LENGTH-WEIGHT RELATIONSHIP, CONDITION FACTOR AND SEX RATIO OF TWO FRESHWATER FISHES IN OVIA RIVER

ABSTRACT

This study estimated the sex ratio, length-weight relationship and condition factor of two freshwater fishes’ species, Chrysichthys nigrodigitatus (Lecepede, 1803) and Mormyrus rume (Cuvier and Valenciennes, 1846) from Ovia River Edo State, Nigeria. Fish were collected on monthly basis by local fishermen using diversified fishing gears, such as, beach seine net, gillnets, cast net, hook and lines and hand lines from June to August, 2019. Specimens were stored in coolers containing ice and transported to the laboratory for analysis. Total length and weight were measured using standard methods. A total of 13 fishes made up of 11 C. nigrodigitatus (5 males and 6 females), 2 M. rume (2 males) were examined. The parameters ‘a’ and ‘b’ were determined from the linear regression of the logarithm of length and weight of the fish when transformed into the growth equation, W= aL^b. The Chrysichthys nigrodigitatusvalues for ‘b’ are 3.6658, 2.0433 and 7.9005 for males, female and combined sex indicating that the males showed positive allometric growth pattern while the females showed negative allometric growth pattern.Mormyrus rume had a ‘b’ value of 0.8749 indicating negative allometric growth pattern. The condition factor for the male, female and combine sex (1.6608, 1.0685 and 1.0430) in C. nigrodigitatus and male (0.5675) in M. rume indicating that the fishes are in good condition. The population of Chrysichthys nigrodigitatus had a sex ratio of 1:1.2 and Mormyrus rume 1:0 which were not significantly different from the 1:1 expected distribution. Finally, the results obtained should be useful for the sustainable management of these freshwater fish species in Ovia River and other waterbodies.