Length-Weight Relationship, Fulton’s Condition Factor and Sex Ratio of Nile Perch (Lates niloticus, Linnaeus- 1762) in Lake Abaya, Ethiopia

Abstract

The length-weight relationship of fish is an important fishery management tool. The objectives of the study were to determine the length-weight relationship, Fulton’s condition factor and the sex ratio of Lates niloticus in Lake Abaya. Total length (TL), total weight (TW), and sex data were collected from 755 fish samples (377 females and 378 males) for one year (January to December 2021) from the commercial fishery of Lake Abaya. The collected data were summarized by using descriptive statistics and analyzed with the application of Microsoft Excel 2010 and SPSS software. There was no significant deviation in sex ratio (M: F) from hypothetical 1:1 ratio (χ2= 0.00; P > 0.05). The length-weight relationship was calculated using power function and obtained as TW = 0.0077*TL^3.1176, (R²= 0.8834), TW = 0.0078*TL^3.1372, (R²= 0.8548) and TW =0.0098*TL^3.0723, (R²= 0.8713) forfemales, males and combined sexes, respectively. The regression coefficient “b” was significantly different from the cubic value “3” (P<0.05) and implied that L. niloticus of Lake Abaya follows a positive allometric growth pattern. The one-way ANOVA (P > 0.05) revealed that Fulton’s condition factor between sexes was insignificant but highly significant by month’s interaction (ANOVA, P < 0.05). The t-test also revealed a highly significant difference in a month’s interaction (t-test, P = 0.000) indicating the seasonal variation in the mean monthly condition factor. The average value of Fulton’s condition factor was higher than one and indicates that L. niloticus in Lake Abaya was in good health condition. The present study was focused only on L. niloticus and recommends that similar studies including feeding and reproductive biology should be conducted to determine the status of other fish species in Lake Abaya.