Trout in Lake Ontario tagged, tracked with hopes of resolving a fishy mystery

Jun. 26—OSWEGO — A binational study involving researchers in the U.S. and Canada hopes to uncover a mystery involving the trout of Lake Ontario.

"We've been trying to restore lake trout for the last 50 years in Lake Ontario," said Alexander J. Gatch, a United States Geological Survey biologist at the Tunison Laboratory of Aquatic Science, Cortland, one of USGS's Great Lakes Science Centers.

The trout do pretty well when they are stocked.

"They survive until adults," Mr. Gatch said. "But we're not seeing natural reproduction. We're just seeing the introduction of more fish from hatcheries."

Mr. Gatch said that it's believed something is happening in the early life stages of the trout trying to become natives of Lake Ontario.

"They can physically reproduce," Mr. Gatch said. "The males produce milt, the females produce eggs and they fertilize." The eggs incubate from about November to April.

"Somewhere in that period, we're losing the eggs," Mr. Gatch said. "Or, we're losing the early life stage of the eggs after they hatch."

To help unlock that fishy mystery, Mr. Gatch is one of the researchers from five agencies who spent time this past spring putting tags on lake trout after they were caught.

The U.S.-Canada Cooperative Science and Monitoring Initiative is being led by the U.S. Fish and Wildlife Service in collaboration with the USGS, New York State Department of Environmental Conservation, Fisheries and Oceans Canada, Ontario Ministry of Natural Resources and Fisheries, with outreach assistance from New York Sea Grant.

The CSMI is a binational effort instituted under the Science Annex of the 2012 Great Lakes Water Quality Agreement to coordinate science and monitoring activities in one of the five Great Lakes each year to generate data and information for environmental management agencies.

"We're trying to identify where in the lake they are spawning," Mr. Gatch said of the trout. "To do that on a lake scale, we want to tag fish from all different areas because lake trout are like homebodies. Where they are stocked in the lake — they stay within 50 miles of that area."

The bilateral research team is using specialized tags that communicate with acoustic receivers stationed on the lake bottom. The tags will provide information about the migration patterns and habitats used by adult lake trout. This technology is particularly useful for locating spawning habitats and will assist in restoration efforts for potentially degraded spawning sites.

degraded spawning sites eyed

One possible reason for the spawning sites having difficulties is increased sediment, Mr. Gatch explained.

"Lake trout spawn on rocks," he said. "The important function of those rocks is to protect eggs from currents, storms that might occur over the winter and also predadation — fish that eat those eggs."

Zebra and quagga mussels create degradation at those spawning sites.

"When a mussel attaches to a rock, or when that mussel is crushed by waves or other rocks, the resulting shell of that mussel physically fills in spawning substrates," Mr. Gatch said. "Zebra and quagga mussels fill in those spaces on cobble rocks, so those eggs are no longer safely incubating down in the cracks and crevices of those rocks."

Stacy L. Furgal, Great Lakes Fisheries and Ecosystem Health Specialist for New York Sea Grant, Oswego, said that some of the historic spawning sites used to be "pristine," where eggs could develop in spaces between rocks. "Those spaces no longer exist," she said. "It's all been filled in with mussel shell fragments. We're thinking once the fish lead us to the habitat they're using, we can get a feel for what state those habitats are in and potentially do some habitat restoration projects on those. But the first step is figuring out where the fish are going."

Mr. Gatch added, "We don't have it pinpointed as to what is actually happening. But the first part of trying to pinpoint it is finding out where they spawn and looking at the environmental conditions at those spawning sites."

He said that lake trout usually spawn near shore in about 15 feet of water down to about 45 feet. "They spawn on rocky shoals and reefs," he said. "So any area where you have kind of like an outcropping of rocks — those seem to be hot spots for trout spawning."

There's also evidence that lake trout are spawning in tributaries. "We have a paper that's published that shows lake trout are using the Niagara River as spawning habitats," Mr. Gatch said.

charter industry assisting

The charter fishing industry is assisting the research from ports at Mexico Bay, in eastern Lake Ontario, and Wilson, along the western end of the lake. In Pulaski, Capt. Casey Prisco and first mates/captains Roy Letcher and A.J. Berry of Dirty Goose Sport Fishing Charters were contracted to help the research team catch lake trout for the tagging study.

Mr. Gatch said 319 lake trout were tagged between the five agencies involved in the U.S.-Canada Cooperative Science and Monitoring Initiative. The tags' battery life allows the fish to be tracked over the next 10 years.

"We've been tagging lake trout since 2016, but this is this is the first time we've taken a lakewide approach," Mr. Gatch said. "We're tagging fish in all areas of the lake in a really large scale which we haven't done before." By tagging trout in different areas of the lake, researchers can look at a variety of areas of Lake Ontario that may have impediments leading to the lack of trout maturing.

"This is a way for us to quantify how many spawning sites there are, at least from our sample size," Mr. Gatch said. "We can then go look at those spawning areas to see what has changed."

'wiped out'

When it comes to trout in Lake Ontario, a lot has changed in the last century. Ms.Furgal said the fish are a native species of the lake, but they were extirpated from it about a half-century ago. "Lake trout were totally wiped out from the lake at one point," Ms. Furgal said. "We've got strains from other lakes and other areas that we've done the stocking with."

The reason for the wipeout, Ms. Furgal said, is the "full gamut" — a combination that includes over-fishing, invasive species and pollution.

She added that the stocking program has overcome some impediments to make it successful, such as controlling sea lampreys. "Vitamin B was also kind of an issue, but it seems those levels are looking good," she said. "It's all these boxes we've checked, but we're still not seeing natural reproduction. A study like this is really going to help us clue in on possibly one or several of the missing links to that restoration success."

Ms. Furgal said the team at Dirty Goose Sport Fishing Charters was great to work with. "They are so into the fishery and the science."

Mr. Gatch said that their Canadian counterparts mainly used gill nets to capture trout for the study.

"When you're on a charter boat, you can have more control," Ms. Furgal said. "In particular, these fish were pretty deep, being it's spring time, in about 150 feet of water. By catching them with hook and line, we were able to control really well how quickly we were bringing the fish aboard."

"We were trolling for lake trout," Mr. Gatch said. "Yes, one at a time, but those charter captains are so good at catching fish that it wouldn't be uncommon to have three fish on at once and kind of having a rodeo going on in back of the boat to get fish tagged, make sure we had the right one and then making sure that they went back as healthy as possible."

tagged, released

The lake trout received one of two types or tags before being released. One was a "Floy" tag. Floy Tag Inc. is the leader in the manufacture of visual marking devices for fish and wildlife.

"They're external, basically just a little piece of plastic that has our phone number on it and it lets people who are angling for lake trout to know that the fish is tagged," Mr. Gatch said. "They're welcomed to do whatever they wish with it."

The other tags installed were acoustic trackers, which Mr. Gatch said are about three-quarter the size of a Sharpie marker. Those tags were "surgically' implanted, the fish were sutured and returned to the lake.

"The process is super fast," Ms. Furgal said. "They are also using some new technology, so the recovery time is really quick."

"We'll be collecting data for that entire 10-year time period," Ms. Furgal said of the tags. "Each individual tag is communicating with all these listening devices that are spread across the lake. Another component of this project was the funding of getting more of these listening devices so we can really hone in on as to where the fish are moving across the lake, both sides, the U.S. and Canada."

Mr. Gatch said there are about 500 receivers on the bottom of the lake. "It's gridded," he said. "Every few kilometers there's another receiver so we can get a pretty good idea of where the fish are. They can pick up not just our lake trout, but any fish that is tagged with an acoustic tag and there are lots of species out there that are tagged. All that data is shared in one database with all the researchers. That's really nice because those receivers are quite expensive."

The data must be physically retrieved by going to the receivers. "Most are stationary and anchored on the bottom," Ms. Furgal said. Many of those receivers can be retrieved by grappling hook. Others pop up to the surface on a buoy after an electronic release. "And some have to be retrieved by divers," Ms. Furgal said.

Ms. Furgal said that as part of the study, researchers this fall plan to investigate spawning sites as part of a "lakewide habitat survey."

"We'll be going out with cameras in some small boats and actively imaging and categorizing the habitat," she said.

Ms. Furgal said it's a rarity, but it's possible to catch a native trout in Lake Ontario. A trained eye can tell the difference.

"All of our hatchery fish are clipped," she said. "They have an adipose clip or a fin clip in combination with, on the U.S. side, a coded wire tag."

"If we find a fish with all its fins and no coded wire tag, we assume the fish is a wild fish," Ms. Furgal said. "It's a very low level of reproduction, much lower than you would anticipate with the sheer number of adults that are out there. Some of them have found a way to be successful, but it's such low numbers that it's not enough to sustain a population."