Giant Damselfish: The Reef's Feisty Farmer

Pound for pound, few reef fish have as much attitude as the giant damselfish — a dark, stocky fish that tends its own patch of algae and defends it against all comers. Here's how to spot it near Jacó, plus five fun facts.

Giant Damselfish · Microspathodon dorsalis

How to spot the giant damselfish near Jacó

Look around rocky reefs and boulders, where giant damselfish guard small territories. Adults are a dark slate-blue to black and fairly chunky for a damselfish; young ones are darker with brilliant electric-blue spots. Watch one for a moment and you'll often see it chase off any fish that drifts too close.

5 fun facts about the giant damselfish

• The biggest damsel here. It's the largest damselfish in the Eastern Pacific, reaching close to a foot long — large for a family of usually tiny fish.
• A dedicated algae farmer. It tends a patch of algae like a garden, grazing it and weeding out species it doesn't want.
• Fearless for its size. Giant damselfish will dart out to chase away fish many times their size — and sometimes even nip at snorkelers who linger over the territory.
• Juveniles wear blue jewels. Young fish are dark with glowing blue spots, so bright they look almost artificial against the rock.
• An Eastern Pacific local. This species lives only along the Pacific coast of the Americas, from Baja down toward South America.

The giant damselfish 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.