PLAYING TAG UNDERWATER

Glimpses into the lives of ocean animals

- Nora Nickum

Ocean animals can be tough to study. Living in the dark, deep, and expansive ocean often keeps them hidden from humans. To learn about marine animals and their behaviors, scientists tag them with small devices. These attachments are similar to the Fitbits or smart watches that some people wear to track their exercise or sleep stages or measure their heart rate. Tags offer scientists a more detailed picture of what's happening in the ocean.

Fishy Research Buddies

At a depth of 200 to 1,000 meters (656 to 3,280 feet), the twilight zone is mostly out of reach of sunlight. Scientists interested in its mysteries have recruited partners who can easily dive to those depths: swordfish. Researchers attach one tag high on a swordfish's dorsal fin and another to its back. This isn't easy. "You have to hold [the animal] alongside the boat and try to fix the tags while it tries to whack you or bash a hole in the boat with that razor-sharp sword," Peter Gaube told Knowable Magazine. He's an oceanographer at the University of Washington in Seattle.

Whenever the fish breaks through the ocean surface, the antenna on one tag will transmit its location to satellites. The second tag records conditions like depth, light, and temperature on the swordfish's daily travels from the surface to the deep sea and back.