Gill length-volume relation of cichlids (Sarotherodon melanotheron) in two Ghanaian lagoons

In sub-Sahara African nations like Ghana, Sarotherodon melanotheron is steadily gaining attention as an alternative to the popularly over-burdened cultured cichlid species Oreochromis niloticus for animal protein. We investigated the relation between gill length and gill volume as well as the relation between some morphometric parameters of the S. melanotheron inhabiting Benya (an open lagoon) and Fosu (closed lagoon) lagoons in Central Ghana. All relations were positively correlated, with the strongest correlation occurring between body weight and standard length. We also describe a “Five-Step Approach to Extracting Gill from Cichlids”. Analysis of morphometric parameters indicated that the S. melanotheron populations from Fosu lagoon were generally bigger (15.35 g, S.E. = 0.42) than those from Benya lagoon (9.54 g, S.E. = 0.64), although very big size fish were absent in the former, coupled with significantly wider size distribution from probability plots for length (AD = 8.471; p < 0.005) and weight (AD = 18.877; p < 0.005) for the latter. Mean condition indices were 3.39 and 3.51 for Fosu and Benya Lagoons respectively. Gill length and volume (GL – GV) relation had a fairly strong association and was better defined by the expression GV (mL) = 0.1596GL (cm) 1.4599 (R2 = 0.45) for the Benya population, GV (mL) = 0.1401GL (cm) 2.0521 (R² = 0.3343) for the Fosu population.