April 20, 2010

Alewives: Fish in troubled waters

Maine researchers delve into the mysterious decline of the alewife

By Beth Quimby bquimby@pressherald.com
Staff Writer

(Continued from page 1)

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Researcher Zach Whitener shows Kim Little, a University of New Hampshire student who will be interning at the Gulf of Maine Research Institute this summer, what to look for when examining alewives. The alewife population has dropped dramatically since the 1950s.

John Ewing/Staff Photographer

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“There is a lot of pseudoscience out there, but we really don’t know” much about alewives, says Jason Stockwell, a scientist at the Gulf of Maine Research Institute.

John Ewing/Staff Photographer

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• Spawning alewives average 11 to 12 inches long and weigh about 8 ounces.
• They range from Labrador to South Carolina.
• They spawn when the water temperature is 55 to 60 degrees.
• Each female produces 60,000 to 100,000 eggs.
• Most adults return to sea after spawning.
• Eggs hatch in about six days in 60-degree water.
• The young fish go to sea from mid-July through early November.
• Fewer than 1 percent survive long enough to make it to sea.

With the alewives just beginning to show up now in Maine rivers and streams, the two-year project -- which is trying to determine whether each river and lake has its own distinct population of the fish -- is shifting into high gear.

The 12 full-time and 12 part-time researchers and assorted volunteers are taking fish samples from 14 rivers and nine lakes and ponds from Saco to East Machias.

The work started last week with a cooler full of alewives from the Nemasket River in Massachusetts, which will serve as a comparison population. Each of the 100 fish in the batch is measured, weighed and photographed.

The researchers also conduct tests on the ear bone to determine the age of the fish. A fin sample is taken for genetic analysis.

At the same time, the researchers will be studying alewives caught at sea inadvertently as bycatch by fishermen who are trying to harvest other species. Stockwell said if it is determined that alewife populations are distinct and they return to where they were born to spawn, researchers can assess the alewives caught in bycatch and be able to predict a drop in population in their specific spawning grounds.

Knowing the answer to that question will help scientists understand what is happening to other species, such as cod and other groundfish that feed on alewives.

Stockwell said the project will develop an accurate method for monitoring the alewife population in the future, and it could provide answers to other mysteries surrounding the fish.

"This population has been ignored," Stockwell said.


Staff Writer Beth Quimby can be contacted at 791-6363 or at: bquimby@pressherald.com


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