Population, growth pattern and biometric characteristics of the bonga, Ethmalosa fimbriata (Bowdich) from marine, brackish and freshwaters of South-Western Nigeria

Abstract

The length-frequency distribution, length-weight relationship, condition factor and biometric features of Ethmalosa fimbriata (Bowdich) from Lagos coastal waters, Lagos Lagoon and Lekki Lagoon were investigated for 6 months (January-June). The major fishing methods employed for the collection of the specimens were cast-netting and gill-netting (mesh size 67 mm and 76 mm). The standard lengths ranged from 15.6 to 26.1 cm for the marine specimens; 3.5 to 15.3 cm for the brackish and 7.2 to 11.3 cm for the freshwater. The total body weights ranged from 97.7 to 540.0 g for the marine specimens; 3.6 to 77.8 g for the brackish water specimens and 5.00 to 19.85 g for the freshwater specimens. The fish exhibited positive allometric growth pattern in the marine, while the value of b was negative in the brackish and isometric in the freshwater specimens. The mean condition factors were 2.55, 1.82 and 1.88 in the marine, brackish and freshwaters respectively. There was a slight increase in the condition factor with increasing size of fish in the marine, while a decrease in K-value with increasing size of fish in the brackish and freshwaters occurred. There was an increase in the values of the morphometric and meristic features which were not statistically significant (p > 0.05) from the freshwater to the brackish and marine waters.

Keywords: Ethmalosa fimbriata, Lagos Coast, Lagoon, Lekki, morphometric, meristic

The Zoologist, 10:6-12 (2012)