Kona scuba diving offers a natural-history lesson in endemic reef fish

The Hawaiian Archipelago stretches 1,523 miles, or more than 2,500 kilometers, from the Island of Hawaii to Kure Atoll and includes eight major islands and 124 minor ones. Kona sits inside one of the most isolated archipelagos on Earth, and that isolation shaped a fish community you can actually learn species by species. Hawaii has far fewer marine fish and invertebrate species than many other Indo-Pacific destinations, yet more than 20 percent of Hawaiian reef fishes are found nowhere else in the world, so a routine Kona dive can become a repeatable natural-history checklist.

Why Kona is a fish-ID classroom

That distance and isolation helped produce the kind of long evolutionary separation documented in a 2020 Journal of Biogeography paper on Hawaiian reef fish assemblages, received on March 14, revised on August 1, and accepted on August 4.

That paper reinforced what Kona divers already notice when they start paying attention: Hawaiian reefs are not a random sample of Indo-Pacific fish life. They are a compact assemblage with a high share of endemics, which makes them unusually learnable. A 2004 study by E. E. DeMartini and colleagues put shallow-water reef fish endemism at 20.6 percent in the Northwestern Hawaiian Islands and 20.9 percent in the Main Hawaiian Islands, which is close enough to say the pattern holds across the chain. A 2020 Kona Honu Divers webinar put endemic Hawaiian reef fish at 21 percent of the fish found on Hawaii’s reefs.

A short spotting guide that actually pays off

If you want a practical Kona checklist, start with four names: bandit angelfish, Hawaiian cleaner wrasse, saddle wrasse, and milletseed butterflyfish. These are exactly the kinds of fish that reward repeat dives because they are distinctive enough to lock into memory and common enough to become familiar landmarks on the reef. Jack’s Diving Locker’s Underwater Naturalist course uses saddle wrasse, Hawaiian cleaner fish, and milletseed butterflyfish as teaching species.

A useful way to sort them in your head is by shape and behavior:

• Bandit angelfish are deep-bodied and showy, the sort of fish that reads well in a still frame.
• Hawaiian cleaner wrasse are fast, busy, and tied to cleaning behavior.
• Saddle wrasse are active reef fish that move constantly and can change the feel of a site the moment you recognize them.
• Milletseed butterflyfish are small, laterally compressed, and easy to spot once you learn the outline.

The point is not just naming them. It is pairing the fish with the kind of reef work they do. A cleaner wrasse on a cleaning station, a wrasse cruising a reef edge, or a butterflyfish holding a patch of coral all tell you something about the site.

Where to look on Kona reefs

The most practical place to find these fish is the everyday reef diving you already do around Kona, not some special expedition. Hawaiian endemism is strong in the Main Hawaiian Islands, and NOAA found that unique fish species dominate deep coral reefs in the Northwestern Hawaiian Islands. Endemicity is part of the whole Hawaiian system, from shallow shore reef to deeper structure.

The same fish show up again and again on ordinary local dives, especially when you return to familiar reef structure and start noticing what lives where. Kona Honu Divers launched an intermediate Hawaiian reef fish identification class on January 10, 2024, and one of its practical features was a focus on species frequency ranked from 60 to 120 by REEF fish surveyors. Build the list around fish you are likely to encounter often enough to learn, not rare unicorns you might miss for years.

The National Fish and Wildlife Foundation puts Hawaii at the world’s highest percentage of endemic species, with 90 percent of terrestrial species and more than 25 percent of marine species found nowhere else on Earth.

How to observe and photograph without stressing the fish

The easiest way to do this well is to slow your dive down. Hover off the bottom, keep your buoyancy clean, and watch for behavior before you move closer. A cleaner wrasse at work, for example, is giving you a live interaction to observe, not a target to crowd.

A few habits help immediately:

• Stop swimming and let the fish settle into normal behavior before taking a shot.
• Use a calm approach instead of chasing a fish for a better angle.
• Stay out of the reef itself and avoid kicking up sand that can interrupt feeding or cleaning.
• Take the first usable broadside frame instead of pushing closer and risking a spook.

On repeat Kona dives, one familiar reef becomes a stronger logbook page each time. Instead of asking whether the dive had enough action, you start asking which endemic species were present, how they were using the reef, and which ones you can identify faster next time.