The working group noted with satisfaction the progress made in statistical data collection. However, problems of separation of species still remain, notably between the two sardinella species in the Ivorian industrial fishery as well as in the artisanal fisheries. In all the countries, except Ghana, substantial amounts of Sardinella rouxi were included in the statistics of S. maderensis.
Nominal effort and the potential of the fishery for the main fisheries of Ghana, Côte d'Ivoire, Benin and Togo are shown in Tables 1 and 2 (effective effort not available).
4.1.1 Potential of the fishery
The available data show different evolutions, since 1986–87, according to the type of fishery.
the number of industrial units was stable in Côte d'Ivoire and increased in Ghana where the number of semi-industrial units, on the other hand, experienced a substantial decrease between 1988 and 1989.
the total strength of the artisanal fishery decreased everywhere, except for the beach-seines in Ghana.
4.1.2 Fishing effort
In Ghana: past years have shown that the number of trips in the semi-industrial fisheries seem to be independent of the number of fishing. units. In 1987, for example, the number of trips was reduced compared to 1986, because the high temperatures registered at the port discouraged the captains from putting out to sea. In 1988 and 1989, this number increased. Regarding the artisanal fisheries, the number of trips decreased in 1988 and reduced in 1989. There was an inverse trend for the beach-seines.
A reduction in the mesh sizes of the watsa net, bringing its characteristics close to those of the poli net (except for the size of twine), was noted.
In Côte d'Ivoire, the effort of the industrial fishery has increased since 1985, and in 1989 attained a level which had never been observed since 1979. The absence of data or the estimated characteristics of the artisanal fishery did not permit the provision of exact figures. The departure of numerous canoes in 1988 which had returned home (to Ghana) to be fitted for line fishing on rocky grounds was noted. This trend which disengaged the sardinella fishery, at least partially, was maintained in 1989 and 1990.
Benin/Togo: the number of trips of the purse-seiners and sardinella crafts decreased after the record level of 1987. For the beach-seines, the situation was similar to that in Ghana.
Sardinella aurita
The total catches of this species remained higher than that at the beginning of the decade and were close to the record of 1985 (Table 3); the collapse anticipated by the 1987 working group did not take place. On the contrary the phenomenon of compensation in annual catches among the different fisheries in the region was noted. Even though a reduction was observed in almost all the fisheries since 1987, the spectacular increase of catches of the Ghanaian artisanal fishery made up the deficit registered in all the fisheries together (Figure 7a).
In Côte d'Ivoire, the scientists of CRO explained the clear reduction in catches in 1988 by the non-availability of the species during the first five months of the year. From the month of June, the upwelling settled and the second half of the year is considered normal for the industrial fishery. It would have been the same for the artisanal fishery had there not been the problem of fuel supplies during the last quarter of the year, which grounded part of the fleet.
In 1989, the upwelling was average, resulting again in average availability of the round sardinellas. The catches of the industrial fleet therefore remained at the level of 1988 and those of the artisanal fleet reduced considerably; the problem of supply of fuel had worsened.
In Ghana, the same phenomenon had led to low catches during the first five months of 1988. The resource then became available and abundant during a very short period, to the east of Takoradi. The abundance in the other sectors remained very low. The very mobile canoe fishery was able to take advantage of this concentration and caught in two months (August and September), a large part of the annual catch (a similar phenomenon had taken place in 1972). For the industrial fishery, the low level of catches in 1988 could be explained by the limited range of operation of the vessels based at Tema which did not permit the exploitation of the area of concentration of the resource.
In 1989, there was a concentration of fish in the Central and Greater Accra sectors and the industrial fishery was able to take advantage of it this time, resulting in a good fishing year. The artisanal fishery was not able to participate in the exploitation as much as in the preceding year, nevertheless the catches were very good. The different gears of the artisanal fisheries (ali, poli and watsa) were separated during the 1989 census, but the catches remained combined in the statistics.
In Benin, a reduction in catches between 1987 and 1988 and an increase in 1989 were observed. The catches depended greatly on the availability of the species to the beach-seines which fish mainly juveniles, a large number for a small weight.
In Togo, after the outstanding Figures of 1984–86, the catches were low in 1987 and 1988, and increased in 1989.
Sardinella maderensis
With a total of 20 000 t in 1988, the catches returned to a level comparable to those of 1980–84, after the high values of 1985–87 (Table 4 and Figure 7b).
In 1989, the catches in the area were estimated at about 26 000 t, an increase of 30% over those for 1988. This increase was observed in all four countries and was comparable to similar observation for 1982–83, but the bulk of the recent increase cames from Ivorian catches.
Scomber japonicus
After the large variation of catches observed between 1985 and 1987 (with a peak in 1986), catches increased continuously during the last three years (Table 5 and Figure 7c). It was essentially the Ghanaian artisanal fishery which contributed to the global catch in the region. It is noted that in Benin only a few individuals were observed in the catches.
Engraulis encrasicolus
Total catches attained unprecedented levels since 1987, due mainly to large Ghanaian catches (Table 6 and Figure 7d). No other explanation could be given at this stage. There is no doubt about the underestimation of the Ivorian artisanal catches of this species: indeed, the beach-seines alone operating in the Jacqueville region would have caught about 3 000 t of anchovies. As for Togo, the beach-seine figures were not available.
Total catches for all the countries and all gears
Apart from the four principal species, the catches of which have been commented on above, there exists an entire group of fish species belonging to the category of coastal small pelagics, fished in a varying fashion according to area and year. The taxonomic list of these species is giving in Annex 5.
For certain recent years (1981–86) it was possible to estimate almost exactly the total weight of these species (Table 9). The contribution of these species raises the total pelagic catches in the area to around 260 000 t in 1986, and an estimated total of 200 000–250 000 t/year in the last years.
The catch per unit of nominal effort was the only abundance index available. This has two main defects:
the effect of gears: it is very difficult to distinguis between the part of the effort which is aimed, for example, at Sardinella aurita rather than S. maderensis, although it is suspected that certain mobile fleets can make such a choice. This, for example, is the case with the fleet of big Ghanaian canoes which carry the ali/poli/watsa nets.
the effect of the environment: it is clear that there exists a strong environmental component linked inter alia to the upwelling which, affects the availability of the fish. This has a major effect on the CPUE.
Consequently, the CPUE in Tables 7 and 8 are only nominal CPUE and they should be interpreted as indices of abundance with caution. Only the CPUE of the two sardinella species were examined by the working group.
Sardinella aurita (Figures 8a, Table 7)
In Ghana, the indices of abundance of 1988 showed a clear contrast between the semi-industrial and the canoe fisheries using ali/poli/watsa nets. Even though the CPUE of the two types of exploitation evolved together as far as 1987, they oppose each other in 1988. It is equally surprising that the yields of the Ghanaian purse-seiners decreased to a new level equivalent to that observed in 1973 (the year of collapse of the catches of this species) even though the CPUE of the canoes were the best observed since 1972. The scientists of FRUB attributed this to the exceptional availability of the resource concentrated in the Central Region which only canoes could exploit. In recent years, the CPUES of the beach-seines have increased but are still lower than the exceptional values of 1986.
In Côte d'Ivoire, after the very high values in 1985–87, the CPUE of industrial purse-seiners decreased to new levels similar to those of 1982–84. The CPUE of the artisanal gears seemed to have followed a similar evolution.
In Benin, a certain alternation in the CPUE of purse-seines and the beach-seines in 1986–89 was noted; when one gear gave good yields, the other recorded nearly nil yields.
Sardinella maderensis (Figure 8b and Table 8)
In Ghana the yields of purse-seiners increased in 1987 but attained very low levels in 1988 and 1989. The CPUE of the Ghanaian poli/ali nets followed an evolution relatively similar to those of the purse-seiners during the last three years, with very low values. The index of recruitment provided by the Ghanaian beach-seines was also at the lowest values registered since 1972 (Figure 10).
In Côte d'Ivoire, the CPUE of purse-seiners, which decreased from 1985 to 1988, stabilized in 1989.
In total (all gears, all countries), the CPUE of S. maderensis experienced a decline in 1988 then recovered in 1989 to previous mean levels. The apparent abundance of the species in the area as a whole, therefore appeared to be average.
