Atlantic herring  (Clupea harengus)

Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
Lateral line: a row of receptors that can detect movement via vibrations in water. The receptors are typically embedded in the skin, and in fish they form a line along the sides of the body.
Pectoral fins: in fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.
Pelvic fins: in fish, the pair of fins found on the underside of the body.