5. POTENTIAL RESOURCES AND PRESENT STATE OF EXPLOITED SPECIES

5.1 NOMINAL CATCH DATA

Historical catch and effort data on the industrial fleet are given by Laure (1969, 1971). There has been a gradual increase in number of vessels, GRT and engine horsepower (HP). It is reported that in 1951 one trawler operated in Cameroonian waters and landed 60 t of demersal fish. In 1961, nine trawlers were available and they landed a total of about 3 800 t of fish. The industrial fleet expanded rapidly during the sixties and by 1973 there were 29 trawlers and 13 shrimpers which landed a total of about 17 616 t of fish and shrimp. Total catch and effort trends of the industrial fleets are given in Table 7. The catch of the industrial fleet peaked at about 20 400 t in 1976 and since then catches have generally declined. The decline in catch of the industrial fleet in the early eighties might be due to a shift in fishing grounds by the industrial fleets operating in Cameroonian waters.

Available catch data indicate fluctuations in shrimp catches. In 1970, the shrimp catch was about 940 t, but by 1972 the shrimp landings had risen to 2 360 t. This was followed by a sudden drop to 1 696 t in 1975 and a sharp rise to 2 438 t in 1977. There has been a gradual decline in the shrimp catch of shrimpers/trawlers since 1977. Trends in shrimp catches of the entire industrial fleet and the allocation of shrimp between shrimpers and finfish trawlers are shown in Table 8. The size composition of shrimp landed in Cameroon is shown in Table 9.

Catch data on the artisanal fisheries are not yet adequate, but fishery administrators and research scientists are making great efforts to improve the supply of information on the artisanal sector. The first attempt to establish a data base on artisanal fisheries was undertaken in 1978. On the basis of this work SCET-International (1980) made the following preliminary estimates:

1 Estimate based on part of the year

In 1983, the Limbé Fisheries Research Station (Station de Recherches Halieutiques de Limbé, IRZ) made a Frame Survey of Fishing Units along the entire Cameroonian coastline and determined the number of fishing villages, canoes, fishermen as indicated in Table 2. The artisanal fishery production estimates still need updating.

The collection and compilation of nominal catch data for the artisanal sector is made more difficult by the inaccessibility of most coastal fishing villages. Besides, allocation of catches by species is difficult because some local names refer to several species as shown in section 3.1.2.

5.2 CATCH PER UNIT EFFORT (CPUE) DATA

Information on fishing effort expended by the artisanal sector to obtain a certain quantity of catch is scanty. In most instances only the catch and the value of fish are recorded. Information on number of gillnets, castnets, hooks, beach-seines, etc., used by the artisanal fishermen is still inadequate.

Historical data on fishing effort of the industrial fleet (trawlers and shrimpers combined) are given in Table 7. It has been reported that some foreign vessels sometimes operate in Cameroonian waters, but information on catches and catch rates of these vessels is not available.

Trends in fishing effort of the national industrial fleet for the period 1979–1984 is given in Table 4, whereas the characteristics of fishing vessels are given in Table 5. During the seventies some distant water trawlers with over 500 GRT used to fish off Angola and Namibia. These vessels were owned by the “Société Industrielle des pêches du Cameroun” (SIPEC). These vessels stopped fishing in distant waters in 1976 due to financial constraints and changes in the regime of the sea. The data in Table 5 indicate that the most popular and possibly appropriate size of trawlers and shrimpers have a range of 50–250 GRT. The popular trawling grounds frequented by industrial fleets are reflected by activities of the COTONNEC Company shown in Table 10.

The industrial shrimp fishery is presently dominated by the COPEMAR fishing company. Prior to 1981 CRECAM had the largest fleet of shrimpers. Fishing trends in the industrial shrimp fishery for the period 1970–1984 are illustrated by catches and catch rates of CRECAM in Tables 10 and 11 respectively.

The estimates presented in this report are based on the results of several acoustic and exploratory fishing surveys conducted in Cameroon. Acoustic surveys have enabled the study of bottom types, distribution of species by depth and determination of biomass by species groups. Exploratory fishing has facilitated determination of species composition, total catch magnitudes, vital biological factors of available species, rates and catchability. Finally the exploratory surveys have provided information through observations on temperature, salinity, dissolved oxygen levels and turbidity, all of which affect the distribution of fish. A summary of information concerning various surveys conducted in Cameroon waters is given by Van der Knaap (1985) and shown in Table 13. Different estimates have been made by Forest (1959), Crosnier (1964), Williams (1968, 1969), Robertson (1977) and Strφmme et al. (1983).

Most of the exploratory fishing surveys were conducted in the open shelf waters of more than 25 m depth in the sector of the thermocline zone and in the zone of “cold waters” below the thermocline. The estimated densities on the shelf of Cameroon and neighbouring countries are relatively low. Since the richer littoral areas were not covered, the biomass and potential of the continental shelf were somewhat underestimated. There is high fishing effort of both artisanal and industrial fleets in the inshore waters of less than 25 m where catch rates are higher.

5.3 POPULATION STRUCTURE AND PARAMETERS

Recent data on population structure (i.e., length/age frequencies, sex ratio, mean size, etc.) of individual species in the catch made by the artisanal inshore fishermen are not available. Information on selectivity of mesh sizes (range 33–45 m) used in the shallow inshore waters by the canoe fishermen exploiting the coastal pelagics is missing. Since the creeks and estuaries are nursery grounds for some species, it is difficult to assert that the small mesh-sized drift nets, gillnets and cast nets used by the artisanal and coastal inshore fishermen harvest mostly mature individuals.

The artisanal demersal fishery is mainly exploiting the croakers, threadfins, soles, catfish, sharks and rays using bottom-set gillnets of 35–90 mm mesh size. This fishery catches a good portion of mature demersal fish. The size composition and age structure of catch of artisanal demersal fishery are not yet available.

The seasonal effect of an intensive artisanal nyamtolo fishery using 10 mm meshed nets on fish populations in the littoral areas has not been assessed, but it would appear the capture of juvenile bonga, sardine and croakers is significant in the Wouri region, particularly around the estuary of Cameroon River.

There is already valuable information on some aspects of the biology of a number of commercially important fish species, but the main limitation in the use of this information for management purposes is that some of the results for length frequencies, age, sexual maturity and fecundity had been focused on catches of industrial fleets. Therefore, the management picture is made more confused by the fact that the artisanal fishermen and the industrial fleets fish the same demersal stocks, but most probably take different age and size groups. Nevertheless, management of the coastal fisheries may be still possible if changes are monitored in population parameters which are sensitive to increasing fishing intensity, that is, maximum length (L_oo), length at first maturity (1_m) mean size at first capture (1_c) and the mean size of different species landed in the catch.

5.4 BIOMASS AND POTENTIAL ESTIMATES OF EXPLOITED SPECIES

The available data are not adequate to enable the use of conventional management models in assessing the yield potential of exploited species of the Cameroon continental shelf, estuaries and creeks but preliminary estimates of potential yield made in the sixties indicate that the magnitudes are modest. These estimates do not match the present combined catches of the industrial fleet (12 000–20 000 t) and the artisanal catches which amount to more than 20 000 t. Troadec and Garcia (1980) discuss the fishery resources of the Gulf of Guinea. FAO (1979a, 1979b and 1986) gives results of the assessment of shrimp and demersal fish of Cameroon.

5.4.1 Biomass estimates

During the period 1963–1964, the Guinean Trawling Survey (GTS) made two cruises on the continental shelf of Cameroon (see Table 12). The survey results lead to an estimated biomass of about 45 100 t of demersal fish assuming 100% efficiency of the trawl (Williams, 1968, 1969).

The Soviet vessel R/V FIOLENT, chartered by FAO, surveyed a shelf area between 20 and 1 000 m depth in January/May and July/December 1976. The results of the survey led to an estimated biomass of 22 400 t of demersal fish assuming 100% efficiency of the trawl. The average fish density was put at 10 t/n.mi². The catch rates of various species groups (kg/h) are given in Table 14. More detailed information on the R/V FIOLENT survey are given by Robertson (1977).

In August 1981, an acoustic survey was carried out in Cameroonian waters using R/V DR FRIDTJOF NANSEN. The survey covered a depth of 50–200 m and the acoustic results led to an estimated average density of about 61 t/n.mi². The estimated biomass for the covered area was put at about 100 100 t (Strφmme et al., 1983), mostly coastal pelagic fish (bonga, sardine and shads). It has previously been argued that the biomass of clupeids and carangids is scanty on the continental shelf of Cameroon. This interpretation might have been based on biased sampling and surveys of the sixties and mid-seventies.

1 based on Njock (1985)
2 based on FAO (1986)
3 standardized effort based on Adetayo (1982)

The catch magnitudes of bonga, shad and sardine by artisanal fishermen using beach-seines, purse-seines and drift nets appear to indicate a higher biomass of small coastal pelagics on the shelf. There are also substantial discards of shad and bonga by trawlers operating in the thermocline zone at 25–50 m depth. In these circumstances, the biomass estimate of 100 100 t derived from the results of the DR FRIDTJOF NANSEN survey is plausible. There is, however, a need to verify previous estimates.

5.4.2 Potential estimate

Determination of yield potential of exploited stocks cannot easily be made using the data available. The exact magnitudes of catches of industrial vessels obtained outside the Cameroonian EEZ, but which are landed at Douala, are difficult to determine.

FAO (1985) used global production model and standardized effort of the entire industrial fleet (trawlers and shrimpers) to estimate optimum yield. The natural variability in density of fish stocks and undetected changes in catchability coefficients of various vessels may affect the validity of the model. The results given in Table 6 lead to an estimated maximum sustained yield (MSY) of 19 360 t for an optimum effort of 5 425 days using a vessel of 400 HP. The correlation coefficient (r) = 0.75. This somewhat crude model shows that the exploitable stocks were fully exploited in the early seventies since most of the data points are to the right of the optimum fishing effort and yield as indicated in Figure 7. This was further confirmed by the decline in catches when the Cameroonian distant-water fleets shifted to national waters. It is observed that at present a number of vessels fish close inshore within 2 miles offshore and even in the creeks and estuaries. The mesh size used by the industrial fleet is quite small, i.e., 32–36 mm for shrimpers and 36–41 mm for trawlers.

The trends in catch of shrimp in the coastal sectors of Nigeria and Cameroon are shown in Table 15. The decline in shrimp catch of the CRECAM shrimpers is matched by an increase in magnitude of finfish landed. During the early seventies shrimpers landed small quantities of finfish whereas today shrimp comprise less than 10% of the catch of shrimpers (see Table 11). The data shown in Table 14 have been applied to a global production model to determine the MSY for the combined coastal sectors of Cameroon and Nigeria. The Fox and Schaefer models give a maximum combined potential of 3 600 t for this sector in 1978 (FAO, 1979a). The correlation coefficient (r) for both models is not high (only 0.69). The results should be verified when more CPUE data are available. The combined shrimp catches were 2 000, 4 000 and 3 100 t in 1980, 1982 and 1984 respectively. The results of the analysis are shown in Figure 8.

There are differences in surface areas of the muddy biotopes of Penaeus notialis between Nigeria and Cameroon. The muddy biotopes of Nigeria are about 7 times greater than those of Cameroon (Burukowski and Bulanenkov, 1969). Hence, the pink shrimp stocks in Nigeria should be greater than those of Cameroon. If densities were similar and effort evenly distributed, the shrimp catch from the Cameroonian shelf should be about 13% of the total for the combined Nigerian-Cameroonian sector. In 1982, Cameroon shrimpers landed about 570 t of shrimp whereas the catch for the entire Cameroonian-Nigerian sector was about 4 100 t (i.e., 13–14%). The shrimp catch trends given in Table 15 appear realistic. The maximum yield potential for Penaeus notialis and Parapenaeopsis atlantica for Cameroon could therefore be between 500 and 1 000 t/year.

Data on exact catches of white shrimp (Palaemon) are not available, but it is known that at Mabeta fishing village (10 km from Limbé) about 120 artisanal fishermen using conical small-meshed nets caught about 1 500 t of Palaemon in 1984.