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New Study Says This Fish Jumps on Land to Cool Off

University of Guelph

The saying “like a fish out of water” doesn’t normally indicate a good thing.

For the mangrove rivulus fish, a new study says that being out of water on hot days is good for the species.

The study was published in the journal Biology Letters, and it describes how the fish jumps out of the water onto land to escape hot water and cool its internal temperature.

“If the fish are prevented from jumping out of the water, they would die,” said integrative biology professor Pat Wright, senior author of the study.

“The water evaporates off the fish and they cool down their body temperatures slightly. It only takes about a couple seconds for the fish to start to cool down.”

The species is found in waters from Florida to Brazil. The water temperature in that region can reach up to 100.4 degrees Fahrenheit.

Wright said that the fish also jump out of the water to avoid conflict with other rivulus fish over food. However, cooling is the species’ main reason for going ashore.

The researchers, undergraduate students Dan Gibson and Emma Sylvester, studied the fish with an underwater camera that regulated the fishes’ body temperature. The fish would then fling themselves onto land and wriggle to a specific spot where their body temperature would cool and they would return to the water.

The published study is titled, “Out of the frying pan into the air: Emersion behaviour and evaporative heat loss in an amphibious mangrove fish.”

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New Study Says This Fish Jumps on Land to Cool Off