The entrainment of fish in irrigation canals has long been a management concern in western North America. In north‐central Montana, United States, the presumed but unexamined entrainment of the “threatened” bull trout (Salvelinus confluentus Suckley) in the St. Mary Canal was considered a major impediment to the species' Federal Endangered Species Act recovery. Between April and September, 2002–2006, we systematically netted fish entrained at four canal gates. Among the total 9,981 fish caught during 21,064 net hours, 207 were bull trout mainly 120–200 mm total length (91%) and age 2 (60%) or age 3 (38%). Because catch per unit sampling effort was small and positive values few, the data were pooled among years. Monte Carlo simulation was used to estimate entrainment within months, hours of the day, and individual nets, as well as total annual entrainment. Bull trout entrainment was lowest during daylight and highest during darkness. Seasonally, entrainment was highest in spring, lowest in summer, and of moderate size in early fall. We estimated 140–274 (95% prediction bounds) bull trout were entrained annually under current canal operations; a 90% reduction in that entrainment if there were no April–May operations; and an 80% reduction if operations were limited to daylight hours. That final result suggested bull trout entrainment may be reduced by operation of non‐physical barriers (e.g., artificial illumination of the river) near the canal gates at night. Our approach provided a tool that could be used to reduce bull trout entrainment while potentially meeting water‐delivery needs.

中文翻译：

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每年在美国蒙大拿州圣玛丽河上的主要灌溉渠中夹带的斗牛鳟鱼的数量和特征，并确定可以减少损失的经营变化

长期以来，在北美西部，将鱼带入灌溉渠一直是管理上的问题。在美国蒙大拿州中北部，“受威胁的”鳟鱼（Salvelinus confluentus）的推测但未经检验的夹带圣玛丽运河的萨克利（Suckley）被认为是该物种《联邦濒危物种法》恢复的主要障碍。在2002–2006年4月至9月之间，我们系统地在四个运河闸门处捕捞了鱼。在21,064个净小时内捕获的9,981条鱼中，有207条是鳟鱼，主要是120-200毫米长（91％）和2岁（60％）或3岁（38％）。因为每单位采样工作量的捕获量很小，而正值很少，所以这些数据是按年汇总的。蒙特卡洛模拟用于估计几个月，一天中的小时，一天中的小时和单个网的夹带情况以及年度总夹带情况。白天，鳟鱼的夹带率最低，而在黑暗中的夹带率最高。从季节上讲，春季的入学率最高，夏季最低，秋季初有中等水平。我们估计，根据目前的运河运营情况，每年约有140–274（预测界限的95％）的鳟鱼被夹带。如果没有4月至5月的手术，则减少90％的夹带；如果操作仅限于白天，则可减少80％。最终结果表明，夜间通过在运河闸口附近使用非物理性屏障（例如，河道的人工照明）可以减少牛鳟的夹带。我们的方法提供了一种工具，可用于减少夹带红鳟鱼，同时潜在地满足供水需求。最终结果表明，夜间通过在运河闸口附近使用非物理性屏障（例如，河道的人工照明）可以减少牛鳟的夹带。我们的方法提供了一种工具，可用于减少夹带红鳟鱼，同时潜在地满足供水需求。最终结果表明，夜间通过在运河闸口附近使用非物理性屏障（例如河道的人工照明）可以减少牛鳟的夹带。我们的方法提供了一种工具，可用于减少夹带红鳟鱼，同时潜在地满足供水需求。