Direct and Indirect (Foodweb Mediated) Effects of Metal Exposure on the Growth of Yellow Perch (Perca flavescens): Implications for Ecological Risk Assessment

ABSTRACT

Yellow perch (YP) are metal tolerant fish that form large populations in many metal-impacted regions across Canada. While they are able to survive and reproduce successfully in environments with water and sediment metal concentrations that are toxic to many invertebrates, perch experience a suite of direct and indirect impacts. YP were studied in a series of Canadian Precambrian Shield lakes near Sudbury, Ontario, along a gradient of metal exposure downwind from metal smelters. In lakes at the high end of our exposure gradient, concentrations of metals (Cu, Ni, and Cd) in YP liver and kidney were well above levels seen in fish from reference lakes. Direct effects linked to metal-exposure were observed, ranging from effects at the cellular level, to effects in organs and tissues, individuals, and populations. In addition to direct or physiological effects, we also documented indirect, foodweb-mediated effects of metals on YP in the most contaminated lakes resulting from the elimination of metal-sensitive large benthic invertebrates and their replacement by small metal-tolerant taxa. The most common indication of such indirect effects on YP is severely stunted growth coupled with a high degree of zooplankton dependence throughout their life. Such indirect effects have important implications for ecological risk assessment (ERA) because they indicate that higher trophic levels may be functionally altered even though the functional groups that they depend on are present and abundant. Although the functional groups important to yellow perch can be abundant in metal-impacted lakes, their benthic communities are impoverished and this is strongly reflected in their size structure upon which energy transfer to higher trophic levels depends. Thus indirect (foodweb-mediated) effects can be important in situations where invertebrate size structure is impacted in such a way as to reduce the efficiency of energy transfer to higher trophic levels, and therefore measures should be taken to protect and/or restore large sensitive benthic species.

Key Words:

• metals
• fish
• yellow perch
• direct effects
• indirect effects
• foodweb
• cortisol
• energetics

ACKNOWLEDGMENTS

This research was supported by the Metals in the Environment Research Network (MITE-RN). This network received financial contributions from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Mining Association of Canada, Ontario Power Generation Inc., the International Copper Association, the International Lead Zinc Research Organization, and the Nickel Producers Environmental Research Association. We are greatly indebted to the Co-operative Freshwater Ecology Unit (Sudbury), for their hospitality and helpfulness in providing us laboratory space and facilities essential for this project. Useful review comments were provided by four anonymous referees.

Present address for G. D. Sherwood, Gulf of Maine Research Institute, Portland, ME, USA

Present address for A. Iles, Arizona Co-operative Fish and Wildlife Research Unit, School of Natural Resources, The University of Arizona, Tucson, AZ, USA

Notes

*Gagnon and Hontela, unpublished data,

^†Couture, Laurentian University, pers comm.,

^†† Keller et al. (2004).

**Carbone et al. (1998),

^§J. M. Gunn unpublished data.

^a Modified from Iles and Rasmussen (2005),

*dw indicates dry weight and fw indicates fresh weight.

^a Modified from Iles and Rasmussen (2005).