Between October 2 and 3 in 2009, a sea of dead mudpuppies, Vermont’s largest salamander, floated down the Lamoille River into Lake Champlain. The final count reached 512 individuals, and all had died from a government-authorized pesticide release at the Peterson Dam. This devastating event was the highest mortality of the salamander in Lake Champlain’s history of lampricide use. The pesticide, designed to kill larval sea lampreys, has been justified for this use to save lake sturgeon, the host of the parasitic lamprey.
Until the late 1960s, lake sturgeons were commercially harvested from Lake Champlain and soon thereafter were added to the endangered species list. Despite new legal protections and their high fecundity, the population in Lake Champlain has not recovered. One of the non-human factors decreasing lake sturgeon’s numbers is the sea lamprey, an eel-like ancient fish with a circular mouth ringed with teeth. It latches onto large fish to drink their blood and bodily fluids, leaving circular wounds on its host. Lake sturgeon with “naked,” scaleless skin are especially vulnerable to sea lampreys.
Equipped with evidence of high mortality rates among many of Lake Champlain’s large fish species, including lake trout and land-locked Atlantic salmon, governmental conservation agencies proposed using a lampricide in their breeding tributaries. These same tributaries are home to mudpuppies, striking salamanders with feathery red gills. Mudpuppies are one of many amphibians affected by the lampricide, but fortunately, most other species are not dying in numbers as high as those tallied in the 2009 event. A couple of questions come to mind when weighing all the pieces of this restoration effort. Is saving the endangered lake sturgeon in Lake Champlain by reducing sea lamprey with lampricide worth potentially endangering mudpuppies and other amphibians? How do we weigh the value of one species over others?
The complexity of sea lamprey control resonated with me as an ecological restorationist. Although I never worked on managing animal species or in river ecosystems, it brings up questions that have been swirling in my mind for a number of years. Questions with no definitive answers. Deeply ethical questions about the consequences of restoring habitats with herbicide. In my restoration work, I saw many ecosystems where invasive species had replaced native ones. I managed the invasives in hopes of doing what was “right” for the ecosystem, and often this meant using herbicides.
I have seen ecosystems change drastically from proper herbicide treatments. A coastal pond surrounded by a monoculture of phragmites turned back into a basin of native plant species. In another instance, I treated a purple loosestrife-dominated wetland to aid in the re-establishment of monkeyflower, a critical resource for a native bee species that had not been seen on the site for a number of years. That bee returned the following growing season.
Unfortunately, with native habitat restoration come the consequences that are harder to see, which often go unmonitored due to lack of funding or observability. Few consider the native shrubs outside of the survey area that are affected by herbicide translocation through the soil or drift on a windy day. It is difficult to count the bees that visit the recently sprayed crown vetch.
Most restoration projects use post-vegetation surveys to analyze the benefit to the ecosystem. Most do not conduct amphibian and insect population inventories before or after treatment – even in those studies that do conduct post-application mortality surveys, many amphibians will die at the bottom of rivers, never counted. Most projects do not collect soil samples to understand if the herbicide traveled away from the treatment area or its effect on microbes. The consensus within the restoration community is that the restored habitat will bring about more biodiversity than those species that were killed by the herbicide treatment. I have often sat with this statement and contemplated its truth.
Ask an expert about herbicide use in restoration, and they will talk about the importance of protecting umbrella species and using a variety of management methods. Scientists have made incredible strides in understanding how to use pesticides in effective, responsible ways by lowering the necessary concentration or shifting the timing to lower its effect on other species. Dr. Ellen Marsden, a restoration ecologist working predominantly on lake trout and sea lampreys in the Great Lakes, said, “[Better use of pesticides] is going in the right direction. It’s just achingly slow.” Restorationists do what we think is right based on the data and then shift management methods when new research suggests better possibilities. Despite the methods being strongly rooted in current science, many restorationists still ask themselves moral questions about whether their efforts are benefiting the natural world. Most believe the benefits outweigh the consequences without knowing the true burden of the consequences.
Since the 2009 event on the Lamoille River, mudpuppies have been suggested as an addition to the endangered species list three separate times. U.S. Fish and Wildlife has refused to conduct the required population inventory in Vermont, and mudpuppies’ status has not changed since the first use of lampricides in the 1990s.
Although the lake sturgeon population continues to decline, Atlantic salmon and lake trout sustain far fewer wounds from sea lamprey, and their populations have recovered to a sustainable size. Yet lampricides are still being poured into Lake Champlain’s tributaries, and amphibians continue to die. U.S. Fish and Wildlife will treat the Lamoille River in 2024 and 2028. When asked if she expects the treatment of sea lampreys to slow, Dr. Marsden said, “The experiment of simply stopping lampricide applications is too scary. We suppress sea lamprey populations because we assume lake trout populations will collapse if we don’t. But what happens if we didn’t kill the larval lamprey? If we are wrong and we lose this hard-won progress toward lake trout population restoration? That would be sad.”
