Changes in cpue by species from the national fleets of Sierra Leone and Ivory Coast in Sierra Leone were reviewed (Appendixes 4,8,9). There is an interesting anomaly, for the apparent abundance of species of grey fish (Longhurst's sciaenid community) seems to have increased in recent years. The increase is abrupt in the Sierra Leone fleet yields, but appears more regular in the Ivorian fleet yields (Fig. 1). The concordance of the two series indicates a true phenomenon. The reasons for this could depend on:
increased fishing pressure on this community (increase of catchability) due to shifting of the effort towards the coast. The phenomenon might be linked to the recent increase in value for this fish making it more profitable to harvest. Should this be the case, the increase resulting from fishing-related mortality should lead, in the medium term, to younger catches: so monitoring of mesh sizes and sizes landed should be accentuated;
fewer size-related discards for economic reasons without modification of distribution of effort. In this case, the average individual size of captures should also drop;
a real increase of the biomass, catches increasing with no change in sizes caught.
Fontana noticed a similar phenomena in Cameroon during the same period which was clearly related to shrimpers moving closer inshore for economic reasons. It may be that this reorientation is in the process of becoming a general phenomenon, following the stagnation of shrimp yields and the present, very high exploitation levels (Garcia and Lhomme, 1979).
Should this hypothesis be confirmed, special attention must be devoted to the protection of nurseries, monitoring of mesh sizes and sizes landed in order to prevent destruction of juveniles.
