mostly Lagenorhynchus obscurus, in fine meshed surface trawl nets used off the northern coast of Argentina to fish for this species in February.
Tunas
Thunnus atlanticus Blackfin
This species is coastal in its habits, and is distributed around the shelf edge, off the coast of north east Brazil, between about 4 and 6°S, and in another concentration around 13°S. There is no estimate of potential yield, but neither is there any record of this species being fished, so it is presumably underexploited.
The remaining four species all occur in 2 general areas of the south west Atlantic (FAO 1981). The first of these is a large area off the north east cape of Brazil from about 5°N to about 10 or 12°S, and extending out into the mid-Atlantic to around 20°W. The second is a smaller area from about 18 to about 26°S, in a band along the Brazilian coast, well offshore. These species are:
Thunnus alalunga Albacore A catch of around 8 000 tonnes in 1980, of which Brazil took about 1 000 tonnes, the rest going to ‘foreign’ fleets.
Thunnus obesus Big eye
A catch of 1141 tonnes in 1980, all of which went to foreign ships.
Thunnus albacares Yellowfin
A catch of 2 661 in 1980, most of which was taken by Brazil.
Katsuwonus pelamis Skipjack
Around 3 000 tonnes taken in 1980, of which 2/3 was taken by Brazil.
CARANGIDAE
Seriola spp. Amberjacks
A small fishery exists in Argentina, of around 200 tonnes per annum, but Uruguay is also apparently expanding its Seriola fishery. This is the same genus of fish which is involved in the Iki Island dolphin controversy, although in that instance the use of hooks and lines is largely responsible for the conflict (See area 61).
INVERTEBRATE RESOURCES
CEPHALOPODA
The total potential of this resource is unknown but the biomass is thought to exceed 3 million tonnes. The current catch is around 30 000 tonnes, of which 2/3 are Loligonidae and Ommastrephidae. The fishery has expanded massively in the last 4 or 5 years, and presumably will continue to grow. The greatest known concentrations at the present are on the edge of the continental shelf off the Rio Plata estuary, and on the Patagonian shelf around 45°S.
Of the three countries with coastlines in this area, Brazil has the largest recorded catches, of around 850 000 tonnes in 1980. Over 130 000 tonnes of this is freshwater fish, largely characins and catfish from the Amazon which are caught in gill and seine nets. These nets are also responsible for the incidental capture of an unknown number of Inia geoffrensis and Sotalia fluvescens.
Over 200 000 tonnes of sardine are also caught, presumably by surface trawl or seine nets. This occurs in the south of the country in inshore waters, and also presumably represents the possibility of some interaction with marine mammals in the area, although this has not apparently been documented. Unlike its South African relative, the local fur seal does not apparently follow sardine boats, but this does not preclude some conflicts arising.
The relatively large catches of marine catfish, and of other coastal species which are locally important, such as the mullets, suggest that artisanal fishing may play an important role in the Brazilian fishery, in which case interactions with marine mammals might be expected more frequently than if benthic trawling were the most important type of fishery.
Over 100 000 tonnes of miscellaneous fish are also taken by the Brazilians, but there is no indication how this catch is taken, neither is there any other apparent documentation of interactions between marine mammals and fisheries in Brazil. Brazil, however, does make an annual catch of about 900 minke whales and also a few sperm whales.
Uruguay has an annual catch of around 120 000 tonnes, mostly marine fish. The Uruguayan fishing fleet is apparently largely composed of industrial boats, chiefly trawlers taking two species of Sciaenid from the mid-shelf area and also the sea bass Acanthistus. These types of fishing operation are usually less likely to involve interactions with marine mammals.
There are also, however, a number of fisheries operating in the Rio Plata estuary on a smaller scale. These include the gill net shark fishery which annually takes several hundred Pontoporia blainvillei, although this shore based fishery is now giving way to a boat fishery for sharks which may reduce the incidental catch of Pontoporia and other dolphins.
Uruguay also takes an annual 9 or 10 000 fur seals, but despite the hundreds of thousands of these animals breeding on offshore islands in this region, there appears to be relatively little conflict with fisheries.
Catches by Argentina amounted to some 350 000 tonnes in 1981. This represents a drop from 560 000 tonnes in 1979, though the general recent trend in Argentine catches has been upward. Goodall and Cameron (1980) state that “The fishing industry is being rapidly developed in Argentina, with ample government support, and the next few years should see more open sea fishing with large boats. Inshore fishing is unlikely to increase.” As they also point out it is the inshore fisheries that are more likely to cause mortality to marine mammals, and it is also these types of fishery which most often see marine mammals as competitors. Open sea conflicts are more likely to arise where a stock is being heavily exploited and thereby affecting the feeding of marine mammal populations, such interactions are unlikely in this region at present.
Inshore fisheries include those for hake, smelt, anchovy, sea bass and chimaeras along the coast around Mar del Plata. In this area also fisheries for anchovy and for mackerel using fine meshed surface trawls are known to catch some dolphins. There is also a purse seine fishery for bonito which is known to have had dolphins in the nets in the past. In the La Plata estuary there is a gill net fishery for Micropogon (croaker) which is also known to take dolphins occasionally, which may then be prepared for human consumption. Some dolphins, possibly up to 100 Cephalorhynchus commersoni, may also be taken by the gill net fishery for Patagonian blenny in the Province of Santa Cruz. In Tierra del Fuego there are shore based fisheries for Eleginops and for Lithodes, the southern king crab. Until 1976 both of these species were caught using long tangle nets. These nets used to trap at least 4 species of small cetacean. Since 1976 this practice has been banned in the Lithodes fishery, and only traps are used. The tangle nets are still used for the capture of Eleginops and P. spinipinnis, P. dioptrica, C. commersonii, and L. australis are all still accidentally caught in this manner.
Sea lions and fur seals are also known to get into purse seine nets for pelagic fish, and also into the nets of smaller trawlers. This presumably also occurs in both Uruguay and Brazil to some extent.
Operational interactions
An unknown number of Inia and Sotalia are caught in gill nets and seine nets in freshwater fisheries in Brazil. Some of these animals are also taken deliberately for food, and the suggestion is that as the Amazon becomes more populated these problems are becoming worse.
The shark fishery in Uruguay yields several hundred Pontoporia per year as a by-catch. Other species are also known to be caught in these nets, including Otaria and Arctocephalus australis. The status of the Pontoporia population is unknown, but given the size of the incidental catches, these could have significantly affected the population. The populations of Otaria and Arctocephalus have probably not been affected as the catches are fewer and the populations larger. This problem may decline as less fishing is done for sharks from the shore, and more at sea from boats where Pontoporia is less numerous.
Along the Argentinian coast fisheries for a number of species, including purse-seine fishing for bonito, midwater trawling for mackerel and for anchovy, and gill net fishing for croakers and also for Patagonian blennies all have incidental catches of a number of cetacean species. These include Pontoporia, Phoecoena dioptrica and P. spinipinnis, Lagenorhynchus obscurus and L. australis, Cephalorhynchus commersonii and possibly Tursiops and Stenella spp. The numbers of these species caught are unknown, but are probably few. There does not seem to be any expansion in these coastal fisheries and so no increase in interaction can be expected, unless the abundance of either the fish species or the dolphin species changes markedly.
In Tierra del Fuego a number of small cetaceans are known to be taken in tangle net fisheries. Goodall and Cameron (1980) give figures suggesting that about 100 animals, P. spinipinnis, P. dioptrica, C. commersonii and L. australis were known to have been taken in tangle nets for crabs and blennies between 1975 and 1979. Nearly 3/4 of these were C. commersonii, and the actual numbers may be considerably higher. Since 1976 tangle nets for crabs have been banned, but on at least one occasion fishermen have harpooned dolphins to bait crab traps which have replaced the nets, though this is illegal in Argentina. The numbers of animals killed in this way should have declined since 1976, but there are no comprehensive data.
There is no information on either the extent of damage done to gear by marine mammals in area 41, nor on damage to catch. Inasmuch as most operational interactions appear to be accidental drownings, it is possible that damage to catch is minimal. Presumably however there is some degree of damage to nets whenever a marine mammal becomes entangled.
Biological interactions
There are no documented cases in this area of marine mammals being deprived of food due to heavy fishing, possibly as few stocks are heavily exploited. There is one instance on record of fishermen in Mar del Plata, Argentina, becoming alarmed at a large number of dolphins being seen in the area. According to Goodall and Cameron (1980) they assumed these were frightening away the schools of mackerel and asked the navy to eliminate them. Argentinian scientists were able to argue in support of the dolphins however and the navy did not intervene. Nevertheless it is possible that some dolphins have been killed in this or possibly other similar incidents. In general it would seem that the abundance of fish in this area may help to reduce the likelihood of fishermen being deprived of fish due to excessive numbers of marine mammals. Few of the commercially caught species have been found in stomachs of marine mammals, but this may be simply a reflection of the paucity of such data.
