STUDIES ON THE GROWTH-PATTERN, FEEDING-HABITS AND REPRODUCTIVE CHARACTERISTICS OF THE MORMYRID BRIENOMYRUS-LONGIANALIS (BOULENGER 1901) IN THE UPPER WARRI RIVER, NIGERIA

Some aspects of the biology of the mormyrid, Brienomyrus longianalis ( Boulenger 1901) in the upper Warri River at Abraka inland are discusse d. Fish were captured in the river throughout the flood period (May-De cember) with peak abundance in September. The largest specimen obtaine d measured 12.1 cm standard length and weighed 10.0 g. The length/weig ht relationship indicated allometric growth, and the mean monthly cond ition factor (k) values ranged from 1.13 to 2.98. Generally, k values increased with length of fish irrespective of sex and were higher in m ales. Females were more numerous than males. Fecundity estimates range d from 417 to 2252 eggs and were weakly correlated with female length and body weight. Spawning occurs in July during the rising flood. The Gonadosomatic Index values ranged from 0.8 to 4.79%. B. longianalis wa s basically a bottom feeder with a diet consisting principally of Chir onomus and Chaoborus larvae. Plant remains and seeds were also importa nt food. In addition, periodic emerging insects were utilized as food. No distinct qualitative variations occurred in the feeding habits in relation to size.