Biological and environmental aspects of tilapia (Oreochromis niloticus) in the Jatibarang Reservoir, Central Java

Abstract

Tilapia (Oreochromis niloticus) is an invasive fish species in Indonesia. A study on biological aspects is expected to be used as an assessment to implement fisheries mitigation, restoration, and enhancement. This study aimed to analyze the environmental conditions, biological aspects of the sex ratio, total length-weight relationship, maturity stages, and tilapia fecundity in the Jatibarang Reservoir. Fish samples were collected four times in July-October 2020 using gill nets (mesh size of 3 inches). The sampling sites were 2 stations located in Jatibarang Reservoir. Environmental parameters were measured, including water temperature, pH, and dissolved oxygen. Fish were measured for total length, weighed for gonads, and total weight. Water temperature, pH, and dissolved oxygen ranged from 28.0-31.9 oC, 6.41-6.70, and 6.04-7.39 mg/l, respectively. The sex ratio of tilapia was 1:1.9 (females: males). Total length ranged from 95 to 349 mm, and total weight ranged from 13 to 798 g. The growth pattern of tilapia was positive allometric. The condition factor of male and female fish was 0.94-1.16 and 0.95-1.21, respectively. 36.8% of the female fishes were ripe stage (IV), and 65.8% of the male fishes were immature stage (I). The fecundity ranged from 28 to 7,852 eggs.