The blue tilapia, Oreochromis aureus is an invasive species that has successfully established itself in most of the Iraqi waters. However, there is little information on the population dynamics of the species in these waters. Hence, the growth parameters, mortality rates, probability of capture, recruitment pattern and yield per recruit of blue tilapia in Garmat Ali River, Iraq was assessed using FiSAT II software. A total of 1664 blue tilapia fish were collected by different fishing gears from October 2019 to September 2020 for recording the relevant data. The length-weight relationship obtained was W=0.0147*L3.0748 for fish ranging from 7.5 to 26.3 cm total length suggesting that the species shows positive allometric growth. The asymptotic length (L∞), growth constant (K), theoretical age at zero-length (t0), growth performance index (Ø') and longevity (tmax) were 29.9 cm, 0.205, -1.293, 2.345 and 10.7 years, respectively. The total mortality (Z), natural (M), fishing (F) and exploitation (E) were 1.09, 0.61, 0.48 and 0.43, respectively. Length at first capture (L50) was found to be 13.92 cm. The main recruitment pulse was from March to July with a peak in April, which account for 18.4% of the total recruitment in the year. The relative yield per recruit analysis revealed that the present exploitation rate (Epresent) for blue tilapia was below than the biological target reference points (E0.1 and Emax), which denotes that this stock was not over-exploited. For management purposes, higher yields can be achieved by reducing the mesh sizes of the nets during fishing.

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

Cichlid species invaded the Iraqi waters in the mid-2000s and are now dominant fish species. The present study was carried out to investigate the age and growth of two cichlid species, Oreochromis niloticus and O. aureus in Garmat Ali River, Iraq from October 2019 to September 2020. A total of 2707 specimens of O. niloticus ranging from 7.0 to 25.5 cm and 1664 of O. aureus varying from 7.0 to 26.3 cm were examined which were captured by various fishing gears. The length-frequency distributions revealed that fish lengths (13.0-18.0 cm) formed 64.1% of the total catch of O. niloticus and 67.2% of O. aureus. The length-weight relationships were W=0.012*L3.109 for O. niloticusand W=0.015*L3.075 for O. aureus, and both species indicated positive allometric growth. The highest values of the relative condition factor were obtained during spring and the values decrease when length of two species increase. Seven age groups were determined for O. niloticus: 9.9, 12.9, 15.6, 17.9, 19.4, 20.4 and 22.2 cm, and for O. aureus: 9.3, 12.5, 15.2, 18.0, 19.4, 21.3 and 22.2 cm. The theoretical maximum length (L∞) was 29.2 cm for O. niloticus and 28.6 cmfor O. aureus. These results can assist in fisheries management and conservation of the fish species in Iraqi waters.