Proposed standard-weight (Ws) equation and length-categorization standards for brown trout (Salmo trutta) in lentic habitats

We developed a standard-weight (W_s) equation for brown trout (Salmo trutta) in lentic habitats by applying the regression-line-percentile technique to samples from 49 populations in North America. The proposed Ws equation is log¹⁰ W_s = −5.422 + 3.194 log₁₀ TL, when W_s is in grams and TL is total length in millimeters. The English-unit equivalent is log₁₀ W_s = −3.592 + 3.194 log₁₀ TL, when W_s is in pounds and TL is total length in inches. The equation is applicable for fish of 140–750 mm TL. Proposed length-category standards to evaluate fish within populations are: stock, 200 mm (8 in); quality, 300 mm (12 in); preferred, 400 mm (16 in); memorable, 500 mm (20 in); and trophy, 600 mm (24 in).