Elevated turbidity in stream water is a frequent consequence of forestry activity. Elevated turbidity has direct negative effects on fish growth by inducing physiological stress, and indirect effects by reducing both benthic invertebrate abundance and the visual distance over which drift-feeding fish can detect their prey. We developed a mechanistic model to predict the effects of increased turbidity on growth rates of juvenile salmonids based on the reduction in reactive distance (vision) associated with increased turbidity. We tested the model against observed reductions in growth with increasing turbidity from a published study (Sweka and Hartman 2001), and by comparing modelled growth to observed growth of cutthroat trout at low turbidities in a natural stream. The model predicts turbidity-induced decreases in growth well, including the observation that fish can compensate for decreased prey encounter rates at elevated turbidity by moving to faster focal velocities. A spreadsheet version of the model was produced for use by biologists or fisheries managers to estimate the effects of low-level chronic turbidity on juvenile salmonid growth rate.
Rosenfeld, Jordan S.. 2005. Development of sustainability indicators for turbidity impacts on stream ecosystems: annual technical report BC forest science program. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), Salmon, Effect, Habitat, Modification, on
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