Mairs, a naturalist, says in his article about the Great Pond mudpuppies that insects and crayfish have been identified as their primary food elsewhere, though small fish and fish eggs, worms, leeches, snails and other salamanders also are part of their diet. Mairs concluded that the significance of Belgrade's introduced mudpuppies on fish populations, either through competition or predation, hasn't been studied conclusively. "There are just so many questions," he said of the interaction among aquatic species. "Nobody's doing any research because there's no money for research on the subject."
As a lifelong resident of the area who lives near the stream where mudpuppies were introduced, Mairs says he's unfazed by the intruders. "I think they're great," he said, though he admitted it may be a creature only a herpetologist could love. Which is not to say he is unconcerned about introduced species. "Native biodiversity usually suffers," he said.
Mike Little, watershed steward of the Belgrade Regional Conservation Alliance, who has a degree in environmental management and a lifelong interest in "herps," started a conversation about mudpuppies with "I've got a couple in my freezer"explaining that he's collecting samples to try to see what they've eaten. "They probably eat some fish eggs, but they're about as benign an invasion as you can get," was his preliminary conclusion. (This from one of the leaders of a mobilization to stop the spread of invasive aquatic plants, particularly variable milfoil, in central Maine lakes.)
Woodward added: "There have been other changes in the whole biological system that's made it [the effect of mudpuppies on fisheries] hard to track." Most prominent was the introduction of northern pike to the watershed 35 years ago. But a broader history of aquatic fauna puts the introduction of the mudpuppies in a different perspective. Nature isn't what it used to be. Those bass E.B. White caught, practically all of the game fish, most of the minnows and even crustaceans in the Belgrade Lakes, it turns out, are introduced species, scientists say.
It took about 20 or 30 years to eliminate the unwanted walleyed pike from the Belgrades, but soon after that was accomplished the northern pike was illegally introduced. A game fish prized by some for its size, strength and fighting ability, big northern pike can run four feet long. The Maine record, caught in North Pond, adjacent to Great Pond, weighed more than 31 pounds. It's a top-of-the-food-chain predator, so it comes to a body of water at a price, and that price is paid by other species including brook trout, landlocked salmon and white perch.
Woodward said he heard a reliable account that an out-of-state land developer connected with a notoriously shady land deal west of Long Pond who was seen deliberately dumping a tub of northerns into Little North Pond in 1969. Anglers started catching pike in all of the downstream Belgrades during the 1970s ("We thought they were pickerel at first," said Boulette), and by the 1980s they were part of annual fishing derbies. Year after year, the winning fish got bigger.
"We get so used to having these things that it's old news," Woodward said of introduced species. "This is the way it is with pike now. We knew we couldn't get rid of them, so we started managing them." Some fishermen would argue that the pike could stand more heavy-handed management. While the Belgrade chain is the only lake system in Maine with an established pike population, a mature pike was found in Sebago Lake last summer, prompting concerns about the storied landlocked salmon fishing there.
While the burgeoning pike have been blamed for declines in other prized fish species, it turns out that all of those fish except the brook trout were themselves species introduced by previous generations.
Bass, landlocked salmon and chain pickerel were introduced by the state a century ago or more, Woodward said. White perch live in fresh or salt water and occur naturally in coastal drainages, but it's unclear whether they are native to lakes like the Belgrades, Mairs said. Brown trout were originally from Germany, according to Little. Though there are a few native brook trout still in the lakes, most of that fishery has been a put-and-take operation, as the state stocked hatchery-raised trout for anglers to catch.
And it's not just the finned fish. To the extent that mudpuppies prey on crayfish and compete with them for food, the mudpuppies are dealing with more introduced species than native ones. More crayfish species have arrived in fishermen's bait pails than existed naturally in Maine ponds and streams, Mairs said.
So while the mudpuppy in central Maine is an exotic, introduced species, one view is that it is merely one more addition to an aquatic ecosystem that in some respects is a huge and evolving aquarium project. Nature here is untrammeled in fewer ways than we might like to imagine.
And Maine is hardly unique in this respect. In the Cornell paper on introduced species cited above, Professor David Pimentel and his co-authors reported that 98 percent of the U.S. food system is provided by introduced species. Corn, wheat, rice, cattle, poultry and most other livestock and food crops fit that category.
Invasive species have been getting a lot of attention recently, in the news media and from a National Invasive Species Council, a federal interdepartmental initiative established in 1999 (www.invasivespecies.gov). The resulting awareness of risks seems to have raised the public's consciousness, but humanmankind's unprecedented mobility on a global scale makes it hard to be optimistic that the problem may diminish. Still, as with other threats to the status quo, it is important to distinguish between hype and hard facts, histrionics and helpful warnings, terror and trouble of a more routine nature.
Though some see the tale of the Great Pond mudpuppies as a Colby science project turned science fiction, others maintain that, despite its scary countenance, this is one puppy with neither bark nor bite.