Seasonal and Regional Variations in Metal Contamination and Condition Indicators in Yellow Perch (Perca flavescens) along Two Polymetallic Gradients. II. Growth Patterns, Longevity, and Condition

ABSTRACT

Wild yellow perch (Perca flavescens) were sampled from five lakes in each of two metal contamination gradients in Sudbury, Ontario, Canada (n = 1324) and Rouyn-Noranda, Québec, Canada (n = 1125) in the spring and summer of 2002 and 2003, respectively, in order to examine growth patterns, longevity, and the influences of season and region on fish condition. Fish from Rouyn-Noranda began rapid growth at a young age, whereas fish from Sudbury lakes showed slow growth rates between ages 0–3, after which growth rates improved. Fish from contaminated lakes grew faster and died younger than fish from reference lakes in both contamination gradients. Fish from Sudbury had lower condition than in Rouyn-Noranda, higher condition occurred in summer than spring, and fish from contaminated lakes had lower condition than those from cleaner lakes. Tissue Zn concentrations were correlated with fish condition and showed strong temporal stability. However, it is more likely that Zn covariates, such as Cd or Cu (which were more temporally variable) influenced condition, suggesting that long-term, broad-scale processes are more important than short-term, lake-specific processes for establishing growth patterns, longevity, and fish condition in metal-contaminated systems. Results from this study reveal that fish condition must be interpreted in the light of regional, seasonal, and other factors that can potentially influence fish growth patterns. Ecological risk assessments that fail to take these factors into account may draw erroneous conclusions about risk to indigenous populations.

Key words:

• yellow perch
• growth
• longevity
• fish condition
• metals
• gradient analysis

ACKNOWLEDGEMENTS

This research was supported by a grant from the Metals in the Environment Research Network to PC and GP as well as by NSERC Discovery funding to PC. Renée Stewart, Joelle Violette, and Mehran Bakhtiari provided assistance with field work in Sudbury. Useful review comments were provided by four anonymous referees.