STOCK ASSESSMENT OF THE CASPIAN SEA IN KUTUM (RUTILUSFRISII KUTUM) IRANIAN COASTAL WATERS OF THE CASPIAN SEA

Caspian Kutum (Rutilusfrisii kutum) is one of the most important commercial bony fishes in Iranian coastal waters of the Caspian Sea that constitute more than 50% of the total annual catch of the bony fishes. In the fishing season of 2003-2004, 5 mobile working groups gathered biometry data in the regions Anzali, Kiashar, Noshahr, Babolsar and Torkmen.
Catch statistics of bony fishes was gained from fishing and landing harbors. Total catch of the commercial bony fishes was estimated at 15.5 thousand tons from which the Kutum amounted to 8477 tons, 45.5% of the total. Also, catch of the bony fishes of beach seine cooperatives was estimated at 10667 tons where the Caspian Kutum comprised 5180 tons (48.65%). The catch per unit effort (CPUE) of the Caspian Kutum amounted to 93.3 kg/set with the highest value recorded in Noshahr and the lowest amount observed in Anzali and Kiashahr regions. The mean fork length of the species was 36.7±6.1 cm showing a range of 21 to 69 cm. The meanage was measured as 3.82±1.37 years with the range of 1 to 8 years. The age groups 3, 4 and5 years old comprised 87% of the total catch age composition. Von Bertalanffy growth parameters such as L¥ k and t₀ were determined as 70.1cm, 0.138/year and -1.557 years, respectively. Total mortality, natural mortality and fishing mortality rates of the species were estimated at 1.1/year, 0.28/year and 0.83/year, respectively (considering a surface water Temperature of 14°C). The biomass of the fish was estimated at 25 thousand tons.