Unlock the Secrets of Fish Identification – Part 1 Shape

A fish can be identified to its family by shape

Imagine you’re out snorkeling, and you come across a fish that you’re not quite sure about. Sounds familiar, right? But here's the thing: identifying fish doesn’t have to be super complicated. It’s all about learning to recognize a few key features, there are six main things to look at: shape, behavior, habitat, pattern, color, and size. The first three – shape, behavior, and habitat – are the most important ones to start with. These are the key clues that’ll help you figure out which fish family the fish belongs to, like whether it’s a parrotfish, angelfish, or snapper. Once you've got that nailed down, you can use the other three – pattern, color, and size – to get even more specific and figure out the exact species, like a stoplight parrotfish, queen angelfish, or a yellowtail snapper.

This post is part of a series, so we’re kicking things off with shape, but we’ll dive into the other factors, behavior, habitat, pattern, color and size, in the next parts. But for now, let’s unlock the secrets behind fish shape and see how it can help you identify what’s swimming by!

To describe a fish, we need to get on the same page talking about the different parts of the fish. The names of the fins are listed on the diagram below. In addition to the fins, bony fish have a hard covering over their gills called an operculum and the area where their tail joins their body is called the caudal peduncle. These will all be important in your quest to identify fish.

The basic parts of a fish

Shape is super important when it comes to identifying fish because it gives you a lot of clues about what kind of fish you’re dealing with. First off, the shape of the fish’s body tells you a lot about how it moves and where it lives. For example, sleek, streamlined bodies are built for fast swimming. Then, there’s the tail – fish with square/round tails have more maneuverability and live in more complex habitats like coral reefs. And don’t forget the mouth! The direction it opens can give you a huge clue about what the fish eats, downward-facing mouths are built for bottom-feeding. All these shape features together help you narrow down exactly what species you’ve spotted.

Fish Identification: Body shapes - torpedo, disc, and odd

Fish Identification: Tail shape - square, forked, and crescent

Fish Identification: Mouth orientation - upward-facing, center, or bottom-facing

For a little fun, here's a quiz to see how you do in identifying the various shapes of fish. See if you can identify the body shape, the tail shape and the orientation of the mouth. Good luck!

Here's the answer key, let's see how well you did.

Taking a side-by-side look at the yellowtail snapper and the yellow goatfish you can really see why shape is so important. Based on color, pattern, and size the two fish look almost identical, but the biggest difference is the location of the mouth. Since goatfish are bottom feeders, they also have barbels, the two whisker-looking appendages below the mouth, but they can fold those up. 

So, there you have it! Understanding the shape of a fish is a game-changer when it comes to identifying species. Whether it’s the body, tail, or mouth, the shape can tell you so much about where a fish lives and how it behaves. By paying attention to these key features, you’ll be well on your way to becoming a fish identification pro!

But we’re just getting started! In the next part of this series, we’ll dive into Behavior – another crucial factor in helping you get even more specific with your IDs. Stay tuned!

Next time you’re out in the water, take a moment to observe the shapes of the fish around you. It’s an easy first step in learning to identify them, and I promise it’ll make the experience even more exciting!

A fairy basslet which belongs in the seabass/grouper family

I’d love to hear about your own fish identification experiences! Drop a comment below and share what fish you've spotted or any tips you've picked up along the way.

To help you along your fish ID journey, some great resource are the app Fishes: Greater Caribbean by D. Ross Robertson and James Van Tassell and the ID books Reef Fish Identification Florida, Caribbean, Bahamas by Paul Humann and Ned DeLoach and Caribbean Reef Life – A Field Guide for Divers by Mickey Charteris