Invasive species have mucked up Lake Ontario's food webs; many scientists, environmentalists, conservationists, and anglers have observed the disruptions themselves.
Take the alewife — a species of herring — which entered the lake in the late 1800's via the Welland Canal and never left. In time, the more aggressive fish pushed out the native lake cisco.
As the cisco population plummeted, the trout and salmon that fed on the fish turned to alewife as their major food source, and the results haven't been good. The predator fish like the alewife and grow fast eating them. But an enzyme in the alewife causes nutritional problems in the trout and salmon, which lead to reproductive difficulties.
But alewife populations are declining across the Great Lakes — for reasons that aren't entirely clear — and nature is starting to right some of the aquatic food webs, says Jeff Wyatt, director of animal health and conservation at the Seneca Park Zoo. And officials with the US Geological Survey see an opportunity to help the cisco retake its niche in Lake Ontario.
The agency is working with the State Department of Environmental Conservation to restock the lake with cisco drawn from Great Lakes stocks. (In Lake Superior, the lake cisco is so plentiful that the population supports a commercial fishery.)
A few weeks ago, the Seneca Park Zoo placed juvenile cisco on exhibit alongside its lake sturgeon, another fish that the USGS, DEC, and zoo have been working to reintroduce to the Genesee River and Lake Ontario. The goal is to educate the public about the fish and its importance to other key species in Lake Ontario.
And last month, the USGS and DEC released 145,000 juvenile cisco into Irondequoit Bay. The agencies have released about 165,000 cisco over the past few years, says James Johnson, eastern branch chief of the USGS Great Lakes Science Center.
The work has been funded through the Great Lakes Restoration Initiative, which provides $300 million annually for water quality and habitat projects across the lake system. Johnson says that the USGS will also look to restore spawning habitat for the cisco. The fish spawns in rocky areas of embayments such as Irondequoit Bay and Sodus Bay, but those habitats have been inundated with muck and sludge.
But improving water quality in the bays and the streams emptying into them means that the worst of the muck is over, Johnson says.
The cisco restoration is actually part of a larger federal effort to restore one of Lake Ontario's most prominent and prized predator fish: Atlantic salmon. For the past few decades, the state DEC has stocked approximately a dozen watersheds with the fish, but few have spawned, according to the DEC's website.
The USGS is taking a multi-pronged approach to restoring the fish, Johnson says. Restoration of the cisco, the salmon's key prey, is happening alongside stocking, spawning habitat restoration, and research work, he says.