Biologists’ study fills brook trout data void

loading...

Maine enjoys a well-earned reputation as a haven for wild brook trout, as well as the anglers who fish for them.

And while Department of Inland Fisheries & Wildlife biologists spend plenty of time working on management plans for the species, they’ll admit that there’s always room for more research.

On Thursday evening, past and present members of the Moosehead Region fisheries staff met in Brewer with a group of interested anglers who gathered to hear the results of a yearlong study that is nearing completion.

That project, the Chamberlain Lake Brook Trout Study, began in the fall of 2006, when grant money was used do fund an ambitious project.

The goal: Fill a hole that existed in the data the state has compiled over the years and learn more about how brook trout live and behave in large, oligotrophic lakes.

Oligotrophic lakes, fisheries staffer Steve Seeback explained, are a bit different than those small ponds many think of when they think about brook trout.

“In layman’s terms, it’s basically a very sterile environment, not a lot of vegetation along the shorelines … and there’s good oxygen all the way down to the deepest part [of the lake],” Seeback said.

That describes Chamberlain Lake well. The 11,084-acre lake sits in northern Piscataquis County and is part of the Allagash Wilderness Waterway. It’s 154 feet deep at its deepest, and anglers often target togue, cusk, whitefish … and brook trout.

“For a long time biologists assumed that the trout populations we see in our smaller trout ponds, as well as our stream environments, were basically the same on our larger lakes,” Seeback said. “Through our work we found that this is not the case.”

Among the discrepancies: Most of the wild fish in Chamberlain don’t reach sexual maturity until at least 3 years of age, while those in smaller ponds – those under 200 acres – are often mature at 1 or 2 years old.

In addition, far more of the fish you’ll find in those small ponds are 1- and 2-year-olds: More than 70 percent of the fish caught in a previous small-pond study were in those age classes, with very few reaching the age of 5.

Other fisheries staffers who worked on the project were Tim Obrey and Jeff Bagley, while retired Moosehead region biologists Paul Johnson and Scott Roy were present Thursday to hear the results of the study. Johnson introduced the program in his role with its sponsor, the Natural Resources Education Center of Greenville.

In September and October of 2006, fisheries staffers trap-netted and marked 276 trout, implanting radio tags in 52 of them. Among those were 39 adult males, eight adult females and five immature trout.

Over the ensuing year, they tracked the fish on foot, using planes and boats and through a stationary tracking station on the lake.

The first surprise for biologists came during last winter’s ice-fishing season.

Fish stayed in their spawning streams through much of November, then dropped back into Chamberlain Lake.

Then they got comfortable … and stayed put.

“Wherever they set up by the middle of December, that’s pretty much where they stayed throughout the entire ice-fishing season,” Obrey said. “So you need to think about that as a fisherman. If you’ve got your shack set up someplace that’s good for trout fishing and you do well in January and you’re not catching fish in February and March, it may be time to move.”

Not only are the fish not moving very far during the winter months, there aren’t many of them around to target. And that combination can make them tough to catch.

Obrey said the study helped form a population estimate of fewer than 1,100 legal (14 inches or longer) trout in the entire lake.

In some more fertile small ponds, Obrey said the trout population could range from 10 to 100 trout per acre.

While the fish stayed put during the winter months, they moved extensively during the spring and summer months and ranged from one end of the lake to the other.

Come spawning season, though, the fish knew exactly where they were going.

By fall of 2007, the depleted stock of radio-tagged fish that had previously spawned – 13 trout at this point – all headed back to the streams they had spawned in a year before.

All of which leads to the big question: What happened to the other fish that were tagged?

A good question.

As it turns out, the chore of spawning isn’t all fin-and-fun for the fish. It can be downright dangerous.

“By Jan. 1 of 2007, we only had 44 percent of our brook trout left alive, that we had radio-tagged,” Obrey said. “Most of them suffered from what we call post-spawning mortality. They went up in the streams, they spawned, and then they died.”

Sixty-four percent of the adult males died, as did 50 percent of the adult females. None of the sexually immature fish, which did not spawn, died, helping to show Obrey and his staff that spawning mortality was a key concern.

Some subsequent searches for the radio tags – which emit a different “mortality” signal when the trout remains stationary for more than 24 hours – turned up a few. One was deep in a beaver dam, another was deep in the woods, in the burrow of a predator.

One of the driving forces of the study was the desire to understand more about big-lake brook trout populations, and Obrey said the lack of data had thwarted management decisions in the past.

“A few years ago we proposed to close a large area on the north end of the lake to fishing, and that proposal was denied because we didn’t really have enough data,” Obrey said.

There is already a smaller area on that end that is closed to fishing during the winter, Obrey explained.

But by looking at the radio-tag data, he can see that closing a larger area could have protected more fish.

“We had six fish stay in this general area [during the winter],” Obrey said. “One of them stayed in the closed area the entire winter. The other five just moved in and out [from the presently closed area to the area that would have been closed, according to the proposal that was denied]. We actually had two of those fish caught, and I think one of them died as a result of the hooking. What we learned is, this area does protect a few trout.”

Another lesson, Obrey said, was that requests to open all of the state’s waters to fishing year-round – a proposal that is regularly debated by anglers -might not be a good idea.

“What happens if you’re up in one of these streams and you start fishing over these fish that are already suffering a real high natural mortality rate [during the fall]?” Obrey asked. “The stress is probably going to be worse, and you’re going to see really, really high mortality rates from the added stress of hooking.”

Obrey said fisheries staffers would finish up work later this winter, tracking the remaining tags to see where the fish are.

And he said the study poses more questions that his staff plans to address in the coming years.

On the agenda: Revisiting a study performed at Socatean Stream on Moosehead Lake by biologist Roger Auclair in 1957.

Repeating that study, during which Auclair set up a weir and captured every fish that headed up and downstream, will help biologists further understand the brook trout in Maine’s largest oligotrophic lake.

MYFGA stages youth fishing day

Over the past several years, Maine’s Youth Fish & Game Association has offered a number of fun and educational programs to area kids.

That record of service will continue Jan. 19 when the group stages its annual youth ice fishing day.

The event will run from 8 a.m. until 3 p.m. and gives parents a great opportunity to spend some time outdoors with their children.

No experience is necessary, and all equipment and bait will be provided.

A free lunch will also be served.

I’ve attended a few of these ice fishing days over the years, and they’re always a great time … even if the fishing is slow.

Some kids choose to bring sleds (or slide down hills on their bellies) when the flags aren’t flying, and a couple years back some older children opted to set up a game of hockey, using bait spoons for sticks and rocks for pucks.

The MYFGA clubhouse is located on Pickerel Pond outside of Milford. To get there, follow County Road out of Milford to Stud Mill Road. Turn right, drive three miles, and the clubhouse will be on your left.

In case of rain, the event will be held Jan. 20.

jholyoke@bangordailynews.net

990-8214