Mimic nature, expect more salmon

In Maine rivers from the Androscoggin to the Dennys, Salmo salar has been on the Endangered Species List since 2000. At Craig Brook and Green Lake hatcheries, the U.S. Fish and Wildlife Service maintains the lineage of each river, matching reproduction to maximize genetic diversity, and raising millions of salmon to be placed in their native rivers as a long-running strategy to recover the species.

But only a small percentage return as adults, and scientists including John Kocik of NOAA’s Northeast Fisheries Science Center largely blame changing marine conditions.

“The most important strategy we can use to address low marine survival is to get more young salmon to the ocean,” said Kocik. And wild salmon – those that have grown up in their home river instead of in a hatchery – have better survival at sea, said Kocik. Such a strategy appears to be succeeding at the Peter Gray Hatchery on the East Machias River, where since 2012 the Downeast Salmon Federation has been experimenting with a more “natural” approach.

Fish hatch from eggs into unfiltered, fast-flowing East Machias River water in tanks with black sides and bottoms meant to mimic the gravelly river bed. Each fall, tens of thousands of young salmon, known as parr, are distributed throughout the East Machias River. These conditions and density are modeled after methods developed by the late Peter Gray on the Tyne River in England that are credited with restoring that river’s salmon population.

At a presentation in late May, Downeast Salmon Federation reported a “breakthrough”: more parr are surviving to become smolts, the life stage that migrates to the ocean, and more smolts are surviving at sea and returning as adults to the East Machias River. “The return rates we are seeing are higher than any other stocking techniques used in Maine,” said hatchery manager Zach Sheller.

“NOAA is very intrigued and interested in these results,” said NOAA’s John Kocik. “But it still means less than 1,000 smolts and only 20 adult salmon, only a fraction of what we want to see for recovery.”

According to Peter Lamothe, Program Manager of the Maine-New Hampshire U.S. Fish and Wildlife Service Complex, 500 salmon need to return to the East Machias to consider the fish as threatened instead of endangered, and 2,000 to remove them from the Endangered Species List completely.

“I hope this leads to something significant,” said Lamothe, “but we still have some work to do. Conditions in the marine environment are still the limiting factor.”

In order for salmon to return to Maine rivers, two things have to happen: there has to be hospitable habitat in both fresh and salt water, and there has to be fish to fill it. There’s been a lot of momentum on the freswhater habitat side: removing dams, replacing culverts, cleaning up pollution. According to Shaw, conservation genetics and hatcheries are equally necessary. 

“We can fix the river, but if we’re putting in fish that won’t survive, we won’t succeed. We have to fix the fish, too,” he said. Their aim is to prevent domestication and be as hands-off as possible.

Shaw can’t tease apart what piece is critical. The habitat is certainly not ideal: the East Machias river hosts invasive fish species, like smallmouth bass, that compete with salmon. Water temperature has increased, and drought has been common over the last decade. “That’s what’s remarkable to me about all this,” said Shaw. “It’s been like a worst-case-scenario test, and we’ve still seen these results. What happens when we get ideal conditions? We have to be ready.”

Downeast Salmon Federation is trying to raise $751,000 in private funding to match a challenge grant from U.S. Fish and Wildlife Service to expand their approach to the Narraguagus and Pleasant rivers, a plan that is also supported by NOAA and the State of Maine. “We’re not going to have an impact population-wide unless we scale up,” said Shaw.

Shaw’s hopes that one day people may again fish for wild salmon in Downeast Maine are sustained by stories of success in the salmon rivers of Denmark, Norway, and England, where the Tyne continues to be an inspiration. Peter Gray’s old hatchery there has been repurposed (currently for culturing mussels) and the river is full of salmon anglers. Closer to home, Shaw finds hope in the the bald eagles that perch and soar along the East Machias, and in the hatchery’s dark-sided, gravel-bottomed tanks, where thousands of tiny salmon swim against the current.

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This story appeared in the July 2021 print issue of The Working Waterfront.