The biomass of shrimps at sea, and consequently the catch rate and catches, depends highly on the annual recruitment, since the fishery mainly depends on a single age class. This recruitment affects juveniles coming from lagoons; it is thus influenced by the intensity of the artisanal fishery during their lagoon-to-sea migration. An increase in catches in lagoon will be followed by a decline of catches at sea. Studies made in the Ivory Coast (Garcia, 1977) using simulation techniques on a Ricker’s model, showed that, for exploitation levels close to the maximum yield, a variation of the exploitation rate in lagoon from 0 to 50 percent had little effect on the total catch (sea + lagoon). If this observation can be generalized, the overall potential of the region could be calculated at a first approach by adding up the potential at sea to the catch in lagoon. Unfortunately statistics of artisanal catch of juveniles are practically nonexistent. The state of the statistical information on the lagoon fishery can be summarized as follows:
- Ivory Coast: estimated catches from 1955 to 1966. From 1967 onwards, 75 percent of the catches are known accurately and 25 percent of the catches are estimated (Table 2). In 1976 and 1977, the catches amounted to 630 and 620 tons.The overall potential (sea + lagoon) of the whole of the sector, could therefore reach 8 000 tons or so.- Ghana: fragmentary and incomplete data for the 1970/71 period.
- Togo: no information.
- Benin: according to Crosnier and De Bondy (1967), the yield of lakes Nokoué and Ahémé amounted to 320 tons in 1967. Recent information indicates that 933 tons were caught in 1974, 967 tons in 1975 and 105 tons in 1976. This recent fall is thought to be the consequence of the closure of certain processing plants.
- Nigeria: the artisanal fishery is estimated at 250 tons for the Lagos sector (Obakin 1969) and at 500 tons for the whole of the lagoon system (FAO, 1969); this figure is quoted here with reservation because the method of estimation is not known.
- Cameroon: no data, although the artisanal fishery may be important there.
- Equatorial Guinea: no information.
- Gabon, Congo, Angola: no artisanal fishery. Total catches throughout the region are supposed to reach 2 000 tons without Cameroon and Togo. If these values are correct, the order of magnitude of total catch is believed to be 3 000 tons.
