It’s time alewives were allowed into the upper reaches of the St. Croix River.

Research, in addition to dozens of ponds and streams in Maine, show that alewives can coexist with smallmouth bass. Until there is solid scientific evidence that bass populations will diminish with an influx of alewives north of the Grand Falls Dam in Washington County, holding them back from their natural spawning ground will only harm the greater habitat.

The matter has been a contentious one since the 1980s when alewives were blamed for the decline of the smallmouth bass population in the St. Croix, threatening the livelihoods of local bass fishing guides.

Prior to 1980 there was an inefficient fish passage at Milltown Dam on the St. Croix that allowed only a small number of alewives to pass through, according to a 2007 report completed by Lewis Flagg for the Atlantic Salmon Commission. A new fishway was constructed in 1980, and alewives swam north. By the mid- to late-1980s, smallmouth bass — a non-native fish introduced by sportsmen — had substantially declined.

So the Maine Department of Inland Fisheries and Wildlife and the New Brunswick Department of Natural Resources completed a 10-year study of Spednic Lake, a part of the river. The study concluded: A lake drawdown of nine to 14 feet made the young bass’ protective rock habitat disappear, and they were forced to compete for food and habitat with young perch and alewives.

It was not the alewives that caused the bass decline but the loss of protective habitat.

Still, the St. Croix River Steering committee agreed to close the Vanceboro fishway during the alewife run. And in 1995 the Maine Legislature passed a bill that closed the Woodland and Grand Falls fishways. Bass rebounded, but the move resulted in a dangerous drop in the number of alewives, from 2.6 million in 1987 to 900 fish in 2002. The law was amended in 2008 to unblock the fishway at Woodland, but the fish are still prevented from reaching 98 percent of their traditional spawning ground.

Sportfishing guides and camp owners also argue alewives historically had no access to the upper St. Croix, but it’s not clear where they got their information. In an 1867 report, the Maine Commissioners of Fisheries described the St. Croix as having many salmon, shad and alewives. And archaeological findings by the Maine Historic Preservation Commission provide evidence of alewives being in the upper part of the river at least 4,000 years ago.

People still claim that alewives will harm bass populations, even in the face of mountains of data to the contrary. The Department of Marine Resources reports there are more than 90 lakes and ponds in Maine where sea-run alewives coexist with healthy populations of freshwater fish. Bass and alewives live together in bodies of water near the St. Croix, including Gardner Lake, Meddybemps Lake, Cathance Lake and Hadley Lake.

Many other streams or lakes connected to the ocean, such as the Kennebec River and Sebasticook River, have thriving alewife runs and good bass fishing. The Department of Inland Fisheries and Wildlife describes Webber Pond, in Lincoln County, as having sea-run alewives that provide excellent forage for bass.

A 10-year study on the effects of alewives was completed in the 1990s by the Department of Marine Resources, IF&W and the Maine Department of Environmental Protection. The Lake George Study concluded that alewives had no negative effects on water quality, zooplankton or freshwater fish. In fact, smelt and pickerel grew better in the presence of alewives.

A more recent study of bodies of water near the St. Croix itself also found no evidence that the presence of alewives harmed smallmouth bass. Maine Rivers, an organization that works to improve the health of rivers, sponsored the 2006 study. It found alewives were not significant predators on smallmouth bass and that they did not appear to compete for food.

Opening the Grand Falls Dam to alewives will provide the Passamaquoddy Tribe with a cultural food source. The Passamaquoddy at Pleasant Point and Indian Township, the Aroostook Band of Micmacs and the Houlton Band of Maliseet Indians have sent a letter asking Gov. Paul LePage to support legislation to open the passage.

The environment deserves consideration. Alewives serve as food for other fish, in addition to birds and mammals. They attract bald eagles and make good bait for the lobster industry. The U.S. Environmental Protection Agency wrote on July 9 to Attorney General William Schneider warning that keeping the passage closed violates the Clean Water Act.

The LePage administration is continuing to consider the matter, according to a spokeswoman. The governor should introduce legislation to open the perfectly good fish passage at Grand Falls Dam. The only things blocking it are a lack of political will and a wooden board.