Abundance, spawning season and type of Gattan (Barbus xanthopterus Heckel, 1843) in south of Karkheh River and Hour-Al-Azim marsh (Khuzestan Province)

In this study 401 specimens of Gattan (Barbus xanthopterus) caught by drifting and set gillnets, cast nets and forks were studied. Samples were collected monthly (October 1996 to September 1997) from Hamidieh Dam to Hour-Al-Azim Lagoon. Morphometric and meristic parameters and biological characteristics were studied in the laboratory. The Highest frequency of Gattan in the river was in March and in Hour-Al-Azim was in December. The length range of the fish in the river was broader than in the hour, and fishes with lengths more than 700mm were only observed in the river. Sharp decrease in GSI in May and occurence of spawning in May and June showed that reproduction of this species occurs in spring (in a two month period) and is relatively short. Minimum and maximum ova diameter were 0.01mm and 2.25mmin stages II and IV of gonad maturity respectively. An increasing trend in ova diameter up to April and decreasing in June showed one time spawning of this species. Surface water tempera....