As New England fishery regulators meeting in Mystic this week approved the latest in a series of steps intended to shore up river herring populations, thousands of these small but important fish swam from Long Island Sound into local rivers and streams in their annual spring migration.

"At Bride Brook there were two nights this week when 30,000 fish came through, and we've already had a couple thousand arrive at Latimer Brook," Steve Gephard, head of the Inland Fisheries Division at the state Department of Energy and Environmental Protection, said Friday, referring to two waterways in East Lyme. "We're having a good year at those streams so far."

Bride Brook, which flows into the Sound at Rocky Neck State Park, and Latimer Brook, a tributary of the Niantic River, have seen recent dramatic surges in annual runs of these anadromous species, so-called because they spend most of their lives in marine waters, but travel to freshwater streams, ponds and lakes to mate and spawn.

Two factors have contributed to the local river herring boom: a new culvert built at Rocky Neck in 2009 reopened a previously constricted channel; and beaver dams upstream of Latimer Brook that had cut the fish off from ponds where they mate and spawn have been removed, Gephard said. At Bride Brook, last year's run topped 363,000 fish - more than six times the number before the new culvert. Thus far this spring, the fish counter near Bride Lake where they reproduce already has recorded more than 224,000 fish, Gephard said. At Latimer, where a fish ladder enables the herring to surmount a dam, the numbers have gone from a low of 903 in 2007 to 33,065 last year.

"We think the fish are still holding back from swimming in because of the cold nights," Gephard said.

These two local streams represent success stories in long-term efforts to restore alewife and blueback herring, the two bottom-of-the-food-chain species collectively known as river herring. But they are also, thus far, more the exception than the rule.

"Overall, these fish are still in decline. In some areas, they're stable, but not getting better," Gephard said.

Once abundant, numbers of these sleek, silvery swimmers have been in a decades-long plummet as dams and development blocked access to spawning areas, and they became victims of overfishing and, more recently, accidental mortality as they get caught in the nets of large oceangoing trawlers harvesting a different species, Atlantic herring. That's where the fisheries panel's actions in Mystic this week come in.

The New England Fishery Management Council, which met for three days at the Hilton Garden Inn, brings together representatives of all the states in the region to establish rules for the coastal and offshore commercial fisheries. Last fall the panel set limits on how many pounds of river herring the Atlantic herring trawlers would be able to take as bycatch in the three main regions where they operate: the Gulf of Maine, off Cape Cod and southern New England including offshore Block Island, where vessels based in Point Judith, R.I., fish. The caps would take effect this year and in 2015, pending approval by the National Oceanic and Atmospheric Administration, said Pat Fiorelli, spokeswoman for the New England council.

At its meeting Wednesday, the council approved further actions to reduce river herring bycatch and generate more accurate measurements of how many are ending up as bycatch. The issue, said Mark Alexander, Connecticut's representative on the council and supervising fisheries biologist at DEEP, is that river herring and Atlantic herring "hang out together" at certain times of the year. Any river herring that accidentally end up in trawlers' nets are killed as they are crammed together and furiously "pumped" onboard.

"Herring die pretty easily," he said.

The council's actions this week sought to address concerns that fishermen looking to avoid exceeding the new caps on river herring might "slip" their nets - basically empty the catch overboard - if they realize they've ended up harvesting the wrong species. The herring would die, and observers who accompany the herring vessels to record and verify catch and species data wouldn't get a chance to count them.

"We decided that if there's a slippage event, if you dump fish out of the net, you can't fish in that area," Alexander said.

After a slippage, the vessel would be required to move at least 15 nautical miles away before it could drop its nets again.

"It gives them an incentive" not to slip the nets, he said. It also will give on-board observers the chance to quantify more accurately how many river herring are being caught, he added.

Chris Cryder, special projects coordinator for Save the Sound, a program of the Connecticut Fund for the Environment, said the council's action this week is another positive step in the multifaceted efforts to restore river herring. This new restrictions, like the bycatch limits adopted in the fall, also need NOAA's approval before taking effect.

"Millions of dollars in time, energy and construction have been spent on reopening fish passage in Connecticut, but this effort will be for naught if depleted river herring ... do not receive needed protections at sea," he wrote in a statement to the council.

Cryder's group partnered with DEEP in the rebuilding of the Bride Brook culvert at Rocky Neck, and is also embarking on four dam-removal projects this year including one at Hyde Pond in Mystic. Construction of fish ladders, and habitat and tidal-flow restoration are among other projects Save the Sound, DEEP and other groups have undertaken in recent years to help river herring and other migratory fish species recover from decades of decline.

"Connecticut is a leader in fish passage restoration," Cryder said, noting that thus far around the state, 45 fish ladders have been built and 13 dams removed, reopening almost 300 miles of freshwater spawning habitat.

Given the numbers pouring into Bride Brook and Latimer Brook, Gephard said he is encouraged that all the restoration efforts will pay off, though it may take many more years and many more projects before anyone can say river herring are out of danger.

"We can improve runs, stream by stream," he said.

j.benson@theday.com

How many herring?

River herring counts at Bride Brook, East Lyme:

Average for 2003-09: 60,000 to 120,000

Average since culvert project completion:

2010: 160,000

2011: 180,000

2012: 287,000

2013: 363,000

River herring counts at Latimer Brook, East Lyme:

2006: 1,654

2007: 903

2008: 2,556

2009: Not available

2010: 2,560

2011: 2,679

After removal of beaver dams upstream:

2012: 22,154

2013: 33,065Source: Steve Gephard, supervising fisheries biologist, Inland Fisheries Division, state Department of Energy and Environmental Protection.