Ontario is getting help from the United States Geological Survey (USGS) in assessing the health, abundance, age range and make-up of the prey fish species in the deeper offshore waters of Lake Huron.
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| Adult Diporeia, a rice-sized crustacean and food source for Great Lakes fish - Actual size 7.8mm - Photo: Courtesy of NOAA, Great Lakes Environmental Research Laboratory |
Prey fish are the food supply of the top predators we fish, like Chinook salmon and lake trout. To sustain these valuable commercial species, fisheries managers need to know the health of the smaller species that make up their food supply. It’s critical for maintaining the Great Lakes as a world-class commercial and sport fishery.
Sailing over to assist Ontario were research vessels from the USGS Great Lakes Science Center. The crews conducted 10 mid-water trawl-netting surveys every year for three years in Lake Huron’s main basin, the North Channel and Georgian Bay.
While in the lake’s offshore waters, the American researchers also went below mid-water levels and conducted hydro-acoustic surveys. These would provide Ontario fisheries managers with more detailed information about pelagic fish, which are fish living in the deepest waters, farthest from shore.
Hydro-acoustic surveying is rather like using a fish finder; it involves transmitting into the water a pulse of energy that travels 1,500 metres per second. When the pulse encounters a fish, an echo is reflected back to the equipment on the boat.
The data on prey fish density and biomass (the total weight of sampled fish) will be compared to the results of similar surveys in Huron’s U.S. waters. It will be used by planners from both nations who are working together to protect and improve this Great Lakes fishery.
Click here to view a map of the project area
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About Prey Fish Abundance in the Great Lakes
• Prey fish are vital to the health of aquatic ecosystems. Their populations reflect the amount of food available for them to eat – and what’s available to eat them. Valuable prey species include alewife, gizzard shad, emerald shiner, rainbow smelt, sculpin and lake herring.
• Since the 1990s, prey fish numbers in the Great Lakes have declined, thanks to the dominance of non-native alewife and rainbow smelt, and plunging populations of Diporeia.
• Diporeia (pronounced die-puh-RIE-uh) is a tiny rice-grain sized crustacean in the same biological class as krill and shrimp. This bottom-dwelling creature is the middleman of the aquatic ecosystem; an important food source for a host of Great Lakes fish species that inhabit the pelagic or offshore waters of the lakes. But in Lake Huron in the past seven years, Diporeia numbers have dropped by 93 per cent.
Project Partner
- United States Geological Survey’s Great Lakes Science Center
For more information, contact:
- David M. Reid, Supervisor, Upper Great Lakes Management Unit – Lake Huron, Ministry of Natural Resources, Owen Sound (519) 371-5031
- Andy McKee, Lake Huron COA Basin Coordinator, Upper Great Lakes Management Unit, Owen Sound (519) 371-5449