Threebanded Butterflyfish: Costa Rica's Everyday Beauty

If you see a flat, silvery, disk-shaped fish crossed with dark bars gliding calmly along the rocks, you've found the threebanded butterflyfish — the butterflyfish you're most likely to meet on a snorkel tour near Jacó. Here's how to spot it, and five fun facts to make the next sighting even better.

Threebanded Butterflyfish · Chaetodon humeralis

How to spot the threebanded butterflyfish near Jacó

Look along the rocky edges of the cove where the water is calm and shallow. Threebanded butterflyfish are usually swimming in pairs, moving slowly and picking at the rocks. Their thin, round bodies and the bold dark bars across a pale silver background make them one of the easiest reef fish for a first-timer to recognize.

5 fun facts about the threebanded butterflyfish

• A true Eastern Pacific native. Most of the world's butterflyfish live in the Indo-Pacific, but this one is a genuine Eastern Pacific species, found from Mexico down to Peru. It's the butterflyfish of our coast.
• They travel two-by-two. You'll usually see them in pairs. Many butterflyfish form long-term bonds and patrol the same stretch of reef together, side by side.
• Markings that fool predators. The dark bar through the eye and the patterns toward the tail help confuse a predator about which end is the head — buying the fish a head start.
• Built for tight spaces. That flattened, disk-shaped body lets it turn sharply and slip into narrow gaps in the rocks to feed or hide.
• A sign of a healthy cove. Butterflyfish are sensitive to water quality, so a cove full of them is a good sign the little ecosystem is thriving.

The threebanded butterflyfish is just one of many characters down there. See the whole cast in our Snorkel Jaco fish directory, or read real guest photos and reviews on the Snorkel Jaco reviews.