The Elusive Oarfish Has Joystick-Like Fins That May Inspire Future Underwater Robots

A retired fish expert's interest in oarfish led scientists to study the unique anatomy that allows these long, slender fish to swim without disturbing the surrounding marine life. The study, published in the journal Ichthyology and Herpetology, reveals that each of the oarfish's hundreds of fin rays operates independently on a ball-and-socket joint, enabling the fish to ripple its fin and move without bending its body.

This discovery could inspire the design of quiet underwater robots that can gather data on ocean health without startling fish. The researchers studied eight preserved oarfish and analyzed X-rays and CT scans, as well as a video clip of a wild oarfish filmed off Louisiana. With 401 fin rays on a single fish, engineers face the challenge of building small enough components to replicate the fish's movement.

The study also notes that ribbon-fin swimming has evolved independently in multiple groups of bony fish, and researchers plan to test whether other species also spin their fin rays.