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Monitoring Shows Alewives’ Comeback

May 23, 2011 - Benton - Nate Gray looked over at five small monitors at Benton Falls Dam, each showing live underwater footage of alewives.

The fish had just been lifted into a sophisticated man-made channel late Thursday morning. Next they'd each be counted and sent safely to the other side of the dam.

Gray, a scientist with the Maine Department of Marine Resources, said the high-tech monitoring system shows a remarkable comeback for alewives: given the opportunity, the fish can once again flourish in the Sebasticook River.

And that turnaround -- which is being closely watched by Gray and his team of state scientists -- is pointing to a teachable moment, Gray said.

"They're the teachers," Gray said of alewives. "We're the students. We have to watch what they do. We're not a bunch of theorists here. We base our knowledge on what we see."

All of this research is aimed at the restoration of the alewife, Gray said. And while many people may not appreciate its importance, the project could have profound implications for just about every plant and animal in the area, Gray said.

The alewife is Maine's most common river herring. They migrate to the ocean to mature -- a 70-mile journey for fish in this area -- then return after four years to freshwater spawning areas to lay eggs.

Alewives are key to the local environment, Gray said, describing them as the base of the food chain. Everything from bacteria, to fauna, to birds, and humans, are touched by alewife and their place in the cycle, he said. Adult alewives are also used as bait for lobster fisheries.

They're food for osprey, eagles, great blue heron, loons and other fish, while they also tie together the ocean, rivers and lakes with important nutrients, Gray said. Bald eagles and osprey, in particular, are now flourishing along the river, he said.

Put simply, the purpose of an alewife is to be eaten and sustain the food web, Gray said.

But the construction of dams, industrial pollution, and over-fishing all contributed to alewives being "erased from the picture," he said.

"They're a mere shadow of what they used to be, but this sort of restoration is totally do-able," he said. "It's not a question of whether we should do it, but when. And it should be done as soon as possible."

The restoration effort has been years in the making. Gray said the monitoring project at the Benton dam began in 2006 and has cost millions of dollars, but it's providing valuable insights into the best ways of granting alewives safe passage all along the state's rivers. Since the removal of the Fort Halifax Dam in Winslow in 2008, alewife have had free passage at the beginning of the Sebasticook River.

One key benefit is knowing how many adult alewives are returning from the ocean to spawning areas. Years ago, none were. Now, scientists are counting more than a million so far, an encouraging number since there are still a few weeks left to the window.

When fully restored, there should be 5 million alewives-- both adult and juvenile –traveling the Sebasticook each year, Gray said.

Gray said his team has worked well with the owner of the dam, Essex Hydro, to make the fish passage "better, stronger, faster." A lift that runs on a variable schedule hoists loads of alewife and other fish up an elevator into a flume, where dozens of cameras watch their path across the dam. The fish are counted by sensors.

"We monitor about everything here," Gray said. "And we basically see just about every species of fish that exist in this river region," which includes blueback herring, bass and Atlantic salmon.

Harry Isbister, an employee of Essex Hydro, has been assigned to check in visitors to the dam and watch the monitors all day. He finds it interesting watching the alewives gather together once they are in the dam's channels and beside a set of bars that separate them from the other side.

"It usually takes one brave one to go through the bars first," Isbister said.

Gray said he and state scientists are also tagging some alewife to compile data on their spawning grounds and determine what percentage of the fish ultimately survive.

There's economic incentive to see that they do live, Gray said, referring to their use as bait as well.

"We figured a female that's already eight years old produces $5,000 worth of children," Gray said. "Maine is one of the few states on the Eastern seaboard

that still commercially harvests this fish. Everywhere else, their count is going

down; here, we are actually going up on this river. That's why this is so important."

Scott Monroe, Kennebec Journal, May 2011


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