139736eo.pdf (20MB) - Japan Oceanographic Data Center

Table 3. Seasonal variations in standing stocks of demersal fish at Ras Fartak withdepth (tons km-2).DeDth in m, _October ADril August10-20 1.3 0.6 8.230-50 6.0 0.8 2.180- 100 1.2 0.9 1 .o100-120 0.9 10.3 0.6PELAGIC FISH STOCKSEpipelagic StocksThese have mainly been assessed with integrated echo-sounding from RN Dr. F. Nansen(STROMME, 1984) with an assessment of the stocks of oil sardine, Sardineffa fongiceps, given bySANDERS and BOUHLEL (1984). Figure 18 shows the distributions of the stocks in March andAugust, 1984.In March concentrations of pelagic fish were found to the west and east of Aden, west andeast of Mukalla and around Ras Fartak. The oil sardine was identified around Aden and at Mukalla,extending east to Ras Fartak. The scads, Trachurus indicus and Decapterus russefli, were found atAden and Ras Fartak. A further concentration of sardines to the east of Ras Fartak, suggested inANON (1981), was located in August. During the August upwelling, the pelagic stocks appeared tohave migrated offshore along the eastern part of the coast, although the ship did not go close to shore.A large concentration was found to the south of Mukalla, with another one south of Ras Fartak. Theformer contained Sardineffa fongiceps and Scomber japonicus (chub mackerel), while the latter wasmainly chub mackerel. Around Ras Fartak were scads, Trachurus indicus.The fish in the offshore area south of Mukalla had ripe gonads and were in spawningcondition. A stock estimate given by STROMME (1984) was 290 x 103 tons for the entire coast, butthe area west of Aden was not surveyed. The previous estimate was 376-495 x lo3 tons for 1975/76.A stock of pelagic fish not covered by these surveys was the Indian mackerel, Rastreffigerkanagurta, which occur around Aden and supports a large seasonal fishery. Further, the considerablestocks of Spanish mackerel, Scomberomorus commerson, which are fished between Aden andMukalla, probably were underestimated since they avoid ships. Resident in the western waters arestocks of bonito tuna, Euthynnus afinis, while in the east are mainly skipjack, Katsuwanus pelamis.In about April through June the larger yellowfin tuna, Thunnus afbacares, appears off Mukalla andsupports a fishery. SANDERS and BOUHLEL (1984) calculated the stocks of Sardineffa fongicepsbetween Mukalla and Ras Fartak as 32 x 103 tons after upwelling in October.From these various estimates of pelagic fish stocks it is likely that the estimate of STROMME(1984) may be more applicable to the total stocks at the present time, which may be of the order of300 x 103 tons. However, sufficient data to divide this stock into constituent species are not available.Mesopelagic StocksThese stocks, composed mainly of myctophid fish (with Benthosema pterotum as dominantspecies), have been studied from the R/V Dr. F. Nansen and reported by SANDERS and BOUHLEL(1982) and GJOSAETER (1984). These fish are of small size but have a fast growth, reaching 4 cm268