Over the past couple of centuries, Maine’s previously free-flowing rivers and streams have been altered in hundreds of ingenious ways, by man and beast alike.

Beavers, nature’s engineers, do what they do to survive.

And us? Well, we build dams for a variety of reasons, including flood control and power production.

The Maine Dam Safety Program maintains files on 1,077 separate dams in the state, according to the Maine Emergency Management Agency.

That’s right, 1,077 dams.

And you don’t have to be a full-fledged environmental activist to recognize a sad truth about those dams.

Every time our forefathers built one, they made a compromise that future generations would be forced to deal with … or accept.

Those compromises gave us electricity and kept riverside homes and businesses from being washed downstream during high-water events.

They provided the power for sawmills and grist mills and eventually allowed the rivers to be predictably discharged – an act that provides the rushing water that serves as the lifeblood to our rafting industry.

In addition, those compromises cost us a great deal. Habitats have changed because of those dams, and once-plentiful species are nowhere to be found … or are found in increasingly smaller numbers.

Fish species that migrate between salt and fresh water are among those that have been hit the hardest.

Increasingly, folks have begun reversing the trend of damming up rivers and are rediscovering the benefits of a free-flowing system.

Case in point: The ongoing Penobscot River Restoration Project, which has been praised by anglers, conservationists, even power companies as an accomplishment that may become the model for other bold restoration efforts.

But Down East, things are a bit more complicated.

Just look at LD 1957 – a bill making its way through the Maine Legislature – and listen to the resulting arguments and that becomes readily apparent.

On the surface, LD 1957 is a simple idea with which it seems hard to argue.

Especially if you accept the premise that returning rivers to their former free-flowing state is essentially a good thing.

LD 1957 focuses on the St. Croix River system and seeks to restore diadromous fish runs in the watershed by allowing fish passage at two dams.

Fish passage (not destroying dams outright). Two dams.

The fish passage already exists in both dams, but the use of the fishways has been discontinued in order to keep one species of sea-run fish from moving upstream.

The principal diadromous fish in question is the alewife, a fish that historically spawned in the St. Croix watershed.

If you’ve been following Down East fisheries matters for more than a few years, you may recognize this bill. It’s similar to one that was defeated back in 2001.

And the reason that bill was defeated is the reason people are still fighting this scaled-back rendition.

A group of fishing guides in the Grand Lake Stream region is vehemently opposed to the proposal to allow alewives further passage, claiming that alewives caused a collapse of the bass fishery in Spednic Lake before the fishways were closed.

Bass, you may be interested to know, are not native to the St. Croix system. Alewives are.

But as one Grand Lake Stream sporting camp owner once told me, during the summer months, bass – a fish many Mainers still view with disdain – are the fish that pay the mortgage bill.

Not landlocked salmon. Not brook trout. Not togue. And certainly not alewives.

The two dams in question are at Woodland and Grand Falls, and letting the fish back into Spednic Lake is not being proposed.

The Grand Lake Stream guides have received support from the Maine Professional Guides Association, which has enlisted the aid of its membership in an effort to defeat the bill.

The conflict began back in the 1980s, when the bass population of Spednic Lake crashed. In 1995, a state law was passed that ordered fishways at the two dams to be closed to alewives, in response to concerns about the bass fishery.

The guides who make parts of their livings on Spednic Lake understandably feel they know best, and their argument was a tipping point back in 2001, as some tried to reopen the fishways through new legislation.

When alewives got into Spednic, the guides say, the bass fishing went to pot.

Therefore, one popular argument holds, alewives caused the bass fishery to collapse.

A former teacher of mine once told our class that there’s an inherent danger in assigning a causal relationship when there’s no science to support it.

Primitive people, he explained, believed that trees caused the wind to blow. Their reason for that belief made perfect sense: Every time the wind blew, the branches were flapping back and forth. The harder the branches flapped, the harder the wind blew.

Therefore, it stood to reason, the flapping branches were the culprit.

In the case of the alewives, the crash may as well have been blamed on a combination of other conditions that were detrimental to the bass population.

One factor that has been singled out by proponents of LD 1957: Massive water draw-downs in Spednic left bass eggs high and dry and cost the lake entire age-classes of fish. Alewives were, in fact, in the lake but did nothing to harm the bass population, proponents assert.

Being cautious about harming the bass fishery (which, while dependent on a non-native fish, has been a well-established piece of the sporting landscape Down East for generations) is one thing.

Being reactionary is quite another.

A chief complaint by guides during the 2001 debate was that those who wanted to reopen fishways had no science to prove that alewives ever made it upstream as far as they were assuming. There also was little science that showed bass fishing wouldn’t be impacted negatively if alewives were allowed to return.

Now, according to representatives of the Atlantic Salmon Federation, there is.

The ASF favors allowing the use of the two fishways and allowing alewives upstream.

The alewife, you see, serves a variety of useful purposes, including serving as a “buffer” species for other migrating fish. Now, salmon smolts in many Maine rivers stand out like sore thumbs as they try to head back to the sea. Eagles, ospreys and other fish-eating birds chomp them like candy, and with few other fish around, target them nearly exclusively.

Alewives would arrive (and leave) by the thousands, tens of thousands, or millions, depending on how much habitat was reopened to them.

Birds would eat plenty of those alewives, but presumably fewer salmon.

In addition, the alewives would provide a tremendous source of biomass in fresh and salt water and could be caught and used as lobster bait.

John R. J. Burrows, the Maine coordinator of the ASF, says researchers have established that alewives once ran far up into the St. Croix watershed and co-existed well with native landlocked salmon.

He also said that in other Maine lakes that host annual runs of alewives, no evidence has shown that bass fisheries have been negatively impacted.

On the one similar lake I’ve fished – bass and alewives coexisting at certain times of year – the bass were not only plentiful but also amazingly fat.

Other anglers across the state have observed the same thing, and it seems reasonable that sea-run alewives – not the landlocked alewives that even ASF officials admit have caused some problems in Maine lakes – would be able to co-exist with Down East bass as well.

All of which brings us back to the St. Croix, a once thriving river that humans have segmented, piece by piece, dam by dam, over the generations. Habitat be dammed, you might say.

In LD 1957, the legislature has a real chance to begin a process that would return the mighty St. Croix to a more natural state.

It’s hard, after all, to argue against nature’s grand plan, and to speak ill of free-flowing rivers.

Hard. But not impossible.

Just wait and see.

jholyoke@bangordailynews.net

990-8214