Increasing populations of Double-crested Cormorants (Phalacrocorax auritus) throughout North America have had a significant impact on fish resources in areas where they breed. A simple Excel model was used to assess the effectiveness of lethal control methods in reducing fish consumed by a breeding population of cormorants. Egg oiling was found to reduce seasonal fish consumption by an average of 504 ± 75 (SD) metric tonnes (N = 3) while culling reduced consumption by 280 ± 205 (SD) tons (N = 3). Cost-effectiveness of each method was also assessed using values from a control program in Lac La Biche, Alberta, Canada. Egg oiling cost an average of CDN$5.26 ± 0.84 (SD; N = 3) for each ton of fish saved from consumption by cormorants and culling cost $36.14 ± 8.90 (SD; N = 3). While culling alone is capable of controlling consumption by adult and young-of-the-year cormorants, egg oiling provides a practical and cost-effective alternative for management of ground-nesting cormorants when used in combination or when culling is not available as a management option.
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Vol. 35 • No. sp1