Food habits of introduced brown trout and native masu salmon are influenced by seasonal and locational prey availability |
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Authors: | Koh Hasegawa Chitose Yamazaki Tamihisa Ohta Kazumasa Ohkuma |
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Institution: | 1. Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Nakanoshima, Toyohira, Sapporo, Hokkaido, 062-0922, Japan 2. Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita, Sapporo, Hokkaido, 060-0810, Japan 3. Tomakomai Experimental Forest, Hokkaido University, Takaoka, Tomakomai, Hokkaido, 053-0035, Japan
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Abstract: | A knowledge of food habits is important for evaluating interspecific competition and predation between sympatric species. Data on food availability should be combined with data on food habits in this type of survey. Although food availability differs between habitats or seasons, these differences had never been considered in previous studies. We conducted year-round field surveys throughout a stream to compare the food habits of an introduced salmonid, brown trout Salmo trutta, and a native salmonid, masu salmon Oncorhynchus masou. Masu salmon did not constitute a large proportion of the diet of brown trout and vice versa. Thus, predation will likely not affect the population level of either species. The dietary overlap between brown trout and masu salmon varied depending on the presence of Gammaridae and terrestrial invertebrates; i.e., the intensity of interspecific competition for food resources may differ according to food conditions. |
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