Fish diurnal

Common Triplefin

Forsterygion lapillum

The Common Triplefin is the spirited 'rock-hopper' of New Zealand's coastline, a master of camouflage with a surprisingly bold personality.

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Quick Identification

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Size

Maximum length of 70 mm (2.75 inches)

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Colors

Mottled olive, grey, and brown camouflage; breeding males develop a distinctive black head and dark fins.

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Key Features

Three separate dorsal fins along the back
Blunt, rounded head with large eyes
Slender, tapering body
Pelvic fins used like 'legs' to perch on rocks

When You’ll See Them

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Activity pattern diurnal

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Peak hours 10 AM - 4 PM (during low tide cycles)

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Season Year-round

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Diet Small crustaceans including amphipods, copepods, and tiny shrimp, which they snatch from the surfaces of rocks.

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Habitat Coastal rock pools, cobble beaches, and shallow reefs up to 30 meters deep.

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Behavior

The Common Triplefin is a charming and territorial resident of New Zealand's intertidal zones. Unlike many fish that spend their lives in constant mid-water motion, the triplefin is a 'bottom-dweller' that uses its modified pelvic fins to perch on rocks and cobbles. From these vantage points, they keep a watchful eye on their surroundings, ready to dart forward in a sudden burst of speed to grab a passing snack or chase away a rival.

During the breeding season, which typically runs from winter through to summer, males become much bolder and more colorful. They find a suitable nest site—usually the underside of a flat rock—and guard it fiercely. They are remarkably curious fish; if you sit still by a rock pool or place a camera underwater, they will often come out from hiding to inspect the lens, tilting their heads in a surprisingly bird-like fashion.

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Camera Tips

To capture the Common Triplefin, you will need a waterproof action camera or a dedicated underwater housing. The most effective setup involves placing the camera inside a shallow rock pool during low tide. Look for pools with plenty of 'cobble' (fist-sized rocks) and seaweed, as these provide the cover triplefins love. Use a weighted base or a small tripod weighed down with stones to keep the camera steady against the movement of the tide or surge.

Placement is everything for this species. Instead of filming from above, place the camera at the very bottom of the pool facing a clear patch of sand or a flat rock. Triplefins spend most of their time on the 'ground,' so a low-angle shot will capture their three dorsal fins and expressive faces much better than a top-down view. If your camera has a macro setting or a close-focus lens, use it; these fish are small, and getting the lens within 10-20cm of their favorite perching spot will yield the best results.

A pro tip for attracting them to your camera's field of view is the 'rock-flip' method. Gently turn over a rock just in front of your camera to disturb the sediment and reveal tiny hidden crustaceans. The local triplefins will usually rush into the frame within seconds to investigate the easy meal. Set your camera to a high frame rate (at least 60fps) because their movements are lightning-fast—this allows you to slow down the footage later to see the intricate way they flare their fins when landing.

Similar Species

Species that look similar or are commonly confused with Common Triplefin.

Twister

The Twister is more slender and prefers deeper water or vertical rock faces rather than the flat cobble habitats of the Common Triplefin.

Blue-eyed Triplefin

Easily distinguished by its striking bright blue eyes and a more translucent, reddish-brown body.

Frequently Asked Questions

Common Triplefin are diurnal, meaning they are most active during daylight hours. The best time to see them is during low tide when the rock pools are calm and the sun provides enough light to see through the water.

The best way to attract them is to provide a natural food source. Gently disturbing the sand or turning over a small rock near the camera lens will release tiny invertebrates that the Common Triplefin loves to eat.

Their diet consists of tiny marine life, primarily small crustaceans like amphipods, isopods, and copepods found on the surface of rocks and seaweed.

Yes, they are very common along any rocky New Zealand coastline, including those near suburban areas and city harbors, provided there is a rocky or cobble-stone habitat.

Look for the 'triple fin'—three distinct dorsal fins on their back. They also have a very blunt head and 'perch' on the bottom using their front fins, rather than hovering in the water like most fish.

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