Growth, reproduction and food habit of an invasive species of Carassius auratus in the Al-Diwaniya River, Middle of Iraq

Abstract

Carassius auratus is an invasive species that has successfully established populations throughout Iraq. Unfortunately there is no information available regarding the biological properties of the species in Al-Diwaniya River, Middle Euphrates, Iraq. So growth, reproduction and food habit of C. auratus were investigated in this river from November 2016 to October 2017. Length groups of the fishes from 19 to 21cm were prevailing the catch and formed 30.8%. Length-weight relationship was calculated as W= 0.013L 3.129 for all individuals, with allometric growth. The condition of the fish increased in early spring. The maximum age recorded was 5 years with 30.1 cm. The parameters to the von Bertalanffy growth curve fitted to mean total lengths at age were L?= 43.0, K= 0.225 and to= - 0.412. The index of growth performance (?) was 2.612. The unbalanced overall ratio of males to females was 1:3.81. Higher values of gonado-somatic index (GSI) for males and females occurred in early spring. C. auratus is an herbivorous, with a diet that includes algae (52.6%), macrophytes (22.0%), diatoms (15.8%), crustacean (4.8%) and aquatic insects (4.8%). Our results highlighted basic biological aspects of the invasive C. auratus which can assist in fisheries management and conservation of the fish species in Al-Diwaniya river.