An analysis of available data on region-wide inshore demersal stocks (0-50 m) shows this sector to be fished close to, but generally somewhat below, the average maximum potential yield. Stocks in the deeper layer (50-120 m), instead, are thought to be lightly fished. The most accurate data we have for Ivory Coast and Congo suggest that the present catch could be more than doubled, at least in biological terms.
The reason why exploitation rates are thought to have stabilized at levels below the possible mean maximum is because yields are low due to the fact that fishing stops being profitable for the fishery as a whole short of reaching the potential maximum. This is particularly clear in the case of the deeper part of the shelf (50-120 m) which is only fished on a seasonal basis and for the continental slope (+ 120 m) which is not fished at all.
Data is too inaccurate and scanty, except for Ivory Coast (and Ghana, to a lesser extent), to be able to assess potentials. Nonetheless, the following orders of magnitude can be retained:
|
|
0-50 m |
50-120 m |
|
Ivory Coast |
5 300 |
5 5001/ |
|
Ghana, Togo, Benin |
(15 000) |
(5 000)1/ |
|
Nigeria, Cameroon, Equatorial Guinea |
(22 000-30 000) |
(7 500)1/ |
|
Gabon, Congo, Cabinda, Zaire |
(20 000-25 000)2/ |
(20 000-25 000)1/ 2/ |
|
Total (approximate) |
60 000-75 000 t |
38 000-43 000 t1/ |
1/ Biological potentials, now very partially feasible (2/5 in Ivory Coast) for reasons of economicsThere was not enough available data to make a comparison of the productivities of the different sectors. Nonetheless, the figures for the Ivorien sector - 0.9 and 1.1 t/km2 for the coastal strip with or without Balistes, and 0.4 or 0.7 t/km2 (with 0.2 t now being landed) for the offshore sector (50-120 m) - do seem indicative of an order of magnitude of the fishery potential of the region. The figure of 1.3 t/km2 was obtained for hard bottom communities off Ghana where the productivity of grounds more than 50 m deep seems to drop off less sharply than elsewhere. We found many examples which showed that maximum sustainable yield could in fact fluctuate considerably according to the distribution of effort exerted for the different species and the use made of those species of lesser economic appeal.2/ Sixty percent of the Gabonese fishing grounds are untrawlable: the theoretical potential yield can be achieved to the extent that other types of gear (lines, traps, trammels, etc.) can be successfully put into operation
Region-wide, the GTS findings clearly show that biomass densities vary parallel to the productivity of the ocean. The Gulf of Guinea, properly speaking, is clearly poorer than the areas north of Cape Verde and south of the Congo River (Figure 8). Also, inside the Gulf, the potential of the Ivory Coast-Ghana-Togo-Benin sector and of the Gabon-Congo-Cabinda sector, which enjoy seasonal upwelling, seem clearly superior to those sectors which do not, such as southern Sierra Leone-Liberia and Nigeria-Cameroon-Equatorial Guinea-northern Gabon.
In summary, the generally poor level of marine productivity and the narrowness of the continental shelf explain the low figures for the preliminary estimates of regional potential given in the above table.
The swift bloom of Balistes stocks in several areas of the shelf (Guinea, Gabon) does not appear to have affected the overall productivity of grounds occupied by these stocks. One result has been that the potential of those stocks conventionally fished and preferred have fallen off in proportion to the rise of Balistes - about one-third for Ivory Coast.
