A national activist group is trying to block the imminent sale of several salmon farms in Maine, alleging their current owner is not properly maintaining them.

The U.S. Public Interest Research Group has asked the Maine Department of Marine Resources to block the sale of farms owned by Heritage Salmon to another company.

In February, the Canadian conglomerate that owns Heritage, George Weston Ltd., announced it was selling its Connors Bros. aquaculture unit, which includes Heritage and sardine company Stinson Seafood. The sale includes all of the company’s farms and processing facilities in Maine, Canada and Chile.

PIRG wants the sale blocked unless the new owner commits to preventing fish escapes, cleaning up the ocean bottom beneath the pens and stopping the use of toxic chemicals for pest control, among other things, it said in a letter to DMR Commissioner George LaPointe earlier this month.

Connors Bros. is the third largest salmon aquaculture company in Maine with 137 acres of lease sites in Eastport and Lubec. It owns a salmon processing plant in Eastport.

According to PIRG, Heritage Salmon is being purchased by Nutreco, a Dutch company that, in addition to owning fish farms, produces fish and animal feed.

A Norwegian fishing industry analysis group, IntraFish, reported on its Web page this week that the Nutreco /Weston deal was stalled. The deal was supposed to be completed last week, IntraFish reported, but negotiations were hung up over the corporate structure of Heritage Salmon.

“We want the new owner to operate within the confines of the law,” said Joshua Kratka, an attorney with the National Environmental Law Center, which is representing PIRG.

Michael Nelson, a lawyer for Heritage, said PIRG is simply asking for a hearing on the permit transfer. He said he had no comments on the letter’s assertions that Heritage was allowing fish feed and feces to pile up on the ocean floor or that the company was polluting the water with toxic chemicals.

Last year, the center and PIRG sued the state’s three largest fish farming companies, including Connors Bros., for operating without permits from the U.S. Environmental Protection Agency to discharge pollutants in the water.

The companies applied for discharge permits from the EPA in the late 1980s. The agency said it was in the process of developing national discharge standards for fish farms, and that, in the interim, Maine’s Department of Environmental Protection licensing requirements, which include water quality certification, were sufficient. More than a decade later, the EPA is still developing its own standards.

An EPA spokesman in Boston said his agency felt water quality standards contained in the DEP licenses and in U.S. Army Corps of Engineers permits that all Maine aquaculture facilities must obtain were effective.

The PIRG lawsuit is still pending in U.S. District Court in Portland.

Kratka said Thursday that Heritage is not being singled out. He said all the state’s fish farming companies let excess feed and fish feces pile up on the ocean bottom and that all have had farmed fish escape from pens.

Heritage is being targeted because, if the company is sold, its leases will have to be formally transferred, he said. During that process, a public hearing on the transfer can be held if requested by five people. Kratka said his group would have no problem finding five people to request such a hearing.

Kratka said PIRG became especially concerned about fish farm conditions when it learned through court papers that escapes of farmed fish and cases of a deadly disease, infectious salmon anemia, were not being reported to the public.

Earlier this year, the state’s three largest aquaculture companies signed an agreement with several conservation groups pledging to strengthen fish containment and health practices.

These are the same areas federal regulators have singled out as the most problematic. Escaped farmed fish, with their potential to spread disease and genes to wild fish, are one of the top threats to wild Atlantic salmon, listed as endangered in eight Maine rivers.

Kratka said his group doesn’t put too much stock in the agreement because it is strictly voluntary.

“Our view of the agreement is that it’s not worth the paper it’s written on,” he said.

Commissioner LaPointe said Thursday, “There’s no sale yet, so I plan to do nothing soon.”