~ 555 ~ International Journal of Fisheries and Aquatic Studies 2019; 7(5): 555-561 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 5.62 (GIF) Impact Factor: 0.549 IJFAS 2019; 7(5): 555-561 © 2019 IJFAS www.fisheriesjournal.com Received: 20-07-2019 Accepted: 22-08-2019 Assefa Tessema Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia Abebe Getahun Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia Seyoum Mengistou Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia Tadesse Fetahi Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia Eshete Dejen Intergovernmental Authority on Development (IGAD), Senior Fisheries Expert, Ethiopia Correspondence Assefa Tessema Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia Length -weight relationship, condition factor and some reproductive aspects of Nile tilapia (Oreochromis niloticus) in Lake Hayq, Ethiopia Assefa Tessema, Abebe Getahun, Seyoum Mengistou, Tadesse Fetahi and Eshete Dejen 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. Keywords: Gonadosomatic index, length at first maturity, total length, total weight, sex ratio Introduction Fish is used as source of cheap protein source in most of African countries. Small-scale fisheries operating mostly in the developing countries accounts half of the total fish production globally. The contribution of inland catches in Africa covers about 25% of global inland catches [1] However, the production of fish has drastically decreased and catches per unit of effort (CPUE) have become low in natural water bodies [2] [3] . The major factors for reduction in production of fishes in Africa are, postharvest loss, illegal fishing and overfishing [4] . Nile tilapia fish species, one of the most important fish species in tropical and subtropical freshwater bodies in Africa are also faced many challenges, illegal fishing (overfishing, fishing during breeding season and ground, fishing with narrow sized mesh size and destruction habitat) [5]. Ethiopia has many lakes and rivers harboring more than 200 fish species [6] . The fish production potential is estimated to 94,500 tons per year in Ethiopia [7]. However, only 30-38% of this potential is currently used [8] . Though the contribution of fishery for GDP is insignificant, the sector is being used as means of livelihoods for many people involved from production to marketing. Artisanal freshwater fishery is one of the most important economic activities in Ethiopia [9] . Improvements in fishery sector would contribute to poverty alleviation and environmental sustainability in Ethiopia [10] Nile tilapia (Oreochromis niloticus) contributes for more than 50% of the total landings in Ethiopia [7] . Oreochromis niloticus is widely found in Rift valley lakes such as Abaya, Chamo etc.