Maine DMR concludes annual assessment of Atlantic salmon smolts
Survey conducted
on four rivers
including Piscataquis
AUGUSTA — The Maine Department of Marine Resources Division of Sea-run Fisheries and Habitat staff recently concluded annual assessments of Atlantic salmon smolt populations in the Narraguagus, East Machias, Sheepscot and Piscataquis rivers.
Maine DMR photo
SALMON SAMPLE — Department of Marine Resources seasonal contractor Andrew Gibbs shows off an Atlantic salmon smolt pulled from a DMR trap on the Piscataquis River. The DMR uses rotary screw traps on the Piscataquis to trap smolts as part of its annual effort to assess the health of Maine’s Atlantic salmon and their habitat.
The work will help the department and its partners at the state and federal level understand the status of Atlantic salmon and the quality of habitat in Maine waters.
The rivers were chosen because their geographic range provides an indicator of Atlantic salmon and habitat health along the coast.
A smolt is the life stage of Atlantic salmon that transitions from freshwater river and stream habitats to saltwater coastal and open ocean areas.
Listed as an endangered species since 2000, the Atlantic salmon is one of Maine’s iconic fish species, long the favorite of recreational anglers.
However factors including overexploitation, degradation of water quality, and damming of rivers have been associated with the decline in abundance. The populations of Atlantic salmon present in the Gulf of Maine represent the last wild populations of U.S. Atlantic salmon.
“Our efforts to preserve and protect the Atlantic salmon population in Maine include the spring trapping and evaluation of both wild and hatchery grown smolts to assess their abundance and related management actions, as well as adult returns,” said Oliver Cox, Director of DMR’s Division of Sea-run Fisheries and Habitat. “Our objective is to increase the population of smolts through management actions including stocking and habitat restoration. Data from these assessments, which will be reviewed over the next year, will help us determine future management actions.”
On their way to the sea, migrating smolts were captured for DMR assessments in rotary screw traps which were suspended from a cable and float on pontoons. A “cone” portion of the traps has vanes inside that prevent fish from swimming out. The fish were directed to the back of the trap where they end up in a container called a live car.
During May and June DMR scientists tended the traps daily, counting trapped fish, recording biological data such as length, weight, age, and origin before releasing the smolt to continue their migration.
The scientists estimated the total number of smolts passing by the traps since all the smolts leaving the river cannot be captured. “Use of smolt traps gives the best estimate of smolt production in salmon habitat located above trapping sites,” said Cox. Data obtained during the smolt trapping season is used by DMR scientists to estimate freshwater and marine survival when used in conjunction with the juvenile or adult abundance of the same year class.
Since 2008, Atlantic salmon smolt production has also been evaluated in the Upper Piscataquis River to understand how smolt produced from direct adult releases compared to previous fry stocking efforts. In 2009, adult Atlantic salmon were trapped at the Veazie Dam and transported to the U.S. Fish and Wildlife Service Craig Brook National Fish Hatchery.
The fish were held at the hatchery until October when they were released in to the Upper Piscataquis to spawn on their own.
“Since 2012, smolts handled at this site have been the result of adults spawning in the wild. Preliminary results indicate that this management action can successfully produce smolts at densities equal to what we would expect for a healthy Atlantic salmon run,” said Cox.
Funding and equipment for smolt assessments is provided by NOAA Fisheries through a Cooperative Agreement with Maine Department of Marine Resources.