Smolts abound: Making Atlantic salmon spawn in upstream habitat paying dividends

Posted May 19, 2014, at 10:32 a.m.
Last modified May 19, 2014, at 6:13 p.m.

ABBOT, Maine — Every day for a four-week period during this time of year, marine scientist Randy Spencer hops in his pickup truck, drives to a spot on the Piscataquis River 120 miles from Penobscot Bay, and checks the status of his Atlantic salmon “tollbooth,” looking for smolts.

Traffic at the tollbooth — actually a rotary screw trap that catches the immature salmon as they try to head downstream on what will be a 5,000-mile round trip to Greenland and back — has been heavy.

Just as the 31-year biologist, who now works for the Maine Department of Marine Resources, hoped it would be.

“The results today are very encouraging,” Spencer said Thursday as field technicians Derik Lee and Andrew Gibbs prepared to check the trap’s livewell for salmon. “This is some of the finest habitat I’ve seen anywhere.”

The current work on the Piscataquis is part of the latest phase in a research project that began in 2008. First, Spencer had to figure out if he could convince adult Atlantic salmon to spawn in the habitat he thought was perfect for a fish listed as endangered in Maine under the federal Endangered Species Act.

And if he could, he would then try to figure out how many offspring those salmon were producing, and how those numbers compared with salmon production in tributaries lower in the Penobscot River drainage.

Seven years into the study, Spencer said the results have been eye-opening. And he thinks the progress that he and his crew have documented may add a powerful component to salmon restoration work.

“My hope and belief is, this is really going to have management implications,” Spencer said.

Short-circuiting Mother Nature

When Spencer began formulating the plan for this multiyear project, he thought the habitat that existed on the Piscataquis River above Guilford had the potential to be better than some of the downstream habitat where stocking was being done.

And he says he thought natural spawning would be the best way to elicit natural returns to the region when any offspring tried to return from the sea.

He did face a problem, though.

“Biological theory says [salmon] should go back to where they were born, or their stocking site,” Spencer explained.

Because of that, the fish that were trapped at the former Veazie Dam site were most often imprinted to return to spawning sites far downriver.

Spencer explained that if adults were captured in Veazie, spent some time at a hatchery, then were stocked in the Piscataquis, the fear was that they might immediately head back downstream, eventually arriving at the Veazie Dam or at less productive spawning habitat.

The solution: Don’t give the salmon time to roam before their spawning urge hits.

“We took fish just before spawning, thinking we could circumvent that roving period,” Spencer said. “Before salmon settle down to spawn, it’s very typical to rove considerable distances in the river. So I said, ‘I’ll short-circuit all of that and get them to stay in this really good habitat where we want ’em.’”

It worked.

“About 20 percent of our fish went right back to where they were stocked, right above Veazie,” Spencer said. “Very rapidly, like seven days. Within a week they had gone 150 kilometers, over seven dams, right back to where they wanted to be.”

But 45 percent of those fish stayed in the Piscataquis, and another 25 percent remained somewhere upstream. Spencer said that was a tremendous success.

During three years of stocking adults just before they spawned — 2009-2011 — Spencer and his crew documented the arrival of salmon fry in the river. And they were pleased with the results, especially compared with data generated at sites farther down the Penobscot, where predators such as pike, smallmouth bass and pickerel chomped down the tiny salmon.

By looking at salmon nests, called redds, scientists could tell where spawning activity was taking place. Electrofishing for juvenile fish the next year helped indicate how well the spawning went.

“We had 44 redds at Great Works Stream [farther south]. I think it was 2011,” Spencer said. “We went back and electrofished and we found only one or two juveniles. Out of 44 nests, only one or two survived.”

The habitat farther from the Penobscot, on the Piscataquis, is much more productive, Spencer said.

“One female salmon in the [Piscataquis] could probably produce as many juveniles as 30 salmon spawning in one of the lower river tributaries,” Spencer said. “And that’s because water temperature here is superior and there are so many fewer predators.”

Counting smolts

Once Spencer established that he could short-circuit the natural urges of Atlantic salmon by having them remain to spawn in the Piscataquis, he had to learn how many young they were producing and how well those offspring survived the two or three years to get to “smolt” stage.

Enter the “tollbooth.”

Spencer and his crew catch smolts at the rotary screw trap, mark them by removing a predetermined piece of the smolts’ fins, and release the fish.

The project is a “mark-recapture study,” meaning that some fish will be caught twice.

Here’s how it works:

If a fish is caught for the first time, it’s marked and released nearly 2 miles upstream from the trap. That fish may well end up in the trap a day or two later, as it makes another attempt to get to the open ocean.

If it’s trapped twice, the crew can tell, because it already has a piece of its fin missing. At that point, the smolt is released 2 miles downstream from the trap, and is allowed to continue its journey.

Spencer explained that the methodology of the trapping technique correlates to an established mathematical model, and makes it possible to estimate the total population of smolts in the habitat.

“If we marked 100 fish and moved ’em up [the river], then we recaptured 20 of those, 20 percent, we’d say, ‘Out of all the fish passing this site, we’re probably catching 20 percent,’” Spencer explained.

And after crunching numbers like that for three years, Spencer is confident that the Piscataquis River habitat is teeming with Atlantic salmon.

Spencer said that trap-tenders have been plucking 40 to 50 smolts from the trap each day recently, and expects that in the next couple of weeks that number will range from 100 to 200 smolts per day as the migration peaks.

“The highest estimate that we have at this particular site is about 10,000 smolts,” Spencer said. “So based on the amount of habitat above here, that’s two to three smolts per habitat unit, which is 100 square meters, which is very good. It’s excellent production.”

Spencer has heard criticism from some who say that the state and federal governments have spent too much money — millions of dollars over more than 100 years of salmon conservation work — with little to show for it.

Adult Atlantic salmon returns on the Penobscot River last year were dismal, with just 372 fish making their way to the Veazie Dam trap.

But he says the recent removal of two dams on the Penobscot will help restoration efforts, as will study of the ocean-based challenges that salmon face.

“Asking someone why we should care if Atlantic salmon go extinct is like asking a miner not to worry if the bird dies. It’s only a canary,” Spencer said. “It’s our responsibility. We’re here, right now, and it’s our job to do what we can. I’m absolutely convinced that we have not destroyed this environment to the point that salmon can no longer survive here.”

Spencer said the project has been funded on a shoestring budget.

“Phase 1 of the project — the adult translocation and telemetry part — was mostly accomplished as part of our routine fish trapping and broodstock collection program,” Spencer wrote in a follow-up email. “I did write and receive a grant for the radio tags [$6,000 per year for three years] from the Penobscot Indian Nation. I borrowed some old, unused smolt traps from NOAA Fisheries and my salary is also paid, 100 percent, by an annual NOAA Fisheries grant, so the state of Maine really got a lot for little, thanks to a lot of support from our friends at NOAA Fisheries and the Penobscot Indian Nation.”

And as conservation work continues, he hopes what the DMR has discovered on the Piscataquis can help mold future management plans.

“Each one of these fish has made this incredible trip,” he said. “We’ve got to maximize the contribution of every one of those fish that comes back. Leaving their spawning location up to chance, you might get lucky and you might not. This way, you’re almost guaranteeing success.”