High quality habitat is essential to sustaining the Great Lakes fishery. The Great Lakes provide environments where fish, waterfowl and other aquatic organisms can find food, shelter and space. The abundance of a species will vary from lake to lake, depending on the availability of suitable habitats such as nearshore wetlands and riverine systems. Many fishes such as walleye, perch, pike, suckers and sturgeon, depend on wetlands or river spawning beds and nursery areas for juveniles. River systems are estimated to yield as much as thirty percent of Great Lakes salmon.
Habitat can be affected by disturbances in the physical, chemical and biological environment, such as water level fluctuations and pollution.
Maintaining good water quality is very important for fish survival and health because fish swim among the lakes, affected by variations in water quality, but unaware of and unrestricted by political boundaries. The two countries, eight states and province that border the Great Lakes are responsible for implementing and enforcing water quality laws. Also important is the Great Lakes Water Quality Agreement between Canada and the United States. The International Joint Commission, a bi-national treaty organization, oversees the implementation of the agreement and reports to the national governments on efforts to implement it.