Scientists Seeking Smolts -- May 10, 2001 2001/05/10 Scientists Seeking Smolts

Vessels Will Trawl

Surface Waters

in Penobscot Bay

George Liles
(508) 495-2378
Teri Frady
(508) 495-2239


NMFS Northeast Fisheries Science Center

N         E         W         S

Orono, Maine -- Earlier this spring a team of scientists from the Commerce Department's National Oceanic and Atmospheric Administration (NOAA) tagged and released 170,000 young Atlantic salmon, or smolts, in the Penobscot River. On Monday the scientists will begin trawling the surface waters of the upper Penobscot Bay to determine how many of the stocked fish survived their migration down river into the bay's salt waters.

(Note May 18: a progress report on the smolt trawling project is available.)

"In the past 15 years, the number of stocked salmon that return to the Penobscot to spawn has been declining," says senior NOAA Fisheries researcher, Russell Brown. "Last year, a 30-year low of only 532 adults returned to the Penobscot. We are trying to measure how many of the stocked fish are lost in the early part of their migration, when they make the transition from freshwater to marine environments," Brown says.

Using two chartered commercial fishing vessels, researchers hope to recapture some of the tagged smolts in a large net towed at the water's surface. The information gained from the tagged fish will help Brown and his team measure the smolts' survival rates during the first leg of the two-year migration that will take the salmon as far as the shores of Greenland. The team will take tissue samples from some of the smolts to see if juvenile salmon are successfully making the transition from freshwater to sea water and are in good condition for their long ocean journey.

The trawl survey will be conducted May 14 to May 24 on both sides of Isleboro Island, during what is believed to be the peak period of juvenile salmon movement into the upper bay. Researchers will try to avoid trawl tracks in places where lobster gear is evident. The captains of the trawlers will also be taking precautions to avoid harbor porpoise.

"We are using commercial trawl vessels for this work, but they will not be bottom trawling," says Brown. "They will be paired in order to tow the net, which has to be at the surface to catch smolts."

The F/V Nobska and F/V Morue out of Woods Hole and New Bedford, Mass. have been chartered for the work and will carry four to five scientists, as well as their operating crews. The surface net (originally developed and used successfully in Norway) has a specially designed box that allows fish to be captured, examined on deck, and released unharmed.

"We are keenly aware that lobster gear is set in the area and are taking every precaution that we can to avoid it," says Brown. "After talking with folks from the Maine Lobstermen's Association and Penobscot Bay Lobstermen's Association, we have tried to pick a time that will coincide with high juvenile salmon densities, but not be at the busiest part of the lobster season," he said. Researchers plan to have a representative from the local lobster industry on board to help vessel operators avoid lobster gear that may be set in the area.

The Penobscot River currently hosts approximately 60 to 70 percent of all adult Atlantic salmon returning to United States rivers. The 532 adult fish known to have returned to the Penobscot in 2000 are less than 10 percent of the number of spawners required for a healthy population. Information about juvenile survival rates could be useful in making plans to rebuild healthy, self-sustaining populations of Atlantic salmon.

For more information on NOAA, please visit the NOAA website.

NOAA/National Marine Fisheries Service * 166 Water Street * Woods Hole, MA * 02543
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