Fisheries biologists regularly count trout or Arctic grayling in Montana’s streams by introducing an electrical field to stun and capture the fish.
When trout encounter the electrical field their muscles contract, drawing the fish toward the electricity. Biologists then net the trout or grayling and place them in a bucket of fresh water until the fish are retrieved to be measured, weighed, fin clipped on occasion and sometimes tagged.
The fish are then typically returned to their home waters.
The process occasionally injures or kills trout or grayling but is generally accepted among fish and wildlife agencies as a necessary tool for tracking the size and health of fish populations.
Electrofishing, along with tagging trout or grayling, becomes more controversial when populations are in decline, raising questions about whether the interventions and handling of the fish are worth the data recovered.
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In other words, to paraphrase Leo Tolstoy, perhaps the fish survive despite the biologists’ best efforts.
Steve Fisher, a Missoula-based aquatic biologist with decades of field experience, believes electrofishing causes more harm to fish than is generally acknowledged by fish and game departments. He has followed the saga of declining trout populations in the Big Hole, Beaverhead, Ruby and Jefferson rivers and feels it is quite possible electrofishing is contributing to the decline.
Yet Jim Olsen, fisheries biologist for Montana Fish, Wildlife & Parks, reported that electrofishing-related injury and mortality rates in fish are generally less than 1%.
Fisher contends the actual number probably ranges from 5% to 10%.
“You never sample the fish you don’t see,” he said. “The point is fish are still getting damaged.”
Fisher said he believes the much-published photo last summer of a so-called “zombie fish” caught in the Big Hole River shows injury from electrofishing that was subsequently colonized by fungus or parasites.
Yet many fisheries biologists and FWP’s electrofishing policy say the sampling tool provides vital population data and has advanced since studies decades ago found evidence of spinal cord and other injuries in fish.
“Electrofishing is one of the few methods that allows fishery professionals to quantitatively sample fish populations for assessment of, among others, population dynamics, age and growth and movement,” the policy observes.
‘All necessary precautions’
Ryan Kreiner, an FWP native fish biologist, has been involved with efforts to sustain the declining adfluvial Arctic grayling population in the Red Rock Lakes National Wildlife Refuge.
Kreiner said electrofishing is used in the spring, during the spawning run, to capture and tag grayling in Red Rock Creek.
“Based on our training, experience and our state’s electrofishing policy, we take all necessary precautions and use the safest settings and equipment for capturing fish,” Kreiner said. “I personally have seen that electrofishing mortality is greatest at higher [water] temperatures — fish don’t recover as well — and we typically sample grayling when the temperatures are between 45 degrees and 51 degrees Fahrenheit. In cold water, they rebound quickly.”
Kreiner said estimates suggest mortality rates in Red Rock Creek are very low, probably between 0.26% to 0.8%, due to precautions taken during sampling and handing.
FWP’s “Electrofishing Methods Policy” was last revised in 2003. It referenced a 1992 study that “demonstrated a significant rate of injury to certain fish species.”
The policy document noted, “Electrofishing may result in adverse consequences for affected fish of a variety of species and life history stages.”
And it noted, “The use of electrofishing gear in waters containing Species of Special Concern should be minimized.”
Montana’s list of such species, updated in March 2022, includes the Arctic grayling. It also includes the bull trout, westslope cutthroat, Yellowstone cutthroat and more.
Jim Reynolds, Ph.D., a professor emeritus at the University of Alaska Fairbanks and a recognized electrofishing expert, communicated with Kreiner, Michael Bryant, manager at the Red Rock Lakes National Wildlife Refuge, The Montana Standard and others in Montana about the pros and cons of the sampling technique as refined in recent decades.
Reynolds noted that electrofishing in Red Rock Creek is not done in areas where grayling eggs are incubating.
“However, mature females can be stressed by electroshock to the point of not spawning,” Reynolds said.
He said reports suggest that this outcome is unlikely in Red Rock Creek because “the grayling recover immediately after recapture, indicating minimal stress.”
“After a lengthy conversation with Ryan, I conclude that the FWP is using electrofishing properly and expertly,” Reynolds said. “They used direct current that has no on-off pulsing that more likely causes injury. Direct current is widely recognized to be the least harmful electric waveform for fish.
“They start at low voltage and increase the current until they have a threshold response — that is, fish are caught without injury or death and recover in holding tanks very quickly before being released,” Reynolds said.
Internal hemorrhaging
During the 1990s and early 2000s, numerous research studies described major concerns about the impacts of electrofishing.
A 2004 study by J. F. Schreer and co-authors in the Journal of Fish Biology found negative effects of electroshocking in rainbow trout, including erratic heart function and internal hemorrhaging.
The authors acknowledged variability in the results and limitations of a small sample size, but observed that “the strongest conclusion that can be drawn from this work is that electrofishing, regardless of the settings, has a considerable negative impact on rainbow trout that is often not apparent externally.”
A study published in 1994 by Bruce Hollender and Robert Carline in the North American Journal of Fisheries Management found evidence of internal hemorrhages and spinal misalignment or fracture. The fish were captured with alternating current or pulsed-direct current, technologies no longer used by FWP.
Mike Duncan, FWP’s Region 3 fisheries program manager, said the agency’s research and review of peer-reviewed studies of mortality and injury rates informed FWP’s approach to electrofishing.
“That combination of information has led FWP staff, and most other biologists and researchers I’ve worked with, to use settings that minimize injury and mortality,” Duncan said. “The major issue was the use of alternating current in electrofishing efforts. Although using AC current increases catch rates, it also increases injury and mortality primarily because of spinal injuries. Therefore, it’s now standard practice to use direct current, which significantly reduces stress on the fish.”
Caleb Uerling is an FWP fisheries biologist whose territory includes the Upper Clark Fork River. Brown trout populations have declined dramatically in recent years in the upper river — where Superfund remediation affected habitat — and theories abound as to the causes.
Uerling said electrofishing crews he’s worked with use smooth DC current “at the lowest voltage possible to effectively capture the species and size of fish they are working with.”
He added, “I have witnessed mortality, mostly in mountain whitefish. Mountain whitefish tend to be very sensitive to stressors and this is also the case with electrofishing. Sometimes the current necessary to capture trout is enough to harm whitefish if they are not removed from the current in a timely manner.
“Observed mortalities in trout and other species that I work with are rare.”
The value of data
Uerling said sampling or any activity that requires handling of fish will increase stress and ultimately the risk of mortality. He said sampling techniques are selected for use that weigh the value of data retrieved to potential negative impacts.
Doug Austen, Ph.D., is executive director of the American Fisheries Society. He said advances in electrofishing technology and techniques, along with improvements in fish handling, have likely contributed to fewer research studies in recent years about injury and mortality.
“Being able to efficiently and effectively capture and handle fish, take whatever data is needed, and return them safely to the water is such a fundamental requirement of fish conservation and management, that these improvements have all been well received and incorporated into most agency standard procedures,” Austen said.
Tagging
The summer of 2023 stirred angst and anger after reports of declining trout populations in rivers within the Jefferson River Basin, a region that includes the internationally renowned Big Hole River. Predictably, conflicts spiked at times between fishing outfitters and ranchers who pull water from the river for irrigation.
Many observers emphasized the need for research to discover the factors driving the declines.
In response, FWP announced a partnership with Montana State University. Separately, a privately-funded nonprofit, Save Wild Trout, entered the fray.
In mid-March, FWP and MSU issued a press release asking anglers who catch a tagged trout in the Big Hole, Beaverhead, Ruby and Madison rivers to use clippers to remove the numbered tags and submit a report for each tagged fish caught.
“Anglers play a critical role in this study,” said Duncan of FWP. “When they submit reports on tagged fish, they are helping gather important information on the health of the fishery.”
Anglers who submit reports may also be eligible for rewards. Blue tags will be entered into a drawing for gear and fishing trips. Yellow tags are each worth $100.
Trapper Badovinac, a longtime fishing guide and author of fly fishing books, said encouraging increased handling of fish by the average angler is a bad idea.
“The average angler is painfully ill equipped to handle Montana trout out of the water even for the time it takes to retrieve their fly,” Badovinac said. “If the fish swallowed bait, every study I’ve read shows mortality rates off the charts.
“I know of zero anglers who carry any sort of clippers adequate to remove a tag from a fish without harming it,” he said. “Rewarding bad behavior is worse than ignorant. It’s stupid and there’s no cure for stupid.”
Duncan addressed concerns about handling.
“Increased handling came up during our initial meetings with MSU,” he said. “Unnecessary or improper handling is always a concern with inexperienced anglers, which is why our Communication and Education Division staff have increased outreach efforts to educate anglers on proper handling techniques.
“Clipping tags should minimize handling and any associated injury or mortality, so we don’t expect the extra effort to have measurable effects,” Duncan said. “However, if we learn that’s not the case through our own observations or reports from anglers or guides, there are ways we can assess increased mortality that would allow us to revisit our approach or account for it in the study.”
Alternatives
Uerling said new technologies and techniques have emerged for monitoring fish populations.
He said techniques that require less handling or no handling of fish are becoming more prevalent and being used where practical.
For example, Uerling cited:
- Sampling DNA from water samples (eDNA) is being used to get presence/absence information and maybe someday abundance information.
- Genetics techniques are being used (including on grayling in southwest Montana) to where only a fraction of the population needs to be sampled and then genetics information from the sampled individuals help determine a population size.
- Hydro-acoustic sampling techniques are being developed to sample fish population in lakes and reservoirs. This technique is replacing or augmenting more invasive techniques such as gill netting in some places.
A January 2021 article in ScienceDaily highlighted related research at Oregon State University.
“Delivering a minor electric shock into a stream to reveal any fish lurking nearby may be the gold standard for detecting fish populations, but it’s not much fun for the trout,” the article observed.
“Scientists at Oregon State University have found that sampling stream water for evidence of the presence of various species using environmental DNA, known as eDNA, can be more accurate than electrofishing, without disrupting the fish,” the article reported.
Scientists believe eDNA also has the potential to detect pathogens causing fungal diseases, which has been a concern on the Big Hole River.
Researchers determined that eDNA is a useful complement but is not yet a replacement for electrofishing.
“Electrofishing provides researchers the opportunity to record other physical data about the fish, including size, health and appearance, that eDNA detection does not allow,” the article in ScienceDaily reported.
Christopher Caudill, an associate professor of fisheries at the University of Idaho, said researchers should consider the pros and cons of electrofishing, especially when sampling a dwindling population.
"Clearly, the stakes increase for a small population and thus it becomes even more important to articulate how the risks compare to the benefits of the information to be gained and why electrofishing is needed as a sampling method over other approaches," Caudill said.