Population dynamics and the risk of stock extinction of Persian sturgeon (Acipenser persicus Borodin) in the Caspian Sea
Persian sturgeon, Acipenser persicus Borodin, has been the most significant proportion of Iranian commercial sturgeon catches in the Caspian Sea over in the last three decades. This endemic species has suffered continuous population declines from the impact of anthropogenic factors. The present study filled in information gaps on underlying population biology parameters, evaluated the population status, and determined the vulnerability risk of the stock extinction of Persian sturgeon in the south Caspian basin of Iran. Growth parameters were L∞ = 224.7 cm, K = 0.058 years-1, t0 = -3.4 years. Sexual maturity of 50% for males and females was FL = 127.2 cm and 137.5 cm, respectively. The long-term age composition data showed 35 age groups, and the ages of 14–18 years comprised 80% of the total catch. Natural mortality was 0.123 years-1, and fishing mortality ranged between 0.104 and 0.331 years-1. The total biomass trend decreased and collapsed from 6,071.3 tons in 1990–91 to 144.1 tons in 2014–15. Although >93% of the catch included maturing specimens, the Persian sturgeon stock is now critically endangered because of several anthropogenic factors.