Smelt-runs up lake tributaries are always a sight to see. Some are better than others. The first one you ever see — with thousands of slithering, wiggling silver fish fighting their way upstream under the glow of the flashlight — leaves an impression.

So does a run of alewives, or so-called river herring. Have you ever seen one of these spring phenomena?

In mid-May at the inlet to Webber Pond in Vassalboro, an alewife run of amazing proportion left me and my friends entertained and amazed by the mass of protein making its way up the fish ladder into the pond.

Don Lettre, a volunteer counter at the dam, told us that last year 335,000 alewives made it into the pond. From what we could gather, an equal number were sold off as lobster bait before they made it into the pond for spawning. After four or five weeks, the alewives will, if all goes well and the water is high enough, work their way back downstream into the Kennebec River and out to sea.

Before hydro dams blocked their passage, alewife runs like this were a common occurrence. In those days, the herring were smoked and eaten, or used for fertilizer and bait. Legend has it that before food stamps, free alewives were given to widows of the town for their consumption.

Witnessing the run, the fisherman in me prompted a question: What kind of impact does this sudden introduction of so many fish have on the sport fish population? During the past decade the Down East fishing guides fought hard in a futile effort to prevent alewives from being introduced into the St. Croix watershed.

Steve Whitman, a retired hydro engineer who operates Long Lake Camps in Princeton and has done years of research on this issue, makes these claims: One, historically, alewives were never in the St. Croix watershed and could not have gotten there if they had wanted to, and two, Alewives have ruined the bass populations at Spednik Lake.

“At first, when the alewives get in the lake, the bass get big and fat from the alewife forage, but eventually the bass fry all get eaten and, presto, no more bass,” Whitman contended.

Nate Gray, a marine resources biologist who has been involved in the alewife restoration from year one, believes that it was a lake water drawdown, not alewives, that raised havoc with the Spednik bass numbers.

As a result of the alewives in Webber Pond, “the bass are bigger than they have ever been and the fishing is great,” according to Gray. Bass anglers I talked with at the pond agreed with him. Arguably, when you introduce that kind of a protein mass into a body of water, the biological calculus becomes complex.

Gray noted that 335,000 alewives drop billions of eggs, many of which become food for fish and other critters.

During my day at the “run” a number of eagles and osprey were hovering above the dam waiting for a herring meal. This was a testimonial to Gray’s assertion that the alewife, as a so-called “keystone species,” feeds many other critters and, to quote the biologists, provides a “cascading effect on the biological community.”

If, indeed, there is a downside to Maine’s sport fish population as a result of the alewife restoration, the truth will be known in time. Whitman predicted that the alewives in the St. Croix watershed are a prelude to “ecological disaster.” He argued that we need to monitor all of this closely, but it is not being done at either the federal or state level.

With the Penobscot River Restoration Trust predicting that the Penobscot River itself could in the near future experience alewife runs in excess of a million a year, isn’t it important that we stay grounded, and couple our elation over nature’s restorative powers with a sober assessment of what it all means down the road, economically and socially, as well as ecologically?

The author is editor of the “Northwoods Sporting Journal.” He is also a Maine guide and host of a weekly radio program — “Maine Outdoors” — heard Sundays at 7 p.m. on “The Voice of Maine News-Talk Network.” He has authored three books; online purchase information is available at www.maineoutdoorpublications.com.