Fish Fallacies

Solving an environmental problem with a natural solution is often preferable to using toxic poisons. However, a proposal to allow grass carp to eat invasive plants in Maine lakes and ponds could cause more problems than it would solve.

The bill, LD 1646, is well intentioned and the search for ways to control, or perhaps even eradicate, invasive plants other than dumping herbicides into the water should be encouraged. But this particular solution is premature and fraught with potential negative consequences.

First, one has to look at the scale of the problem that would purportedly be solved by the fish, which are native to Asia and have been imported to the United States to eat invasive aquatic plants, also from Asia. While local infestations of variable leaf milfoil, of which there are now 16, and hydrilla, of which there is one, are terrible for those who live on or use those lakes or ponds, Maine’s invasive plant problem is nowhere near as bad as what many other states are dealing with.

That could be because of Maine’s climate and topography. Or, it could be because what the state is doing now – an aggressive monitoring program involving hundreds of volunteers, inspections of boats moving from one lake to another and the sale of invasive species stickers to boat owners to finance it all – is working.

When hydrilla was reported growing in Pickerel Pond, by a local homeowner, the Department of Environmental Protection debated using grass carp to eat the plant because it is loath to use pesticides. In the end, the DEP decided the risks of introducing grass carp to the pond in Limerick outweighed the benefits and decided to try using an herbicide first. After one application, the hydrilla is in retreat and it has not spread to nearby water bodies. The DEP will continue to monitor the situation, but their approach seems to have worked as well as expected.

The second problem with grass carp, even a limited experiment as LD 1646 calls for, is the many potential downsides. These fish eat everything in sight, including native plants. So rather than rid a lake of invasive plants, the fish rid the lake of all plants, which in turn means that native fish die off for lack of food and shelter. There is also the remote chance that these voracious eaters may escape and, although those that are introduced must be sterile, the process is not foolproof.

Asian carp brought to the United States in the 1970s to control algae in catfish farms have escaped and are now the dominant fish in the Illinois River and have infested large portions of the Mississippi and Missouri rivers. There is great fear that they will make it to the Great Lakes with the potential to destroy a $4.5 billion fishing industry in the states that border the northern lakes.

What Maine is doing now has controlled, if not lessened, a serious problem. There is no need to try additional risky solutions.