Length-Weight Relationship and Growth Parameters of Grey Mullets (Pisces: Mugilidae) in Two Estuaries in Ghana

Abstract

Grey mullet populations in the rivers Pra and Volta estuaries in Ghana were studied to provide information on their length-weight relationship and growth parameters. Fish samples were collected monthly for 18 months from local fishermen using cast net, drag net and gill nets. Six species of grey mullets were identified: sickle fin mullet, Liza falcipinnis (Valenciennes, 1836), large-scaled mullet, Liza grandisquamis (Valenciennes, 1836), grooved mullet, Liza dumerilii (Steindachner, 1870), white mullet, Mugil curema Vallenciennes, 1836, banana mullet, Mugil bananensis (Pellegrin, 1928) and striped mullet, Mugil cephalus Linnaeus, 1758. Length-weight relationship for the various species in the Volta and Pra estuaries, respectively, were: L. falcipinnis, BW = 0.0158 SL3.06 and BW = 0.0255 SL2.85; L dumerillii, BW = 0098 SL3.24 and BW = 0.0223SL2.92; M. bananensis, BW = 0.0191SL3.03 and BW = 0.0175 SL3.10; M. cephalus, BW = 0.0574 SL3.14 and BW = 0.0134 SL3.17; M. curema, BW = 0.0311 SL2.85 and BW = 0.0247 SL2.5. That for L. grandisquamis, which was found only in the Pra estuary, was BW = 0.0204 SL3.01, indicating isometric growth since the regression coefficient b was not significantly different from 3.0 (P > 0.05). The regression coefficient b for the other species was either significantly higher or lower than 3.0 (P < 0.01), suggesting allometric growth. Except L. dumerilli, L¥ and K for the same species from the two estuaries differed. The highest L¥ of 56.6 cm (SL) and growth performance index (∅) of 4.99 were estimated for M. cephalus. The L¥ estimated in the study indicates that the sizes of grey mullets in the two estuaries were smaller compared to the same species from other countries in the tropics.