Validation of Habitat Preferences for Select Native Freshwater Fishes in the Chehalis River, Washington State

Understanding the riverine distribution and habitat preferences of fishes is essential to understanding how natural and anthropogenic impacts will affect them. However, basin-specific fish habitat preferences for non-salmon or steelhead, native freshwater fish are lacking for many watersheds, including the Chehalis River in southwest Washington State. Subsequently, validations of habitat preferences, in terms of habitat suitability indices/criteria (HSCs), were identified as a data gap in section 4.1.3.1 Validation Studies in the Aquatic Species Enhancement Plan Data Gaps Report (Aquatic Species Enhancement Plan Technical Committee 2014a).

In this study, we identified microhabitat preferences in terms of HSCs for water depth, water current velocity, and substrate for largescale sucker, speckled dace, Pacific lamprey, and mountain whitefish at rearing and spawning life stages. We compared these preferences among species and life stages and with studies from other basins. Each species exhibited unique, life-stage specific habitat preferences, and these preferences were generally similar to those observed in other drainages. However, some were novel, such as the spawning habitat preferences for speckled dace, which included a range of depths (1-3 ft.), 2 ft./sec. velocity, and sand and gravel substrate as the most preferred spawning habitat. In addition to flow-habitat models, our HSCs will be used to predict and compare available habitat for these fishes under different river flow scenarios. This information provides a management and decision-support tool for evaluating potential impacts from proposed flood-retention dams or restoration actions.