MOUNT DESERT — Since mid-May, alewives, also called river herring, have been working to reach Long Pond, a mile and a half swim from Somes Sound, to mate.
On May 19, the first 20 alewives of the season were counted on their spring spawning migration from saltwater to freshwater as they navigated the Somesville Mill Pond fish ladder.
“We are up to about 18,000 now,” said Billy Helprin, director of the Somes-Meynell Wildlife Sanctuary in Mount Desert. “That’s good compared to last year, but it’s not good compared to the year before.”
Last year was a year of low numbers for the alewives; only 7,608 were counted entering the Mill Pond.
“Most likely due to the very dry summers we had the years before,” said Helprin. “If there’s just not water exiting the ponds or lakes, they’re going to be stuck in there, subject to predation.”
And that means fewer of them will return to the ocean to start the process all over again the next year. There are several predators to the alewives, including osprey, eagles, seals, loons, cormorants, otters and minks.
“We would like to get as many as possible in and out,” Helprin explained about the fish. “There’s more safety in numbers if you can move in a big group. For the survival of the species, it’s good to move in groups.”
Counters, people who volunteer to count the fish as they move upstream, are consistently planted at the fish ladder on Mill Pond around high tide in order to record how many alewives are making the trek into any of the four freshwater spots along the route to Long Pond.
“Our biggest day, so far, is May 28,” said Helprin, adding there are 25 volunteers with the organization working on various aspects of recording and assisting the alewife navigation. “We had almost three and a half thousand that single day. Each day is different.”
Their migration begins when water is running from higher elevations through the waterways and begins to increase in temperature. Without rain to continue to keep those water levels high, the alewives can struggle to maneuver up and down the water route to the larger bodies of freshwater where they lay and fertilize their eggs.
“Strategically placed sandbags and rocks help create easier ‘steps’ for them,” said a recent Facebook post on the Somes-Meynell site highlighting a video of the fish migrating. “Watching their athleticism and determination in action is truly awe inspiring.”
A recently released video funded by the National Science Foundation, “The Greater Connection,” is about alewives on Mount Desert Island. It was a collaborated effort involving faculty from the University of Maine, College of the Atlantic and Winston-Salem State University. It can be found online at https://vimeo.com/373442327 and talks about how pathways for alewives were closed over the years because of dams, mills and other activity on the waterways they travel, but how that is shifting.
Alewives are an important part of the food chain and when their numbers decrease it has a ripple effect on the ecological structure. In 2005, when Helprin’s predecessor at the sanctuary, David Lamon, began working to repair the fish ladders on migration route from Somes Sound to Long Pond, only 361 fish came into the Mill Pond. Adding fish to the ponds, or stocking, has happened in the last 15 years to help that number grow.
In the last few years, there has been work done on the fish ladder located at the mouth of Seal Cove Pond in Tremont led by Maine Coast Heritage Trust. According to Town Manager Chris Saunders, that organization is slated to install an informational kiosk at that site for visitors.
“It’s a tough stream channel below that for them to get up,” said Helprin about why numbers of alewives in that area have been small. “It’s a big climb and not very many steps for them to get up there.”
Last year, just over 500 alewives completed the mile and a half journey from Somes Sound to Long Pond, less than seven percent of the number that made the spawn migration. This year, so far, 4, 000 have reached Long Pond, 20 percent of the 20,000 that have made it into the Mill Pond. In 2016, 60 percent of the 33,159 counted fish made it, which, at 20,100, is closer to the total number migrating this year.
“Some factors out of our control, like how much rain we have, and can make a huge difference in their ability to get in and back out,” said Helprin, explaining the adults come in and spawn in the span of a week to 10 days and return to the ocean. “It’s amazing what these fish can do if given a chance. This project is about giving them a chance.”
CORRECTION: The print version of this story misspelled Helprin’s name. The Islander apologizes for the error.