At more than 77 per square meter of ocean, this crab swarm is one of the densest patches of the creatures ever seen.
Pleuroncodes planipes, or red crabs swarming more than a thousand feet below the surface off the coast of Panama had scientists smiling and their cameras rolling. When they chose the Hannibal Seamount region to explore they couldn’t have known what an amazing experience awaited them.
Scientists armed with the Deep Rover 2 had picked this flat-topped undersea mountain to explore because of its rich diversity of plants and animals found nowhere else on earth. What the researchers saw in the lights of their submersible was incredible: an underwater storm of red crabs the likes of which has never been seen.
One of the biologists, Jesús Pineda, said of the experience, “When we dove down in the submarine, we noticed the water became murkier as we got closer to the bottom. There was this turbid layer, and you couldn’t see a thing beyond it. We just saw this cloud but had no idea what was causing it. As we slowly moved down to the bottom of the seafloor, all of the sudden we saw these things. At first, we thought they were biogenic rocks or structures. Once we saw them moving—swarming like insects—we couldn’t believe it.”
The researchers said that red crabs have been seen in large masses such as this before, but not so far south of their normal range and never on film. The biologists said that the crab swarm was probably a social event such as for feeding or reproduction.