Alewives in the pacific northeast have had a rough few decades as the population has declined drastically from the significantly higher numbers in the 1950s or 1970s. In states like Maine, the declines have been attributed to overfishing, watershed pollution and river dams that block fish passage populating the state. Concerned over the decline, the College of the Atlantic and other groups have spent the past several years working to restore alewife populations in Maine.
The college has worked in partnership with organizations like the Somes-Meynell Wildlife Sanctuary and the Maine Department of Marine Resources (DMR). Chris Peterson, a professor at the College of the Atlantic, shared that he and his students have focused most on building effective fishways, removing unnecessary dams, repairing neglected runs, restoring and conserving stream habitats, and keeping a close eye on populations. The efforts began in 2008 when Petersen began partnering with local organizations working to help restore historic alewife runs.
The success of such restoration efforts can be assessed through biological sampling, counting, water chemical testing and scale collection. As such, sampling is a significant part of the labor invested into any alewife-focused program. At the COA, this means that students help to count fish, set up fish ladders and clear debris from waterways.
Alewives are relatively small fish, at least when compared to some of the trophy catches of the region, but they are nevertheless important to the environment. The state DMR states, “Alewives are important to the ecology of freshwater, estuarine, and marine environments. They provide an alternative prey item for osprey, eagles, great blue heron, loons and other fish-eating birds at the same time juvenile Atlantic salmon are migrating downriver.” In short, alewives are essential to protect and support other life that runs through the state.
In order to understand how a species that once ran through densely populated waterways ended up needing intervention, one must consider the history of the fish. Alewives are anadromous fish that spend a part of their life at sea and some in freshwater environments. Unfortunately, the circumstances of their lifecycle lead them to be easy casualties of trawling. Peterson explains to the COA, “A herring midwater trawl can be huge, unbelievably huge […] Because they’re harvesting millions of fish, you don’t need a very high percentage of bycatch to end up with a lot of alewives.”
Even after making it to their freshwater habitat, alewives in Maine are still threatened. Dams and other obstructions currently block around 52% of historical alewife spawning habitat in Maine, making the work of institutions like the COA and its faculty and students so vital as they hope to mitigate these impacts.
One of the alumni from Peterson’s program, Emily Argo, led a study in 2010. Argo looked at the possibility of restoring Denning Brook, a stream in Somesville, Maine, as an alewife run. In it, Argo lays out some of the histories of the stream, along with a summary of physical and water quality characteristics that would need to be met in order to maintain a successful alewife run in the waterway.
Another project from COA was led by Alex Brett, who graduated from the school in 2011. Brett looked to determine if bird predation went up or down on days when more fish were coming through Somes Brook. His investigation found that the more fish that were swimming through, the less likely it was that they would be eaten by a bird—proving how an alternative prey option can protect more-threatened species. Most of Brett’s work involved using nets and other collection devices to count fish, something that Petersen maintains is one of his favorite activities. He loves to count fish and root them on, he says, and is especially fascinated by the relationships between the fish and their predators–eagles, ospreys, cormorants and mergansers.
From his perspective, as well as ecologically, alewives are important. Strengthening their populations benefits the fishermen who collect them, the lobstermen who value them as bait, and watersheds themselves.
Alewives are vital for more than just biodiversity. They’re a critical part of Maine’s lobster industry, and the species also serves as a transporter of nutrients between freshwater and marine ecosystems. Furthermore, they’re a crucial part of the established food chain in the region, serving as prey for a host of species in both freshwater and marine environments. In short, alewives are integral members of the ecosystems they’re native to–in order to protect them in the future, increasing connectivity in waterways must become a priority.
Fortunately, thanks to the work of researchers like Peterson, and some of the alumni of the program, Alewife populations are on the rise in Maine. In 2014, Maine alewife landings totaled around 1.6 million pounds.