Today we hear from Curt Karboski, fish biologist with the Lower Great Lakes Fish and Wildlife Conservation Office located in western New York. He’s part of a team working to restore iconic fish species such as lake trout and lake sturgeon to the Great Lakes. Join Curt and his team in the Niagara Gorge, located below Niagara Falls as they search for lake trout – the largest trout native to the Great Lakes.
In a time of year when only the most die-hard lake trout and steelhead anglers flock to Niagara Gorge, it is rare to see fish biologists plying the waters alongside them. But on a cold rainy day in November, biologists from the Lower Great Lakes Fish and Wildlife Conservation Office were there, relying on the knowledge and skill of a local charter captain to help catch lake trout they needed in order to complete a study. The highly turbulent waters and strong flows downstream of Niagara Falls make it impossible to use standard fish-sampling gear without harming the fish or endangering the crew. An estimated 100,000 cubic feet of water per second comes over Niagara Falls, and our GPS has shown us moving as much as 15 mph with the motor idling. Thus, we enlisted assistance from a local captain who has years of experience angling for lake trout in these waters, and in spite of the weather, we collected 22 lake trout!
In conducting our study, we were looking to answer specific questions such as; where do lake trout spend their time in the river and is it seasonal?, when do they leave the river and enter Lake Ontario?, and is their location important to their growth and reproduction? This information will help guide biologists when making decisions on stocking lake trout and conserving their habitat to restore this valuable fishery.
In a protected area along the gorge, we moored the U.S. Fish and Wildlife Service’s vessel Linnaeus, to be used as a stream-side platform for measuring fish and implanting them with a tag. After collecting the lake trout, we transferred them on board the Linnaeus where we recorded length, weight and gender; then anesthetized ten females and surgically implanted them with acoustic tags.
Lake trout are real wanderers traveling many miles in search of food, and some return to the same spawning beds each year. The acoustic tags transmit a series of pings that can be decoded by underwater receivers and deliver information on individual fish. As the tagged fish move through the river, an array of acoustic receivers detect the pings sent out by the tag, helping us identify the location and depth of each fish, and the amount of time they spend in any given area. The long battery life of the acoustic tag makes it possible to track the fish for several years, allowing us to learn more about spawning behavior and the types of habitats that are key to maintaining a healthy population.
As top predators, lake trout are ecologically important in helping to maintain balance among other species, creating space for aquatic life in the lake. Lake trout are economically important and have historically supported a strong commercial and recreational fishing industry. But by the 1930’s, pollution, over-fishing and the invasive sea lamprey led to their decline throughout the Great Lakes, and by the 1950’s they had completely disappeared from Lake Ontario.
Since lake trout do not reproduce until they are at least 6 to 10 years old, it takes a long time for populations to rebuild themselves when their numbers are very low. A stocking program, in concert with active sea lamprey control that began in 1971, has been helping to restore the lake trout. The Service conducts these programs with state, Tribal and Canadian partners on the Great Lakes. According to USGS Biologist Brian Lantry, recent trawl surveys found wild lake trout juveniles, suggesting there may be natural reproduction occurring again in the Niagara River region.
Beginning in spring, we will be back on the river and on the lake alongside our fellow die-hard anglers in search of evidence that our Great Lake trout are coming back from the brink. Understanding their spawning behavior and habitat preferences in the Niagara Gorge will help us manage towards a self-sustaining population and inform future decisions on conserving habitat.
Read other blogs about the work of the Lower Great Lakes Fish and Wildlife Conservation Office: Secrets of the Lower Great Lakes: The search for lake sturgeon and Setting the stage for sturgeon