The combined impact of intensive egg oiling and culling activities on double-crested cormorant populations in Lac La Biche, Alberta, Canada, with implications for the local fish community

In the last 100 years Lac La Biche, a 22,000 ha lake located in northeastern Alberta, has changed from a system with walleye (Sander vitreus) as the top fish-eating predator to one where Double-Crested Cormorants (Phalacrocorax auritus) are at the top of the aquatic food chain. Since 1988 cormorant growth in the area has increased by an estimated 11% per year resulting in a peak population size of 18,000 nesting adults in 2004. Intensive egg oiling (2003, 2005, 2006) and adult culling (2005, 2006) campaigns have resulted in an 18% decline in nesting birds thereby returning the system to 2001 levels. A simple Excel model of cormorant consumption for the Lac La Biche area in 2006 indicates potential decreases in fish consumed of up to 1 million kg. Annual monitoring of the Lac La Biche fish community has been conducted since 2003 and provides a basis for predicting and interpreting fish composition changes in response to cormorant control activities. Local cormorant and fishery data have been incorporated into an ecosystem model to be used in assessing the potential for restoration of walleye dominance within Lac La Biche.