Cornell research contains unexpected lessons for managing invasive fish
By Zachary Matson
Cornell University scientists studying Adirondack fish may have inadvertently discovered a method to increase a lake’s smallmouth bass population: try eradicating them.
In 2000, Cornell researchers launched a campaign to rid Little Moose Lake, located within the private Adirondack League Club, of invasive smallmouth bass. For 25 years the scientists removed bass each year, but the bass created their own scientific twist. Not only are smallmouth bass still in the lake, while smaller and younger, their population has soared.
The Adirondack Explorer thanks its advertising partners. Become one of them.
According to a dissertation study by Liam Zarri (now a postdoctoral fellow with the Smithsonian Institute), the eradication efforts didn’t just fail to remove the smallmouth bass; they triggered rapid evolutionary changes. Published this month in the scientific journal “Proceedings of the National Academy of Sciences,” Zarri’s research reveals the bass responded to annual cullings by growing faster and dedicating more energy to early reproduction.
The findings have implications for fisheries management across the Adirondack region.
Digging into the DNA
Cornell researchers have annually removed as much as a quarter of the lake’s bass through electrofishing along the lake’s shoreline. The bass population’s annual survival rates have plummeted and few old or large specimens remain, but the species’ resilience is shown in a yearly “bumper crop” of young fish.
Zarri identified a set of key adaptations the bass appeared to make in response to the suppression program and analyzed fish tissue to pinpoint the particular regions of their genome associated with those changing behaviors.
The Adirondack Explorer thanks its advertising partners. Become one of them.
In an attempt to identify how the evolution manifested within the fish’s genome, Zarri compared DNA samples from 2000 to 2019, discovering three chromosomes where genes showed significant change between the two points in time. Those areas were associated with the observed changes in growth and reproduction, Zarri said.
Adopting more of what scientists refer to as a “fast lifestyle,” the bass in Little Moose Lake are growing faster and devoting more energy resources to early reproduction. Researchers found that reproductive organs of both males and females were increasing as a proportion of their overall body mass.
“Evolution also acts on very fine scales within a single population,” Zarri said in a recent interview. “Through time they are becoming less susceptible to our suppression efforts.”
Bass speed up, other species slow down
“These fish have made a strategic shift where they allocate much more of their energy to reproduction than their ancestors,” said Pete McIntyre, a Cornell fisheries scientist who leads the research team studying Little Moose Lake. “The bass managed to evolve in response to our removing them year after year in the same way.”
The Adirondack Explorer thanks its advertising partners. Become one of them.
Cornell researchers also published recent articles on how the lake’s native fish responded to attempted bass suppression. The other fish species mostly increased in relative abundance in the years immediately following the start of the bass eradication program, but ultimately showed varied outcomes over 20 years. Lake trout, a key native species that motivated the effort to eradicate smallmouth bass, shifted to a more piscivorus diet during those two decades but took the longest to show positive responses, according to researchers.
RELATED READING: Lake Placid’s lake trout caught in derby crosshairs
Thomas Detmer, a Cornell senior research associate who led the study on the fish community’s response, documented another changing behavior among the under-siege bass: they became more fearful of humans. The bass in Little Moose were much quicker to flee a human presence than bass in other lakes, suggesting the suppression activity instigated behavioral adaptations in addition to the genetic and reproductive shifts.
“These are not static populations, they are capable of evolution and evolution at a very rapid timescale,” Zarri said.
The Adirondack Explorer thanks its advertising partners. Become one of them.
Implications for other Adirondack lakes
McIntyre said the research has important lessons for Adirondack fisheries managers, as well as invasive species prevention. First, it underscored the importance of minimizing new invasions, he said. Control programs are expensive and challenging and can create unintended outcomes. He said the Cornell researchers are mulling strategies to alter their control program to achieve the benefits of suppression without provoking evolutionary changes.
McIntyre said there is evidence that smallmouth bass have potentially spread to more Adirondack lakes than are currently recognized.. While developing protocols for a broad survey of Adirondack lakes, McIntyre said, researchers found environmental DNA evidence of ongoing invasions of both smallmouth and largemouth bass across ever more Adirondack lakes.
“This is an Adirondack-wide phenomenon,” he said. “We are trying to outsmart the bass, and the bass are trying to outsmart us.”
Top photo: A Cornell University research vessel used during a 25-year effort to rid Little Moose Lake of invasive smallmouth bass.
A most excellent article by Mr Matson and the Adirondack Explorer. Many Kudos to the continued great work being done at Cornell University.
Leave the smallmouth alone they are so much fun to catch a kid will have the best time reeling in a smallmouth with them jumping out of the water and dancing please leave them alone
This does not seem like a big surprise. It has been well known for a long time in molecular biology that you “speed” up evolution by putting an organism under stress. More stress, more mutations, faster evolution. Some experiments have even found that under the stress an organism can slow down it DNA repair systems so that more mutations don’t get “fixed” and speed changes. Famous experiments in a french lab in the 80’s and 90’s showed than when you shut off DNA repair you could get different species to cross. They did it with E. coli and Salmonella – Salmoricchia!
This isn’t evolution. Look at naked mole rats. Hormones/pheromones from the dominant members of a group supress reproduction in the mostly younger smaller members of the group. There is an upside to this, the supressed members are free to feed and grow bigger without the physiological stress of reproduction. Call it physiological plasticity if you want but not evolution.
Saturate the water with dominant female pheromones and no other members will spawn. Good luck sussing out which pheromone that is.
Leave them alone they are so fun to catch there is no reason to kill them
On the West Coast we were proud of our trophy trout lakes. However, some people wanted bass tournaments to improve the economy, so they illegally released bass into the lakes. The bass fishing never took hold as expected, but they did destroy the trophy trout fishing by eating every bug in sight. I think the bass should eat the ‘ bass bucket biologist’.
Why would u try & take out one of the funnest species of bass to catch? It makes no sense to me. Small mouth bass fishing is some of the most exciting fish to catch. I hope you guys r relocating them & not letting them go to waste or at least give them to some people who would want to eat them.
As a retired fisheries biologist, I am struck by the lack of understanding of basic population management. Off hand I can think of several research papers going back to the 1980s I used in my thesis work that showed stimulated population growth of largemouth bass in small impoundments when harvesting up to 50% of adult fish. What becomes evident is researchers are not sport anglers and Ivy League schools mis associate evolution whenever possible for adaptations already existing in the population. Spending sport fisherman’s taxes to wander into the particular genetic mechanism of an unanticipated population shift in lieu of doing a more exhaustive literature search to show what other more savvy and experienced field biologists or anglers could have told seems par for the course for Cornell. Like chasing the extinct Ivory Billed Woodpecker for 2 years to justify Obamabucks. Some advice…..buy a boat and a fishing pole and put away your computers. You will find, your efforts are not helping the world that needs its tax money back.
I wondered why the biologists didnt encourage just eating them? Its cheaper than using tax dollars.
In Maine while the state doesnt like invasive Northern Pike; anglers do. Some spread by buckert. Other by connecting waterways.
Catch and kill was the states answer but fishermen learned by keeping trophy fish populations grew. Oddly fishermen learned big pike eat smaller pike and help its own population control.
Aint that odd!
SPOT ON!!!!!!
Another swing and miss by the “smartest people in the room”. Please knock it off… Mother nature knows her business better than we do…