BIOMETRIC INDICES AND REPRODUCTIVE PARAMETERS OF Chrysichthys nigrodigitatus AND Lates niloticus IN IKERE GORGE RESERVOIR, ISEYIN, NIGERIA

Abstract

C. nigrodigitatus and Lates niloticus are commercially important fish in Ikere Gorge Reservoir. Knowledge of
the reproductive biology of fish species is necessary for evaluation of the reproductive potential. Length and
weight measurements can give information on the stock composition, life span, growth and production.
Therefore, this study was conducted to determine the length-weight relationship, growth pattern and some
reproductive features of C nigrodigitatus and L. niloticus in Ikere Gorge Reservoir for the sustainable
exploitation of these fisheries resources. The length-weight relation analyses for C. nigrodigitatus had b value
of 2.45 and for L. niloticus, b = 3.34 indicating a negative allometric growth pattern for C. nigrodigitatus and
an isometric growth pattern for L. niloticus since b value was not significantly different from 3. The Fulton’s
condition factor for C. nigrodigitatus was 1.56 + 0.34 and 1.62 + 0.29 for L. niloticus, thus studied species
were in good condition in the reservoir. Gonadosomatic index was significantly higher in females for C.
nigrodigitatus (1.84 ± 3.32) and L. niloticus (1.77 ± 2.62), and dropped during the rainy season months
suggesting spawning occurs at this period. The mean hepatosomatic index for C. nigrodigitatus and L. niloticus
was 1.59+1.22 and 0.94+0.69, respectively. The absolute fecundity for C. nigrodigitatus (total length of 15.5cm – 33.2cm and body weight of 33.0g -260.3g) ranged from 695 eggs – 9253 eggs and for L. niloticus (total length
of 15.60cm – 47.20cm and body weight of 35.0g -1065.90g) was 493 eggs – 28000 eggs. The absolute fecundity
for the two species is more correlated to length than weight.