A study on age, growth, reproduction, and diet of Leuciscus vorax (Heckel, 1843) in Al-Diwaniya River, middle of Iraq

In this study, age, growth, sex ratio, size at first sexual maturity, gonad development (GSI) and food habit of Leuciscus vorax (Heckel, 1843) in Al-Diwaniya River, middle of Iraq were described between November 2016 and October 2017. L. vorax constituted about 6.4% % of the fish assemblage. The total length of all individuals ranged from 10.2 to 55.5 cm, the length-weight relationship was calculated as W= 0.007L 3.035 and isometric growth was observed. The mean value of the relative condition factor was 0.98. von Bertalanffy growth parameters were L∞= 61.0 cm, K= 0.227 and t0= -0.196 years. The growth performance index (Φ) was found to be 2.93. The overall male to female ratio was 1:1.51. Length at maturity was 29 cm for males and 31 cm for females. The maximum gonado-somatic index was in January then dropped dramatically for both sex, suggest that the species may spawn in February. The feeding intensity and feeding activity were low during winter and high during summer. The species is a carnivore fed mainly on fish, shrimps, aquatic insects, and crustacean. In conclusion, it is found that the population of L. vorax reflects the expected and previously observed features of the species in natural waters, but it is necessary to activate the national law of fishing, exploiting and protecting aquatic resources to continuation the fish populations in the river as an economic resource.