AUGUSTA — The LePage administration wants to create a working group to examine the scientific arguments over alewives in the St. Croix River as a way to defuse the latest flare-up in a debate over the fish that has raged for two decades.

When the Legislature voted two years ago to reopen the St. Croix to migrating alewives, bill supporters hoped it would finally end the fight pitting Grand Lake Stream-area fishing guides and sporting lodge owners against biologists, lobstermen and Passamaquoddy communities in the U.S. and Canada.

Yet Monday’s hours-long legislative hearing showed that alewives – a type of river herring occupying a critical niche in the Gulf of Maine ecosystem – remain divisive even though they have yet to return to the St. Croix in large numbers.

“What you’re going to hear today is an argument and a disagreement on the science, and this is a very tough place to argue science,” Patrick Keliher, commissioner of the Maine Department of Marine Resources, told members of the Legislature’s Marine Resources Committee.

Keliher and his counterpart at the Maine Department of Inland Fisheries and Wildlife, Chandler Woodcock, said the LePage administration opposes a bill, L.D. 800, to once again block alewife passage above Grand Falls Dam near Princeton.

Instead, the commissioners proposed taking the scientific debate out of the legislative arena and having an independent third party review the working group’s findings before recommending potential changes. Keliher said Gov. Paul LePage is willing to issue an executive order along those lines.

“We don’t want to persecute lobstermen, and we don’t want to persecute guides from Down East,” Woodcock said. “We now believe that … a more independent review of this could be made that might strike a comfortable position for everybody involved.”

Finding common ground could be a challenge because of the intense distrust and starkly different beliefs ingrained in the two sides after 20 years, emotions that were on full display during Monday’s hearing. Yet a compromise might be the only path for guides and sporting camp owners judging by the skeptical response to the bill from some lawmakers.

Supporters of L.D. 800 argue that allowing alewives access to the Upper St. Croix could destroy the smallmouth bass fishery and potentially the landlocked salmon fishery that create much of the Grand Lake Stream economy.

As evidence, they point to a collapse of the Spednik Lake bass fishery in the 1980s when more than 2 million alewives were able to swim upstream when fish passage was briefly provided around dams on the St. Croix. Bill supporters also claim waterfalls created a natural barrier to alewives reaching upper parts of the river before dams.

“Their presence poses a serious economic risk and it makes no sense to us to inflict this threat, jeopardizing many jobs and livelihoods, without fully understanding the impact of alewives in this region,” said John Arcaro, a registered Maine guide and owner of Canal Side Cabins sporting camp in Grand Lake Stream. “By allowing the continued passage and stocking of a nonnative species, you are creating a biological invasion that you have no control over.”

But defenders of the alewife said smallmouth bass are an invasive species in a river that one federal biologist said has the potential to harbor the largest alewife spawning run in Maine. They also pointed out that alewives coexist with bass and landlocked salmon in many other watersheds in Maine as well as in Canada.

Using the Passamaquoddy word for alewife, Passamaquoddy Vice Chief Vera Francis said the “siqonomeq” is an indigenous fish that supported her tribe for thousands of years. The St. Croix flows through historic and present-day Passamaquoddy lands on both sides of the U.S.-Canada border.

“This fish is sacred,” said Francis, who is from the Passamaquoddy’s Pleasant Point reservation. “This fish is very important to our culture and to us as a people. The river itself is named after us, the Passamaquoddy, so we have had a long relationship with the entire watershed.”

Spawning alewives were blocked from swimming upstream on the St. Croix for more than a century until the 1980s. But sportsman, concerned about the crash of the Spednik Lake bass fishery, persuaded Maine lawmakers to block passage at the Woodland and Grand Falls dams in 1995.

After years of debate, the Legislature ordered the state to allow alewife passage around the Woodland dam in 2008. Lawmakers then passed a bill to remove the barriers at Grand Falls in 2013 after the U.S. Environmental Protection Agency ruled the barriers violated the Clean Water Act and EPA regulations.

Alewives are eaten by many fish and bird species – including eagles, cod and Atlantic salmon – and are a major type of bait for the lobstermen who comprise Maine’s largest commercial fishery.

Unlike most East Coast states, Maine still has several sizable alewife runs during the spring spawn. Nearly 2.4 million were counted at the Sebasticook River’s Benton Falls fish trap last year while 187,429 were counted at the Penobscot River at Milford and 59,960 at the Androscoggin River dam in Brunswick.

Slightly more than 27,000 alewives passed above the St. Croix’s Milltown Dam located below Grand Falls last year, which is a fraction of the an estimated 2.6 million during the years when upstream passage was allowed in the 1980s.

Federal officials in Canada and the U.S. have long supported restoring the alewife spawning runs in the St. Croix. On Monday, Acting Canadian Consul General Frank Ruddock testified that the bill to block passage would harm “a shared resource” after years of cross-border work to restore the fish.

“The decision (to reopen passage) was based on sound science, including clear evidence that shows alewives can coexist wtih smallmouth bass in lakes and waterways throughout Maine,” said Ruddock, who is based in Boston.

But registered guides and sporting camp owners – backed up by their retired biologists and studies of historic alewife habitat – cautioned that alewives could decimate sport fisheries that draw an estimated $15 million in economic activity to impoverished Washington County annually.

Lance Wheaton, owner of The Village Camps in the border community of Forest City, said last year was his worst financially in 45 years in the sporting camp business because of the weak fisheries. He accused alewife proponents of failing to provide all information about the fish’s potential impacts.

“We know what we are talking about,” Wheaton said. “We live there.”