Fish And Climate: To 'Beat The Heat,' They Swim To Greater Depths

Just because fish have the luxury of being in a "pool" of water, doesn't mean they aren't victim to hot weather, just like humans. New findings reveal that to escape the heat, our gill-bearing, aquatic friends like to dive to deeper depths to get away from warmer temperatures. 

In this recent study, researchers tagged 60 redthroat emperor fish at Heron Island in the southern Great Barrier Reef. All the fish were equipped with transmitters that identified them individually and signaled their depth to an array of receivers around the island.

After monitoring the fish for up to a year, researchers found that fish were less likely to be found on the reef slope on warmer days; they think that many may escape to deeper water as a result of warmer temperatures. 

The researchers also kept certain factors in mind, including temperature, air pressure, wind, rainfall and moon phases as reasons for the shift. Yet they discovered that the only significant correlation was due to temperature- the redthroat emperor were consistently monitored when water was less than 24 degrees Celsius.

Lead researcher Dr Leanne Currey noted how most studies examined the effect that ocean warming would have on fish biology and not how the animals would distribute themselves to compensate for higher temperatures.  

"This is a commercially important fish and we are looking at a significant depth shift," she said in a news release. "If it's not around in the shallows in the future then fishers will have to redirect their efforts and it may be significantly harder to catch them."

Furthermore, researchers noted that instead of going deeper, the fish might actually go south in search of cooler waters located at the same depth, where the same redthroat emperor had even been recently caught off Perth, further up the West Australian coast from their natural habitat.

According to researchers, the next step in research would be to examine whether the fish could adapt physiologically to warmer sea temperatures, as other species appear to. 

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