Eubalaena glacialis Right whale
The report of the Right Whale Workshop (IWC SC/35/Rep 2 1983) indicates that right whales are known along the west coast of North America as far south as Baja California, with one record from Hawaii. The calving sites in this region are unknown, as is the population size, but this is presumably now no more than a few hundred. There are no apparent indications of conflicts with fisheries, but net entanglements are always possible, and could have significant consequences.
Eschrictius robustus Grey whale
The eastern Pacific stock of this species is estimated to number around 16 000 (Rice et al 1981). Rice and co-authors suggest that this is close to the virgin population size. The diet has been studied by Zimusko and Ivashin (1980). No commercial species are consumed in area 77. Wolman and Rice (1979) have suggested that increased boat traffic may threaten the breeding population, and Miller et al (1983) record 3 killed in 1980 in gill nets in California, with 3–5 gill nets being destroyed by grey whales every year.
Balaenoptera physalus Fin whale
Berzin and Vladmirov (1981) have given an estimate of 14–19 000 fin whales for the North Pacific. The number of fin whales in area 77 is unknown, but there do not appear to be any reports of interactions with fisheries, except for one record of a possible entanglement in a Californian drift net for shark (Miller et al 1983).
Balaenoptera musculus Blue whale
The population size in area 77 is unknown, but Berzin and Vladimirov's (1981) estimate of 1 400 to 1 900 for the whole North Pacific implies that the population may not exceed the hundreds here. There do not appear to be any interactions with fisheries reported.
Balaenoptera acutorostrata Minke whale
There appear to be no population estimates for minke whale stocks in this area, nor any data relating to feeding. Interactions with fisheries seem unlikely and do not appear to have been reported.
Balaenoptera borealis Sei whale
Gambell (1977) records population estimates of this species, which is said to have had an exploitable population size of about 8 000 animals in 1967 in the eastern North Pacific. This might suggest a total population size at present of less than or around 15 000 animals. Nemoto and Kawamura (1977) suggest that the main diet item in the North Pacific is copepods, with fish forming 3.4% of the diet in this area. This would suggest very little interaction with fisheries, and there are apparently no records of such.
Balaenoptera edeni Bryde's whale
There do not appear to be any population estimates of this species in area 77, but Ohsumi (1977) has suggested a population in excess of 9 000 animals for the waters of the North Pacific east of 150oE. The diet in the eastern tropical Pacific does not appear to have been studied, but might be expected to include shoaling fish, such as sardines, as well as shoaling crustacea. There do not appear to be any recorded interactions with fisheries.
Megaptera novaeangliae Humpback whale
Catches of this species have been recorded by Townsend (1935) along the coast of Mexico and Baja California, and the species is known to breed in these waters, and around Hawaii (Tomilin 1967). There seem to be no reliable population estimates for area 77, but the population is presumably in the thousands. Feeding is generally confined to colder waters (Mackintosh 1965), and there appear to be no interactions with fisheries in this area.
Berardius bairdii Baird's beaked whale
The range of this species is known to extend as far south as southern California in the eastern North Pacific. The number of animals which move into this area is unknown, and the diet is presumably squid here as elsewhere. There do not appear to be any records of interactions with fisheries.
Mesoplodon densirostris Blainville's beaked whale
Galbreath (1963) records this species from Midway Island, and it is generally assumed to range throughout tropical and warm temperate waters (Mitchell 1975). There are no population assessments, nor any data on feeding for this area. Interactions with fisheries seem unlikely.
Mesoplodon hectori Hector's beaked whale
Leatherwood and Reeves (1983) report one record of this species from California. Interactions with fisheries seem unlikely.
Mesoplodon ginkgodens Ginkgo-toothed beaked whale
Leatherwood and Reeves (1983) state that only one specimen has been found in this area, at Del Mas in California. There are no detailed data on abundance or feeding, but the species may be more common in area 61. Interactions with fisheries seem unlikely.
Mesoplodon carlhubbsi Hubb's beaked whale
Leatherwood and Reeves (1983) state that this species is recorded from as far south as San Diego, California; as with the previous species, no detailed data are available, but Leatherwood and Reeves suggest its range is broader in the eastern Pacific than in the western. Interactions with fisheries seem unlikely.
Ziphius cavirostris Cuvier's beaked whale
Orr (1948) records this species from California and Galbreath (1963) from Midway Island. There are no detailed data on diet or abundance in this area, and no obvious reference to any interactions with fisheries, which would seem unlikely.
Physeter macrocephalus Sperm whale
Townsend's (1935) maps show a continuous and year round distribution of this species extending from off the coast of Ecuador along the equator, with smaller concentrations off Baja California. Although there are no estimates of the size of the population in area 77, Rice (1977) estimated the population size within 10 degrees of the equator from 80 to 110°W to be around 80 000 by sightings cruise. There are no apparent indications of interactions with fisheries.
Kogia breviceps Pygmy sperm whale
Recorded from Washington State to California (Leatherwood and Reeves 1983), this species does not appear to be very numerous in this area, or elsewhere. A few strandings have been reported. No detailed data on feeding are available for this area and interactions with fisheries seem unlikely.
Kogia simus Dwarf sperm whale
Leatherwood and Reeves (1983) record this species in this area only from central and Baja California. As with the previous species, this is apparently uncommon, and unlikely to interact with fisheries to any great extent.
Steno bredanensis Rough-toothed dolphin
Recorded from California and the Galapagos Islands (Hershkovitz 1966), Perrin and Watkin (1975) found fish and molluscs in the stomachs of some animals. Rough-toothed dolphins are known to be taken occasionally in the tuna seine fishery in the Eastern Tropical Pacific : the size of the population involved in this fishery has been estimated at 450 (IWC 1978 annexe E). It is not clear how this relates to the entire population in area 77,but Berzin (1978) states “Steno bredanensisis universally considered rare”, so that the entire population in area 77 could number in the thousands. Despite its apparent rarity, this species is reported to remove bait (Decapterus sp.) from longlines in Hawaii fishing for tuna, marlin and shark (Mate 1980).
Peponocephala electra Melon-headed whale
Rarely recorded in the Eastern Tropical Pacific tuna fishery as an incidental capture (Perrin 1976), there are no population estimates of this species in area 77, and no other indications of interactions with fisheries.
Feresa attenuata Pygmy killer whale
This species has also been recorded rarely in tuna nets of the Eastern Tropical Pacific (Mitchell 1975); it is generally considered a rare species, but there are no abundance data and no information on the diet of this species in area 77. There do not appear to be any other interactions with fisheries.
Pseudorca crassidens False killer whale
Perrin and Oliver (1982) record one incidental capture in tuna purse seining operations. Mitchell (1975) cites unpublished data by Nishiwaki of 30–50 individuals taken accidentally in tuna longline fisheries “in the Pacific”, and also states that false killer whales damage fish on longlines worldwide. Mate (1980) also reports that fishermen in Hawaii have claimed this species may take tuna from longlines there. There are no population estimates for this species in area 77. Perryman and Foster (1980) report that this species is known to feed on dolphins in this area, as well as on fish and squid.
Orcinus orca Killer whale
Dahlheim et al (1983) found that strandings of this species in and around area 77 were uncommon, with only 11 such records. Sightings were frequent in some areas, and 581 unpublished sightings records were found. The authors state that the diet of killer whales in their study area was unknown. There do not appear to be any records of interactions with fisheries.
Globicephala macrorhynchus Short-finned pilot whale
Pilot whales are reported by Donovan (1983) to have been commonly seen during research cruises through the southern parts of area 77. There do not appear to be any detailed data on diet, but Perryman and Foster (1980) report that this species is know to chase dolphins occasionally. This species is known to be included occasionally in the tuna purse seine fishery, an estimate of this population size having been given as 60 000 (IWC 1978 annexe E). De Master et al (1984 in press) also state that it may conflict with a Californian squid fishery for squid, and Miller et al (1983) report that up to 30 may be killed in each of the squid and shark gill net fisheries. Miller et al (1983) also report pilot whales scaring squid away from fishermen's nets, but were unable to quantify this.
Lagenorhynchus obliquidens Pacific white-sided dolphin
Recorded as far south as Baja California (Mitchell 1975), the diet of this species is known to include hake, anchovies and squid (Fitch and Brownell 1968). There are no detail data on abundance, but the main area of distribution lies outside area 77. There seem to be no reports of conflicts with fisheries, though the diet might indicate some competition.
Lagenodelphis hosei Fraser's dolphin
Once thought to be extremely rare, data from other areas suggests this species may not be uncommon. Perrin et al (1973a) recorded 3 in a tuna net in area 77, and one population estimate based on such captures suggested a size of 7 800 for the population involved with this fishery. (IWC 1978 annexe E). Jackson (1980) reports about 60 of this species spotted during aerial surveys of the Eastern Tropical Pacific. There appear to be no data on the diet of this species in area 77.
Tursiops truncatus Bottlenose dolphin
This species is apparently abundant in this area as in other warm water regions. Some individuals are known to become trapped in tuna nets; Allen and Goldsmith (1981) estimate the number of mortalities from this source to be about 9 per year; the size of the population involved has been estimated as around 588 000 (IWC 1978 annexe E). Leatherwood and Reeves (1982) cite Iverson, and Shallenberger, in stating that this species also steals fish from longlines in Hawaii and steals skipjack tuna and damages gear in trolling and jigging fisheries in Hawaii. Mate (1980) also refers to bottlenose dolphins taking bait from handline fisheries for bottom fish in Hawaii. Leatherwood and Reeves (1982) also mention that as many as 50 animals a year may die in shark and sea bass gill netting fisheries in the Gulf of California, primarily near San Felipe, Mexico. There appears to be little data on the diet in this area.
Grampus griseus Risso's dolphin
Found throughout tropical and temperate seas (Mitchell 1975), Leatherwood et al (1980) describe the movements and distribution of this species, which they state occurs up to around 50°N, with greatest abundance near Monterey Bay in California. This species is evidently occasionally trapped in tuna nets, a population of 7 500 having been estimated to be involved in this fishery (IWC 1978 annexe E). The diet is presumed to consist largely of squid.
Stenella longirostris Spinner dolphin
Perrin (1975) has described 3 separate populations in this area, all of which are involved to some extent in the tuna seine fishery. Perrin (1969) describes the tuna fishery in the Eastern Tropical Pacific, in which fishermen set their nets around schools of dolphins as these are known to associate with tuna. By using the dolphins as a marker, fishermen locate the tuna school, but in the process of catching tuna, some dolphins are also killed as they become entangled in the netting. A population of more than 1.8 million spinner dolphins may be associated with this fishery in the Eastern Tropical Pacific. Hammond and Kao-Tsai (1983) have estimated that between about 7 and 9 000 spinner dolphins were taken in the tuna fishery in 1981; this is considerably less than the numbers in the late 1960's which may have been in the hundreds of thousands, so the stocks are presumably recovering after some depletion. Perrin and Henderson (1979) suggested that, at that time, the eastern spinner population was between 38% and 83% of its original size. Perrin et al (1973a) have found mesopelagic fish and epipelagic and mesopelagic squids in the diet of this species in this area.
Stenella coeruleoalba Striped dolphin
This species has not been so heavily affected as other Stenella species by the tuna fishery. In 1981 only around 60 are estimated to have been caught (Hammond and Kao-Tsai 1983). The population level has been estimated at around 250 000 animals (IWC 1978 annexe E). Miyazaki et al (1973) found mainly mesopelagic fish in the stomachs of this species in Japan.
Stenella attenuata Spotted dolphin
These are the dolphins most heavily affected by the tuna fishery, as described by Perrin (1969). In 1981 between 24 and 33 000 animals are estimated to have drowned in tuna nets (Hammond and Kao-Tsai 1983). The populations were estimated in 1978 to number more than 3.5 million animals; in 1979 the offshore stocks were estimated to be between 34% and 55% of their 1959 level (NMFS LJ-79-41 1979). Presumably stocks are at present recovering. The diet in this area is thought to consist of epipelagic fish such as flying fish, and squids (Perrin et al 1973).
Delphinus delphis Common dolphin
Another species which is partly involved with the tuna fishery, around 1,400 animals are estimated to have been killed in seine nets in 1981 (Hammond and Kao-Tsai 1983). The population size in 1978 was estimated to be around 1.5 million animals in total for the Eastern Tropical Pacific. Presumably such catch rates have little effect on the population; the 'central tropical stock' has been estimated to be between 86% and 100% of its 1959 value, when it became involved with the fishery (NMFS LJ-79-41 1979). The diet of this species does not appear to have been studied in any great detail in area 77.
Lissodelphis borealis Northern right whale dolphin
Mitchell (1975) states that this species occurs as far south as northern Baja California. There seem to be no data on abundance in this area, but this is presumably not a particularly common species in the warmer waters of this area. The diet is thought to include squid and myctophids. There are no apparent interactions with fisheries in this area.
Phocoena phocoena Harbour porpoise
Gaskin et al (1974) describe this species as occurring as far south as San Pedro in California, which would suggest that this is not a particularly numerous species in area 77. Gaskin (1983) suggests that the population in Monterey Bay may be around 600, and states that on the western U.S. seaboard about 20 are killed per year due to illegal sport shooting and incidental captures. The diet consists of a great number of species, and includes commercial species such as mackerel clupeids and gadoids. Some overlap with commercial fisheries would seem likely in this area as elsewhere, although this has not yet apparently led to any conflict.
Phocoena sinus Cochito Brownell (1983) reviews the information on this species, stating that it is probably limited to the upper part of the Gulf of California, from where a total of about 30 confirmed records have been reported. This appears to be the only indication of abundance, and Brownell points out that this species is listed as vulnerable by the IUCN's Red Data Book. The diet is reported to include striped grunts (Orthopristis reddingi) and gulf croakers (Bairdiella icistius), as well as some squid. Brownell describes incidental captures of this species, suggesting that prior to 1975 a number of porpoises, possibly in the range of tens to hundreds, were taken in a commercial gill net fishery for shark and totoaba. This fishery was officially closed in 1975, but Brownell suggests that incidental captures may persist in gill net fisheries for other sciaenids and sharks, and in shrimp trawl fisheries, the combined effects of which may represent a substantial impact on a localised and relatively small population.
Phocoenoides dalli Dall's porpoise
Mitchell (1975) states that this species ranges as far south as central Baja California. The population size in area 77 is unknown, but the main area of distribution lies to the north. The diet in this area is known to include hake (Merluccius productus), squids (including Loligo opalescens) and horse mackerel (Scheffer, cited in Wilke and Nicholson 1958). There do not appear to be any recorded interactions with fisheries, although some amount of competition would seem to be expected.
Eumatopias jubatus Steller sea lion
Mate (1982a) describes the distribution and status of this species, the total population of which, in Californian waters, he states may be stable, at around 5 000 to 7 000, although in some (southerly) areas, it may be declining. Fiscus and Baines (1966) have studied the diet of this species which includes flatfishes and rockfishes in this area. Although Mate (1982a) refers to conflicts with fisheries, these do not appear to be important in area 77. Nevertheless, the diet suggests some overlap with commercial fisheries for prey items.
Zalophus californianus Californian sea lion
Mate (1982) describes the status and distribution of this species. The range extends from Canada to Mexico, with a subspecies (Z.c. wollebaeki) breeding in the Galapagos Islands. The Californian population was heavily exploited last century, but is currently either stable or growing, numbering around 7 500 – 100 000 animals. 20 000 animals are thought to breed on the Galapagos. Mate suggests the diet includes squid, various rockfish, Clupea and other small fish including Engraulis and Merluccius, but that the extent of competition with fisheries for food is unclear. Protection of the sea lion in an area which is heavily fished has led to a great number of operational interactions between fishermen and this species. De Master et al (1984 in press) have summarised the situation in California, where this species and the harbour seal are said to do most damage to gear and catch. The salmon trolling fishery is said to have lost more than $130 000 in May 1980, not including damage to gear; sea lions have learned to follow boats and remove hooked fish. Losses to other salmon fisheries may be around $17 000. Sea lions also interfere with river gill net fisheries and sport fisheries, where losses of catch may be worth around $700 000. Gill and trammel net ocean fisheries are also affected, and De Master and co-authors estimate a loss here of around $80 000. Sea lions are known to become entangled in such gear and may cause considerable financial loss by damaging nets in this fishery as well as catch. Herring are also known to be taken from a number of herring fisheries. Miller et al (1983) estimate that in U.S. waters an annual total of around $380 000 is lost in fish and gear in salmon fisheries, and about $120 000 in gill net fisheries, nearly all of which is attributable to sea lions. They also estimate around 1 900 sea lions die each year as a result of fishing activities.
Callorhinus ursinus Northern fur seal
The most southerly breeding colony of this species is at San Miguel Island off California; the population there numbers around 2 000 animals (Gentry 1981), which may be roughly the number present in area 77 for most of the year. Kajimura (1984 in press) states that the main food items in Californian waters are anchovy, Engraulis mordax, Pacific whiting, Merluccius productus, the market squid Loligo opalescens, and in lesser quantities, Pacific saury, Cololabis saira, jack mackerel, Trachurus symmetricus, rockfishes, sablefish and oceanic squid. The diet suggests some competitive overlap with commercial species, but as yet little conflict has been reported in this area, presumably as the population is very small, especially when compared with other local mammal species.
Arctocephalus townsendi Guadaloupe fur seal
The population is severely depleted and confined to areas around Baja California. There do not appear to be any interactions with fisheries. (see species account also).
Arctocephalus galapagoensis Galapagos fur seal
The population is severely reduced, but may now number around 5 000 (Clark 1979). The diet consists of cephalopods. Interactions with fisheries seem unlikely, as the Galapagos Islands are a reserve.
Phoca vitulina Harbour seal
Occurring as far south as Baja California (Bonner 1979c), Bigg (1981) suggests around 40 000 animals are present from British Columbia to Baja California. Food species commonly eaten include herring, anchovy and rockfish (Bigg 1981). De Master et al (1984 in press) state that this species causes considerable damage to fisheries in California. Harbour seals are responsible for removing salmon from gill nets, where some individuals become entangled, and are known to remove herring from a variety of gear types. Miller et al (1983) estimate that around 200 are killed in California every year, in ocean gill net fisheries, and in the Klamath river subsistence gill net fishery for salmon. They also estimate that around $74 000 worth of fish are damaged in this latter fishery every year.
Monachus schauinslandi Hawaiian monk seal
Kenyon (1981) describes this species. The population is thought to be in danger, and may be declining, with current numbers totalling less than 700 animals. The diet is said to include lobsters, eels, flatfish, scorpaenids and octopus. Kenyon suggests that some gear interactions may occur and contribute to the decline of this species. Some individuals have been observed with scars similar to those caused by netting in other species. Other individuals have been observed tangling themselves in fishing gear, and Kenyon gives one undocumented case of an animal dying in a fish trap.
Mirounga augustirostris Northern elephant seal
Breeding sites of this species are confined to area 77, from Baja California, on offshore islands, to the Farallon Islands, due west of San Francisco. The population may total nearly 50 000 and is expanding after depletion last century (McGinnis and Schusterman 1981). McGinnis and Schusterman cite Huey's (1930) feeding data for this species, which included ratfish, dogfish, shark, puffer, skates and squid, all deepwater species. The only example of interaction with fisheries at present appears to be the entanglement a small number of this species in gill and trammel nets in ocean fisheries (Miller 1981).
At least 10 of the 42 species listed above consume some commercial species, or may be assumed to do so, and a further 8 or 9 are presumed to eat squid for the most part. 7 species of baleen whale may not feed very much in the area, and the diets of the remaining 16 species are unclear.
DEMERSAL FISH RESOURCES
The demersal finfish potential in this area has been estimated at around 1 million tonnes (FAO 1981); the commercial catch in 1981 totalled around 50 000 tonnes (FAO 1983).
The U.S. sports fishery presumably takes a large catch also, but figures for this are not available. The shelf in this region is not very wide, so that productivity of demersal resources is not high; neither is there a very large number of species listed amongst the demersal catch.
SCORPAENIDAE
The largest single group in terms of catch is the scorpionfish. Catches in 1981 totalled 10 297 tonnes. Although such fish are known to be eaten by a number of pinniped species, there does not appear to be much interaction.
No other group of demersal finfish yielded catches in excess of 8 000 tonnes, suggesting that demersal fisheries in this area are not very important. Ainley et al (1982) refer to the closure of the whiting fishery off California in 1977 under the Fishery Conservation and Management Act of 1976. They relate this to changes in the distribution and feeding behaviour of California sea lions. Currently (1981) whiting, or hake (Merluccius productus), catches are negligible in this region, though this stock is harvested further north. Kajimura (1984 in press) also relates the importance of this species to the Northern fur seal population in Californian waters.
PELAGIC FISH RESOURCES
The total potential of the pelagic resources of this area, excluding tuna, has been estimated at between 2 and 2.5 million tonnes (FAO 1981). The catch in 1981 was over 2 million tonnes, including tuna, which accounted for 300 000 tonnes (FAO 1983). The estimated potential and current yield would appear then to be in reasonable agreement at present, suggesting that the resources as a whole may be close to full exploitation.
Engraulis mordax
The North Pacific anchovy is distributed mainly in coastal waters from Baja California to Washington. Catches in 1981 totalled 424 000 tonnes, whereas the potential may lie between 500 000 and 1 million tonnes. Kajimura (1984 in press) states that this species is the most abundant and largest fishery resource in the California current system. This is also said to be one of the main food species for Northern fur seals, and is eaten by harbour seals and sea lions, and probably by a number of small cetacean species also. Gulland (1983) has also pointed out the importance of this fish resource both as a food supply for larger fish, and as a bait supply for sport fishermen.
Sardinops caerulea
The Californian sardine fishery was once one of the most important in the Pacific, with catches of up to 800 000 tonnes, but has since declined especially in the northern part of its range to a fraction of this; catches in 1981 were around 345 000, almost entirely off Mexico (FAO 1983). Although Kajimura (1984 in press) does not list this as a food species in Northern fur seals, possibly as the main distribution of this fish species is currently around Baja California, this would seem to be a likely prey species for a number of other marine mammals.
Cololabis saira
The Pacific saury ranges throughout the North Pacific, and is one of the most abundant fish in the area (Kajimura 1984 in press). This would seem likely to play an important role in the feeding of certain marine mammals, including some of the oceanic dolphins, and Kajimura (1984 in press) has affirmed its importance in the diet of the Northern fur seal.
Salmon
Although not a very large fishery in this area (1 688 MT in 1981), there are some serious gear interactions between Californian sea lions and harbour seals on the one hand, and a number of salmon fisheries, including troll and gill net fisheries on the other. Miller et al (1983) estimate nearly $300 000 worth of fish are removed from fishermen's nets and lines per year, mosty by Californian sea lions.
Tuna
Although not important as a food fish for marine mammals, tuna are nevertheless probably the most important fishery in economic terms for the whole area. More than 300 000 tonnes of all species were landed in 1981 (FAO 1983). In the central Pacific tuna longliners operate, mostly from eastern Asia. The American and Mexican fleets are mostly purse seiners, and it is these vessels which have become involved in the controversy over the incidental capture of small cetaceans. The current incidental take is only around 30–40 000 per year (Hammond and Kao-Tsai 1983), but in the late 1960's hundreds of thousands of animals were killed every year.
Other important fish species of the area include jack mackerel (Trachurus symmetricus) which has an estimated potential yield of 300 000 tonnes, but a current catch of only 15 000 tonnes, and which is among the leading forage species of the fur seal; jack mackerels would also seem likely to be important in the diet of other marine mammals, as they are both abundant and schooling. In more southerly areas of area 77, thread herring (640,000 tonnes in 1981) and anchoveta (110,000 tonnes caught in 1981) are evidently important fish stocks, but there is little data on marine mammal feeding on these species.
INVERTEBRATE RESOURCES
CRUSTACEANS
Over one hundred thousand tonnes of various shrimp and crab species were landed in 1981 from this area. Gulland (1983) states that this is the main fishery in tropical areas. Offshore, shrimp trawlers operate, whilst in the coastal areas, artisanal methods predominate. There seems to be little reported interaction between these fisheries and marine mammals.
CEPHALOPODS
More than 30 000 tonnes of cephalopods were reported caught in this area in 1981 (FAO 1983), an increase from only 10 000 tonnes in 1976. This is a productive area, however, in which Voss (1973) states, “undoubtedly a large resource is waiting to be tapped”; the total potential is unknown, but jumbo squids (Dosidiscus gigas) alone may have a potential of more than 1 million tonnes (FAO 1981a).
The fisheries of this area are dominated by Mexico, which in 1981 took 1.2 million tonnes of a total catch of 2.6 million tonnes. The USA took 354 000 tonnes, Ecuador 686 000 tonnes and Panama 132 000 tonnes. Japan was the principal foreign nation represented in the 1981 catch statistics by a catch of 86 000 tonnes. Mexican catches in particular have increased dramatically from 286 000 tonnes in 1972.
The main fisheries in this area are undoubtedly the pelagic ones. Mexico's catches of sardines and anchovies have increased from 40 000 tonnes in 1970 to over 400 000 tonnes in 1979 (Gulland 1983), and pelagic fish dominate the landings statistics.
Gulland (1983) states that the main U.S. interest in fisheries is in tuna seining. Other fisheries in California are also important, however, and De Master et al (1984) and Miller et al (1983) have reviewed their relation to marine mammals. Further south shrimp trawling and pelagic fisheries for thread herring, anchoveta and mackerel are all important, down to Ecuador. Demersal fish are lacking, although Gulland states that more of these are caught than appear in the statistics, as there is considerable by-catch in shrimp trawling. The sport fishery cannot be ignored in this respect either, with large catches being taken particularly in Californian waters, though no statistics on these are available. Small scale fisheries are clearly important along much of the central and south American coasts, as well as in Central Pacific islands, but there is very little information on interactions between marine mammals and those fisheries, beyond some records of bait-stealing from longlines and handlines in Hawaii.
The reported interactions between marine mammals and fisheries in this area are most notable in that they are heavily concentrated in two areas, around California and in the offshore tuna fishery operations. This almost certainly represents a heavy bias in the reporting rather than in the numbers of interactions.
Operational interactions
The most significant interaction is undoubtedly that of the U.S. tuna purse seine fishery which annually takes up to 40 000 small cetaceans. Most of these are spotted and spinner dolphins of the genus Stenella but small numbers of a range of other species are also taken incidentally. The number of porpoises killed in the tuna fishery has been greatly reduced by changes in the gear (e.g. addition of special panels in the nets) and in the way it is operated which allow marine mammals to escape much more easily after the net has been closed. These are also large year to year changes in the kill rate, depending on the pattern of fishing, and the proportion of sets made on porpoises, in the expectation that there are tuna under-neath, compared with direct sets on school fish.
Californian salmon fisheries, troll and gill net, are seriously affected by sea lion depradation, and in the Klamath River at least, by harbour seal damage also.
Californian coastal and oceanic gill net fisheries suffer from heavy depredation at times, mostly by Californian sea lions, and to a lesser extent harbour seals. Northern elephant seals and pilot whales are also implicated in damaging nets and frightening off squid respectively.
The cochito was known to become trapped in gill nets in the northern Gulf of California, and although the main fishery involved in this interaction has been stopped, there are some suggestions that the population may still be threatened by such entanglements, although data is sparse.
Hawaiian monk seal numbers appear to be declining, and there is some suggestion that entanglement in fishing gear may play a part in this.
Other miscellaneous gear interactions involve the bottlenose and rough-toothed dolphins, which steal fish from line fisheries in Hawaii. The former is also subject to some entanglement in Mexican waters, and there is some reported entanglement of harbour porpoise also. Grey whales and possibly fin whales, may also be entangled occasionally in gill nets in U.S. waters.
It would seem likely that incidental captures occur all down the American coast, but there is very little published information concerning the fisheries of the more southerly areas.
Biological interactions
Marine mammal species in northern parts of area 77 appear to be free from very much competition with fisheries. Stocks of anchovy, Pacific whiting and Pacific saury are all either under-exploited by fisheries, or not fished at all. These species are important in the diets of pinnipeds at least, and as they are all abundant in the area, are presumably available to cetaceans which feed on small schooling fish such as Bryde's whale, common dolphins and possibly other species too.
Squid resources are also under exploited, but throughout the region, and so presumably little competition occurs between squid fisheries and squid eating marine mammals.
It is interesting to speculate upon what effect the reduction of sardine and mackerel stocks in this area might have had on feeding behaviour of any marine mammals feeding on these species in former years. It is also interesting to ponder the possible effects of an expansion of fisheries onto those stocks already mentioned, which appear at present to be under-exploited. Data on the possible competitive interaction between marine mammals and fisheries are lacking for much of the rest of area 77.
Although strictly outside the scope of this report, it is worth noting in passing the considerable conflict which has arisen between the sea otter (Enhydra lutris) and U.S. shell fisheries. A number of studies have been made of the diet and feeding behaviour of sea otters, and their impact on fisheries, particularly for clams and abalone. The report of the IUCN workshop on Marine Mammal/Fishery Interactions (IUCN 1981) discusses some of the findings. Sea otters, whilst eating commercially valuable shellfish, also eat sea urchins. In areas without sea otters, urchins graze kelp beds, whereas where sea otters are present, the kelp beds flourish, to the benefit of a number of commercial fish species which use kelp beds as refuges prior to recruitment. The sea otter may therefore be both benefactor to and competitor with commercial fishermen.
Eubalaena glacialis Right whale
The Report of the IWC's Sub Committee on Protected Species and Aboriginal Whaling (IWC 1983) indicates that 264 right whales were sighted in the 1981/2 sightings programme, mostly around Campbell Island (53°S). Not all of these were necessarily different whales. The population size in this area is unknown but unlikely to exceed a few hundred. No interactions with fisheries are recorded.
Caperea marginata Pygmy right whale
Baker (1972) states that this species is rare in New Zealand waters, with only 12 having stranded until that date. No interactions with fisheries would seem likely.
Balaenoptera physalus Fin whale
The population size in area 81 is unknown. Area 81 covers the IWC's Antarctic areas VI and parts of I and V, for which there are some baleen whale population estimates, but it is not possible to say how these stocks distribute themselves in the Sub-Antarctic and temperate waters of area 81. A population of more than a few tens of thousands would seem unlikely. Interactions with fisheries also seem unlikely.
Balaenoptera musculus Blue whale
The population size is again unknown, but is unlikely to exceed a few thousand. Interactions with fisheries are unknown.
Balaenoptera acutorostrata Minke whale
There are no reliable estimates for this species in the area, but presumably the population size is no more than a few hundred thousand at most. There are no records of minke whales eating commercial species in area 81.
Balaenoptera borealis Sei whale
The population in area 81 is unlikely to exceed a few thousand, and no interactions with fisheries are likely.
Balaenoptera edeni Bryde's whale
There are no reported interactions with fisheries, but as this whales is known to eat commercial fish species in similar latitudes, it would seem possible that some competition for prey species could occur. The population size is unknown, but Baker (1972) states that they are fairly common north of East Cape in New Zealand.
Megaptera novaeangliae Humpback whale
Humpback whales are well known as migrants from the Antarctic to breeding sites around New Zealand and Tonga as Townsend's (1935) maps demonstrate. The population size is unknown but is severely depleted and may number in the hundreds at present. Baker (1972) states that 500 were seen in Cook Strait in 1953, but that only 23 were seen in 1963. Feeding in this area is not known and there are no indications of interactions with fisheries at present, although Baker states that this whale frequents the coastal waters of New Zealand, where there is presumably some risk of gear interaction.
Tasmacetus shepherdi Shepherd's beaked whale
Recorded only from a few strandings, the population size is unknown, and nothing much is known of the diet, though squid might be expected to play a major role in this. No interactions with fisheries seem likely.
Berardius arnuxii Arnoux's beaked whale
Baker (1972) records 19 strandings in New Zealand until that date; the population is of unknown size but evidently may not be very large. The diet is presumed to include squid; interactions with fisheries would seem unlikely.
Mesoplodon densirostris Blainville's beaked whale
Watson (1981) gives a record of this species from Lord Howe Island in the Tasman Sea, but this species is said to be confined to tropical and warm temperate waters (Marcuzzi and Pilleri 1971). There is no indication of population size in area 81, and interactions with fisheries seem unlikely.
Mesoplodon layardii Strap-toothed whale
Baker (1972) states that more than 20 of these whales have stranded in New Zealand. Their abundance and diet are not known. No interactions with fisheries seem likely.
Mesoplodon hectori Hector's beaked whale
Baker (1972) describes this as a rare species, there are no data on feeding, and interactions with fisheries seem unlikely.
Mesoplodon grayi Gray's beaked whale
Baker (1972) describes this species as a regular strander on New Zealand beaches, so it is evidently not too uncommon in those waters. The diet is unknown, and there seems little likelihood of interactions with fisheries.
Mesoplodon bowdoini Andrew's beaked whale
Baker (1972) describes this species as rare in New Zealand, which is one of the few places it has stranded. Nothing is known of the diet, which, as for all beaked whales may be assumed to include squid (Gaskin 1982). Interactions with fisheries seem unlikely.
Ziphius cavirostris Cuvier's beaked whale
Numerous strandings of this species are known from New Zealand (Baker 1972), so it is evidently not too uncommon. Little is known of the diet in these waters, but this presumably includes squid and deepwater fish as elsewhere. No interactions with fisheries would seem likely.
Hyperoodon planifrons Southern bottlenose whale
Although Mitchell (1975) describes this species as widespread throughout its range, Baker (1972) suggests that it is rare in New Zealand. The diet is thought to include squid, and no interactions with fisheries are known.
Physeter macrocephalus Sperm whale
Townsend's (1935) maps show a distribution of this species to the north of New Zealand in winter, and more densely through the Tasman Sea and around New Zealand in summer. Baker (1972) also states that this species is more frequently found around New Zealand in summer. The population size in area 81 is unknown, but may be in the hundreds of thousands, in summer at least. There are no apparent interactions with fisheries, and these seem unlikely.
Kogia breviceps Baker (1972) states that at that time 23 of this species had stranded on New Zealand. He also states that they consume squids, shrimps, crabs and fish. There are no apparent interactions with fisheries and these seem unlikely
Pseudorca crassidens False killer whale
At least 3 mass stranding of this species have occurred in New Zealand waters (Baker 1972). There are no apparent population estimates nor records of interactions with fisheries for this area specifically. In other areas this species is said to cause problems with tuna longlining operations, and it is possible that such problems exist in area 81, where tuna are the most important catches in terms of weight.
Orcinus orca Killer whale
Baker (1972) describes this as a common species around New Zealand where it feeds on seals and dolphins as well as squid and fish. There appear to be no more detailed data than these on the diet of the killer whale in area 81. The population size is also unknown, but may be in the tens of thousands. The New Zealand Progress Report to the IWC in 1980 (IWC 1981) records one Orcinus found dead due to gear injury. Operational interactions are also known in the dropline fishery off eastern Tasmania, referred to in the Australian Progress Report of the same year (IWC 1981), in which killer whales take up to 30% of the fish on a dropline. It is not clear whether this fishery operates in area 81 or 57. Killer whales, like false killer whales, have been known to harass tuna longline fisheries also, and may be presumed likely to be involved in such interactions in this area as elsewhere, although there appears to be no record of this.
Globicephala melaena Long-finned pilot whale
Baker (1972) refers to many strandings of this species in New Zealand, and although there are no population estimates, this would seem to be a relatively common species. There do not appear to be any data on the diet of this species in area 81, but the pilot whale is known to consume squid in other areas (Sergeant 1962). The New Zealand Progress Report to the IWC in 1981 (IWC 1982) refers to one pilot whale caught in a set gill net off the New Zealand coast. This appears to be the only record of any interaction with fisheries in area 81, and if this reflects the scale of incidental capture, it can have little effect on the pilot whale population.
Lagenorhynchus obscurus Dusky dolphin
Baker (1972) suggests that this coastal species is fairly common in New Zealand from Hawke Bay, south to Fiordland. There do not appear to be any feeding data for this species in area 81, but some are evidently taken in fish nets. The New Zealand Progress Report to the IWC in 1981 (IWC 1982) states that incidental captures have been observed but not reported in two South Island set gill net fisheries. In one of these, in which gill nets are set to depths of up to 370 metres, about 120–150 dolphins are estimated to have been taken per year, of which the dusky dolphin was the principle species. The report continues :“L. obscurus is particularly abundant in this area and there is no evidence as yet that these incidental catches are having any effect on the stock”.
Lagenorhynchus cruciger Hourglass dolphin
Baker (1972) states that this is a coldwater oceanic species found south of New Zealand, occasionally straggling north to New Zealand. There do not appear to be any abundance estimates nor feeding data for area 81 and this species is not so far recorded in any interactions with fisheries.
Tursiops truncatus Bottlenose dolphin
Baker (1972) describes this species as common in New Zealand waters, and Mitchell (1975) records its incidental capture in midwater trawls around New Zealand, where he suggests, hundreds may be taken per year. There do not appear to be any detailed data on the diet, and so nothing can be said about the likelihood of competition with local fisheries.
Grampus griseus Risso's dolphin
Baker (1972) states that this species is rarely found in the south Pacific, with only 4 records from New Zealand. The diet is elsewhere thought to consist of squid, and no interactions with fisheries have been recorded.
Stenella coeruleoalba Striped dolphin
There seem to be no reports of interactions between this species and fisheries in area 81, nor any data on feeding or abundance though individuals are said to come near to New Zealand occasionally in summer (Baker 1972).
Delphinus delphis Common dolphin
Said to frequent New Zealand coastal waters, often in schools of several thousand (Baker 1972), the population is clearly considerable. There do not appear to be any detailed feeding data in this area, but this species is often caught accidentally in nets around New Zealand. Progress Reports to the IWC from New Zealand list 9 animals killed in pair trawls, 2 in single trawls and 5 in gill nets in the Bay of Plenty in 1978. In 1979 11 were reported killed in pair trawls, 12 in single trawls, and 1 in a crayfish pot line (IWC 1981). Other incidental captures reported include two fouled in a rock lobster pot line in 1980, 2 in purse seines in 1980, 1 in a single bottom trawl in 1980, 9 in purse seines in 1981 and 2 in set gill nets in 1981. In addition an unspecified number (less than 120) were taken in deep set nets, together with some other species from 1980–81 (IWC 1982). The effects of all of this mortality on the common dolphin population are unknown, but if the actual numbers killed are not very much in excess of this, it would seem unlikely that the population is being depleted. Competitive interactions with fisheries cannot be assessed at this stage.
Lissodelphis peronii Southern right whale dolphin
An oceanic species found in the south of this area, there are no obvious data on abundance or feeding in this area, and no by-catches have been reported to the IWC.
Cephalorhynchus hectori Hector's dolphin
Baker (1978) describes this species. It is found in inshore waters (out to 8km), often in muddy water, all around New Zealand. The food is said to include Trachurus novaezelandiae, Physiculus bachus (red cod) and Crepatalus novaezelandiae (stargazer). Engraulid otoliths have also been found in samples; the implied diet is of pelagic and benthic fish below the surf zone. Baker states that about 11 are caught incidentally per year in gill net fisheries for elephant fish, and in bottom trawls too; he also states that there is no evidence of a decline in the population. The New Zealand Progress Report to the IWC in 1981 (IWC 1982) supplies records of Hector's dolphins caught incidentally in 1980-82; 1 was reported in a set gill net off Waiheke Island, an estimated 6 are thought to have died in set gill nets on South Island, and an unspecified number (less that 120) in another deep set net fishery off South Island.
Phocoena dioptrica Spectacled porpoise
Baker (1977) records this species from Enderby Island in the New Zealand Sub-Antarctic. It is presumably rare and interactions with fisheries would not seem likely.
Phocarctos hookeri Hooker's sea lion
Warneke (1982) states that the main population is centered on several of the small islands of the Auckland group rather than on the mainland. Other breeding groups occur at Campbell Island, the Snares and at Stewart Island. Stragglers are said to occur as far north as the Otago Peninsular in South Island, and at Macquarie Island in the south. Warneke estimates the population at around 4 000. Walker and Ling (1981) summarise the data on feeding, food items including squids and octopuses, small fish, including flounder, and crabs, mussels, penguins and other sea birds.
In recent years Soviet and Japanese joint venture squid fisheries have opened up around the Auckland Islands. These are said to last for 2 months of the year and involve about 15 boats taking 30 000 tonnes of squid. The fishery is said to take a by-catch of females feeding after paturition (Mike Donahue, pers. com.). The number of casualties are unknown, but for such a small population, the loss of these females could be important. The amount of competition with fisheries, for prey species, has not been analysed.
Arctocephalus pusillus doriferus Australian fur seal
Breeding occurs from seal rocks in New South Wales (area 81) to Southern Tasmania and Victoria (area 57), the diet is said to consist mainly of squid and octopus, as well as a wide variety of fish such as barracouta (Thyrsites) and sometimes whiting (Sillaginodes), flathead (Platycephalus), red mullet (Upeneichthys), parrot fish (Pseudolabrus), leather jackets (Aluteridae) and small fishes such as pilchards (Clupeidae), (Warneke 1982). The population size is thought to be around 20 000, most of which breed in area 57 (Warneke 1982). Marlow (1967) stated that at that time many individuals were killed illegally by fishermen either for crayfish bait or for their supposed competition for fish of commercial value. Warneke (1982) states that significant numbers of immatures are lost by accidental drowning in nets and rock lobster traps and by shooting. Warneke (1982) adds that although it is widely claimed by fishermen that fur seals damage fish stocks, such claims have not been substantiated by evidence from fisheries statistics or the contents of stomachs, or ejecta.
Arctocephalus forsteri New Zealand fur seal
Breeding occurs at many sites on South Island, and on a number of offshore and Sub-Antarctic Islands, which are described by Crawley and Warneke (1979) in detail. Crawley and Warneke also provide a population estimate of around 38 500. Bonner (1981) summarizes information on the diet which is thought to consist mostly of octopus (Octopus maorum), squid (Notodarus sloanii and Sepioteuthis biliheata and barracouta (Thyrsites atun). other minor items include penguins. Crawley and Warneke (1979) state that some accidental drownings in net and rock lobster fisheries probably occur. with respect to biological interactions, whilst Bonner (1981) suggests that fur seals are often accused of damaging fish harvests, especially in New Zealand, he also states that the amount of commercial fish consumed is less than might appear to fishermen who may observe the seals with large fish, which they are forced to come to the surface to eat. Warneke (1982) suggests that commercial fish are incidental in the diet and adds elsewhere that the population is expanding. An expanding population of pinnipeds may still be seen as a threat by fishermen anywhere.
Mirounga leonina Elephant seal
About 100 000 elephant seals are said to breed on Macquarie and the New Zealand Sub-Antarctic islands (Laws 1979). Warneke (1982) states that the feeding habits in this area have not been studied in detail, though fish, small crustaceans and cephalopods may all be important. Warneke adds that stragglers are found on New Zealand and Australian shores, where they may eventually recolonize former breeding sites, which were occupied before the advent of commercial sealing operations. There do not appear to be any interactions with fisheries in this area at present.
Hydrurga leptonyx Leopard seal
Marlow (1067) states that during spring some individuals wander northward from Antarctic water to Macquarie Island and as far as the Australian mainland. The numbers involved probably constitute very little risk of interaction with fisheries.
Leptonychotes weddelli Weddell seal
Marlow (1967) and De Master (1979) confirm that this species occasionally wanders as far north as Australia and New Zealand. Presumably this species too is not numerous enough in area 81 for any significant interactions with fisheries.
The diet of most of the species occurring in this area are poorly known in detail. What is known seems to suggest that squid is very important as a food source. Of the 36 species listed above 7 species of baleen whale probably consume only pelagic crustacea (see Nemoto 1959 eg) and one may consume some fish (Bryde's whale). Squids are thought to be important in all the beaked whales diets as well as the diets of a number of the other small cetaceans and pinnipeds.
Of the remaining species little is known of the diets, and there are to substantiated suggestions of any species consuming large amounts of commercial fish, as yet.
The total biological potential of this region has not yet been surveyed. A number of stocks, however, in coastal areas have been assessed.
DEMERSAL FISH RESOURCES
Demersal stocks in area 81 include not only the demersal fish of New South Wales and New Zealand, but also the resources of a number of island states in warmer waters. Catches in 1981 amounted to only around 160 000 tonnes.
GADIFORMES
A few species of this group are found in New Zealand and other waters. The southern poutassou, Micromesistius australis, has an estimated potential of 50 000 tonnes off the south of New Zealand (FAO 1981), but catches amounted to only 6 632 tonnes in 1981 (FAO 1983). Similarly, grenadiers may have a potential of 10 000 tonnes, though only 3 000 were taken in 1981 (FAO 1983).
Chrysophrys aurata Golden snapper Stocks in Victoria and New South Wales provided catches in 1981 amounting to 13 000 tonnes.
Arripis trutta Austrialian salmon/ruff A total of 3 412 tonnes of this species were taken in 1981; this is one of the very few commercial species where any interaction with marine mammals is recorded. (The Australian sea lion is said to annoy salmon fishermen by attacking the nets to get at salmon in area 57 (Warneke 1982)).
Very few demersal species are listed in the fishery statistics yearbook. Other species which may be locally important include snappers and groupers off reefs in some of the Pacific islands, and other reef fish. There seems to be no report, however, of any interactions between marine mammals and such fish stocks in these islands.
PELAGIC FISH RESOURCES
The total pelagic resource potential for the southwest Pacific has been estimated at 1 million tonnes, but this includes the area off southern Austrialia and Tasmania which is actually in area 57, and excludes a large part of area 81 to the west. This latter region is mostly open ocean, which is not likely to be very productive (Rhyther 1969). The total pelagic catches in area 81 amounted to around 140 000 tonnes in 1981 (FAO 1983). Clearly these resources, like the demersal ones area, taken as a whole, under-exploited.
Tuna
A glance at the Yearbook of Fisheries Statistics (FAO 1983) reveals that tuna and tuna like fishes form by far the largest group of catches in this area. Catches in 1981 were around 65 000 tonnes, or over half of the total pelagic catch. Serveral different species are caught; most tuna fishing in the area is by longline, although there are some long-established local live-bait fisheries, and purse seining is beginning to develop (Gulland 1983). Longlining, however, may involve other forms of conflict, with killer whales, or false killer whales (see above).
Other stocks include some sprat and pilchard around New Zealand and Australia, which at present appear to be almost entirely unfished. These could be food supplies for a number of species including common dolphins and Bryde's whales but there are no data on this. Snoek or barracouta (Thyrsites atun) yielded around 2 700 tonnes in 1981 (FAO 1983), and is known to be eaten by a number of pinnipeds; this is not thought to present any particular problem as yet, although fur seals have been known to disrupt line fishing for this species. Mullet (Mugilidae) occur around the coasts of New Zealand and Australia. Catches are only of the order of 3 - 4 000 tonnes, but these species are elsewhere known to be eaten by the bottlenose dolphin (see area 37, 34).
INVERTEBRATE RESOURCES
CRUSTACEA
Under 8 000 tonnes of crustanceans were taken from these waters in 1981, most of which, 4 500 tonnes, were cok lobsters. Stocks of these species are described as being the most economically important in the region and are fully exploited. Although known to be eaten occasionally by fur seals (Warneke 1982), this does not seem to be a major area of conflict. Several species of marine mammals are known to become entangled in pot lines and lobster traps.
CEPHALOPODS
Cephalopods are said to be common in this area (Gulland 1983), although there appears to be little local fishing for them. Gulland states that a Japanese squid fishery operates off the northwest coast of South Island, and reference has been made to another foreign fishery off the Auckland Islands (see Arctocephalus forsteri above). The catch statistics for area 81 reveal that a some 60 000 tonnes of squids were caught in 1981 in this area (FAO 1983). Voss (1973) states that the potential may be several hundred thousand tonnes. The implications of this in relation to interactions with marine mammals are unknown, but many species present in the area feed on cephalopods.
Gulland (1983) states that until recently few Australian or New Zealand boats were longer than 15 to 20 metres, but that recently larger boats have been added to the fleets for deepwater trawling, and purse seining. Local fisheries have been very varied and have included trawl fisheries in coastal waters, beach seining and lobster fishing. Larger boats are mostly from the USSR and Japan, which trawl for grenadiers, poutassou, barracouta and jack mackerel. Longlining for tuna also appears to be important throughout the area, including warmer waters, where island fisheries are chiefly confined to small scale artisanal forms, using a variety of gear.
Operatinal interactions
Operational interactions are most fully documented, in the case of cetaceans, in the Progress Reports of Australia and New Zealand to the International Whaling Commission. There are no large scale incidental captures, and the main conflicts seem to arise in the case of pinnipeds which, in this area as elsewhere, annoy fishermen by taking fish from nets.
Bannister (1977) states that most kills of small cetaceans are “due to fishermen shooting dolphins because of their real or assumed interference with fishing operations”. There are no data on this.
Bannister also mentions a small number of small cetaceans, possibly one every two years, that are killed in New South Wales shark nets.
The New Zealand Progress Reports to the IWC have listed a number of species which have been reported as incidental captures. The species involved are pilot whale(s), dusky dolphins, killer whale, common dolphins and hector's dolphin, as well as an unidentified baleen whale, and an unidentified beaked whale. The gears involved are purse seines, trawls, set gill nets, and crayfish pot lines. The most frequent mortalities appear to involve set gill nets, and dusky dolphins.
Pinnipeds are also recorded as having drowned in nets and lobster traps, and as annoying fishermen by damaging both nets and catch. Both species of fur seals are known to become involved in such interactions.
Hooker sea lions are said to be taken in significant numbers by a squid fishery in the Auckland Island region.
Considering the amount of tuna longlining which occurs in this area, it would be surprising if either the killer or false killer whale were not involved in some conflict with this fishery, although this does not seem to have been recorded yet.
Biological interactions
The diets of most of the species in this area are too poorly known for any assessment of the extent of any biological interaction, The exceptions are the diets of the pinnipeds.
Both species of fur seal are apparently thought of as competitors by fishermen, as are, from the report by Bannister (1977) small cetaceans in Australia. The data on fur seal feeding reveal that they are unlikely to be competing to any great extent with fishermen. The data on small cetaceans are not complete enough for any such parallel analysis. The Potential interaction between squid fisheries and marine mammals should not be ignored in this area where many of the species, including some of the rarest species of marine mammals, feed largely on squid. The fact that at least one marine mammal population is known to be increasing, in an area where fisheries are still relatively undeveloped, should also give some cause for thought about the possible future interactions.
Eubalaena glacialis Right whale
There are no population estimates of this species in area 87. The Report of the Right Whale Workshop (SC/35/Rep 2 1983) lists the maximum number of right whales seen in any one day as 2. Clearly the population is small whilst recovering from commercial whaling, and may number no more than a few hundred. There are no recorded interactions with fisheries. Net entanglements have been recorded in other areas, and if they occur here could affect the population recovery.
(Caperea marginata Pygmy right whale
Although this species does not seem to have been recorded in this area, Ross et al (1975) describe its distribution as circumpolar in all southern oceans).
Balaenoptera physalus Fin whale
The Peruvian Progress Report to the IWC in 1982 (IWC 1983), reports 2 fin whales seen off the Peruvian coast in 1981/82. There appears to be no more detailed description of abundance than this. The stock must be presumed small, after depletion by commercial whaling and may number no more than a few thousands. There appear to be no detailed data on feeding nor any reports of interactions with fisheries in area 87.
Balaenoptera musculus Blue whale
The Peruvian Progress Report to the IWC in 1982 IWC 1983) lists 644 blue whales sighted in 1981 and 622 in 1982. There are no population assessments for area 87, nor any records of interactions with fisheries. The population however, seems unlikely to be more than a few hundred.
Balaenopetra acutorostrata Minke whale
Although there are no population estimates for area 87, this species is known to occur in all southern oceans and a population of at least a few tens of thousands might be expected. There are no apparent records of interactions with fisheries.
Balaenoptera borealis Sei whale
There are no reliable estimates of the population size of sei whales in area 87, but a population in the thousands might be expected. There are no records of interactions with fisheries, and none would seem likely.
Balaenoptera edeni Bryde's whale
Estimates have ranged from 11 316 to 8 571 (IWC 1981 Annexe F) for a total population size of the stock fished off Peru. Cooke (1983) has criticized these estimates as being too high. The population is depleted at present due to commercial whaling. There appear to be no data on feeding in this area nor any records of interactions with fisheries, but some overlap with commercial fisheries for prey species might be expected.
Megaptera novaeangliae Humpback whale
A total of 37 humpbacks were sighted in the 1981/82 season (Peru Prog Rep : IWC 1983). There are no population estimates, but this stock presumably numbers in the hundreds rather than the thousands. There are no indications of any interactions with fisheries, although this species, like the right whale, is known to frequent inshore waters, exposing it to a risk of gear entanglement.
Tasmacetus shepherdi Shepherd's beaked whale
Leatherwood and Reeves (1983) refer to one record from Chile, which appears to be the only record from area 87. The species must be regarded as rare, and although commercial fish were found in the stomach of an animal in Argentina (Mead and Payne 1975), extensive interactions with fisheries are unlikely.
Berardius arnuxii Arnoux's beaked whale
Leatherwood and Reeves (1983) describe the distribution of this species in all southern oceans up to about 30°S. There seem to be no detailed data on abundance or diet, nor any records of interactions with fisheries, but this does not seem to be a common species.
Mesoplodon layardii Strap-toothed whale
Leatherwood and Reeves (1983) describe the distribution of this species as similar to the previous one. There appear to be no detailed data from area 87; this is another rare species, and interactions with fisheries seem unlikely.
(Mesoplodon grayi Gray's beaked whale
There do not appear to be any records of this species in area 87, but Leatherwood and Reeves (1983) suggest a circumpolar distribution in southern waters. There are no indications of interactions with fisheries).
Ziphius cavirostris Cuvier's beaked whale
Mitchell (1975a) describes this species as occurring in all oceans. There appear to be no detailed data on diet nor abundance in this area, although it does not appear to be very abundant anywhere. There are no records of interactions with fisheries in this area.
Hyperoodon planifrons Southern bottlenose whale
Mitchell (1975) describes this species as widespread in all southern oceans. There appear to be no detailed data on feeding or abundance, and no indications of interactions with fisheries.
Physeter macrocephalus Sperm whale
Peruvian Progress Reports to the IWC indicate that between 1.8 and 3.4 thousand sperm whales have been sighted off Peru for the past 7 years. The population size is unknown, but may be in the tens of thousands. There are no records of interactions with fisheries.
Kogia breviceps Pygmy sperm whale
Leatherwood and Reeves (1983) refer to a stranding in Peru, but there is no detailed information for this area. Interactions with fisheries seem unlikely.
(Kogia simus Dwarf sperm whale
Not yet recorded from this area, Watson (1981) amongst others believes the distribution is throughout all oceans).
Feresa attenuata Pygmy killer whale
There appear to be no records of this species in area 87, but the distribution is thought to include all tropical and temperate waters(Mitchell 1975).
Psuedorca crassidens False killer whale
There seem to be no detailed data for this area,and no records of interactions with fisheries. The possibility of conflict with tuna longliners as in other areas, should be borne in mind.
Orcinus orca Killer whale
There does not appear to be any detailed data on the feeding of this species in area 87, nor any indication of abundance. Some interaction with fisheries might be expected but does not appear to have been reported.
Globicephala melaena Long-finned pilot whale
Aguayo (1975) refers to this as one of the most abundant species on the Chilean coast. There do not seem to be any detailed data on feeding nor records of interactions with fisheries.
Lagenorhynchus obscurus Dusky dolphin
Mitchell (1975a) states that a few of this species are taken in catches of porpoises off western South America, but there appear to be no data on abundance, numbers of this species caught, nor on the diet.
Lagenorhynchus cruciger Hourglass dolphin
Leatherwood and Reeves (1983) state that this species has been sighted as far north as 34°S off the South American coast, but AguaYo (1975) does not record it from Chile. It is presumably uncommon, in coastal waters at least, and prefers cooler waters. There are no indications of likely interactions with fisheries.
Lagenorhynchus australis Peale's dolphin
Aguayo (1975) records this species from 32° to 60°S. There seem to be no detailed data on abundance or feeding, but Goodall and Cameron (1980) state that it is taken for baiting traps for southern king crab. They state that the actual numbers involved are unknown but suggest these may be in the thousands. The effect that this may be having on the population is unknown.
Tursiops truncatus Bottlenose dolphin
Aguayo (1975) provides records of this species in Chilean waters where it is apparently not uncommon. Aguayo (1975) also states that some are taken incidentally by small boat fishermen, but gives no figures. There do not appear to be any data on feeding for this species in area 87.
Grampus griseus Risso's dolphin
Aguayo (1975) records this species in Chilean waters, and Leatherwood and Reeves (1983) state that it ranges as far south as central Chile. There are no detailed data on feeding for area 87, and no apparent records of interactions with fisheries.
Stenella longirostris Spinner dolphin
Although this species is known to occur in all warm tropical waters, there seems to be a paucity of records from area 87. The influence of the Peru coastal current may exclude this species from all but the northern end of area 87, in the coastal area at least. There are no apparent records of abundance in this area nor of any interactions with fisheries.
Stenella attenuata Spotted dolphins
Spotted dolphins are also presumably confined to the warmer northerly regions of area 87; there are no apparent data on abundance nor indications of interactions with fisheries.
Lissodelphis peronii Southern rightwhale dolphin
Aguayo (1975) describes the distribution of this species in Chile from around 19°S to Cape Horn, suggesting that it may be quite common in some areas, even in coastal regions. Aguayo also records the accidental capture of one specimen on a hook and line; presumably others are also caught incidentally, but there are no figures on such captures.
Delphinus delphis Common dolphin
Aguayo (1975) describes the distribution of this species in Chilean waters as extending from around 29°–41°S, where it appears to be quite common. Although incidental captures might be expected, there do not appear to be any such records.
Cephalorhynchus eutropia Black dolphin
Aguayo (1975) describes this species as rare, with a distribution along the Chilean coast from around 35°S to 60°S. Goodall and Cameron (1980) mention that this species is caught incidentally along the Chilean coast in surface gill nets but no figures are available.
Cephalorhynchus commersonii Commerson's dolphin
Records from the southern end of South America are summarized by Aguayo (1975). There appear to be no detailed data on the feeding habits, nor on abundance. Goodall and Cameron (1980) report that an unknown number of this species, at least 30 a year, are accidentally captured in crab nets in Chilean Tierra del Fuego. They also describe the use of this species, together with Peale's dolphin, as crab bait in Chilean Tierra del Fuego. They suggest that thousands of animals (of both species) may be taken every year, but there are no data on this.
Phocoena spinipinnis Burmeister's porpoise
Brownell and Praderi (1982) describe this species throughout its range, and describe it as the most abundant small cetacean in coastal waters around southern South America. They describe reported incidental captures in small boat fisheries in Peru. Although the type of gear involved and the species of fish are not stated, Brownell and Praderi suggests that at least 2 000 animals are taken per year. The effect of this mortality on the population is not known.
Otaria flavescens South American sea lion
Occurring on the Pacific coast of South America from Cape Horn to the Galapagos, and to 4°S on the Peruvian coast (Vaz-Ferreira 1982). Vaz-Ferreira has given estimates of the population in this area suggesting a minimum of 40 000 animals in the area, although not all of it has been surveyed.
Vaz-Ferreira states that “sea lions are decimated by human agency including regular exploitation, clandestine exploitation, and killing by fishermen on account of damage to nets; and a reduction in population is the rule over most of its area of distribution”. Data on feeding is summarized by Vaz-Ferreira, and in Chile is known to include ‘cabrilla’ Sebastodes oculatus, ‘merluza’ Merluccius gayii, ‘sardina’ Clupea bentinckii as well as some molluscs and crustaceans. Birds are also known to be eaten, including penguins. Vaz-Ferreira concludes that “competition of sea lions with man for food resources is evident,… but no estimation of the total competition can be worked out with the scanty data available”, and also mentions that direct interference with fisheries is well known, involving the severe damage of fishing tackle and removal of fish. Recently, the Diario Oficial De La Republica De Chile (11 July 1983) modified decree 4844 in order to include the sea lion as a pest species which may be shot.
Arctocephalus philippii Juan Fernandez fur seal
Confined to a few islands off the coast of Chile, the species was presumed extinct until 1965 (Bonner 1981), after a period of heavy exploitation (Aguayo 1979). Aguayo states that up to 750 seals have been counted, and that there is some illegal killing by fishermen, who may use them for lobster bait. There are no detailed data on feeding.
Arctocephalus australis South American fur seal
Vaz-Ferreira (1982a) states that the population on the western coast of South America is distributed from the Paracas Peninsular in southern Peru to Cape Horn, and may number in excess of 50 000 animals, the population being either stable or diminishing. There do not appear to be any detailed data on diet from this area, but various fish, including anchovies, horse mackerel, weakfish, and invertebrates including cephalopods are said to be eaten in general. Although Vaz-Ferreira states that this species feeds over a wide area of the continental shelf and beyond, and causes no important damage to fisheries, he also cites Brownell as having examined 13 individuals which had drowned in trammel nets, and continues that there is perhaps some interference with fishing gear placed too close to the rookeries. There are no quantitive data on these interactions.
Leptonychotes weddelli Weddell seal
De Master (1979) states that this species has been sighted as far north as the Juan Fernandez Islands, but this is principally an Antarctic seal. There are no indications of the number of animals migrating into area 87, but these are presumably few. No interactions have been reported with fisheries, and none would seem likely.
The diets of most of the 38 species of marine mammals listed above are unknown in this region, as are the population sizes. Antarctic baleen whales are generally held (eg Mackintosh 1946) not to feed much in the northern or breeding end of their migratory routes. Bryde's whale presumably does feed, and given the abundance of anchovies and sardines in this area, it might be considered safe to suggest these as 2 items likely to occur in the diet.
At least 7 or 8 species mentioned above are generally held to feed on squid. These include all the beaked whales, the sperm whale and Risso's dolphin. It is interesting to speculate upon the diets of the remaining species, many of which are coastal species. Even the southern rightwhale dolphin, normally described as oceanic, is here, according to Aguayo (1975) found in the coastal zone.
The fish resources of this region are dominated by 2 or 3 pelagic species, but some demersal species too are caught in appreciable numbers. The reasons for the predominance of pelagic fish are that the shelf area along this coast is relatively narrow, but there are strong upwelling currents making the area very productive.
DEMERSAL FISH RESOURCES
The total demersal catch in 1981 was around 230,000 tonnes, 100,000 tonnes of which came from just one species. The stocks are probably fully exploited except in the southern part of Chile.
Merluccius gayi Chilean hake The Chilean hake fishery is one of the few commercial fisheries for demersal fish in area 87. 104 000 tonnes were taken in 1981, a decline from over 380 000 tonnes in 1978 (FAO 1983). Sea lions are known to include this species in their diet but the extent of the competition is unclear.
Other demersal species which are caught in relatively large numbers include Patagonian hakes Merluccius polylepis and Patagonian grenadier Macruronus magellanicus, presumably these are also mainly trawled for.
Much of the fishing in this area is still apparently from small boats, and other species caught include a small range of groupers, snappers and drums, amongst other fish.
PELAGIC FISH RESOURCES
The pelagic fish stocks of this area are very large and have produced in good years over 10 million tonnes of fish, but there is considerable variation. Catches in 1981 for all pelagic species amounted to around 6.5 million tonnes.
Engraulis ringens Anchovy
The Anchoveta fishery was once the largest in the world in terms of weight, but having been severely overfished in the late 1960's and early 1970's, currently (1981) yielded only 1.5 million tonnes. Gulland (1983) describes the history of this fishery. It is interesting that, as Gulland notes, the sea bird population is said to have undergone a decline during the period of greatest anchovy catches, and these 2 events have been linked: the decline in bird numbers may have been related to a reduced food supply. This prompts the speculation as to what effects the fishery may have had on any marine mammal populations. Unfortunately not enough is known of the diets or population dynamics of marine mammal species in this area to answer this question. Both fish and bird stocks also seem sensitive to changes in the ocean environment, particularly the el Nino phenomenon.
Sardinops sagax
As in other parts of the world, the decline of one fish stock seems to have lead to an increase in another and the collapse of the anchoveta has roughly coincided with a rise in the pilchard stock. The pilchard fishery in this region now exceeds the anchovy fishery and catches totalled 2.8 million tonnes in 1981 (FAO 1983).
Other important pelagic species include the Chilean jack mackerel Trachurus murphyi which yielded 1.6 million tonnes in 1981, and yellowfin tuna, which yielded over 100,000 tonnes.
INVERTEBRATE RESOURCES
CRUSTACEA
Crustacean resources are an important part of the fisheries of this area, and those species which are fished include squat lobsters (Galatheidae), lobsters and king crabs (Lithodes). This latter species is the most interesting in terms of marine mammals as it is this which is fished for off Tierra del Fuego, using tangle nets which entrap at least one marine mammal species (L. commersonii).
CEPHALOPODS
At present these resources appear to be greatly under-exploited with only a few hundred tonnes landed in 1981 (FAO 1983). The total potential may be around 500 000 tonnes (Voss 1973).
Gulland (1983) states that prior to the anchoveta fishery, the main fisheries of this area were the Peruvian bonito and Chilean hake (trawl) fisheries. Other fisheries in the area are mostly artisanal, using small boats and a variety of gear. The anchoveta fishery amploys purse seiles, which, after the collapse of the anchovy stocks are also used to fish for sardines and other species.
Marine mammal fishery interactions in this area are not well documented, and although there is some evidence of a number of incidental captures, there are few data to show the extent of these.
Aguayo (1975) refers to a number of species taken in small boat fisheries along the Chilean coast. These include P. spininnis, L. obscurus,, L. australis, Lissodelphis peronii and C. eutropia
Goodall and Cameron (1980) report that 2 species are taken for bait in Tierra del Fuego, L. australis and C. commersonii, and that C. commersoni may also be taken in crab nets.
Sea lions are known to be regarded as pests by fishermen throughout the area, as they damage nets and catch, having learned to follow fishing boats.
South American fur seals are taken, possibly in small numbers only, as an incidental catch in some fisheries.
Juan Fernandez fur seals may occasionally be taken by fishermen for bait.
Biological interactions
There are no documented examples of any effects of competition between marine mammals and fisheries in this area, although the collapse of the anchovy stock could well have affected some species, such as Bryde's whale.
Squid fishing appears to be of minor importance, though as elsewhere, any development of this fishery could lead to increased competition with marine mammals.
Eubalaena glacialis Right whale
The southern hemisphere population has been found mostly between 30° and 50° South, although Mackintosh (1965) states that right whales are known to range south of the Antarctic Convergence. The southern hemisphere population may number in the low thousands at present (Report of the Right Whale Workshop, IWC 1983), but the proportion of these which move into areas 48 58 and 88 is unknown. The food is principally copepods (Mackintosh 1965) and no interaction with fisheries is likely.
Balaenoptera physalus Fin whale
Migrating south during the austral summer, fin whales are distributed in their feeding grounds south of the Antarctic Convergence, as far south as about 60°S (Mackintosh 1965). The migration routes and feeding areas are more well documented than for many of the other species, as fin whales have a long history of commercial exploitation. Laws (1977) has suggested that the stock may have been reduced from around 400 000 animals initially to around 80 000 in the 1970's. Grenfell (1983) has estimated the total population in Antarctic areas 2, 3, and 5 (60°W to 70°E and 130°E to 170°W) to be around 80 000 also. The total population for the whole region could therefore exceed 100 000, but is still only a fraction of the initial population size. The food has been studied amongst others by Nemoto (1959, 1970) and in Antarctic waters is restricted to euphausiids, mostly the commercially caught E. superba, but also Thysanoessa macrura. There are no records of conflicts with fisheries, but Laws (1977) and Beddington and de la Mare (1984) have pointed out some of the possible interactions between recovering whale stocks and krill harvests.
Balaenoptera musculus Blue whale
Blue whales in the southern oceans are apparently less common than fin whales, but no satisfactory population estimate has been made. Laws (1977) gives a total figure of 6 000 for the whole region, and figure of 200 000 for the initial stock size. The diet consists mostly of Euphausia superba, although some other euphausiids are also taken (Nemoto 1959, 1970). Laws (1977) states that the blue whale feeds at high latitudes on first year krill.
Balaenoptera acutorostrata Minke whale
The smallest and currently most numerous of the Antarctic baleen whales, minke whales are found right up to the ice edge. The population has been estimated to number around 580 000 animals (IWC 1984), and is currently still hunted in Antarctic waters, around 6 000 being taken every year. Laws (1977) suggests that the minke whale population may actually be higher today than it was prior to commercial whaling in the region, as the reduction in stocks of other species has resulted in an increase in minke whales through reduced competition. Nemoto (1970) states that the diet of the minke whales in southern oceans is restricted to euphausiids. The fact that minke whales are more abundant near the ice edge compared with some of the larger species implies that it may be less likely to conflict with krill fisheries in the future, as these tend to operate further north.
Balaenoptera borealis Sei whale
Preferring warmer waters than fin and blue whales (Tomilin 1957), sei whales nevertheless penetrate into Antarctic regions; Mackintosh (1965) states that the extent of the geographical range is similar to blue and fin whales, although sei whales appear to favour warmer waters, and that their movements are less regular and predictable. The stock size has been estimated by Grenfell (1983) to have fallen from around 65 000 in 1904, before commercial whaling in Antarctic waters, to around 19 000, in areas 2, 3 and 4 (60° eastwards, to 130°E) at least. Laws (1977) suggests a decline overall, from around 75 000 to 40 000. Elsewhere the population has been estimated at between 15 and 30 000 in the southern hemisphere (IWC 1980). The diet, according to Nemoto (1979), includes not only euphausiids but also other swarming crustacea such as the amphipod Parathemisto.
Megaptera novaeangliae Humpback whale
Five or six seperate stocks are known to spend the austral summer in Antarctic waters, with little inter-mixing between the groups (Mackintosh 1965). The population is thought to number a few thousand; Grenfell (1983) estimated that in Antarctic areas 2, 3 and 4 (60°W eastwards, to 130°E) the recruited stock numbered 4 670. Laws (1977) gives figures of 100 000 and 3 000 for total southern stock sizes before and after exploitation. Chittleborough (1965) states that Euphausia superba is the main food item, but that Thysanoessa macrura is also eaten. The latitudinal range of this species whilst in Antarctic waters falls somewhere between the fin and sei whales (Laws 1977).
Physeter macrocephalus Sperm whale
Sperm Whales migrate towards the poles in spring and summer, but it is thought that it is mainly the mature males which venture into Antarctic waters (Laws 1977). Stock estimates have been made for females for southern hemisphere sperm whale divisions (see appendix in IWC vols.) 2, 3, 4, and 6, and for males in divisions 2 to 7 by Cooke, de la Mare, and Beddington (1983). They estimate the total initial stock for these areas to have been in excess of 380 000 whereas the current stock size is estimated to be more than 235 000. The total population of such whales in Antarctic waters might therefore exceed 400 000. The diet is almost exclusively cephalopods (Laws 1977). Laws (1977) and Beddington and de la Mare (1984) have pointed out the possible ramifications of a change in the population of sperm whales, which as they feed higher up the Antarctic food chain, may have a more dramatic effect on the whole system through smaller population changes than would be necessary in baleen whales.
Berardius arnuxii Arnoux's beaked whale
Known from the Antarctic peninsula and the Subantarctic Islands of the Atlantic, this is a cephalopod eating species, with an unknown population size, but frequent strandings suggest that the species may be most abundant in the waters around New Zealand. (Leatherwood and Reeves 1983)
Hyperoodon planifrons Southern bottlenose whale
This species is not frequently observed, but is recorded from the Pacific, Indian and Atlantic Ocean Sectors of the Antarctic (Leatherwood and Reeves 1983). The diet consists of squid, and the population size is unknown.
Orcinus orca Killer whale
Occurring throughout the region, this species is found even in the polar ice floes. The diet is very varied, and in this area includes seals and cetaceans, as well as penguins (IWC 1982). The Antarctic population size may be around 160 000 (Hammond 1983). The only overlap with ‘fisheries’ is the killer whales predation on minke whales, which are also hunted in Antarctic waters, but this does not seem to have been isolated as problematic.
Lagenorhynchus cruciger Hourglass dolphin
A little known dolphin, with a distribution north and south of the Antarctic Convergence, there are no population estimates for this species (Leatherwood and Reeves 1983). Interactions with fisheries seem unlikely for the present.
Lissodelphis peronii Southern rightwhale dolphin
Described by Leatherwood and Reeves (1983) as a marginal Antarctic species, there are no population estimates for this area, although presumably the population is small. Food for this species is thought to include squid and non commercial fish, and interactions with fisheries seem unlikely.
Cephalorhynchus commersonii Commerson's dolphin
Brownell (1974) record this species at South Georgia (area 48) and at Kerguelen (area 58). The population status is unknown. Leatherwood and Reeves (1983) refer to krill crabs and cephalopods in the diet, but few data are available. Nothing is known of actual or potential interactions with fisheries.
Phocoena dioptrica Spectacled porpoise
Brownell (1974) records this species from area 48 around South Georgia and Leatherwood and Reeves (1983) from Kerguelen. The population size is unknown, as is the diet. Interactions with fisheries are therefore also unknown.
Arctocephalus gazella Antarctic fur seal
Distributed throughout the islands south of the Antarctic Convergence, the major breeding population is on South Georgia. Payne (1977) has studied the dynamics and structure of the fur seal population at South Georgia. At that time the population was estimated to be expanding at a rate of 16.8% per year. The population size was estimated at 369 000 in 1979 (Payne 1979 cited in Bonner 1981). Payne (1977) suggested that the rate of increase would decline possibly within a decade of 1977, and suggested that food availability may come into play as a regulating factor. The diet consists most of krill, although fish, squid and penguin remains have also been found (Bonner 1981). Recent reports (Anon 1984) have suggested pup survival has fallen markedly, with females spending up to 3 times as long searching for food. Although the report suggests over-fishing of krill as the cause of this, the extreme variability of krill density, coupled with Payne's (1977) predictions concerning food supply, warn against too hasty a conclusion being drawn.
Arctocephlaus tropicalis Subantarctic fur seal
Although occasionally reported from South Georgia there are also colonies on Prince Edward and Marion Islands in the Southern Indian Ocean, and stragglers are reported from the Isles Crozets (Bonner 1981). The population size in areas 48, 58 and 88 is unknown, but the total population may number around 110,000 (Bonner 1981), and the centre of distribution is outside Antarctic waters. The diet is composed of squid, penguins, and euphausiid crustacea, but the distribution of this species is away from krill harvests, except around South Georgia.
Mirounga leonina Southern elephant seal
With breeding populations on Heard Island, Kerguelen, and through the Scotian Arc and South Georgia, much of the species distribution falls within areas 48 and 58. Individuals are also known from around the Antarctic continent, where there are a number of moulting areas (Ling and Bryden 1981). The population in these areas must at some times of year include much of the estimated total of about 580 000 individuals (Ling and Bryden 1981). The diet consists of squid and fish, and Ling and Bryden (1981) suggest that fish (mainly Notothenia spp) may be consumed in inshore waters, and cephalopods elsewhere. Pascal (1984 in press) has linked an apparent decline in the Kerguelen population with fishing for notothenids in the waters thereabouts, but McCann (1982) has disputed this idea. Clearly the potential for interaction exists where fishing for Notothenia occurs.
Lobodon carcinophagus Crabeater seal
Found throughout the Antarctic area, expecially in the pack ice, this is the most numerous of seal species with an estimated population size of 15 million (Laws 1977). The diet is mainly euphausiids, and although the distribution of this species, close to the ice (Kooyman 1981), may limit operational interactions with commercial fisheries, the size of the population and the amount of krill consumed may involve some competitive interaction with the krill fishery.
Ommatophoca rossi Ross seal
Ray (1981) states that this species is the least known of all seal species, and that it prefers the consolidated pack ice areas of Antarctica. Laws (1977) gives a population estimate of 220 000. Ray cites Oritsland (1977) for the food of this species, found to consist of 64% cephalopods, 14% other invertebrates including some krill, and 22% fish. No conflict with fisheries has yet been recorded.
Hydrurga leptonyx Leopard seal
Kooyman (1981) described this species as occuring throughout the pack ice, south to the Antarctic continent, and also on the Subantarctic Islands of South Georgia and Heard, mainly in winter. Population estimates have ranged from 100 000 to 300 000, and the diet is known to include a wide range of food organisms, including krill, penguins, seals, squid and fish (Kooyman 1981). There appear to be no records of interactions with fisheries.
Leptonychotes weddelli Weddell seal
Distributed most densely near the coast of Antarctica, breeding colonies occur as far north as South Georgia. The population size is unknown, but is believed to exceed 750 000, and the diet consists almost entirely of fish, especially Dissostichus mawsoni. (Kooyman 1981). Interactions with fisheries are not known at present.
Of the 19 species of marine mammal inhabiting these waters, 8 are thought to feed entirely or mainly on krill, especially E. superba. 8 more feed wholly or in part on squid, and 2, the killer whale and leopard seal have very catholic diets, including other marine mammals. Fish play a relatively minor role in the diets of marine mammals in these areas, only the weddell seal being truly piscivorous. 3 or 4 other species do take some fish, notably the elephant seal.
The main pototential fishery resource in the southern oceans is a crustacean, Euphausia superba, rather than a fish. Fish are not numerous in the region when compared with the biomass of krill, but have nevertheless been heavily harvested. The slow growth of Antarctic species of fish means that the potential sustainable yield is not very large. Whales and seals have been important in Antarctic harvests in the past, but currently only minke whales are taken in any large numbers. Laws (1977) suggests that enormous depletion of whale biomass, which he estimates is now around 15% of that prior to commercial exploitation, may mean that there is at present a very large ‘surplus’ amount of krill production, which could be harvested, but much of which may be at present consumed by other species.
DEMERSAL FISH RESOURCES
NOTOTHENIIDAE
Catches of notothenids reached a peak of 400 000 tonnes in the 1970/71 season, taken mostly by the USSR in the waters around South Georgia, and crashed to almost nothing the next year (Gulland 1983). In the 1980/81 season over 63 000 tonnes were taken, again mostly in the Atlantic sector, although over 16 000 tonnes were taken in the Indian ocean sector. The total potential for Antarctic cods is not known, but Gulland (1983) suggests that they are very heavily fished.
CHANNICHTHYIDAE
Icefish were exploited after the boom and crash of the notothenids, again mostly in the Atlantic sector. Around 200 000 tonnes were taken in the 1977/78 season, but catches have dropped off in recent years to 40 000 tonnes in 1980/81 (FAO 1983). These stocks are also heavily fished.
INVERTEBRATE RESCURCES
CRUSTACEA
Krill represents an enormous resource in these areas, the total potential yield of which could be in the tens of millions of tonnes per year. At present, however, the catch is only in the hundreds of thousands of tonnes. In 1980/81 285 000 tonnes were taken in the Atlantic and 160 000 tonnes in the Indian Ocean sectors. Most of this was taken by the USSR. Even though only a fraction of the potential of this fishery has yet been realised, the 448 000 tonnes catch recorded for 1981 (FAO 1983) makes this the 25th largest single species fishery in the world. Beddington and de la Mare (1984) have pointed out that the extreme variability of oceanographic conditions in these waters is likely to produce big variations in local productivity and abundance of krill, which could be exacerbated by fisheries, which are likely to concentrate on areas of high productivity.
CEPHALOPODS
Very little exploitation has occured in Antarctic waters. Japan took 390 tonnes in area 88 in 1977/78, and none since then (FAO 1983). The productivity of the area and the large numbers of sperm whales and other squid eating animals in the area, indicates that there is a potential for a much larger fishery.
Dominated by the USSR in all sectors, Japan, Poland and the German Democratic Republic also take some fish and krill from Antarctic waters. The fishery for krill employs large scale trawlers, which may be unlikely to suffer gear conflicts with marine mammals. Most fishing occurs in the Atlantic sector, around South Georgia and the Scotia Arc, where concentrations of krill are highest, with some fishing also around the Subantarctic Islands of the Indian Ocean sector. As yet interactions with marine mammals are minimal, but the recovering whale stocks, and the sheer size of the biomass of marine mammals in the area, which is largely dependent on a single species resource, clearly make future interactions with an expanded krill fishery potentially a very serious problem. This problem has been discussed by Beddington and de la Mare (1984), and is also one of the main considerations of the various scientific bodies which have been set up in recent years in order to provide a rational management plan for the southern oceans.
Unlike the other areas of the world's ocean, operational interactions appear to be rare or absent, probably due to the capital intensive and highly mechanised fishery which presumably has less chance of gear conflicts than numerous small vessels with other types of gear. The reported interactions so far involve two possible cases where fishing may have affected the life history parameters of a marine mammal. Firstly there has been some suggestion that krill harvests around South Georgia could be responsible for increased pup mortality in the Antarctic fur seal population (Anon 1984). Such suggestions remain unconfirmed at present (Anon 1984). Secondly, trawling for fish may have affected elephant seals on the Island of Kerguelen (Pascal 1984 in press). Future interactions might be expected with any or all krill eating mammals. Laws (1977) has pointed out the enormous potential ‘surplus’ of krill available since the decline of baleen whales, and Beddington and de la Mare (1977) have pointed out some of the problems associated with trying to exploit this krill resource.
