Growth, Mortality and Yield-per-recruit of Nile Tilapia (<em>Oreochromis niloticusM/em>) in Garmat Ali River, Iraq

Abstract

The study was conducted to estimate the growth, mortality, recruitment and yield-per-recruit of Oreochromis niloticus from Garmat Ali River, Basrah, Iraq from October 2019 to September 2020. The population parameters were analyzed using the FAO-ICLARM stock assessment tool (FiSAT). A total of 2696 O. niloticus ranged from 7.0 to 25.0 cm and the sizes 13.0-18.0 cm constituted 64.2% of the total catch. The length-weight relationship was W= 0.012L3.109 suggesting that the species shows positive allometric growth. The growth parameters for the species were estimated as L∞= 30.45 cm, K= 0.45, to= -0.313 and Ǿ= 2.622. The coefficients of total mortality (Z), natural mortality (M) and fishing mortality (F) were 3.26, 1.03 and 2.24, respectively. The exploitation rate for the species computed to be 0.69. Fish were recruited to the fishery at a mean size of L50= 14.92 cm. The peak of recruitment was 23.51% in June. The analysis of yield-per-recruit (Y/R’) indicates that stock is not being overfished since the present exploitation rate was below the biological target reference points (E0.1 and Emax). So, more yields could be achieved by reducing the mesh sizes of the nets for fishing the species

Assessment of two cichlids stocks with virtual population analysis in Garmat Ali River, Basrah, Iraq

“…Moreover, the result of the virtual population analysis (VPA) revealed that the majority of O. niloticus and O. aureus individuals were harvested at lengths 20 cm and 17 cm, respectively. Also, the estimated values for the length at first capture (L50) of O. niloticus and O. aureus in the same river (14.9 and 13.9 cm, respectively) [57,18] were greater than the lengths at first maturity (Lm) of O. aureus, 6.6-9.2 cm and O. niloticus, 7.0-8.0 cm [58,35]. The occurrence of such a situation suggests that individuals of the species get the chance to join the stock before becoming vulnerable to capture by the available fishing gear.…”