MANCHESTER, N.H.  — There was a surprising increase in the number of river herring passing the Amoskeag Fishways Learning Center in Manchester this spring where the herring run was already the biggest it’s been since 2000, biologists say.

On the Kennebec River in Maine, the removal of dams and other projects has boosted the herring run back up to 2 million a year, with a goal of bringing it up to 5 million.

As of May 15, a total of 17,333 river herring were counted passing through the fish lift at Essex Dam in Lawrence, Mass., the first dam upstream from where the Merrimack River empties in to the Atlantic Ocean.

The figure is almost twice the total of all last year’s run and more than 20 times the run in each of the two years before that.

“They were getting close to getting listed as an endangered species last year. To see them coming back in these numbers is really fantastic,” Rachel Brown, a naturalist at the Amoskeag Fishways, tells the Nashua Telegraph. “These are the best numbers that I’ve seen in years.”

River herring are actually two species, blueback herring and alewife. Like the more famous salmon, they lay their eggs in fresh water. The juveniles go downstream to the ocean, where they grow to adulthood and live most of their lives, returning after several years to spawn.

New Hampshire Fisheries Biologist Matt Carpenter said river herring were a huge part of the ecosystem where everything eats them – fish, seals, gulls, ospreys. They were wiped out by out by dams, some overfishing issues, and being preyed upon in the ocean.

It isn’t clear what has led to the increase.

From 1988-91, when adult herring were being stocked in some New Hampshire waterways, more than a quarter of a million river herring passed the Lawrence Dam each year.