Global Warming Could Mean Lazier, Fewer Fish: A Study

As ocean temperatures continue to rise, some fish are having a harder and harder time mustering the enthusiasm to search for food or reproduce -- or anything else that may include movement.

Researchers from the ARC Center of Excellence for Coral Reef Studies at James Cook University made this discovery while observing the commercially important coral trout.

Their study revealed that as the ocean gets hotter, populations of coral trout are becoming more lethargic, opting to spend their days resting on the ocean floor -- the equivalent of humans who have a hard time separating from their couch.

According to researcher Jacob Johansen, the discovery suggests "global warming may reduce the swimming ability of many fish species, and have major impacts on their ability to grow and reproduce."

Even when the fish do manage to find the willpower to move around, they swim at much slower rates, which is likely to affect their ability to overcome prey or make it all the way to spawning sites, the researchers note.

"The loss of swimming performance and reduced ability to maintain important activities, like moving to a spawning site to reproduce, could have major implications for the future distribution and abundance of these species," Johansen said.

In the long run, this could directly impact "where we will find these species in the future and how many we are able to fish sustainably," co-researcher Morgan Pratchett added.

Fortunately, there is evidence that coral trout are able to adapt to higher temperatures, as seen in groups of them located in the northern region of the Great Barrier Reef. Johansen said the coral trout there appear to be "a little better" than their southern peers at tolerating the warmer temperatures.

"Coral trout is one of the most important fisheries in the South-East Pacific. If we want to keep this fishery in the future, it is critical that we understand how global warming may impact the species. This will allow us to develop management plans that will help to keep the species, and its fisheries, healthy."

The study was published in the journal Global Change Biology.