Variations in sturgeon populations in the coastal waters of the Caspian Sea (Guilan province)

The present study was conducted from autumn 2003 to summer 2005 with the objective to estimate distribution and relative abundance in different species of sturgeons as a function of seasons, and regions in the west coast of the Caspian Sea (Guilan province).Gillnets with a different mesh sizes (26, 33, 40, 60, 100, and 150 mm) were set up at different depths(2, 5, and 10 m) for 24 h. Data on variations in catch, catch per unit effort(CPUE) and length and age composition of sturgeon species were analyzed statistically. Data on CPUE in each region and depth and mean estimates of length and age in fish were reported for each season and each year of the study period. CPUE during 2004-2005 was 1.32 fish which was 30.1% lower than CPUE (1.89 fish) recorded in 2003-2004.CPUE for all species except A. nudiventris decreased during 2004-2005 as compared to that in 2003-2004. Acipenser persicus caught during 2003-2004 and 2004-2005 ranged from 15 to 45 cm in length and comprised 91.1 and 97.1% respectively of the total sturgeon catch. These fish belonged to the one year age class. Mean length recorded in sturgeon fish caught in 2004-2005 decreased as compared to that recorded in 2003-2004. Significant differences were recorded in total length of fish caught in 2003-2004 and 2004-2005. Results obtained from the present study reveal that the abundance of fish increased from west to east indicating a direct relationship between the general currents found in the Caspian Sea and the higher density of nutrients in the eastern region.

Iranian Fisheries Science Research Institute

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