Seasonality and size distribution of the grey mullet, Mugil cephalus (Linnaeus) in a tropical lagoon, South-West Nigeria

Abstract

Seasonal occurrence and length-frequency distribution of the grey mullet, Mugil cephalus from the Lagos Lagoon were investigated for 24 months (February 2004–January 2006). The salinity, the principal hydro-meteorological force operating in the lagoon ranged from 0.0 to 23.5‰ (mean: 9.8+ 9.13‰). The size of the 2661 specimens of M. cephalus ranged from 1.7 – 29.5 cm standard length (total length: 1.9 to 39.0 cm) and weight ranged from 0.02 to 450.00 g indicating the suitability of the lagoon as nursery and feeding ground for the species. Small-sized fish predominated the collection during the rainy season; medium-sized fish were available throughout the period of collection, while large-sized fish were less abundant during the rainy season than during dry season. There were five age groups of the grey mullet in the Lagos Lagoon and were predominantly young or juvenile M. cephalus, the most abundant group being the 3-4 year class (12.5 – 13.4 cm size group) and the least group was the >4 year class (23.5–24.4 cm size group) It is suggested that the fishery for mullet species in the lagoon could be concentrated in the dry season when adult specimens are in abundance and allow for maximum sustainable yield of the species.

Keywords: Dry season, rainy season, size, stock assessment, M. cephalus