Uunderstanding fish structure and the functions of fish anatomy will help you see details of the animals you are trying to draw and train your eye to look for critical features. Study these drawings and then look for these features on live fish, specimens, or photos. You can view an amazing searchable database of fish photographs including scientific specimens and photos taken in nature at
Fishpix. The more you understand what you see, the easier it will be for you to get what you observe down on paper.
Click on the first image to start a step-by-step slideshow.
Body Type: Many fish have elongated bodies including the familiar trout and salmon. Note the line along the side of the body. This is the lateral line and it is an important part of the fish’s sensory system. Is some fish the lateral line is straight, in other species it is curved. Body Type: Other fish have sorter bodes. In cross section, the body shape can either be flattened like a pancake, or round. Mouth: Fish that feed from the surface often have upward facing mouths. Mouth: Fish that feed at the bottom often have downward facing mouths. Mouth: Some specialized fish have mouths on the end of long extensions. Tail: Tails come in all sorts of shapes. A round tail is good for bursts of speed but the back edge of the tail creates drag and would burn a lot of energy in long distance (open water) swimming. Expect this tail type in fish who might hide among rocks and dart from one retreat to another. Tail: This tail type also creates drag. Train yourself to note and record the rear tail margin. Tail: Note how the tail margin becomes increasingly notched over the next few examples. Tail: Slightly notched. Tail: Deeply notched. This tail would avoid drag and would be ideal for long distance swimming in open water. Tail: Tuna have a lunate (moon shaped) tail. Note the addition of a stabilizing keel in the middle of the tall and small “finlets” at the tail base. Tail: Sharks have a similar tail shape but it is asymmetrical with a larger, often notched, upper lobe. Pectoral Fins: The disadvantage of the asymmetrical tail is that the upper lobe provides more power, and would drive the fish down. To counteract this forward motion, the sharks front (pectoral) fins are low in the body and stick out to the sides, changing the downward force into forward movement. Pectoral Fins: On fish with a symmetrical tail, the pectoral fin is higher on the side of the body and often is held flat against the side of the body. Pectoral fins are homologous with forelimbs and are paired (one on each side of the body). Dorsal Fin: Fish have a single fin down the middle of the back. This often has two sections. The front section is stiff and spiny. The rear section has softer rays. Dorsal Fin: You can see modifications of the two sections in a tuna. Dorsal Fin: On some species, the dorsal fin separates into two or three distinct sections. These are called (from front to back, dorsal fin one, two, and three). Dorsal Fin: On a shark you do not see fin rays. The cartilage structures that support the fin are covered by tissue. Dorsal Fin: The sections of the dorsal fin may also be undifferentiated, not showing a clear spiny front section. Adipose fin: A small fleshy, rayless fin on trout, salmon, catfish and characins. Ventral or Pelvic Fins: Paired fins on the underside usually behind the pectoral fins. homologous with hind limbs. Ventral or Pelvic Fins: In some fish (e.g. cod) the pelvic fins are forward of the pectoral fins. Anal Fin: Behind the anus fish have a single fin on the center line. This fin may have a forward spiny rayed section and a more flexible, soft rayed section behind. Like the dorsal fin, this fin may be divided into a first and a second anal fin in some fish (e.g. cod). Anal Fin: The anal fin may show specialized shapes. Anal Fin: The anal fin may also have homogenous rays. Tails and Fins: Some fish have tails and fins that merge into a continuous band. Note where these bands start and end. Test time: It’s time to play, name that fin. Can you name all the fins on this fish? What fin is not shown in this picture?