PORTLAND – The protection of America’s seaports has strained the U.S. Coast Guard and raised questions about how much the agency can do.

The Coast Guard’s No. 1 priority since the Sept. 11 terrorist has been maritime security. In Maine, virtually all of its personnel have been funneled into security roles, including patrolling harbors, escorting ships and boarding incoming foreign tankers.

As a result, its law enforcement, fishery patrols and safety programs have suffered. Some worry that the agency’s core mission – saving lives at sea – might slip as it takes on additional responsibilities.

Last week, Sens. Olympia Snowe, R-Maine, and John Kerry, D-Mass., called for a study to measure the effects of the Coast Guard’s shifting role.

“We need to know that the Coast Guard has the resources and capabilities necessary to meet the [security] mission, without undermining crucial functions like fisheries enforcement, search and rescue and drug interdiction,” they wrote in a letter to the General Accounting Office.

The GAO will conduct the study over the winter. Depending on the findings, lawmakers could push for more funding or shift duties to other agencies or the private sector.

Coast Guard officials say the fallout from the terrorist attacks has clearly stretched the limits of its people, equipment and resources. But saving lives, they maintain, is one job that never wavered.

“Search and rescue is our bread and butter and always will be,” said Arn Heggers, the Coast Guard’s fishing vessel safety examiner in Maine. “The fishermen and everybody need to know that’s still what we’re here for. If that means people need to work overtime, then that’s what it means.”

The Coast Guard has always performed multiple tasks.

It monitors fishing fleets and chases drug dealers. It maintains navigation buoys that guide ships, fights and cleans up pollution, provides safety training and boat inspections, and rescues mariners from sinking boats.

But maritime security became its top priority after Sept. 11. And that has some people concerned that the Coast Guard’s other duties will be neglected.

The New England Fishery Management Council, for instance, is concerned that fishing regulations will be flouted with fewer Coast Guard planes and boat enforcing the rules.

On Sept. 27, the council passed a resolution calling for maximum penalties for any fishermen caught taking “advantage of the present national crisis” to break the rules.

“I don’t fault the Coast Guard for the situation we’re in, but it is leaving us with a lack of federal fisheries law enforcement,” said Maine’s Marine Resource Commissioner George Lapointe.

Coast Guard officials say the agency is gradually giving more attention to its other missions as it steps down port security.

“We’ve set some priorities and identified our higher risks within the ports,” said Lt. j.g. Michael McCarthy of the Marine Safety Office in Portland. “Where we were escorting all the tank ships, first we refined it to flammable-cargo tank ships and now we’ve refined it to flammable-cargo tank ships that do not regularly call on Portland.”