The count of migrating gaspereau fish has topped 150,000 in the St. Croix River, the highest number in nearly 20 years.

There were already more of the fish counted in the final week of May than were seen through the entire 2016 migration.

About 44,000 fish made their way up the river that week compared with 33,000 for last year.

"It's pretty exciting when you see the fish start to come up the fish ladder," said biologist Rebecca Goreham, who monitors the migration at the Milltown Dam in St. Stephen. "Afternoons are usually the busiest."

A crazy year

Heather Almeda, executive director of the St. Croix International Waterway Commission, said it hoped to count 100,000 gaspereau, also known as alewives, this year. 

Now, with only three weeks or more of the migration left, the number of fish is expected to surpass that.

"It's a crazy year," she said. "We had hoped to break 100,000, then we hoped we'd break 150,000."

rebecca goreham

Biologist Rebecca Goreham counts gaspereau and other fish at the Milltown fish ladder in St. Stephen. (CBC)

It's a long way from the 900 fish counted in 2002, when the Maine government blocked fish ladders in the international river to eliminate the native fish.

The state government first started the 17-year blockade in 1995, at the urging of smallmouth bass outfitters, who believe the gaspereau are a threat to their own fish, a non-native species introduced for sport fishing.

The blockade was lifted in 2013, after pressure from environmental groups, First Nations, the government of Canada, and the U.S. Environmental Protection Agency.

Paving way for other fish

The 2017 count is uplifting for groups such as the Passamaquoddy Schoodic Riverkeepers, a Maine-based group that worked toward the reopening of the St. Croix River to alewives.

Speaking for the Indigenous group, Paul Bisulca said that returning gaspereau to the river paves the way for other migrating species, including the American shad and, potentially, the Atlantic salmon.

'What we're seeing is those that hatched out in 2013. The [fry] are now adults coming back to spawn.' - Paul Bisulca

There are already first signs of a shad recovery in the river, he said.

So far, 45 shad were counted this summer. Last year, there were none.

Eleven shad were counted in 2015 — the first of the fish seen since 1998, he said.

He added that this year's gaspereau population represents the first of the fry hatched in the summer of 2013, the year the blockade was lifted.

"It's four years now since the Grand Falls fishway was reopened after 17 years of closure," said Bisulca. "So what we're seeing is those that hatched out in 2013. The [fry] are now adults coming back to spawn."