Studies on the aspect of the biology of Mochokidae in the lower Cross River, Akwa Ibom State, Nigeria

Abstract

Some aspects of the biology of Mochokidae in the artisanal fishers landings in the lower Cross River, Nigeria were studied between May and December, 2014. A total of 360 specimens comprising 3 genera and 14 species with 6-29.50 cm total length (mean: 12.80 cm TL) and 0.16-268.21 g total weight (mean: 30.65 g TW) were examined. The largest sample size was recorded in Synodontis schall (61 specimens; 16.94%) while Mochokus niloticus and S. clarias with one specimen (0.28%) were the least. The degree of effective contribution expressed as index of preponderance revealed that S. schall (33.63%) made the most significant contribution while S. waterlofti (0.06%) made the least contribution. Length-weight relationship showed that the growth pattern of the fishes were negatively allometric with the slope, b values ranges of 1.36 and 2.02 for Synodontis omias and S. waterlofti (P<0.05). Gut contents revealed that 11 food items were ingested (sediments, detritus, insect, algae, macrophytes, crustaceans, annelids, molluscs, nematodes and unidentified food); hence they were euryphagus. The present study revealed that Mochokidae is an omnivore-detritivore with highest body condition factor of  (1.46) for  S. obesus and lowest (0.96) for C. batesii; with mean K value of 1.23. This implies that could thrive better even when environmental factors are less favorable; hence, they are recommended for aquaculture.

Key words: Biology, body condition, gut contents, length-weight relationship, lower Cross River and Mochokidae.