Seasonal variations in condition and liver metal concentrations of yellow perch (Perca flavescens) from a metal-contaminated environment.

The relationships between liver metal (Cu, Zn and Ni) concentration and physical condition of yellow perch (Perca flavescens) were compared in fish sampled in five northeastern Ontario Lakes in the spring and seven lakes in the fall of 1997. These lakes represented a wide range of metal contamination, pH, dissolved organic carbon (DOC) and alkalinity. Lakes situated closest to emission point source had lower pH, alkalinity and DOC and higher aqueous metal concentrations than other lakes in this study. Fish from these lakes displayed higher liver metal concentrations. Seasonal variations in liver metal concentrations were observed in the most metal-contaminated lakes, with higher Cu levels in the spring and higher Zn and Ni concentrations in the fall. These fish had lower indicators of physical condition than fish from cleaner lakes. In particular, more metal-contaminated fish were smaller for a similar age, indicating slower growth rate, and had lower relative condition factor and scaling coefficients. The scaling coefficient is a descriptor of the growth pattern of fish, and higher values indicate increased weight gain per unit of growth in length. Negative (P<0.05) relationships are reported between lake alkalinity and liver Cu concentration (in both seasons) and Zn concentration (in spring only). In both seasons mean liver Cu content was negatively associated (P<0.05) with the scaling coefficient of the fish samples. With these data, we propose the use of the scaling coefficient as a simple biomonitoring tool to detect metal effects on the physical condition of yellow perch. Data presented here provide information on seasonal variations in liver metal concentration and condition of yellow perch that should be considered in the design of field studies investigating physiological effects of metals in wild fish. This work also describes a gradient of lake and fish metal contamination that is related to the physical condition of yellow perch. This system provides a unique research opportunity to further our limited knowledge of the effects of metals on the physiology of wild fish.