Abstract
Information on the feeding habits of species is essential to develop appropriate conservation actions. This study aimed to assess spatial and temporal variation in the diet of the Eurasian otter, Lutra lutra in the Anzali Wetland, through fecal and stable isotope analysis. Seven main prey items were observed in the analysis of 300 fresh spraints. The highest feeding index was observed for fish, followed by snakes. Among the fish species consumed, the index of preponderance of Prussian carp (Carassius gibelio) was the highest followed by pike (Esox lucius) and white bream (Blicca bjoerkna). Results of Shannon diversity index suggest spatial variation of species diversity within and between feeding items (p < 0.05); snakes, frogs, and oriental river prawn (Macrobrachium nipponense) showed a seasonal variation. The otter’s trophic level (TL) (3.79) was higher than the TLs of other Anzali Wetland predators, such as pike. Bayesian mixing model showed source proportion contributions of fish 49.5%, reptiles 16.7%, insects 14.8%, crustacean 10.5%, amphibians 4.3%, birds 4.1%, and mollusks 0.1%. When considering only fish species in the Bayesian mixing model, Prussian carp was the main fish prey in the otters’ diet accounting for 47%. Based on the results of this study, the Eurasian otter plays an important role in the ecology of the Anzali Wetland ecosystem even though it preys on exotic species, such as the Prussian carp and the oriental river prawn.
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Acknowledgements
The authors would like to thank the Department of Environment (DOE) of Guilan Province and Japan International Cooperation Agency (JICA) for kindly sponsoring and financially supporting both projects; the first assessment of mammals’ fauna in the Anzali Wetland (under Grant number P15/136264); and diet survey and trophic position of Macrobrachium nipponense in the food web of Anzali Wetland (registered in AREEO under the code number 124-73-12-055-95034-950964). We are much grateful to all responsible persons of JICA, DOE and Inland Waters Aquaculture Research Center for logistics preparation of conditions for this research, and to Dr. Keivan Abbasi, Mr. Mostafa Sayadrhaim and Mr. Yaeghoob Rakhsh Bahar, for their cooperation in most of the field and laboratory surveys.
Funding
This work was supported by "Japan International Cooperation Agency (JICA)" (Grant number P15/136264, and the Department of Environment (DOE) of Guilan Province (registered in AREEO under the code number 124-73-12-055-95034-950964). Saeid Naderi has received the first research support, and Alireza Mirzajani has received the second one. The authors have no conflicts of interest to declare that are relevant to the content of this article. All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript. The authors have no financial or proprietary interests in any material discussed in this article. Authors are responsible for correctness of the statements provided in the manuscript.
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Mirzajani, A., Naderi, S., Ganeh, A. et al. Trophic flexibility of Eurasian otter (Lutra lutra) in Anzali Wetland, Iran, assessed by fecal and stable isotope analysis. Aquat Ecol 55, 401–415 (2021). https://doi.org/10.1007/s10452-021-09832-x
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DOI: https://doi.org/10.1007/s10452-021-09832-x