Canadian Journal of Fisheries and Aquatic Sciences, Ahead of Print.
Salmonids frequently adapt their feeding and movement strategies to cope with seasonally fluctuating stream environments. Oncorhynchus mykiss tend to drift-forage in higher velocity habitat than other salmonids, yet their presence in streams with seasonally low velocity and drift suggests behavioral flexibility. We combined 3D videogrammetry with measurements of invertebrate drift and stream hydraulics to investigate the drivers of O. mykiss foraging mode and movement during the seasonal recession in a California stream. From May to July (2016), foraging movement rate increased as prey concentration and velocity declined; however, movement decreased in August as pools became low and still. In May, 80% of O. mykiss were drift-foraging, while by July, over 70% used search or benthic-foraging modes. Velocity and riffle crest depth were significant predictors of foraging mode, while drift concentration was a poor univariate predictor. However, top-ranked additive models included both hydraulic variables and drift concentration. A drift-foraging bioenergetic model was a poor predictor of foraging mode. We suggest that infall and benthic prey, as well as risk aversion, may influence late-summer foraging decisions.

中文翻译：

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随着水流和无脊椎动物漂移在加利福尼亚溪流中退去，Oncorhynchus mykiss 的觅食模式和运动

加拿大渔业和水产科学杂志，提前印刷。
鲑鱼经常调整它们的进食和运动策略，以应对季节性波动的河流环境。Oncorhynchus mykiss 倾向于在比其他鲑鱼更高速度的栖息地漂流觅食，但它们在季节性低流速和漂流的溪流中的存在表明行为的灵活性。我们将 3D 视频测量与无脊椎动物漂移和溪流水力学的测量相结合，以研究加利福尼亚溪流季节性衰退期间 O. mykiss 觅食模式和运动的驱动因素。5-7月（2016年），随着猎物浓度和速度的下降，觅食运动速度增加；然而，由于水池变低且静止，8 月份的移动量减少。5 月，80% 的 O. mykiss 是漂流觅食，而到 7 月，超过 70% 使用搜索或底栖觅食模式。速度和沟嵴深度是觅食模式的重要预测因子，而漂移浓度是一个较差的单变量预测因子。然而，排名靠前的附加模型包括水力变量和漂移浓度。漂移觅食生物能模型对觅食模式的预测较差。我们认为落入和底栖猎物以及风险规避可能会影响夏末的觅食决定。