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POPULATION-LEVEL RESPONSE OF THE COMMON LOON TO MERCURY IN TWO CANADIAN PROVINCES: A MATRIX MODELING APPROACH
Citation:
Mitro, M. AND N. M. Burgess. POPULATION-LEVEL RESPONSE OF THE COMMON LOON TO MERCURY IN TWO CANADIAN PROVINCES: A MATRIX MODELING APPROACH. Presented at Northeast Fish and Wildlife Conference, Portland, ME, April 21-24, 2002.
Description:
We used data collected from Common Loon Gavia immer populations in two Canadian provinces to demonstrate a matrix population modeling approach for evaluating population-level responses to stressors and to understand how these populations may have responded to mercury contamination. The U.S. EPA is more broadly interested in using such approaches for assessing risks to wildlife populations from multiple stressors. Data were collected in Kejimkujik National Park, Nova Scotia and in Lepreau, New Brunswick from 1988 to 1997. Loons in Kejimkujik National Park had blood mercury concentrations that were the highest recorded in North America, and blood mercury concentrations in New Brunswick loons were similar to those observed in New England states. We used estimates of loon reproductive success and survival rates from these populations to parameterize age-classified matrix models and to calculate population growth rates. We also surveyed the primary literature for estimates of reproductive success and survival to parameterize models for loons exposed to lower levels of mercury in other regions of North America. Our results suggested that lower population growth rates were related to higher levels of mercury exposure. Elasticity analyses of the matrix models indicated that loon population growth rates were less sensitive to changes in reproductive success a population parameter commonly measured for loons than to juvenile, sub-adult and adult survival rates. Future research should better address survival rates to provide more definitive risk assessments for loon populations exposed to high levels of mercury .