enlarge Jack Milton/Staff Photographer

The fishing boat Western Sea unloads its catch of herring at the Rockland Fish Pier last week. These herring will be salted and sold as lobster bait, for which lobstermen will pay about $105 a barrel.

enlarge Jack Milton/Staff Photographer

Capt. Daniel Fill, left, of the Western Sea talks with David Dehlinger as they unload herring at the Rockland Fish Pier.

enlarge Jack Milton/Staff Photographer

Ethan Chase flushes out herring from one of the holds on the fishing boat Western Sea at the Rockland Fish Pier.

enlarge Jack Milton/Staff Photographer

The fishing boat Western Sea unloads its catch of herring at the Rockland Fish Pier last week. These herring will be salted and sold as lobster bait, for which lobstermen will pay about $105 a barrel.

enlarge Jack Milton/Staff Photographer

Capt. Daniel Fill, left, of the Western Sea talks with David Dehlinger as they unload herring at the Rockland Fish Pier.

enlarge Jack Milton/Staff Photographer

Ethan Chase flushes out herring from one of the holds on the fishing boat Western Sea at the Rockland Fish Pier.

"There has been lots of sea life, and it kind of amazes me," said Daniel Fill, captain of a Rockland-based fishing boat, during a cell phone interview from his boat. "I have seen fish where I haven't seen them for years. They're in nice, big bunches for miles."

Fill's observations are echoed by other purse seine herring fishermen, as well as whale-watching companies and tuna fishermen. They also report seeing more sea birds, dolphins, seals and tuna -- which all feed on herring.

This bounty of sea life, they claim, is the result of the new summerlong ban on midwater herring trawlers in Gulf of Maine coastal waters. And it's clear evidence, they say, that the trawler ban they have long sought to establish is working.

"I think the ban has made a big difference," said Zack Klyver, a naturalist who works for Bar Harbor Whale Watching and advocated for the ban.

Trawlers drag massive nets through the water and sometimes work in pairs, dragging an even bigger net between them. Midwater gear is similar to bottom-trawling gear, except it is designed to fish up in the water column, where herring spend most of their time

In August 2006, when 10 to 15 midwater trawlers were fishing in an area 30 miles west of Mount Desert Rock, it was rare to find whales, Klyver said.

This summer, he said, the trawlers are gone, and he's been able to see a dozen whales every day.

Scientists, though, say it will take months, if not years, to determine if the ban on midwater trawlers has had any effect.

The ban extends 50 to 60 miles offshore and is in effect from June 1 until Sept. 30.

Owners of midwater trawlers say the ban is based on politics rather than science.

"This is about a big agenda to eliminate fisheries and trawler fisheries worldwide," said Jeff Kaelin, a political consultant for the Portand-based trawler Providian, a 113-foot vessel that has been fishing here since 1996. "They found a small group of trawlers and kicked us off. We were not big enough or organized enough."

The ban does not apply to the handful of fishing boats that use purse seine nets, which encircle the fish when they come to the surface at night to feed.

The New England Fishery Management Council established the ban in response to pressure from a coalition of groups, including conservationists, tuna fishermen, lobstermen, charter fishing boats, sport fishermen and whale-watching companies.

These groups -- which are often at odds on other issues -- united in their opposition to trawlers, which have dominated the herring fishery since the 1990s.

The trawlers' critics say the large nets break up herring schools and disrupt their breeding behavior.

The trawlers' owners have argued that there is no scientific data supporting these claims and that the overall herring population in the gulf is healthy.

Moreover, scientists say herring stocks have rebounded from the heavy overfishing that occurred in the 1960s and 1970s.

The issue has significance because herring is one of the most important species in the gulf. Herring feed on tiny shrimp-like zooplankton called copepods and are consumed by top marine predators, such as finback and minke whales, seals, harbor porpoises, cod, tuna, hake, bluefish, pollock and striped bass. Maine's $300 million lobster industry depends on herring for bait.

"Everybody out there preys on herring. It's the keystone to the food web," said Don Perkins, president of the Gulf of Maine Research Institute.

MIGRATING WITH HERRING

The herring fishery in New England developed in the late 1800s, spurred by the development of the canning industry and the lobster fishery.

Until the 1940s, fishermen caught herring using weirs, fixed nets used in shallow water with good currents. Fishermen...