Establishment of the impact assessment method for elevated water temperature related to warming on benthic cold-water fish with poor swimming ability

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We examined the effects of eco-physiological stress due to elevated water temperature on survival, movements, and reproductive physiology of benthic cold-water fish (Cottus pollux spp.) with poor swimming ability both by field observations and experimental procedures. Instream obstructions substantially precluded going upstream of amphidromous (middle-egg type) and fluvial land-locked sculpins (large-egg types). Nesting behavior of small-egg type males were rarely observed under high water temperature condition (i.e., 4-5℃ warmer than river water). Together with the finding of lowest survival rates of the larvae of middle-egg type under highest water temperature condition (15 ℃), suggesting negative impacts on their reproductive activity and survival in early life stage. These findings are useful to estimate the negative impacts of elevated water temperature on eco-physiological aspects of Cottus pollux spp.