River egg pits promising salmon sign Fish ‘redds’ Down East make biologists happy

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It will be years before the final results are in, but some of the more than 1,000 adult Atlantic salmon released into Down East rivers last fall have cleared their first hurdle.

Salmon biologists say they’ve counted 60 egg pits in the Dennys River, an indication that the 96 sexually mature fish that entered the river in October are trying to reproduce.

Half of the stocked fish were female, and female salmon usually produce an average of two egg pits, or redds, according to John Kocik, a biologist with the National Marine Fisheries Service in Woods Hole, Mass.

“We’re very optimistic about the early results,” Kocik said. “We didn’t know if the fish would spawn successfully or drift out to the ocean.”

The Atlantic salmon that produced the redds in the Dennys are the first of their kind to be stocked in Maine’s salmon rivers.

They are different from wild salmon or the juvenile salmon that are usually stocked in Maine rivers because they were raised to adulthood in captivity.

The fish are the descendants of brood stock taken from the Dennys and spawned at the Craig Brook National Fish Hatchery in East Orland. But Atlantic Salmon of Maine, one of Maine’s largest salmon aquaculture companies, received the eggs from Craig Brook, hatched them at the company’s freshwater hatchery in Oquossoc, and raised them to sexual maturity in ocean pens off Machiasport.

Given the fact that the fish have never been exposed to the wild, the real test will be whether the Dennys River eggs will produce juvenile salmon that survive life in the river, go to sea and then return to produce another generation, Kocik said.

“We’re looking at this long-term,” he said. “The experiment needs to produce adult fish.”

Tim Sheehan, the federal biologist who oversaw the Maine stocking program, said the next step would be to survey the redds in the spring to see whether the eggs produce juvenile salmon.

It will be 2003 before the salmon produced from this year’s eggs are ready to go out to sea as smolts and another year or two years after that to see if they return to the river to spawn, Sheehan said.

Last fall’s stocking program was a collaborative effort by state and federal fish agencies and Maine’s aquaculture industry to help restore runs of Atlantic salmon to some of the eight Maine water bodies where the fish are listed as an endangered species.

Those water bodies are the Dennys, East Machias, Machias, Narraguagus and Pleasant rivers in Washington County, the Sheepscot in Lincoln County, the Ducktrap in Waldo County and Cove Brook, a tributary of the Penobscot.

The National Marine Fisheries Service and the U.S. Fish and Wildlife Service believe the rivers are home to the last wild runs of Atlantic salmon in the United States.

Last October, Atlantic Salmon of Maine, the Maine Atlantic Salmon Commission, the fisheries service and the Fish and Wildlife Service released 1,083 adult salmon into the Dennys, East Machias, Machias and St. Croix rivers. The St. Croix, which is not one of the rivers where Atlantic salmon are listed as endangered, received 829 salmon because the salmon commission did not want to crowd spawning habitat on the other rivers.

The Dennys River is the best indicator from the experiment so far because salmon biologists operate a weir on the river and had identified only one wild adult fish in the river when the aquaculture-raised fish were released, according to Fred Kircheis, executive director of the Maine Atlantic Salmon Commission.

And, unlike the Machias and East Machias rivers, which are much larger, the Dennys is small enough for salmon biologists to conduct a complete redd count, he said.

Partial counts on those rivers indicate 10 redds in the East Machias and 23 on the Machias, he said. The two rivers received a total of 158 adult fish last fall.

Neither the Machias nor the East Machias has a weir, so biologists don’t know how many wild salmon are in those rivers.

The only way to tell whether the redds were dug by the aquaculture salmon or wild salmon will be when the commission electrofishes the juveniles that come from the redds.

Each adult salmon released this fall was outfitted with a coded wire tag that carries genetic information, including the identity of the parent fish.

“We believe that our redd counts on the Machias river systems would be higher if we had been able to evaluate all of the habitat,” Kircheis said. “Despite the low number of redds observed, we are still quite pleased with the initial results.”

The salmon commission conducts the annual redd counts, and Kircheis said complete counts were conducted on the Dennys in 1995 and 1999. In 1995, biologists counted 49 redds and in 1999, the count was 23, he said.

The only other river where complete redd counts have been conducted is the Narraguagus.

During the past five years, the Narraguagus redd counts have ranged from a high of 161 in 1996 to 21 in 2000, he said.

Sheehan said wild salmon produce approximately 7,000 eggs in two redds. But the aquaculture-raised fish, which are larger and better fed, are capable of producing twice that, he said.

“So even if they put down only one redd, we could be talking about as many eggs as a wild fish,” he said. “We just don’t know.”

Greg Mackey, the Maine Salmon Commission biologist who conducted the redd count on the Dennys, said he has no hard measurements.

But he noticed that about half of the redds appeared several weeks later than he would have expected with wild fish.

And, there appeared to be more test pits – where the female digs to determine if the substrate is a good place to lay her eggs, he said.

Kircheis said the aquaculture industry is raising more river-specific fish that will be ready for release next fall.

The salmon commission and Craig Brook supplied the industry with 3,000 eggs in January 1998 – 1,000 eggs from the Dennys, East Machias and Machias rivers, he said.