U.S. Department of Agriculture-Forest Service, Rocky Mountain Research Station, Salmon, Idaho, United States of America.
U.S. Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University, Corvallis, Oregon, United States of America.
PLoS One. 2020 Sep 4;15(9):e0237716. doi: 10.1371/journal.pone.0237716. eCollection 2020.
Bull trout (Salvelinus confluentus) are challenging to detect as a result of the species cryptic behavior and coloration, relatively low densities in complex habitats, and affinity for cold, high clarity, low conductivity waters. Bull trout are also closely associated with the stream bed, frequently conceal in substrate, and this concealment behavior is poorly understood. Consequently, population assessments are problematic and biologists and managers often lack quantitative information to accurately describe bull trout distributions, estimate abundance, and assess status and trends; particularly for stream-dwelling populations. During controlled laboratory trials, we recorded concealment, resting, and swimming behavior of juvenile wild bull trout in response to: (1) constant and fluctuating water temperature, (2) presence or absence of light, and (3) substrate size. Light level had the strongest influence on wild fish concealment and more fish concealed as light levels increased from darkness to daylight. Wild fish were 14.5 times less likely to conceal in constant darkness and 4.1 times more likely to conceal in 12 h light x 12 h darkness compared to constant light. Wild fish were 6.2 times less likely to conceal in small (26-51 mm) substrate compared to larger (52-102 mm) substrate. As water temperature increased, fewer wild fish concealed. Knowledge of wild bull trout concealment will improve field sampling protocols and increase detection efficiencies. These data also enhance knowledge of bull trout niche requirements which illuminates ecological differences among species and informs conservation and restoration efforts.
虹鳟（Salvelinus confluentus）由于其隐蔽的行为和颜色、在复杂生境中的相对低密度以及对寒冷、高清晰度、低电导率水的偏好，因此很难被发现。虹鳟还与河床密切相关，经常隐藏在基质中，而这种隐藏行为还不太了解。因此，种群评估存在问题，生物学家和管理人员通常缺乏定量信息来准确描述虹鳟的分布、估计数量，并评估其状况和趋势；特别是对于溪流种群。在受控实验室试验中，我们记录了野生幼虹鳟对以下因素的隐藏、休息和游泳行为：（1）恒定和波动的水温，（2）有光和无光，以及（3）基质大小。光照水平对野生鱼类的隐藏行为影响最大，随着光照水平从黑暗到白天的增加，隐藏的鱼类数量也随之增加。与恒定光照相比，野生鱼类在恒定黑暗中隐藏的可能性降低了 14.5 倍，在 12 小时光照 x 12 小时黑暗中隐藏的可能性增加了 4.1 倍。与较大的基质（52-102 毫米）相比，野生鱼类在较小的基质（26-51 毫米）中隐藏的可能性降低了 6.2 倍。随着水温的升高，隐藏的野生鱼类数量减少。了解野生虹鳟的隐藏行为将改善野外采样方案并提高检测效率。这些数据还增强了对虹鳟生态位需求的了解，揭示了物种之间的生态差异，并为保护和恢复工作提供了信息。
