Morphometric relationships and relative condition factor of Synodontis eupterus (Boulenger) from River Rima in north-western Nigeria

Abstract

Samples of Synodontis eupterus (Boulenger) from River Rima in North-Western Nigeria were analysed for morphometric relationships and relative condition factor. A total of 1,610 samples of which 781 were females, 816 males and 13 with unidentified sex (giving a ratio of about 1:0.96 female: male) were examined between November 2005 and December 2008. Morphometric measurements were taken. The samples ranged in total length from 6.00 to 17.50 cm (mean=10.36±1.50cm) and total weight of 2.19 to 72.20g (mean=15.49±1.50g). The b values for the length-length relationships suggested negative allometry. The species exhibited positive allometric growth pattern based on all parameters (b>3) except in dry season, where b=2.917 (isometry). The species were in good condition in the river, with overall Kn of 2.06±0.08SD for females and 2.01±0.08SD for males. In both sexes, larger samples were in better condition (P<0.05) than small ones and samples of rainy season were in better condition (P<0.05) than those of dry season. Samples in stages III, IV, V and VI were in better condition (P<0.05) than those in the maturing and immature stages. The result of this study for S. eupterus in River Rima showed that increase in total length would lead to increase in length of all the other length variables in the length-length relationships; the growth pattern is positive allometry and that the species is in good condition in the river.