Evaluation of the Necessity of Fishway Structures in the Design of Mared Dam and Shipping Locks (Abadan) on the Reproductive Migration Path of Tenualosa ilisha

This study was conducted to investigate the presence and passage of marine upstream fish in the up-water of Karun River in order to investigate the necessity of constructing a fish passage in the Mard dam structure. In Bahmanshir and Arvandrud Rivers the only and most important marine migratory fish that needs to migrate and presence at up-waters for reproduction and offspring survival is T. ilisha. River fish sampling was done using gill net and local fisher man. Among different reported fish, from physiological point of view, only T. ilisha needs to presence along the Bahmanshir, Arvandrud and Karun rivers from the estuary to upstream. Given the high impact of T. ilisha on livelihoods and the preservation of nutritional health of a large number of local and indigenous inhabitants of these rivers, the conservation of these fish stocks as well as the maintenance of river structures to support its reproductive migration from ecological, social and economic perspective of the region is very important. Thus, the authors consider the construction of a fish way as essential for the dam and shipping lock of the Mared structure. Based on the design prepared for the dam and Shipping Lock of the Mard structure, it appears that the dam structure itself have some parts that can be used as fish paths. Under normal conditions of water regime, during the year, side valves in the shipping lock with open water sea level could provide enough volume and velocity of water to stimulate swimming in T. ilisha as fishing path in Mared dam structure.