نوع مقاله : مقاله پژوهشی
1 کارشناس ارشد شیلات، انستیتوی تحقیقات بینالمللی ماهیان خاویاری دکتر دادمان، رشت، ایران
2 مؤسسة تحقیقات شیلات ایران، تهران، ایران
3 کارشناس شیلات، انستیتوی تحقیقات بینالمللی ماهیان خاویاری دکتر دادمان، رشت، ایران
عنوان مقاله [English]
This study carried out in the Iranian waters of the Caspian Sea during 2009-2010, and aimed to determine species composition, relative abundance, and absolute abundance estimated of biomass. Research vessels using 9 m bottom trawl for depths less than 10 m and 24.7 m bottom trawl for depths above 10 m. Trawling was conducted in 90 stations that were selected using a stratified random design. In each station, trawling carried out up to 30 minute and 2.5-3 knot. In 2009 and 2010, 84 and 28 sturgeon fish were caught, respectively. Persian sturgeon was more than 83 to 100 percent of the catch. The mean total length of Persian sturgeon was 61.9±28.7 cm (spring) and 40.5±27.9 cm (autumn) in 2009. This value was 54.7±23.5 cm and 60.2±17.7 cm for spring and summer in 2010, respectively. Absolute abundance of sturgeon was estimated 1.31 million fish in the Iranian waters of the Caspian Sea during spring but it increased to 3.46 million fish in autumn 2009. Absolute abundance in 2010 was 831100 and 779200 fishes in spring and summer 2010, respectively. Biomass of sturgeon fish was 2019.7 and 3014.3 tons in spring and autumn 2009, respectively. These values were estimated 760.6 tons (spring) and 855.0 tons (summer) for the year 2010. The results show that Iranian fisheries organization policy in production and releasing of fingerlings has been unable to prevent the loss sturgeon stocks. Therefore, it seems the only way to recover their stocks is rebuild natural spawning areas, nursery grounds and preservation of them up to they reach commercial size.