Habitat simulation approaches (e.g., PHABSIM) have been used to model instream flows in thousands of streams and rivers and remain the most widely implemented detailed instream flow methodology. However, recent studies suggest that conventional habitat simulation models incorporate assumptions that may systematically underestimate instream flow needs, particularly for drift-feeding fish. These include: (i) systematic biases in velocity habitat suitability curves (HSCs) caused by territoriality where dominant individuals displace subordinate fish to lower velocity micro-habitats at high densities, thereby inflating the fitness value of low velocities; (ii) habitat simulation models do not account for flow effects on prey flux to drift-feeding fishes, which may decrease more rapidly with reduced flow than does available habitat; (iii) use of focal velocities to construct traditional HSCs, which systematically underestimates velocity preference within the broader foraging arena of a drift-feeding fish, and (iv) inadvertent use of low-velocity HSCs associated with daytime refuging behavior from predators that may underestimate the higher velocities necessary for crepuscular foraging. Collectively, these factors suggest that current and historic flow prescriptions using traditional habitat simulation methods may underestimate optimal rearing flows for salmonids and other drift-feeding species by anywhere from 10 to 50%. This implies that traditional instream flow management may be failing to provide the intended level of protection for drift-feeding fishes in multiple streams at landscape scales. We provide guidelines for identifying contexts where model predictions are likely to be biased and approaches for correcting them.

中文翻译：

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识别和减轻鱼类栖息地模拟模型中的系统偏差：估算最小入流流量的意义

栖息地模拟方法（例如，PHABSIM）已被用于模拟数以千计的溪流和河流中的入流流量，并且仍然是最广泛实施的详细入流流量方法。然而，最近的研究表明，传统的栖息地模拟模型包含的假设可能会系统地低估内流需求，特别是对于漂流喂养的鱼。这些包括：(i) 速度栖息地适宜性曲线 (HSC) 的系统性偏差，这是由领地性引起的，在这种情况下，优势个体将下属鱼类转移到高密度的低速度微栖息地，从而夸大了低速度的适应度值；(ii) 栖息地模拟模型没有考虑流量对漂流喂养鱼类的猎物通量的影响，与可用栖息地相比，随着流量的减少，猎物流量可能会下降得更快；(iii) 使用焦点速度构建传统的 HSCs，这系统地低估了漂流喂养鱼在更广泛的觅食领域内的速度偏好，以及 (iv) 无意中使用了与可能低估的捕食者白天避难行为相关的低速 HSCs黄昏觅食所需的更高速度。总的来说，这些因素表明，使用传统栖息地模拟方法的当前和历史流量规定可能会低估鲑鱼和其他漂流喂养物种的最佳养殖流量 10% 到 50%。这意味着传统的内流管理可能无法在景观尺度上为多条河流中的漂流鱼类提供预期水平的保护。