Population structure and dynamics of River Oriental Prawn (Macrobrachium nipponense) in three wetlands (Alagol, Almagol and Ajigol) of Golestan province-northern Iran

Understanding the demographic characteristics of non-native species is very important for species and habitat management. The population structure and dynamics structure of river oriental prawn (Macrobrachium nipponense) were studied in three wetlands (Alma Gol, Alagol and Ajigol) of Golestan province, where the species is considered exotic species. A total of 6539 samples were collected and their biometric data recorded, the maximum total length of specimens ranged 90 -100mm. In this range, 4 age groups (0+,1+,2+and 3+) were identified. The growth parameters, obtained using von Bertalanffys growth function and Somer seasonal growth equation, were as L∞= 108 and 91 mm, K = 0.96/year and 0.98/year for males and females respectively. The lowest mortality rate was observed in age 1. The mean normal mortality rate for males and females was estimated to be M = 1.17 and M = 1.24, respectively. Total mortality rate, based on the length-converted catch curves equation, was estimated to be Z = 1.17 for males and Z = 1.17 for females. The total length at the first sexual maturity was estimated to be 46.9 mm for females and 52 mm for males. The optimum length for females was 64 mm, and for males was 76.8.