Comparison of Length and Weight Characteristics of O. niloticus and O. aureus from Garmat Ali River, Iraq

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.