Adult Stocking Program
an Effort To Help Conserve
and Restore Wild Salmon
NMFS Northeast Fisheries Science Center
N E W SOrono, Maine -- Nearly 800 adult Atlantic salmon are being stocked in three Maine rivers this week in a multi-agency effort to conserve and restore wild Atlantic salmon populations in U.S. rivers. The stocking in the Dennys, Machias and St. Croix rivers is the final phase of a collaborative project begun in 1997 by NOAA's National Marine Fisheries Service (NOAA fisheries), the U.S. Fish and Wildlife Service (FWS), Maine's Atlantic Salmon Commission (ASC) and private aquaculture companies in Maine.
"Atlantic salmon stocking programs usually consist of putting sexually immature fish into the rivers years before they are ready to spawn," said Mary Colligan, head of the NOAA team working to help save the endangered population of wild Atlantic salmon currently found in eight Maine rivers. "In this stocking program, we are able to put adult fish into the water just when they are ready to reproduce."
The fish being stocked Tuesday, Wednesday and Thursday were spawned from broodstock at FWS's Craig Brook National Fish Hatchery in 1997, and were transferred as fertilized eggs to freshwater rearing stations run by Atlantic Salmon of Maine (ASM), a Belfast, Maine private aquaculture company. When they reached the smolt (or ocean-going) stage in 1999, they were transferred to ASM's marine sea cage facility. Two other private aquaculture companies also participated in the adult stocking program: Connors Brothers Aquaculture, Eastport, Maine and Stolt Sea Farm, Lubec, Maine.
The five-year stocking program is the first attempt to stock adult Atlantic salmon in U.S. waters. The program is designed and carried out by teams of biologists and fish farming experts from private industry, the two federal agencies, and Maine's ASC. Oversight for the effort is provided by the state's Atlantic Salmon Technical Advisory Commission (TAC).
"The stocking this year is similar in some ways to last year's," said John Kocik, a NOAA fisheries biologist who chairs the TAC. "We again will attempt to fully seed the Dennys river and to stock half the fish needed to fully seed the Machias. All remaining fish adult fish are being stocked into the St. Croix."
The stocking in the Dennys and Machias is "river specific" stocking, which means that the fish going into those rivers are offspring of broodstock that were collected from those rivers as juveniles. The scientists plan to stock 84 adult salmon into the Dennys and 109 into the Machias.
The fish are large, averaging almost18 pounds in weight and almost three feet in length. Each female is capable of laying approximately 14,000 eggs in a series of nests (called "redds") she digs in gravelly, fast-flowing sections of the river. Each stocked fish carries an implanted tag that will make it possible for scientists who encounter the fish later to know the date, time, and location of stocking and some biological information about the individual fish.
"We have made several important changes to this year's stocking effort based on what we learned last year," said Tim Sheehan, a NOAA fisheries biologist. "Last year we focused on the movement of the stocked fish in an effort to gauge their ability and desire to seek out suitable spawning habitat. This year we are also going to assess their spawning to see whether these adults are successfully depositing viable, fertilized eggs in the rivers."
In 2000, teams of federal and state biologists surveyed the Dennys after the stocking and found 60 redds. Salmon experts were encouraged that the stocked fish built nests, but followup investigations indicated that a lower than expected number of small salmon (called "fry") were emerging from these redds.
"We were only able to monitor a handful of redds, so we don't have a strong grasp of how many fry were actually produced," Sheehan said. "This year we will count the number of redds again but we're also going to monitor the fry production from many redds. In collaboration with the ASC, we will also be conducting fertilization assessments in a hatchery to see whether these fish are producing viable fertilized eggs. This hatchery work will be a critical piece of the puzzle when we evaluate the success of the program."
When the hatchery tests are completed, the fertilized eggs will be placed in man-made redds within the rivers, adjacent to naturally dug redds by their counterparts. These redds will also be monitored for emerging fry.
"This year we are going to monitor every step of the spawning process to see how well these fish are doing, from sperm and egg through to fry," Sheehan said.
The National Marine Fisheries Service (NOAA fisheries), an agency of the Commerce Department's National Oceanic and Atmospheric Administration, is dedicated to protecting and preserving our nation's living marine resources through scientific research, management, enforcement, and the conservation of marine mammals and other protected marine species and their habitat.