Relation among mercury concentration, growth rate and condition of northern pike: A tautology resolved?
Methylmercury is a bioaccumulative contaminant that biomagnifies in aquatic food webs and adversely affects the health of freshwater fish. Previous studies have documented an inverse relation between fish condition and concentration of mercury in fish. However, this relation may be a result of slow‐growing fish accumulating large amounts of methylmercury rather than the effects of methylmercury on fish condition and growth. We evaluated the relation among fish condition, growth, and mercury concentration in northern pike Esox lucius from 26 lakes in the western region of the Laurentian Great Lakes. The relative weight (an index of fish condition) of northern pike was inversely related to mercury concentration in the axial muscle. The concentration of mercury in standard‐size northern pike increased with fish age and suggested that fast‐growing fish accumulated less mercury than slow‐growing fish. However, there was no relation between the mean relative weight of northern pike in each population and mean age or mercury concentration of standard‐size northern pike. These results suggest that the relation between mercury and fish condition is not due to the effects of mercury on rate of growth. Rather, slow‐growing fish bioaccumulate greater concentrations of mercury than fast‐growing fish of the same length. This article is protected by copyright. All rights reserved