PORTLAND – A South Portland man is the first person charged with violating a state law protecting the Atlantic salmon.

Gordon Viola, 38, didn’t know what kind of trouble he was in for when he found a single Atlantic salmon among the 1,500 pounds of monkfish, dogfish, skate and flounder in his net.

“I thought somebody would want to see this thing, because it was rare,” said Viola, who had never before caught such a fish in his 20 years as a commercial fisherman.

Now he faces both state and federal charges for illegal possession of an Atlantic salmon, a fish designated an endangered species in eight Maine rivers last November.

On March 2, Viola became the first person charged under a Maine law that makes it illegal to fish or possess an Atlantic salmon, except one raised at an aquaculture farm. The law carries a maximum penalty of a $2,000 fine and a year in jail.

Viola may also be the first person to face federal charges for possessing an Atlantic salmon in a restricted zone, according to investigators for the National Oceanic and Atmospheric Administration.

The maximum penalty for a criminal violation of the Endangered Species Act is a $20,000 fine and a year in jail.

Viola was fishing about 50 miles off Cape Cod when he netted the salmon on Feb. 14. When the Caroline M docked in Portland three days later, officers from the Maine Marine Patrol and the U.S. Coast Guard came aboard for a routine check and confiscated the salmon.

Viola is to be arraigned March 30 on the state charge, but it’s unclear what charges he ultimately will face, according to Col. Joe Fessenden, head of the Maine Marine Patrol.

First of all, officials will have to determine the salmon’s origins.

The ESA’s protection applies only to Atlantic salmon from the Sheepscot and Ducktrap rivers in midcoast Maine; the Narraguagus, Pleasant, East Machias, Machias and Dennys in Washington County, and Cove Brook, a tributary of the lower Penobscot, according to Paul Nickerson, U.S. Fish and Wildlife Service’s endangered species coordinator for the region.

Officials also will have to determine whether it was spawned in one of the protected rivers and whether it was wild or an escapee from an aquaculture farm.

Even if it’s determined that the fish came from one of the eight protected rivers, a criminal prosecution would be unlikely considering how it was caught, Nickerson said.

Viola said he would have thrown the salmon back if it had been alive. But it was dead, so he noted the details of the catch and put the fish in a separate area of the boat’s hold, he said.

“I saved it to bring it in, to give to Bigelow Science Lab in Boothbay Harbor,” he said.

Nickerson said Viola’s instincts were on the mark, but Lt. Dan Morris of the Marine Patrol said the fisherman’s actions contradict his version of events.

Morris maintains that Viola should have informed the National Marine Fisheries Service or the Marine Patrol if he intended to hand over the fish to scientists. Morris also said that Viola failed to tell officers about the fish until they found it themselves.

Viola, however, insists he told them before they came aboard. And he said it didn’t occur to him to call ahead.

“I don’t know who I would have called,” Viola said. “I never thought of calling them. I didn’t realize it was any problem.”