Status and seasonal dynamics in the fecundity of Bostrychus africanus (Pisces: Eleotridae) in an Estuarine Swamp of South-Eastern Nigeria

Abstract

Fecundity status and seasonality of the sleeper fish, Bostrychus africanus in the estuarine mangrove swamp of Qua Iboe River, Nigeria, was investigated between January and December, 2004. Average absolute fecundity was 16, 098 eggs (range 3 800 – 38 850 eggs), for sleepers with size range 8.5 cm – 15.7 cm TL and weighing 8.661 – 53.679 g TW. Fecundity increased with lengths (total, standard and ovary) and weights (total, somatic, ovary and egg) but decreased only with increasing individual egg weight. The coefficients of determination between egg production and independent variables revealed that total length (r²=82.4%) was the most stable morphometric tool explaining the variation in fecundity of B. africanus. The seasonal regimes showed that mean egg production was 17 724 eggs (range 3 800 – 31 850 eggs) for eleotrid of size range 8.5 cm – 12.9 cm TL and weighing 8.907 – 29.667 g TW in the dry season; and 14 608 eggs (range 6 400 – 38 850 eggs) for fish with size range 8.6 cm – 15.7 cm TL weighing 8.661 – 53.679 g TW during the rains. The seasonality in the coefficients of variation for each fecundity index and reproductive investment indicated that, egg production varied more widely with 9 correlates in the dry season than 3 during the wet months; a pointer to a heightened egg production by B. africanus in the latter vis-à-vis the former season.

Keywords: Sleeper, B. africanus; Eleotridae; fecundity dynamics; Qua Iboe River estuary, Nigeria.