Anatomy of the coho salmon
Nostrils: Salmon are able to smell their home streams and can navigate their way back to where they were born.
Operculum: A flap that protects gills and acts in unison with the mouth to pump water across the gills for gas exchange. Betta fish throw this puppies out when feeling aggressive in a sort of "come at me bro!" move.
Lateral Line: Senses water flow, which helps to avoid predators, detect prey, and possibly even increase hydrodynamic performance while swimming.
Dorsal Fin: Used for stability to keep fish from doing barrel rolls in a turbulent current. Some fish (e.g. oarfish) can use it for propulsion while others (e.g. remoras) have modified it to become suckers.
Scales: Protect their inner yummy flesh from bacterial terrors and river rocks. Salmons have cycloid or smooth scales, but some fish have ctenoid or rough scales (e.g. perch). Shark placoid scales are actually dermal denticles and increase hydrodynamic performance, making them sleek ocean rockets.
Adipose Fin: Not much is known about its function. So far, researchers have found it may detect water flow.
Caudal Fin: Used for forward propulsion. The morphology comes in all shapes and sizes, but salmon have a forked tail, leading researchers to often measure the "fork length," or distance from nose to this spot.
Anal Fin: Acts as a rudder for turning and stability. Some fish (e.g. knifefish) also use it for propulsion.
Pelvic Fins: Used for stability, especially when the fish is putting the brakes on. Some fish (e.g. clingfish) have modified these fins into a suction cup.
Pectoral Fins: Important for braking and maneuvering. To swim forward, most fish flap these at the same time, while fish holding their position or making fine movements will beat them in alternating strokes.
Mouth: Used to feed and pump water across gills. The shape of the mouth changes with different feeding modes such as suction feeding, biting, and filter feeding.
Eyes (not labeled): Used for seeing (duh). Some fish lost their eyes (e.g. cave fish) while others have large well-developed eyes (e.g. bigeye thresher shark).
Drawn by Dana Song. Written by Yuzo Yanagitsuru. Edited by Kaitlyn Lowder and Garfield Kwan.