WASHINGTON, Dec. 22 (UPI) -- Billfish and tuna, important commercial and recreational fish species, are vulnerable to fishing pressure as a result of shrinking habitat, U.S. scientists say.
Scientists with the National Oceanic and Atmospheric Administration say a growing zone of low oxygen, known as a hypoxic zone, in the Atlantic Ocean is affecting these species' preferred oxygen-abundant habitats, forcing them into shallower waters where they are more likely to be caught, a NOAA release said Wednesday.
While hypoxic zones occur naturally in the world's tropical and equatorial oceans, scientists worry these zones are expanding and occurring closer to the sea surface, and are expected to continue to grow as sea temperatures rise.
"The hypoxic zone off West Africa, which covers virtually all the equatorial waters in the Atlantic Ocean, is roughly the size of the continental United States, and it's growing," Eric D. Prince, NOAA's Fisheries Service research fishery biologist, says.
"With the current cycle of climate change and accelerated global warming, we expect the size of this zone to increase, further reducing the available habitat for these fish."
Loss of habitat can lead to more fish being caught since the fish will actively avoid waters low in oxygen and are concentrated near the surface, scientists say.