Somefin Fishy: A Fish Anatomy Guide

Part 1: Fish Tails

This is the first post in a series about fish anatomy. Fish have amazing physical adaptations to survive underwater. Here, we explore just one of those adaptations – the tail.

               You can learn a lot about a fish by looking at its tail. For nearly every fish species, the tail is the primary set of fins for one purpose: generating swimming power.

Though the tail is just one part of a fish’s body, it is one of the most prominent features. Tail shape adds to the character of the fish, and come in a multitude of shapes and sizes. Each tail shape is adapted for a slightly different reason.

So what are the different tail shapes? Keep reading. We’ll explore some of the most common tail shapes, and what it means about the fish sporting that shape.

Rounded

Fish with a rounded tail fin will have large, nearly circular fins. Fish with rounded tails tend to have thick caudal peduncles (the connection between the body and the tail). These fish tend to be slow swimmers, relying on a sit-and-wait approach to capture their prey. Rounded fins may provide a quick burst of speed, but won’t propel a fish at top speed for longer than an initial bull-rush to catch their prey. Common types of fish with rounded tailfins include gobies, anglerfish, and bettafish.

Truncate

A truncate tail ends in a vertical line. Once again, these tails indicate a relatively slow, though strong, swimmer. In fact, many fish with truncate tails may rely on bursts of speed to escape predators and capture prey. These fish also rely on their pectoral fins for extra propulsion, as well as quick directional changes. Common types of fish with truncate tails include trout, salmon, and grouper.

Forked

Forked tails are very common and indicate that the fish likely swims quite fast. If you were able to design your own fish, a forked tail would be a quite balanced option, providing both speed and good maneuverability. Common types of fish with forked tails include sharks, anchovy, tarpon, catfish, carp, and many more.

Lunate

This is the ultimate tail for speed. Highly curved and slim with a very narrow caudal peduncle, lunate tails are reserved for only the fastest of the fast. Though they sacrifice maneuverability in favor of top speed, fish with lunate tails are generally top predators, and rely on chasing down their prey over long distances rather than with tight turns. Common fish with lunate tails include swordfish, sailfish, and tuna.

Though this is not the end-all be-all for tail morphologies, this will help you impress your friends and family next time you are comparing fish at an aquarium, or at the dinner table.

To learn more about fish anatomy, check out the next post in the Somefin Fishy series here.

For more fishy facts, read more of my posts here.