Researchers Work to Understand Alewife Populations in Rivers Along Maine’s Coast

While the alewife run in Maine is in full swing, the Gulf of Maine Research Institute (GMRI) and the University of Southern Maine (USM) are collecting alewife samples as part of an effort to unlock some of the mysteries surrounding this important forage species. Study locations include more than 20 river systems and lakes along the Gulf of Maine coast.

Alewives are currently making their annual spawning runs from the ocean to freshwater lakes. Despite their historical commercial and cultural importance to Maine communities, there is still much to be learned about alewife ecology. Alewife populations along the Atlantic coast have exhibited dramatic declines over the past 20 years despite efforts to remove dams and restore waterways. These efforts have led to recovery in some systems but not in others.

It is unclear where alewives migrate to after leaving freshwater for the ocean or whether the fish born in a particular lake continue to school together or mix with other alewives in the ocean. If alewives from specific freshwater systems can be distinguished from each other, as this research project is investigating, researchers and managers may be able to better monitor population dynamics of alewife from specific runs, evaluate the impact of the unintended capture on specific alewife populations, and unlock the mystery of where alewives go once they leave Maine rivers.

Many communities lease permits to alewife harvesters, and most of the catch is sold as lobster bait. The sheer numbers of alewives that run up rivers provide protection for returning adult Atlantic salmon running up these same rivers and for Atlantic smolts that are moving downstream to the ocean at this time of year. Alewives are also a food source for osprey, herons, otters, cod, haddock, and other animals.

Maine’s alewife population is relatively healthy compared to other states, but scientists do not know why. Massachusetts, Connecticut, Rhode Island, North Carolina and Virginia have closed their alewife fisheries, and Maine may be forced to do the same unless the fisheries are proven to be sustainable.

 Alewives Under the Microscope

The weight, sex, and 15 different measurements on each fish are recorded from the samples that have been taken during the spring spawn run. Genetic information is also taken. The ear bones – otoliths – are removed and studied. The rings in these bones are like the growth rings in a tree, revealing age and growth rates.

Jason Stockwell at GMRI said, “The three different sets of data allow for a more powerful data base.” One of the objectives of the project is to study the types and sizes of different alewife population groups in various Maine river systems.

It might then be possible to learn how alewives organize themselves in the ocean. Ale-wives are sometimes grouped with Atlantic herring on the fishing grounds. Stockwell said this information will be valuable in analyzing bycatch. By knowing what amount of bycatch was from which particular river system, the impact of the removal of that particular bycatch could be evaluated if the population of that river system is known.

Stockwell said the project has blossomed with additional support coming from the DMR, Acadia National Park, Somes-Meynell Wildlife Center, the College of the Atlantic, the Alewife Harvesters Association, and others.

One of the important benefits of the project is that the methods used, a microscope and digital camera, can be done in any lab. This means the population study’s techniques could become part of the standard monitoring process.

Maine’s alewife population is relatively healthy compared to other states, but scientists do not know why. Massachusetts, Connecticut, Rhode Island, North Carolina and Virginia have closed their alewife fisheries. Maine river systems must have a proven sustainability plan in place by 2012 or close it’s alewife fisheries.