Low oxygen cramps tuna and billfish

Have you ever grasped for oxygen, like during a high-altitude hike? Now you know what swordfish and tuna feel like in our Brave New Ocean. According to a new report, expanding zones of low oxygen are occurring in the preferred habitat of tuna and billfish (swordfish, marlin, etc.), forcing them out of preferred habitat and into other areas. Besides leaving fish nirvana for lesser places,