Pectoral fin
The paired fins just behind the gills, used for steering, braking and, in some fish, walking or gliding.
Also: side fins
Pectoral fins sit in a pair, one on each side just behind the gill openings. They match the front limbs of land animals, and in lobe-finned fish such as the coelacanth and lungfish they have bones that recall an arm. Most fish use them to steer, hover and brake. Rays have turned them into the broad wings they swim with, flying fish spread them to glide above the water, and mudskippers prop themselves on them to move across mud. Gurnards use separate pectoral rays like fingers to feel along the sea floor.