Length -weight relationship, condition factor and some reproductive aspects of Nile tilapia (Oreochromis niloticus) in Lake Hayq, Ethiopia

Abstract

The objectives of the study were to assess length-weight relationship, condition factor and reproductive potential of Nile tilapia (Oreochromis niloticus). Data (total length (TL), total weight (TW), sex ratio, maturity stages, fecundity and gonadosomatic index) were collected. The collected data were summarized using descriptive (percentage, graphs, tables) and Inferential (Chi-Square, Two Way ANOVA, Regression) statistics through application of SPSS 16 and R 3.31 Softwares. The length- weight relationship of both sexes was allometric. The FCF (Fulton Condition Factor) value was higher (1.85) for females than males (1.80). A total of 892 samples (339 female and 553 males) were collected during sampling period. There was significant deviation in sex ratio (Females: Males) from hypothetical 1:1 ratio (Chi-Square, P<0.05). The mean fecundity was 217 eggs/ fish and it was positively correlated with TL, TW and gonad weight. The size at first sexual maturity (L50) was 12.8 and 12.9 cm for females and males respectively. The gonadosomatic index was ranged from 0.3 - 0.7 and 1.3- 2.6 for males and females respectively. Nile tilapia breeding season was observed between February and April. The peak breeding season was observed in April. From the average weight (40 g) and L50 (nearly 13 cm for both sexes), we can conclude that Nile tilapia has stunt growth in Lake Hayq. Heavy fishing together with illegal fishing activities (narrow sized mesh size, <8 cm, below the National standard), fishing during breeding season and breeding ground, destruction of breeding and feeding ground are the major problems of Lake Hayq that might contribute for stunt growth of Nile tilapia in the lake. Therefore, appropriate fishery management tools such as closing season and ground, mesh size regulation should be implemented for sustainable fishery utilization in Lake Hayq.The objectives of the study were to assess length-weight relationship, condition factor and reproductive potential of Nile tilapia (Oreochromis niloticus). Data (total length (TL), total weight (TW), sex ratio, maturity stages, fecundity and gonadosomatic index) were collected. The collected data were summarized using descriptive (percentage, graphs, tables) and Inferential (Chi-Square, Two Way ANOVA, Regression) statistics through application of SPSS 16 and R 3.31 Softwares. The length- weight relationship of both sexes was allometric. The FCF (Fulton Condition Factor) value was higher (1.85) for females than males (1.80). A total of 892 samples (339 female and 553 males) were collected during sampling period. There was significant deviation in sex ratio (Females: Males) from hypothetical 1:1 ratio (Chi-Square, P<0.05). The mean fecundity was 217 eggs/ fish and it was positively correlated with TL, TW and gonad weight. The size at first sexual maturity (L50) was 12.8 and 12.9 cm for females and males respectively. The gonadosomatic index was ranged from 0.3 - 0.7 and 1.3- 2.6 for males and females respectively. Nile tilapia breeding season was observed between February and April. The peak breeding season was observed in April. From the average weight (40 g) and L50 (nearly 13 cm for both sexes), we can conclude that Nile tilapia has stunt growth in Lake Hayq. Heavy fishing together with illegal fishing activities (narrow sized mesh size, <8 cm, below the National standard), fishing during breeding season and breeding ground, destruction of breeding and feeding ground are the major problems of Lake Hayq that might contribute for stunt growth of Nile tilapia in the lake. Therefore, appropriate fishery management tools such as closing season and ground, mesh size regulation should be implemented for sustainable fishery utilization in Lake Hayq.