Growth, mortality, age composition and fisheries yields of fish from the Gulf of Aden

Tropical fish were collected by trawling in Yemeni waters. Age determinations were made on sections of vertebrae which were cross checked with scales. The values for the von Bertalanffy growth constants K were in the range 0.08–0.31. Total mortalities (Z) calculated from age compositions were in the range 0.31 to 0.67 for 11 species. The mean of 0.46 agreed closely with that derived from the formula of Pauly (1980a) of 0.45. Since the former included fishing mortality (F) in addition to natural mortality (M) it was suggested that a lower value be used in the Gulland (1968) yield formula: Y = 0.5 M Bo. Recruitment to the fishery for most species occurred by 3 years of age. The demersal fish stocks in Yemeni waters may not exceed 109×103 tonnes at the present time. Using a value for M of 0.3, the annual sustainable yield may be in the region of 16×103 tonnes.