Some reproductive characteristics of Lates stappersII in the Southern part of lake Tanganyika, Zambia

Abstract

The following aspects of reproduction of Laics siappcrsii caught in the /amhian sector of Lake Tanganyika were studied: stages of maturity and spawning season: sixes at maturity: sex ratios and fecundity. Fish samples were collected from Septemher. 1999 to February. 2000 This study shows that, the mean gonado-somatic index (GSI) increases from stage I (immature or inactive) to stage IV (ripe-running) in both sexes, and then drops for stage V for females, as a result of release of sexual products. Monthly evolution of proportions of stages of maturity and mean (iSI indicate that spanning was taking place mainly between December. 1999 and February. 2000. The estimated si/es at maturity arc 21.68cm "IT. for males and 24.89cm IT for females and the maturity ranges were 7.68 cm and 11,7'Ocm respectively. The overall sex ratio of 53% females: 47% males for Laics siappcrsii in the /.amhian waters of Lake Tanganyika is not significantly different from the theoretical one. i.e. 50% females: 50% males. This parameter exhibits significant differences among sexes in Januan and February. 2000. and for length classes larger than 32 cm. where females are predominant. Fecundity in Line* siupperxii must be high because of small eggs. Partial fecundiu ranges from 46 000 to 839 000 eggs per fish (average 273 OOOeggs). Relative partial fecundity varies from 441 to 1685 eggs * g-1 o f f i s h (average 914 eggs * g-1 of fish). Lxponenual functions fit better the relationships between total length and partial fecundity (R2 - 0.861). and between body weight and partial fecundity (R2 ~ 0.857). A linear association exists between partial fecundity and gonad weight (R2 - 0.993). There is no correlation between fish sizes (i.e. total length and body weight) and relative partial fecundity. Key words: Laics \iuppersii. /ambian waters of lake Tanganyika, spawning season, si/e at maturity, sex ratios, fecundilv.