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Minnows can rapidly recover from heatwaves

Researchers from the University of Illinois have discovered that the fathead minnow, a small fish species found in North American streams, can survive heatwaves with few adverse effects. 

“Fathead minnows are really common throughout North America and they’re important prey for a lot of charismatic sport fish anglers care about. So, learning how they handle heatwaves in this study gives us good insights into the potential fate of freshwater food webs under climate change,” said study co-author Cory Suski.

Previous research focused on how well animals can tolerate temperatures 2-3 degrees Celsius warmer than the current average. The U of I team wanted to look at how the minnows responded to short-term increases of 5-10 degrees Celsius.

Doctoral student Qihong Dai simulated three types of heatwaves; single short-term heatwaves, repeated heatwaves three days in a row, and extended heatwaves that lasted 48 hours. 

“After our simulated heatwaves, we tested enzymes reflecting the minnows’ ability to perform aerobic and anaerobic activities. We also were able to test changes in their metabolic rates during heatwaves,” said Dai. “After all three heatwave simulations, most minnows rapidly returned to normal physiological functioning when we cooled the water back down.”

The researchers also discovered that minnows previously subjected to heatwaves were more resilient to higher temperatures than fish that had not been exposed. However, some fish suffered negative effects. 

“The heatwave didn’t impair their ability to swim or go about their business. In fact, they could handle higher temperatures after the heatwaves, but some became more susceptible to oxidative stress. That could lead to long-term tissue degradation from free radical damage and other physiological problems,” said Suski.

Still, most minnows seemed to recover well after exposure to heatwaves. “We are surprised but also excited to see how minnows can be so resilient to heatwaves in the Midwest,” said Dai.

“We witnessed high thermal resilience of fathead minnow to extreme heatwaves,” wrote the study authors. “This result suggests that some fish species, particularly thermally tolerant ones, can withstand current and near-future heatwaves in disturbed ecosystems such as agricultural streams.”

The research is published in the journal Freshwater Biology.

By Erin Moody , Staff Writer

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