Aspects of the Biology of African Moony, Monodactylus sebae from Badagry Creek, Lagos, Nigeria.

Abstract

The present study investigates some aspects of the biology of African Moony, Monodactylus sebae (Cuvier 1831) from Badagry Creek, Lagos, Nigeria. Diurnal fish collections were carried out from the creek between May 2012 and April 2013. Fish were caught with cast (mesh size: 12-22 mm) and gill nets (mesh size: 18-45 mm). Specimens were preserved in 10% formaldehyde. Data on total length (L) and body weight (W) measurements were obtained from standard measuring board and Sartorius weighing balance respectively. The length frequency distribution was determined from Petersen’s method, the growth coefficient parameters ‘a’ and ‘b’ of length-weight relationship (LWR) was obtained from the equation: W= aL^b, and condition factor from the expression: K= 100W/L³. Sexes were differentiated by macro and microscopically examinations of the gonads after making slit from the vent to operculum region of the fish. Ratio of numbers of males to females were determined from equation: ?² = (O-E)²/E. A total 267 individuals were from the Creek, the specimens measured from 56-163 (111.16±19.30) mm TL, and weighed between 5.6 and 151.7 (44.80±24.46)g body weight. The LWR was LogW = -1.444 + 2.918 LogL, K varied from 2.04-6.25 (3.00±0.56). Sex ratio was 1 male:1.17 female. The findings show that the species exhibited a negative allometric growth (b=2.918) in the creek, the value which was within the expected range of 2-4 recommended for normal growth of tropical fish. The K factor was higher in females than males while the sex ratio was insignificantly different (P>0.05) from the expected or theoretical 1male:1female ratio (X²_cal=1.66 < X² _{tab(n=1, ?=0.05)}=3.84).

Key words: Allometric growth, Condition factor, Length-weight relationship, Monodactylidae, Sexual differentiation.