Great Lakes Science

Fisheries technicians take water temperature readings while a State of Ohio research vessel waits in the background to begin a night-time hydro-acoustic survey across Lake Erie.
U.S. agencies and MNR staff cooperate on a night-time fish survey of Lake Erie.

The health of the Great Lakes and our use of the basin's natural resources are interconnected.  If the Great Lakes are in good ecological health (water, habitats, and fish and wildlife are healthy), then Ontario is healthy, too.


The Ministry of Natural Resources is one of several agencies responsible for gauging the health or state of the Great Lakes Basin ecosystem.  The Ministry uses various indicators or clues to determine the health of this ecosystem.


Take fish, for example. Fish are very sensitive to changes in their surroundings. If the health of their aquatic environment declines, fish show signs of stress. Like the "canary in the coal mine", stressed fish are an early warning sign that the environment is in trouble. And, if the Great Lakes are in trouble, then so is our own health and well-being.


The Ministry of Natural Resources collects scientific information about the Great Lakes.



  • to collect base-line information about the health of the Great Lakes and to track any changes in fish and wildlife species and habitats, including coastal wetlands
  • to help resource managers make scientifically-informed decisions about how best to manage the fish, aquatic habitats and the other living resources of the Great Lakes (for example: to help determine the levels of harvest that will a fisheries resource  can sustain)
  • to predict the effects that changes (e.g., climate change, aquatic invasive species) will have on a species or population, or how it will change the structure and function of an ecosystem


Within the Ministry there are two groups that routinely collect information and increase our knowledge and understanding about the Great Lakes.

  • Ministry biologists and resource technicians monitor the state of Great Lakes fish and food webs.
  • Research scientists conduct studies to help us understand why changes are occurring and what we might see in the future.
A biologist measures and tags an adult walleye retrieved from a seine net set in the Thames River.
Monitoring walleye populations in the Thames River, a tributary of Lake Erie.

The work of Ministry biologists, resource technicians and scientists includes:

  • determining the effects of aquatic invasive species on Superior and Huron's prey fish species, and how this will affect populations of predator fish species in these lakes
  • understanding how aquatic invasive species, like the zebra mussel, are disrupting Great Lakes food webs and impacting the abundance of lake whitefish and diporeia (a tiny, shrimp-like organism found in the bottom mud of the Great Lakes)
  • improving the tools (computer models) used to assess current - and forecast future – levels of walleye and yellow perch stocks in Lake Erie to determine allowable catches for commercial and sport fishing purposes
  • understanding how a vitamin deficiency may be hampering efforts to restore natural populations of the Atlantic salmon and lake trout in Lake Ontario


Scientists and biologists report annually on the state of Ontario's Great Lakes fisheries at Great Lakes Fishery Commission meetings.


Just what is the state of Ontario's Great Lakes and their fisheries resources? Read more from the State of the Lakes Ecosystem Conference, on the U.S. Environmental Protection Agency website




Lake Erie Management Unit hydro-acoustic survey vessel and staff: John Cooper, MNR

Walleye sampling: Brian Locke, MNR