Study of Some Environmental and Reproductive Aspects of Some Fish Species in the Tigris River West of the City of Samarra, Salah Al-Din / Iraq

The study was conducted on the Tigris River in the Qalaa area, west of the city of Samarra, Salah al-Din/Iraq, for the period between October 2023 and March 2024, 117 fish were caught, with one catch per month. It has been observed that the higher sex ratio tends to favor females in Carasobarbus luteus, Luciobarbus xanthopterus, Carassius auratus, Leuciscus vorax, and Cyprinus carpio with ratios of 7.0:1, 5.0:1, 4.6:1, 3.5:1 and 3.0:1 respectively, while the lower percentage tends to favor females in Acantho brama marmid, C. macrostomum and Chondrostoma regium in the ratio of 1.8:1, 1.5:1 and 1.19:1, respectively. show the monthly changes in gonad (G.S.I) function for male and female fish (Chondrostoma regium, Carassius auratus and Carasobarbus luteus), (Acantho brama marmid, Leuciscus vorax and Luciobarbus Xanthopterus) and (C. macrostomum and Cyprinus carpio) respectively. The water temperature ranged between 10 and 22°C. The highest water temperature was in October and the lowest in February. The highest value of dissolved oxygen was 8.4 mg/L in March and the lowest value of dissolved oxygen was 6.5 mg/L in October. The highest turbidity value was 49 NTU 1 in December, and the lowest value 39.5 NTU was recorded in February.