Sharks and other large fish are among the most iconic animals of the open ocean. Our team suspects that they are also surprisingly active hunters in the twilight zone, but little is known about where they dive to find food, how often they dive, and how long they stay at depth. 

Thanks to small, accurate ROAM satellite tags, WHOI scientists will be able to track these predators in three dimensions as they move in through the twilight zone over months or years. A titanium dart attached to a short tether holds the tag in place in muscle tissue just below the dorsal fin. Data is transmitted back to shore via satellite at the end of each deployment, giving researchers a first look at where these predators are in relation to physical, chemical, and biological processes that create hot spots of activity in the twilight zone.