Fish Active at night

Shortjaw kokopu

Galaxias postvectis

iNaturalist Wikipedia

Meet New Zealand's reclusive stream-climber. The Shortjaw kōkopu is a master of camouflage, thriving in the cool, boulder-strewn waters of native forests where it lives a secretive, nocturnal life.

0 Sightings

0 Habitats

Quick Identification

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Size

Typically 150–200 mm (5.9–7.9 in) in length, with rare specimens reaching 350 mm (14 in).

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Colors

Olive-brown to grey-brown with subtle dark mottling; often features a dark blue-black spot behind the gill cover.

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Key Features

Distinctively short 'undercut' lower jaw
Large, fan-like pectoral fins set low on the body
Scaleless, slippery skin with a thick mucus layer
Sturdy, muscular build suitable for climbing waterfalls
Large eyes positioned for low-light hunting

When You’ll See Them

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Activity pattern Active at night

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Peak hours 9 PM - 3 AM

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Season Year-round

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Diet A generalist predator that feeds on aquatic larvae (like mayflies and caddisflies) and terrestrial insects that fall from the forest canopy onto the water's surface.

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Habitat Pristine, shaded forest streams with stable boulder-strewn pools and clear, cool water.

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Where Does the Shortjaw kokopu Live?

The Shortjaw kōkopu is a unique treasure found exclusively in the island nation of New Zealand. This endemic species maintains a widespread but fragmented distribution across the North and South Islands, as well as on Stewart and Chatham Islands. They are most commonly found in coastal catchments with high-quality native forest cover, where the cool, clear water provides the pristine environment they require to thrive throughout their adult lives.

Basemap © OpenStreetMap contributors

1 Countries

268K km² Range

Vulnerable Conservation

NZ New Zealand

Marginal

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iNaturalist / Verified observation data

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Behavior

Shortjaw kōkopu are the recluses of the New Zealand stream world. Primarily nocturnal, these fish spend their daylight hours tucked away in deep, shaded crevices between boulders or under submerged logs. They are highly territorial over their chosen pools and exhibit a 'sit-and-wait' predatory style, remaining perfectly still until prey drifts by on the current.

These fish are remarkable climbers, capable of scaling steep waterfalls as juveniles (whitebait) by using their fins and body surface tension to move up damp rock faces. While generally solitary, several individuals may inhabit the same stretch of water if the habitat offers enough cover. They are incredibly sensitive to human disturbance and will vanish into the shadows the moment they sense movement or vibration on the bank.

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Camera Tips

Capturing the elusive Shortjaw kōkopu requires a specialized approach since they are almost exclusively nocturnal and live underwater. For the best results, use a waterproof action camera or a trail camera with a high-quality infrared (IR) flash. Position the camera on a stable tripod or weighted mount at the edge of a deep, bouldery pool where the water is relatively still. Focus your lens on 'slack water'—the calm spots behind large rocks or logs where the fish are likely to rest while waiting for food.

Because these fish are sensitive to light and vibration, avoid using standard white-light flashes, which will cause them to retreat. Set your camera to video mode or high-speed burst to capture their subtle movements. If you are using a bank-side trail camera, aim it at the water's surface on a calm night; you might catch the ripples of a kōkopu rising to snag a moth. Ensure the camera is as close to the water level as possible to reduce surface glare from the IR LEDs.

Timing is everything. Plan your 'camera trapping' for the warmer months (November to March) when insect activity is high and the fish are most active. If your camera setup allows, placing a small amount of fish-safe bait (like a mesh bag with crushed worms) in a nearby crevice can lure them out of their hiding spots for a clearer shot. Always check local regulations regarding baiting in native waterways to protect the delicate ecosystem and avoid introducing invasive species.

Similar Species

Species that look similar or are commonly confused with Shortjaw kokopu.

Banded kōkopu

Features distinct thin vertical stripes and a lower jaw that is equal in length to the upper jaw.

Giant kōkopu

Much larger body with gold spots or lines, and lacks the specific 'short' undercut jaw structure.

Koaro

More slender and elongated body with a more pointed head, typically found in faster-flowing, higher-altitude water.

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Frequently Asked Questions

Shortjaw kōkopu are primarily nocturnal, meaning they are most active during the night. They typically emerge from their rocky hiding spots shortly after dusk to hunt for insects and remain active until the early hours of the morning.

If your property has a clean, forested stream, you can help them by maintaining dense native vegetation along the banks and ensuring there are plenty of large rocks and logs in the water for cover. They require high-quality, shaded water and do not thrive in open, silty suburban drains.

Their diet is a mix of aquatic larvae, such as mayflies and stoneflies, and terrestrial insects like beetles, spiders, and moths that fall into the stream from the overhanging forest canopy.

No, they are quite rare in suburban environments. They are highly sensitive to water pollution, sedimentation, and habitat loss, preferring remote, undisturbed native forest streams with clear water.

The most reliable way is to look at the mouth: the Shortjaw kōkopu has an 'undercut' lower jaw that is shorter than the upper jaw, whereas the Banded kōkopu has a lower jaw that is equal to or longer than the upper. Also, the Shortjaw lacks the distinct vertical white stripes found on the Banded kōkopu.

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