The Biology of Pellonula leonensis Boulenger, 1916 (Osteichthyes: Clupeidae) in Anambra River, Nigeria
The biology of the commercially important clupeid, Pellonula leonensis, was studied from May 1998 to March 1999 in the Anambra river. In the atalla fishery of this river, the clupeid was the dominant species in terms of number and weight. Total length (TL) ranged from 3.4 to 8.5 cm and weight from 0.3 to 4.6 g; males were not longer or heavier than females. The mean exponent (b = 2.66) of the length-weight relationships of 12 populations indicated negative allometric function. Mean monthly Fulton's condition (K) was not dependent on season. There was little variability in the mean monthly gonadosomatic index (GSI) and breeding occurred throughout the year. Maturity occurred earlier in males than females; 50% of both sexes matured at 4.7 cm TL. Fecundity ranged from 126 to 1580 oocytes (mean 896 ± 477 oocytes). Total length was a better predictor of fecundity than ovary weight. Index of food significance (IFS) showed that Insecta (51:67%) was the dominant food group, followed by Algae (15.66%) and plant detritus (8.02%). Food items of primary importance were Ephemeroptera nymphs, Chironomidae, unidentified insects, fish, Microcystis, plant detritus and sand grains. Food richness and diet breadth were dependent on season.
Key Words: Pellonula, Leonensis, Anambra River
Bio-Research Vol.1(2) 2003: 33-50
HMG Ezenwaji, FN Offiah