Detailed project information for Study Plan Number 08036

Branch :	Northern Appalachian Research Laboratory
Study Plan Number :	08036
Study Title :	Effects of double-crested cormorant predation on fish populations in Lake Ontario and the St. Lawrence River
Starting Date :	10/01/2001
Completion Date :	09/30/2006
Principal Investigator(s) :	Ross, Robert M.
Primary PI :	Ross, Robert M.
Telephone Number :	(570) 724-3322 x239
Email Address :	rossr@usgs.gov
SIS Number :	5001464
Primary Program Element :	Fisheries and Aquatic Resources
Second Program Element :
Status :	Completed
Abstract :	BACKGROUND Since 1938 when the first documented nesting occurred in Lake Ontario, the populations of double-crested cormorants (Phalacrocorax auritus) has risen to over 20,000 breeding pairs (Weseloh and Ewins 1994, Weseloh personal communication). The most likely reasons for the dramatic increase in population levels include reductions in environmental contaminant levels that adversely affected reproduction, protection under the Migratory Bird Treaty Act of 1972, and an abundant food supply in the lake, mainly alewife (Alosa pseudoharengus), a nonindigenous forage fish (Weseloh et al. 1983, Price and Weseloh 1986). Double-crested cormorants are piscivorous, consuming about half a kilogram of fish per day (Orta 1992). Proliferation of cormorant breeding populations in Lake Ontario has led to questions about their potential effects on fish populations. Not only are effects on gamefish such as smallmouth bass (Micropterus dolomieu), yellow perch (Perca flavescens), and stocked salmonines a concern, but also the loss of certain forage fishes. Alewife are of special interest since they are the primary forage species of salmonines, and their populations have been declining in Lake Ontario (Jones et al. 1993). At stake for the sport fishing community in New York State alone is an annual catch of nearly 200,000 salmonids (1993 boat survey). The 1988 economic value of all sport fishing in New York waters of Lake Ontario was $87 million (Connelly et al. 1988). The total commercial harvest for the same location in 1994 was 81,000 pounds (in order of importance: yellow perch, brown bullhead [Ameiurus nebulosus], and white perch [Morone americana]) valued at $83,000 (Cluett 1994). A satisfactory resolution to the problem requires accurate information about the cormorant’s life history, food habits, ecosystem role, and impact on other species of special concern. OBJECTIVES The objectives of this study are to (1) determine the annual diet composition of double-crested cormorants in eastern Lake Ontario, (2) estimate the number of fish consumed annually by cormorants, (3) estimate the size of important game fishes, forage fishes, and other significant prey species consumed by cormorants, and (4) evaluate the effectiveness of management activities to reduce cormorant populations in relation to prey fish losses, and (5) quantify impacts of cormorant predation in important game species including salmonines, smallmouth bass, and yellow perch. HYPOTHESIS TO BE TESTED Predation by double-crested cormorants significantly impacts fish populations in eastern Lake Ontario.
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