Smelt population explodes in Lake Huron

[Spiel]

Smelt population explodes in Lake Huron

Trend bodes well for diet of game fish species

 

 

November 4, 2009

Jim Moodie / manitoulin.ca

 

 

ANN ARBOR, Mich.-Nature, it has been remarked, abhors a vacuum, and that certainly seems to be the case with Lake Huron's endlessly repopulated depths.

 

Alewives, once plentiful in the lake, are now practically gone, while other types of fish-both invasive and native, small and big-seem to be thriving, for better or worse, in their stead.

 

As always, with a system of this size and complexity, where gains in the indigenous fishery are often undercut by the latest new foreign threat-or new pressures wrought by commercial and recreational activities-the picture is mixed. But generally, things look fairly promising for our Sweetwater Sea, judging by the impressions of a research crew that performed a recent checkup on the lake's finny fettle.

 

Earlier this fall, the United States Geological Survey (USGS) vessel The Sturgeon made its annual sweep of Lake Huron, in order to gauge densities of various species via acoustic sounding and mid-level trawls. And while the numbers remain to be crunched, there were some intriguing initial finds.

 

"I can only offer preliminary observations, pending analysis, but one thing we saw was a very large hatch of smelt," said Jeff Schaeffer, a research fishery biologist with the Great Lakes Science Centre in Ann Arbor, Michigan. "They were ubiquitous."

 

Alewives, by contrast, were next to non-existent. "We caught maybe four or five," he remarked. "At the same trawl site, there would be 750 to 1,000 smelt."

 

The 105-foot ship, with a crew of six aboard, spent 30 days visiting "all three basins of Huron for a lake-wide survey," said Mr. Schaeffer. This included "23 transects or sampling stations" that spanned the main part of the lake, Georgian Bay, and the North Channel.

 

While alewives-an invasive type of herring, apparently named for their potbellies-formed a significant part of the diet for salmon, researchers aren't really ruing their decline. Nor are they too concerned about the surge in rainbow smelts, even though this is also a non-indigenous species.

 

"I'm not completely unhappy about it," said Mr. Schaeffer. "As an invader, smelt are less of a problem than alewives."

 

The biggest smelt boom was observed in the main basin of Lake Huron, said the biologist, although the North Channel had "a lot there, too."

 

The more striking development in the North Channel was probably the presence of a different little import. "We noticed a lot of three-spined stickleback," said Mr. Schaeffer. "It's not indigenous to the upper lakes, but it's been around a long time in low numbers."

 

In the past couple of years, the population of this spiky species-which really does sport a trio of dorsal spines, plus bony plates on its flanks-has grown quite rapidly, he said. (Hardcore fish appreciators might be interested to learn that, according to the Gulf of Maine Research Institute, "its caudal peduncle may be keeled or it may not." Or not.)

 

As unappetizing as they sound, these crunchy critters are apparently being gobbled up quite readily by bigger fish. "Predators are eating them," said the researcher. "Canadian biologists have noticed this in the stomachs of trout and salmon."

 

A separate analysis of sport fish on the US side of Lake Huron has shown that another invasive species is becoming more commonly ingested. "We did a new study this year where we looked at 2,000 stomachs of salmon, trout and walleye caught by anglers, and found that many of the fish are consuming round gobies," said Mr. Schaeffer. "Walleye and trout, in particular, are feeding heavily on gobies."

 

While baitfish seemed plentiful in the North Channel last fall, when The Sturgeon conducted its previous swing through these parts, by the spring and summer of this year, numbers were generally low across all three basins of Lake Huron. Predators like trout and walleye "apparently responded by eating gobies," said Mr. Schaeffer.

 

The bounteous hatch of smelt this year theoretically bodes well as a future food source for these bigger swimmers-not to mention an enticing catch for net-wielding sports types-"but they're still very small fish, the question we still have is whether they will survive," noted Mr. Schaeffer.

 

At six months old, the baby smelts "are about as long as a little finger and weigh about a gram," said the fishery biologist. "Presumably, if these fish survive, there will be more food for salmon and trout, but I have some reservations. We saw a similar phenomenon in 2005, where there was a strong hatch but few adults materialized, because the mortality was high."

 

The smelt upswing might go some way towards replenishing numbers of baitfish in Huron, but "this is not going to get us out of the woods" on its own, suggested Mr. Schaeffer. Nor should nocturnal scoopers get too excited just yet. "You're not going to see huge smelt dipping as a result of this," he cautioned.

 

There is some encouraging news, though, for anyone who values a resurgence in native species. "We've had good chub hatches in recent years," noted Mr. Schaeffer. "They have survived and are growing, with the average size in catches being up."

 

And in the southern main basin, at least, "we also saw emerald shiners, which is a very positive sign," he added. This fish might be tiny (six-10 centimetres) but it's a naturally occurring species and an indication of ecological equilibrium.

 

The resurgence of this green-tinged shiner, as with that of the much bigger lake trout, is linked closely to the crash in alewife numbers, according to Mr. Schaeffer. "As soon as the alewife disappeared, we saw the return of emerald shiners and the first evidence in decades of wild lake trout reproducing," he said.

 

The transition was quite dramatic for those studying the lake's fish population. "In 28 years of trawling, we had seen about five baby lake trout," noted Mr. Schaeffer. "In 2004, we caught 22, which doesn't sound like a big number, but if you think about the size of the lake, and multiply that across the whole area, it was a very strong hatch."

 

Those newborn lakers observed five years ago "are now adults showing up in our survey," he said. "The lake trout fishery is not recovered yet, but the signs are all positive. Lake trout appear to be very stable, and may even be increasing."

 

The alewife exit in the earlier part of this decade also cued "the onset of walleye reproduction," Mr. Schaeffer noted. "They are definitely increasing, at least on the US side, where record-high catches in Saginaw Bay began immediately after the loss of alewives."

 

The imports had provided food for some species, including salmon and a certain variety of black bird, but had a detrimental impact on others, as "adult alewives can be quite a voracious predator, and we think they consumed the eggs of walleye," said Mr. Schaeffer.

 

While The Sturgeon has wrapped up its investigative tour for this year, a sister vessel called The Grayling is still combing the lower depths of the lake through bottom trawling, and data collected by each craft will be compiled over the winter months, said Mr. Schaeffer. Between the two types of sampling, "we get a more complete picture," he said, adding that a report on the research will be delivered in March.

 

Meanwhile, The Sturgeon will be parked in Cheboygan, where "a relatively ice-free port" means it can stay in the water year-round. "You do get ice, but it's not thick enough to pose a problem," said Mr. Schaeffer. "It has a massive steel hull."

 

While both ships sail out of Michigan, and receive funding from the US government, the work is undertaken jointly with Ontario, which also contributes financially to the research and often has biologists on board.

 

Mr. Schaeffer said he and his American colleagues "always look forward to the Canadian portion of the trip," as these parts of the lake are particularly beautiful and "we like meeting people up there."

 

The vessel docks each night at various ports, and Mr. Schaeffer's habit is to "go out on the back deck in the morning with coffee," at which point he almost invariably encounters a curious passerby, or five, on the dock. "We have lots of interesting discussions," he said.

 

Canadians tend to be "really friendly," he said, while admitting that he was "yelled at" one time by an Islander who had strong feelings about cormorants. He didn't take it personally, though, and just tried to gently remind this individual that birds are really outside the mandate of the USGS crew. "We try to keep the talk focussed on fish," he said.

 

During the most recent jaunt through the North Channel, "I had a wonderful talk with a First Nation person," he said, concerning the traditional Ojibwe belief in an underwater creature, generally referred to as Mishepeshu. The individual "wanted to know if we ever saw them."

 

The answer was 'no,' but Mr. Schaeffer can't entirely rule out the possibility of such a leviathan existing. "I think it's very likely a spirit animal that isn't detectable by science, but the absence of evidence isn't conclusive evidence of absence," he said.

 

He pointed out that, for years, there had been talk among tribespeople in Africa of a strange creature that was a sort of giraffe-zebra hybrid. Scientists scoffed. "No-one believed it existed; it was legendary," he said. "Finally someone did see one-the okapi."

 

While he's not really expecting a half-lynx, half-snake monster to suddenly become snared in a USGS net, he and his colleagues are always braced for a surprise of some sort, and hope it won't be of the Asian carp variety, a documented oversized nasty that has been making its way up the Mississippi and is now banging at the (electrified) gate of the Great Lakes.

 

"Very often it is our group that is typically the first to find invaders," he said. "And that's one of the reasons we're out there-to assess the fish community, and detect change."

 

So far, though, the so-called flying carp has been blessedly absent in USGS catches. "We've heard recently that it was sighted in the Great Lakes, but who knows," he said. "We've had reports in the past, and it turned out to be the common carp. And even if someone sees one, it doesn't mean it's established."

 

Right now, "there is no evidence of the Asian carp being established," he reassured. "We haven't seen one in our surveys, and we wouldn't be secretive about it if we did."

[Twocoda]

Thanks for this ...i was under the impression the clouds on the screen of last two years were alewives on the rebound...im now edumacated

[Spiel]

I'm glad you found it to be useful.

[Raf]

indeed. thanks for that Spiel.

 

however, we do see lake trout and pike coughing up them alewives on a regular basis on the eastern shore.. they're still here.

[LeXXington]

I can remember growing up in Kincardine and going down for smelts glad to see they are coming back