Dive 2: Armored Searobin
Video of a searobin using modified fins to move across the seafloor during a dive within the Ta'u Unit of National Marine Sanctuary of American Samoa. It’s a fish out for a stroll!
Armored sea robins are related to the sea robins found in shallow water along the Atlantic and Gulf of Mexico coasts of the U.S. They differ from shallow water sea robins by having four rows of bony plates along the body. Each plate has a thick, curved, short spine—hence the common name. They also have horn-like projections on each side of the snout and branched barbels (whiskers) on the bottom of head in front of the mouth. The branched barbels have taste buds and are used to sense food on the bottom.
The fan-like fins on each side of the body behind the head (pectoral fins) have stiffened rays. In sea robins, including the armored sea robin, the first few rays are free from the membranes of the rest of the fin and are very thick. The fish uses these thickened, stiff fin rays to "walk" along the bottom. That is the usual form of locomotion for sea robins, instead of swimming like most other fishes.
Video courtesy of the NOAA Office of Ocean Exploration and Research, 2017 American Samoa.