Dynamics in the length-weight parameters of the mudskipperPeriophthalmus barbarus (Gobiidae), in Imo River estuary, Nigeria

Seasonal and intersexual dynamics in parameters of the length-weight relationship of the mudskipperPeriophthalmus barbarus, from Imo River estuary, Nigeria, were studied. The proportionality constant or intercept (a) was aseasonal in males, but in females it was significantly higher in the dry season (November–April) than during the rains (May–October) due to heightened breeding activity. The length exponent (b) depicted seasonal isometry in males. In females, isometry was evident in the dry season while a positive allometry occurred during the wet season. The sizes of the smallest and largest specimens examined did not regulate variations in the magnitudes of (a) and (b) in both sexes. The insignificant intersexual variation in the length-weight parameters suggests the possibility of using a single predictive length-weight equation for the population. However, the sexes exhibited different monthly rank-orders of (a) and (b), thus making such composite estimates unreliable for a study spanning up to a year. Values of (a) and (b) were inversely correlated in both sexes. The population dynamics implications of the results are discussed.