PORTLAND — Conservationists have won a round in a legal battle trying to force fishery regulators to offer more protection for declining populations of river herring.

A federal judge in Washington ruled Friday that that the National Oceanic and Atmospheric Administration hasn’t done enough to protect river herring — a collective term referring to alewives, blueback herring, American shad and hickory shad — from commercial trawlers that catch Atlantic herring in the ocean.

The ruling will force regulators to take steps to give the fish added protections, said Roger Fleming, a Maine-based lawyer with Earthjustice who represented a recreational fisherman, a charter boat captain and the Ocean River Institute in the lawsuit, which was filed in 2011.

River herring once migrated in large numbers up rivers in the Northeast to spawn, but their populations have fallen sharply, he said.

“This is a big ruling for river herring and shad,” Fleming said. “The agency is going to have to go back to its Atlantic herring fishery management plan, add river herring and shad, and set catch limits and other conservation measures.”

A NOAA spokeswoman said the agency is reviewing the ruling.

River herring live in the ocean and return to freshwater rivers and streams to spawn.

While at sea, they intermingle with Atlantic herring, which are caught by commercial fishermen who sell them primarily for lobster bait, Fleming said.

Augusta and Waterville news

Get news and events from your towns in your inbox every Friday.

  • This field is for validation purposes and should be left unchanged.