Diet Survey and Trophic Position of Macrobrachium nipponense in the Food Web of Anzali Wetland

The oriental river shrimp ( Macrobrachium nipponense ), an exotic species, has been well adapted and dispersed in Iranian freshwater ecosystems. The feeding ecology and trophic level of this species in the Anzali Wetland, southwestern Caspian Sea, was investigated by both a traditional method and the carbon and nitrogen stable isotope technique. The highest feeding index (FI) was seen in mollusca at 35.9%, followed by detritus at 31.3%. While no significant differences were observed in the preference of food items among different seasons. A Bayesian mixing model was used to estimate the contributions of the stomach contents to the isotopic signature of M. nipponense . According to mixing model results, M. nipponense obtain food from gastropod, fish, shrimp (as cannibalism), insecta, other crustacea, aquatic plants, worms, zooplankton, and unrecognizable content (as detritus) with 30.6%, 16.8%, 12.7%, 5.2%, 4.3%, 3.5%, 0.6%, 0.3%, and 25.9%, respectively. M. nipponense showed a high δ 15 N and its trophic level (TL = 3.38) was at the top of the Anzali Wetland food web, close to commercially important fish species such as pike, Esox Lucius. Being at this trophic level, this shrimp is expected to possess high nutritional quality for human consumption.