Salmon for Maine's Rivers:
A Novel Approach to Wild Atlantic Salmon Recovery
The Atlantic salmon was once the “king of fish” in rivers in New England. It is estimated that somewhere between 300,000 and 500,000 made annual spawning migrations to rivers ranging from the Housatonic River of New York to the St. Croix River of Maine (Kendall 1935, Scott and Crossman 1973). Dams, log drives, pollution, and overfishing combined to bring Atlantic salmon to the brink of extinction: the only remaining naturally spawning Atlantic salmon return to just eight rivers in the Gulf of Maine. Collectively, the salmon in these Maine rivers make up the Gulf of Maine Distinct Population Segment (DPS), which is listed as Endangered under the US Endangered Species Act.
Current management of Gulf of Maine Atlantic salmon focuses on using hatchery supplementation to prevent extinction and maintain genetic diversity. Each year, hatchery-bred salmon are released into Maine’s rivers at the egg, fry, parr and smolt stages. The hatchery program has succeeded in maintaining genetic diversity and prevented extinction of Gulf of Maine Atlantic Salmon. However, to reach recovery targets we need to increase the number of juvenile salmon that are rearing in Maine’s rivers and to achieve this we need to move beyond the hatchery program. In the Penobscot River, over 90% of returning adult salmon were stocked in the river as smolts but these hatchery smolts have no in-river rearing experience and can’t be counted towards recovery targets. In other words, we need more salmon that spent time in rivers, not hatcheries, before heading to the ocean.
One of the best ways to move towards the recovery criteria is to have more salmon spawning in rivers. The problem is that survival of Atlantic salmon in the ocean is very low. For every 1,000 smolts that leave the Penobscot River for the ocean, only 5 will survive to return to the river as adults.
In 2020, MDMR and partners will launch an ambitious plan to raise smolts to maturity in conservation net pens, allowing them to bypass the high mortality ocean phase of the life cycle. This program is based on an approach being successfully implemented by the Fundy Salmon Recovery program in New Brunswick, Canada. The goal of the “Salmon for Maine’s Rivers” program is to get more adult salmon spawning in the Penobscot River and in turn, increase the number of juvenile salmon in Maine’s rivers.
Step 1: Collect Atlantic salmon smolts from Penobscot Origin broodstock and transfer them to nearshore conservation net pens
Step 2: Feed and care for the salmon until they reach maturity after either one or two years in the conservation net pens
Step 3: Release the mature adults into high-quality but underutilized spawning habitat in the Penobscot River
Step 4: Use radio-telemetry and spawning surveys to monitor spawning success
Step 5: Capture some of the offspring (smolts) from net-pen adults for transfer to an intermediate facility and then the conservation net pen
Step 6: Continue by repeating the above steps in an adaptive management framework