Albert Lleal / Shortfin Mako (Isurus oxyrhynchus) placoid scales, magnified 761x

Paul D Stewart / Woodcut illustration of dolphin's placenta, skull and birth by Gesner. Gesner 'Icones Animalium', 1560. Generally animals were grouped by habitat, so dolphins were thought of as fish. However Gesner d...

Paul D Stewart / Woodcut by Gesner 'Icones Animalium', 1560. Gesner and his contemporaries believed marine mammals were fish based on habitat. However Gesner did note that unlike fish they have no scales, give birth a...

Alex Mustard / Blue-striped fangblenny (Plagiotremus rhinorhynchos) peeking out of its hole in coral reef. These small fish live in holes but dart out to eat the scales from other fish. Sinai, Egypt. Gulf of Aqaba,...

Bryan and Cherry Alexander / Nadia Takui, a Chukchi girl, grips the fish's tail between her teeth as she removes the scales from a grayling at a reindeer herders' summer camp on the tundra. Iultinsky District, Chukotka, Siberia,...

Solvin Zankl / Female Toothed seadevil (Neoceratias spinifer) with male attached, captive from deep sea.

Solvin Zankl / Yellow-ribbon sweetlip (Plectorhinchus polytaenia) close up of stripes, Raja Ampat, West Papua, Indonesia, Pacific Ocean.

Aflo / Crowd of tourists watching Whale shark (Rhynchodon typus) in the Kuroshio sea exhibit, Okinawa Churaumi Aquarium, Ocean Expo Park, Okinawa Commermorative National Goverment Park, Okinawa Main Island,...

Alex Mustard / The skin of a Tassled wobbegong shark (Eucrossorhinus dasypogon), showing the rough placoid scales, commonly called denticles. These scales have the same structure as the shark's teeth and are as roug...

Alex Mustard / Skin of a nurse shark (Ginglymostom cirratum) showing the rough placoid scales, commonly called denticles. These scales have the same structure as the shark's teeth and are as rough as sandpaper when...

Michel Roggo / Close-up of Atlantic Salmon (Salmo salar). Salmon hatchery, France. Captive.

Rob Jordan / 2020VISION / Close up of scales of an Atlantic salmon (Salmo salar) caught by Tweed Foundation scientists netting and tagging migratory fish for tracking, on the River Tweed, Berwickshire, Scotland, UK, September