Industrial fishery at sea
Little is known about the fishery at sea. Until 1967 this was nonexistent. Trawlers from Cotonou searched only for fish and hardly fished on P. duorarum grounds.
Off, Benin, from 15 to 35 m, there exists a wide belt of rough sand surrounded with sandy mud or rocks parallel to the coastline and more and less muddy bottoms off the coast. The belt of rough sand is practically azoic and most trawlers fish on the sandy-mud grounds stretching close to the coastline, ignoring the muddy grounds situated toward 50 m on which P. duorarum dwells more particularly, as shown by the survey cruise of the RV Ombango, a vessel of ORSTOM of Pointe Noire (Crosnier and De Bondy, 1967). The catch rates obtained by the RV Ombango on these grounds with a fish trawl of 20 m headline could reach 20 kg/h, which suggested interesting fishing possibilities, at least in some seasons. The total area of these grounds (about 160 mi2) would indicate that the total industrial catches in Dahomey could not exceed 300 to 400 t.
In 1973, out of 32 boats fishing from Cotonou, 23 were shrimp trawlers. Landings made in Cotonou reached 440 t in 1973 and 502 t in 1974, then diminished between 1975 and 1976. The major part of these catches originated certainly from the fishing grounds off Nigeria. From November 1970 to December 1971, a few Ivorian shrimp boats fished in Benin. The catch rates obtained are summarized in the table below:
Table 6.1
CATCH-RATES (IN kg/h, HEADS-OFF) OBTAINED IN BENIN BY IVORIAN SHRIMP BOATS
|
|
1970 |
1971 |
|
January |
- |
5.0 |
|
February |
- |
5.7 |
|
March |
- |
5.1 |
|
April |
- |
- |
|
May |
- |
- |
|
June |
- |
- |
|
July |
- |
- |
|
August |
- |
- |
|
September |
- |
- |
|
October |
- |
10.5 |
|
November |
7.1 |
9.0 |
|
December |
6.7 |
3.1 |
The catches of P. duorarum account for over 97 percent of the shrimp landings, almost all of which originate from lagoons or lakes (Crosnier and De Bondy, 1967). The fishery is carried out in Lakes Nokoué and Ahémé and, more incidentally, in the Porto Novo, Ouidah and Grand Popo lagoons, with small trawls dragged by two men or with stakenets. Besides nets, pots are also very much in use. The fishing season usually extends from January to July, when the waters are brackish, but it can extend until September. It is practically over in October, November and December, when the water salinity is usually very low. The yield of Lake Ahémé was 120 t in 1966, that of Lake Nokoué 150 t. In 1967 the catches from Lake Nokoué could reach 200 t.
