Abstract
Relative weight (W r) is an easily interpreted index for analyzing fish condition; it is the percentage of a standard weight at length (W s) for a species: W r = 100 × (measured weight)/ W s. A standard length-weight equation must be available to calculate W r for any given length. Thirty-three data sets for northern pike Esox lucius from 23 populations in eight U.S. states and one Canadian province were summarized to develop a proposed W s equation. The proposed equation is log10W s, = –5.369 + 3.059 log10L; W s is weight in grams and L is total length in millimeters. The English equivalent of this equation is log10 W s = –3.727 + 3.059 log10L; W s is pounds and L is inches. Age and growth data were available for 11 of the 23 populations, and W r was significantly correlated with growth. Mean population W r values were also summarized according to the subjective judgement of the biologists who contributed 25 data sets; fast-growth populations had a mean W r of 106, moderate-growth populations ha...

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