Morphometry and Natural Diets of Distichodus engycephalus from Middle Basin of Ogun River, Southwest Nigeria

Morphometry, natural diets, length-weight parameters and condition factor of Distichodus engycephalus in middle basin of River Ogun, Southwest Nigeria were investigated. One hundred and fourteen fish were sampled; consisting of eighty-seven males and twenty-seven females. Stomach contents were analyzed, morphometric and meristic characters were also measured. The analyses of data were based on sexes and combined population using descriptive, regression and correlation statistics. Student t-test was employed to detect significant difference (alpha=0.05) between the mean characters of the sexes. Results showed that D. engycephalus is an herbivore; feeding mostly on Oscillatoria (45.6%), Microspora (43.9%) and Protococcus (43.9) by occurrence method. Numerically, the diets composed of Oscillatoria (40.0%), Phormidium (18.3%) and Microcystis (10.3%). The mean total length, weight and condition factor for both sexes were 24.9 +/- 0.64 cm, 204.6 +/- 16.02 g and 1.09 +/- 0.01, respectively. Student t-test statistics revealed that means of the investigated characters were significantly higher (p<0.05) in female fish except depth of caudal peduncle (DCP) and number of pelvic rays (PVR). However, no significant difference (p>0.05) was detected in the condition factor between the sexes. Observed sex ratio for male: female fish was 1:0.31. The 'b' values of length-weight relationship analysis were 2.90 for male, 2.97 (female) and 0.92 (both sexes) which were not significantly different (p>0.05) from 3; indicating isometric growth pattern. Conclusively, D. engycephalus in the middle basin of Ogun River is herbivorous and grows isometrically.