Temporal changes in physiology and tissue metal levels of wild yellow perch (Perca flavescens) from clean and contaminated lakes under laboratory conditions

This study examined inter-population differences between chronically metal-exposed fish and fish inhabiting a reference lake from a physiological perspective. Similar-sized yellow perch (Perca flavescens ) from three different populations, one from a clean lake and two from metal-contaminated lakes, were captured and maintained in the laboratory under the same conditions in order to minimize variability associated with habitat. Fish were sampled immediately and at regular intervals, and several morphometric and physiological condition indicators along with fluctuations of metal (Cd, Cu, Ni, Se, and Zn) concentrations in liver, gill, and kidneys were determined. Relationships between tissue metal concentrations and condition indicators were also examined. Initially, fish from the clean lake exhibited higher values of condition factor, muscle protein content, and muscle biosynthetic capacities (as measured by nucleoside diphosphate kinase activity) in comparison to fish from contaminated lakes, whereas liver aerobic and anaerobic capacities (as measured by citrate synthase and lactate dehydrogenase, respectively) were higher in fish from polluted lakes. By the end of the experiment these indicators reached similar levels in all three populations. The extent and rate of metal depuration were different with respect to different metals, tissues, and fish populations. This study highlighted the importance of food consumption rather than metal exposure in initial differences of growth-related parameters (e.g., Fulton's condition factor and muscle protein content) among the fish groups. This study also examined the effect of captivity on metabolic capacities and revealed that different fish populations may respond differently to the stress resulting from captivity.