Population Biology of Sbour Tenualosa ilisha (Hamilton-Buchanan) in Kuwait

Abstract

Tenualosa ilisha ( =H11sa ilisha), locally known as sbour, is one of the most important target species in the Kuwaiti drift-net fishery. Average annual landings in 1981--89 amounted to 152 t, and constituted about 2.5% of Kuwait's total commercial fish landing (6,000 t·year1 ). This study provides information on the biology, growth and mortality of T. ilisha in this fishery. Specimens of T. ilisha ranged in size from 14 to 57 cm, and in age from 1 to 5 years. The length-weight relationship was W = 0.011 L2·983 for males and W = 0.007 L3•104 for females. Von Bertalanffy growth equations estimated for both sexes from Gulland's {1964) and Allen's (1966) methods are Gulland: L1 = 52. 70 (l-e-0.28 It + 0.261) Allen: L, = 52.50 (l-e-0.36 11 + 0.0,1) The average total mortality (Z) was ca1culated to be 1.3 ± 0.1 (95% confidence limits) year1• Natural and fishing mortality were estimated to be 0.5 and 0.8 per year, respectively. Length at maturity (L5096) for females was estimated as 41.5 ± 3.5 cm (95% confidence limit). Seasonal changes in the ovarian weight of mature females were used to determine when the spawning season takes place through the relationship between ovary and carcass weight for February-July 1990. It was found that T. ilisha may spawn from May to July with a peak in June.