Cormorant Program

Double-crested Cormorants
on the Leech Lake Reservation

The double-crested cormorant is a native species to Minnesota whose numbers were decimated due to widespread use of organophosphate pesticides such as DDT, human persecution, and contamination of prey at their wintering areas in the Gulf of Mexico. The ban on DDT, protection of the species under the Federal Migratory Bird Treaty Act, and catfish farms that provide an alternative feeding sites in the wintering areas have resulted in the species making a substantial recovery. Although cormorant numbers have increased during the past few decades, they are still not believed to approach the numbers that were historically found here. 

Cormorants feed on a wide variety of fish species but in order for them to obtain their daily energy requirements, they concentrate on abundant, easy to catch species. In Leech Lake, this is small yellow perch and shiners. Perch make up about 50-75% of their diet by numbers and weight. The concern on Leech Lake is whether or not cormorants contributed to the decline of walleyes in the early 2000s, and if so, at what level they should be managed that will not cause a significant negative effect on walleye and yellow perch populations, while maintaining a viable cormorant population. To help answer this question, the US Fish and Wildlife Service awarded a grant to the Leech Lake Band’s Division of Resources Management to conduct a cormorant diet study on the lake. Results of the diet studies and modeling conducted by MN DNR has found that cormorant predation on young of the year walleye has minimal effect on future year classes, but in some years when cormorant numbers were very high their predation and age 1 and 2 walleye was resulting in reduced survival of these fish into the catchable sizes. Work is ongoing to control cormorants at a level where they do not reduce nesting habitat for other colonial waterbirds or significantly reduce recruitment of walleye.

Cormorant Research

Cormorants: Environmental Assessments >

Cormorants: Decision Notice >

Contact Us

DRM (218) 335-7400

Name Title Phone
Mortensen, Steve Fish, Wildlife & Plant Resources Program Director 335-7421
Finn, Jon Fish & Wildlife Field Specialist 335-7424
White, Gary Assistant Hatchery Manager 335-7424
Robinson, Martin Fish and Wildlife Technician 335-7424