1849), and known to be omnivorous (New et al., 2010). Spawning occurs in spring and summer when males appear with a hard shell and females with a soft one mate (Wakefield, 2015). The temperature has an important influence on reproduction. Morphologically, there are differences between males and females. Mature males are larger than females (Bacheler, 2013). M.nipponense was first observed in AnzaliLagoon in 2006, and later on spread in northern Iran's water basins (Coad, 2016). Prawn and shrimp of the genus Macrobrachium and Penaeus are highly appreciated in the whole world. Becaus e of ARTICLE INFO

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Traps and pots are widely used in fisheries worldwide because of their simple structure and convenient operation. However, many factors affect the catch rate of traps, and the most crucial factor is the trap entrance (Li et al., 2006). The entrance number, shape, size, and location significantly affect the catch. For example, Matuda et al. (1984) reported that catch rates were affected by the diameter of the entrance ring. Furevik and Lokkeborg (1994) found that pots with a narrow entrance tended to trap more Atlantic cod and cusk than pots with wider entrances. Side entrance traps are better suited than top-entrance traps for catching prawns and American lobster (Kessler, 1969).

This study estimates growth parameters, length-frequency growth performance index, longevity, and total mortality of the oriental river prawn, Macrobrachium nipponense, from Anzali lagoon, Iran. The von Bertalanffy growth parameters were, L∞ = 8.65 cm, K = 0.82 yr -1 , and t 0 = -0.146 yr -1 . The growth performance index, Ф', was 1.78. Total mortality, Z, from the linearised length-converted catch curve was 4.89 yr -1. Natural mortality M calculated from Pauly's empirical formula was 2.1 yr -1, and fishing mortality F calculated from Z -M was 2.74 yr -1. The exploitation ratio E calculated from F/Z was 0.57. The longevity was about 3 yrs. Length-frequency showed no significant difference between the two sexes (p>0.05). According to the results of this study, it seems that the Anzali lagoon has a suitable environment for the life and growth of M. nipponense.

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