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WVU researchers reeled in answers on muskie mortality

Photo of eye of a fish.

Researchers at West Virginia University have been spending their time fishing for the elusive “fish of ten thousand casts,” the muskellunge – for research, of course. 

In 2020, Muskies Inc., a group dedicated to the well-being and sport of muskellunge fishing, also called muskies, contacted Professor of Ecology Kyle Hartman and graduate students Cory Bauerlien, Taylor Booth and Peter Jenkins at the Davis College of Agriculture, Natural Resources and Design. The angling group asked them to confirm or refute concerns rippling through the angling community—can catching (and releasing) the fish during the hottest months of the year lead to their deaths? 

“For a long time, people would see dead muskies floating in the summertime,” Hartman said. “They attribute it to fish being caught and released in warm summer temperatures. Some people won’t fish in the summertime because of that.”

Photo of hands holding a fish.

Like any diligent researchers, after hearing these concerns, Hartman and his fellow researchers went fishing for answers. With funding from Muskies, Inc., West Virginia Division of Natural Resources and the Hugh C. Becker Foundation, they collaborated with Coastal Carolina University and state agencies to catch and track muskellunge in high temperature waters.

Only one similar study investigating summer musky mortality, done by researcher Sean Landsmen at the University of Carleton in Canada, had been conducted prior to this, and there was no mortality observed; however, the warmest temperature in that study was 75 degrees Fahrenheit. In most reservoirs and rivers in the southern part of the muskies’ habitat range, like West Virginia and Virginia, the water temperature can reach 90 degrees Fahrenheit and higher. 

“The question was still, ‘Does it kill muskies to catch and release them in warmer temperatures?’” Hartman said.

WVU researchers conducted studies in experimental ponds and at Stonewall Jackson Lake while Bauerlien and Coastal Carolina University Associate Professor Derek Crane conducted research at the James River in Virginia. 

In the spring of 2020 and 2021, the researchers sampled Stonewall Jackson Lake and the James River to catch adult muskies over 26 inches long. They did a quick procedure to insert a radio transmitter to track the location of 187 muskies over two years.

When temperatures rose above 75 degrees Fahrenheit in the coming two summers, they tracked the fish they implanted with radio transmitters and documented the location of each fish relative to cold water areas and areas of low oxygen. They planned to catch half of the tagged fish, leaving the other half as a control group.

Photo of young man holding large muskellunge fish.

Thanks to a willing community of anglers, enough fish were caught to evaluate the potential impacts of warm water catch and release fishing on muskie populations.

At Stonewall Jackson Lake, there was an observed mortality rate of 10% in 29 angled muskies. The muskie mortality observed in Stonewall Jackson Lake occurred in the summer months, indicating that the summer months are a much more stressful period for these fish.

At the James River research site, only 12 fish were caught in the summer months, but mortality was much higher at 33%. The stressed fish moved to cooler water located at the mouths of the James River tributaries. 

The cooler water at the bottom of Stonewall Jackson Lake limited musky mortality compared to the James River study; however, the research indicated that having access to cool water made the muskies more comfortable, so they were more likely to bite.

To control for such confounding factors like varying temperatures within a body of water and amount of time in warmer waters, the researchers conducted pond studies.  

“We put muskies into hatchery ponds and caught them at different temperatures across five different states and 12 ponds,” Bauerlien said. 

Photo of hand holding fish in water.

This design allowed Booth to determine the role of water temperature and handling time on muskie survival under more controlled conditions than the other studies. Of the 50 muskies caught in the ponds, mortality was 43.3% for fish caught above 77 degrees Fahrenheit. Fish caught in temperatures below that, or those that were not caught, both experienced a 10% mortality rate. 

However, mortality is more than a number. Higher temperatures in the two days preceding the catch, the day of the catch and the two days following the catch increased catch and release mortality rates. Holding a fish in warm surface waters after being caught also showed to induce more stress on an already stressed fish. The longer a fish stayed in the net after being caught, or the warmer the water temperatures experienced by the fish during capture, the more likely that fish would die following release. 

Hartman noted that the summer months are generally more stressful for muskies. With the control allowed from the pond study, he said that temperature does play a role in mortality. However, that role can be mitigated in the real world by the natural environmental factors found in the lake and river studies such as temperature before and after the catch and access to cool water. 

“I hope the research results allow anglers to make more informed decisions, regardless of what each individual ultimately chooses,” Bauerlien said. “Although there isn’t a statistically significant effect on the populations, there is an effect of mortality which led me to change my outlook on fishing in the summer months.” 

To learn more about the study, visit the Musky Mortality Project

The Davis College of Agriculture, Natural Resources and Design envisions a world sustainably fed, clothed and sheltered. To learn more about the Davis College, visit Keep up with the latest updates and news on Facebook, Twitter, Instagram and YouTube by following @WVUDavis. 




Leah Smith    
Communications Specialist  
Davis College of Agriculture, Natural Resources and Design    


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