Aspects of the biology of the African lungfish, Protopterus annectens (owen, 1839) in orashi and Sombreiro Rivers, Rivers State, Nigeria

Abstract

Aspects of the biology of the African lungfish, Protopterus annectens (Owen, 1839) from Orashi and Sombreiro Rivers in Rivers State, Nigeria were investigated using routine biological approaches. Samples were collected between October 2012 and September 2013. The analysis of the stomach content showed that the fish from both rivers fed mainly on detritus, which accounted for 100% of the stomachs examined. Other food items included remains of higher plants, filamentous algae and diatoms. A sex ratio of 1:1 male: female was observed, although, females were more predominant than males during the greater part of the year, corresponding to rainy season. The proportion of males in the catch gradually increased as females reduced in number with the approach of the dry season. The GSI showed peak in the months of January, February and March. There was a decline from April to June as the fish had finished spawning. The monthly changes in GSI suggest that the fish had distinct period of maturity and breeding. The fish were found to be highly fecund. The individual/absolute fecundity ranged from 32,009 to 147,003 with a mean value of 6,653. Relative fecundity ranged from 362 to 529g^-1 body weight. The fecundity profile of P. annectens shows that the fish has a remarkable reproductive potential in the two Rivers.

Keywords: Detritus, gonado-somatic index, fecundity, Protopterus annectens