Unlock the Secrets of Fish Identification – Part 4 Pattern

Whitespotted filefish without spots

Whitespotted filefish with spots

White-spotted filefish with and without spots (same individual)

Welcome back, fellow fish sleuths! 🕵️‍♀️🐟 If you've been following our fish ID series (and if you haven’t – where have you been?), you already know that shape, behavior, and habitat are the big clues in identifying which family our scaly friends underwater belong in. Today, we’re diving into the world of patterns – those markings that help us to narrow down the exact species. Patterns aren’t as high as shape, behavior, and habitat in our fish ID toolkit because some fish can change their pattern almost immediately (white-spotted filefish), throughout the day (some fish have different colors at night – PJ party!), and throughout their life stages.

Blue tang with typical pattern

Blue tang with bars

Blue tangs will display "disruptive coloration" aka bars to break up the outline of their body at night.

Juvenile yellowhead wrasse

Initial/female yellowhead wrasse

Male/terminal yellowhead wrasse

The three life stages of the yellowhead wrasse: juvenile, initial/female, and terminal/male

Whenever someone asks me, “What’s that fish with the yellow tail?” my brain short-circuits a little – because, guess what? Lots of fish have yellow tails! 😅 It’s one of those features that’s shared across a bunch of different families, so while it’s a great clue, it’s definitely not the whole story when it comes to fish ID.

What's the fish with the yellow tail? (see answer key at the bottom)

So let’s break down the six main types of patterns you’ll want to keep an eye out for: bars, bands, stripes, lines, spots, and ocellated spots. Ready to become a pattern pro? Let’s go!

Bars – Think of bars as the pinstripes of the fish world – but vertical. These are wide markings that run up and down the body, often crossing from the dorsal (top) to the ventral (bottom) side. Another way to remember that bars run up and down, is to think if you were in jail, you’d be looking out through bars.

🔍 ID tip: Bars often help you identify fish like butterflyfish; all butterflyfish have a bar running through their eye, this disrupts the outline of the fish. One famous bar-wearer? The Sergeant Major – named after its bold, vertical black bars.

Vertical lines on a fish are called bars

A juvenile gray angelfish with bars

A sergeant major has bars

Grey angelfish (juvenile) Sergeant major (damselfish)

Bands – kind of like bars’ dramatic cousins, but they tend to be angled.

🔍 ID tip: Many jacks (greater amberjack, lesser amberjack, and almaco) have a band through their eye and the juvenile spotted drum, highhat, and jackknife (adults too) have a band running from the front of their long dorsal fin to the tip of their tails.

Bands are lines that are angled

Amberjacks have a band through their eye

Jackknife fish have one long band from their dorsal fin to the tip of their tail

Amberjack (jack) Jackknife (drum)

Stripes – These run horizontally, from head to tail, and are common in fish that like to blend into their environment.

🔍 ID tip: Many species of grunt have stripes. Horizontal stripes can help break up the fish’s outline – nature’s own optical illusion.

Horizontal lines on a fish are called stripes

Smallmouth grunts have stripes

Reef squirrelfish have stripes

Smallmouth grunt Reef squirrelfish

Lines – thinner than stripes and often more subtle, lines can be solid or dashed and run in any orientation.

🔍 ID tip: Lines are especially useful for IDing wrasses and gobies. Sometimes these lines run across the eye, which can throw predators off! The yellowhead wrasse has two lines above its eye in most of its’ life stages: juvenile (sometimes), intermediate, and terminal.

Thin markings in any direction are called lines

The yellowhead wrasse has two lines by its eye

The seaweed blenny has lines on its face

Yellowhead wrasse, initial phase Seaweed blenny

Spots – dots on the body or fins of the fish. They come in all sizes and patterns, from dainty freckles to bold, round statements.

🔍 ID tip: Think of groupers (graysby, red hind, coney) or the adorably spotted boxfish smooth trunkfish, spotted boxfish). Spots can be regular or randomly placed, but they’re a great ID clue.

Dots on a fish are called spots

Graysbys have spots

Smooth trunkfish have spots

Graysby (seabass) Smooth trunkfish (boxfish)

Ocellated Spots – eyes Where?! Now for the real MVP of fish trickery: the ocellated spot, aka the false eye. These are spots ringed with a border, making them look like an actual eye. Mind. Blown. 🤯

🔍 ID tip: You’ll see these on foureye butterflyfish, some wrasses, and some hamlets. These spots can confuse predators by drawing attention away from the real eye – or just by being super intimidating. Eyes on the back? Classic fish move.

A spot with a ring around it is called an ocellated spot

The foureye butterflyfish has an ocellated spot

Hairy blennies have an ocellated spot

Foureye butterflyfish Hairy blenny

Why Patterns Matter

These markings aren’t just for show – they serve real evolutionary purposes. Patterns can:

• Camouflage the fish in its environment

• Confuse predators (or prey!)

• Signal species identity or mating readiness

• Mimic non-predatory fish – many hamlets (eat small fish) match the pattern and color of damselfish (eat algae)

And for us divers and snorkelers? They help us become underwater detectives, piecing together clues to ID what we see.

What’s Next?

Now that you’ve added pattern recognition to your fish ID toolkit, you’re well on your way to becoming a reef expert. 🎓 Up next in our series: Color then Size – aka the final touches in our fish identification adventure.

So next time you're underwater, don’t just admire the beauty – read the signs. Those bars, bands, and spots? They’re the fish’s way of telling you exactly who they are.

Spotted drums have a little bit of everything: spots, stripes, a band, and bars!

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 resources 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

Fish with yellow tails answer key, from top to bottom, left to right (with the family in parentheses):

Yellowtail damselfish (damselfish), yellowtail hamlet (seabass), rock beauty (angelfish)

Yellow goatfish (goatfish), yellowtail snapper (snapper), schoolmaster (snapper)

Spanish hogfish (wrasse), yellow jack (jack), horse-eye jack (jack)

Yellowtail parrotfish (parrotfish), queen angelfish (angelfish), puddingwife (wrasse, initial phase)

📸 All photos courtesy of Sara and Lee Richter 📸