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Tuesday, December 28, 2010

Billfish and Tuna Habitat Shrinking

The US National Oceanic and Atmospheric Administration (NOAA) reports that an increasing low oxygen zone in the Atlantic Ocean is reducing habitat for billfish and tuna. Tuna and billfish  need oxygen rich water to survive and as their habitat shrinks they are forced into shallower water where they are more vulnerable to being caught.

Low oxygen areas in the ocean are a natural occurrence and are known as hypoxic zones.  What has NOAA concerned are these zones are enlarging and occurring closer to the oceans surface.  One such zone off the coast of Africa is now larger than the continental US and covers almost all the equatorial waters.  Rising ocean temperatures are thought to be the cause of the increase in hypoxic zones.

According to Dr. Eric D. Prince, NOAA’s Fisheries Service research fishery biologist, “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.”

Eventually, less habitat means fewer fish, a consideration fishery managers consider when doing population assessments.  Scientists are expecting ocean temperature to continue to rise and low oxygen zones to continue to increase continuing to force billfish and tuna into smaller areas leaving them even more vulnerable to exploitation.