US hydrographic survey ship shows predator fish dine on fingerling plants

by Alicia McCutcheon

NORTH CHANNEL—The smelt are thick, the shiners are abundant and it appears that stocked fish could be providing a tasty treat for the predator fish of the North Channel, Jeff Schaeffer, biologist with the United States Geological Survey (USGS), told The Expositor.

Mr. Schaeffer recently returned to his home port of Cheboygan, Michigan after cruising Lake Huron’s three basins—the main basin, Georgian Bay and the North Channel—aboard the USGS scientifically equipped Sturgeon.

“We partnered with United States Fish and Wildlife this year which allowed us more time in Canadian waters,” he explained.

Last year, The Expositor reported huge numbers of rainbow smelt were caught by the crew of the Sturgeon in the North Channel, and this year Mr. Schaeffer announced that even more numbers of smelt, albeit small, were also netted.

“It looks like a very good hatch of rainbow smelt—the North Channel was its usual smelt blitz,” the biologist explained. “This year we saw what I would say is far more than last year. They were mostly age ones or twos.”

This could mean a couple of things, Mr. Schaeffer explained: slow growth, a high mortality rate or a combination of both factors.

“They’re not big,” he said of the smelts, “meaning they’re not the size anglers like to dip in the spring. All predators eat smelt, but because of the lack of alewife, the pressure on them may be high.”

Mr. Schaeffer noted that emerald shiners, the fisherman’s typical bait minnow, were also plentiful in the North Channel. “We had one of the largest catches of shiners I’ve seen, but still no alewife—they’re very sparse.”

He explained his survey focuses on the pelagic fish that live in the water column, near the surface of the lake, of which round gobies are not typically a part, but did say he knew the invasive species was part of the Lake Huron food chain, with every predator species enjoying goby snacks. “They are one of the primary prey of lake trout,” he said.

The USGS, over the last three years, has encouraged American anglers to keep and freeze the stomachs of predator fish—Chinook salmon, walleye and lake trout—and gobies have been found in great numbers, along with stocked fish. The biologist said he knows this because the fingerlings (Chinook salmon and lake trout) are all the same size, species and in some cases, clipped fins are noted.

“Some of the stockfish do survive, but survival is lower than it was when there were alewife and this indicates that prey is somewhat limited in Lake Huron,” Mr. Schaeffer noted. He added that the state of Michigan has even cut back on the stocking of Chinook salmon because of this trend.

Jim Sloss, president of the United Fish and Game Clubs of Manitoulin, said he agreed with Mr. Schaeffer that something is definitely taking a bite out of lake trout stocks, noting the Ministry of Natural Resources lake trout rehabilitation program and its poor return, but questions the Chinook stock as food, at least in the North Channel.

“I’m not sure how they would know that—we don’t clip the fins of the Chinook,” he said of the salmon fingerlings produced at the Gore Bay Fish Hatchery and released into the North Channel.

He noted that last year, 94,700 Chinook were planted in Gore Bay, Meldrum Bay and West Bay thanks to the hard work of members and the Gore Bay fish hatchery and said this year members saw a 90-100 percent return of adult Chinook.

This may be bad news for the crew of the MNR vessel Huron Explorer 1 which set off on its maiden voyage this spring from Manitoulin, stocking 200,000 lake trout in northern Georgian Bay before moving on to southern Georgian Bay to stock even more of the trout.

“We saw an expanded fishery in Gore Bay and Meldrum Bay, as well as a diversity of species such as brown trout and rainbow trout,” Mr. Sloss noted. “We also saw quite a strong run of pink salmon in Kagawong and even counted 49 Coho salmon coming into spawn in Gore Bay—you just don’t see Coho.”

The president also noted a good showing of alewife near the south shore of Providence Bay this year, but admitted the North Channel was in better shape as far as fish were concerned than the main basin of Lake Huron.

Dave Reid, lake management supervisor with the Upper Great Lakes Management Team of the MNR told The Expositor that the ministry has also been performing diet studies, although not as extensive as those of the GLGS, and are not seeing any predation of stockfish. “We are also seeing a fair amount of natural reproduction,” he said, noting the complete success of lake trout rehabilitation in Parry Sound, as well as success in South Bay on Manitoulin.

“While numbers are down across the lake since 2004 and the collapse of the alewife, we are seeing many more wild lake trout, which is very encouraging,” Mr. Reid said. “We’re also seeing a resurgence in pickerel and perch.”

“The abundance of forage fish is much higher in the North Channel, so the vulnerability of stockfish is less so in the North Channel,” he said. “This doesn’t mean that cannibalism doesn’t occur, but we haven’t seen it in our studies. They’d be killing their own young and not surviving to adults.”

“The MNR has been stocking lake trout since the 1970s and, as of late, is pleased with the proportions of wild fish we’re seeing,” Mr. Reid continued, noting an increase in Frazer Bay. “That’s encouraging.”

He did note that it is possible for the MNR stockfish to make their way to American waters, which is what Mr. Schaeffer could be seeing, but said it was more likely with Chinook salmon over lake trout, a species that doesn’t travel too great a distance.

Mr. Schaeffer said although these findings are preliminary, he thinks it’s safe to say the food web of Lake Huron, and the rest of the Great Lakes, has probably changed for good.

“Predators have learned how to survive without the alewife and are eating non-traditional food,” he explained. Predator biomass is probably lower than it was, but predators out there seem to be thriving.”

Some more so than others. Mr. Schaeffer noted the Atlantic salmon has a broader diet than its Chinook cousin and seem to be faring better as a result. “Chinook are a kind of an alewife eating machine, but seem to be getting by on rainbow smelt,” he said.

“It’s looking more and more like these changes are permanent,” Mr. Schaeffer continued. “There’s a new food web out there since 2004 and a lower fish biomass, but more native species. The alewife have disappeared because of very heavy predation—food web changes and weather changes may have helped to tip the scales at a critical time.”

Mr. Schaeffer concluded by noting he always enjoys his trips to Canadian waters, especially visiting small towns, and the characters that accompany them, along the way.

“One person thought we should have weapons on board in case of a terrorist threat or piracy,” he chuckled.

The survey was a great success thanks in part to beautiful weather, he added, and a trip to Killarney, which included fish and chips and scrap-eating otters, was also a highlight.

“I did the whole survey in shorts and a t-shirt,” Mr. Schaeffer said. It doesn’t get much better than that.”