Fish nocturnal

New Zealand Longfin Eel

Anguilla dieffenbachii

A majestic giant of New Zealand's waterways, the Longfin Eel is a mysterious predator that can live for over a century. Discover the ancient 'taniwha' of the streams and learn how to witness their secret underwater lives.

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Quick Identification

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Size

Typically 80-150 cm (31-59 in), but can reach up to 2 meters (6.5 ft); weights often exceed 10-20 kg (22-44 lbs).

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Colors

Dark brown, olive-green, or charcoal on the back; creamy yellow, grayish, or white on the belly. No distinct spotting.

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Key Features

Dorsal fin extends significantly further forward than the anal fin
Distinctly wrinkled skin folds when the body bends
Broad, bulbous head with a large mouth reaching past the eyes
Small, rounded pectoral fins located just behind the gill openings

When You’ll See Them

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Activity pattern nocturnal

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Peak hours 9 PM - 4 AM

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Season October-April

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Diet Carnivorous and opportunistic. Juveniles eat aquatic insects and crustaceans; large adults hunt small fish, koura (freshwater crayfish), and have been known to take ducklings or other water birds.

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Habitat Found in a variety of freshwater habitats including stony rivers, lowland streams, lakes, and high-altitude tarns, usually near heavy cover.

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Behavior

The New Zealand Longfin Eel is a legendary wanderer of Aotearoa’s freshwater systems. These eels are remarkably long-lived, with some females reaching over 80 or even 100 years of age. They spend the vast majority of their lives in rivers and lakes before undergoing a dramatic physical transformation for their final act: a one-way, 4,000-kilometer migration to the deep ocean trenches near Tonga to spawn and die.

Despite their somewhat intimidating size, Longfin Eels are often curious and can become quite accustomed to human presence, especially if they are regularly fed in a specific spot. They are masters of their environment, capable of climbing steep waterfalls and damp rocks as juveniles (elvers) to reach high-country streams. As adults, they are solitary and territorial, often occupying the same deep hole or undercut bank for decades.

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Camera Tips

To capture the New Zealand Longfin Eel on camera, you will need a dedicated underwater setup or a high-quality waterproof action camera. Because these eels are almost exclusively nocturnal, ensure your camera has excellent low-light capabilities or infrared (IR) night vision. Position your camera in slow-moving water, specifically near 'snags' like submerged logs, large boulders, or undercut banks where eels hide during the day. Setting the camera at a depth of 0.5 to 1 meter, angled slightly downward toward the riverbed, provides the best perspective for capturing their length and movement.

Baiting is the most effective way to draw a Longfin Eel into your camera's field of view. Use a mesh bag or a perforated plastic container filled with oily fish (such as sardines or salmon) or raw meat. Secure the bait firmly to a rock or stake directly in front of the lens. The scent trail will travel downstream, attracting any nearby eels. Once an eel finds the bait, it will often linger, giving you ample time to capture detailed footage. Check local regulations to ensure baiting is permitted in your specific waterway before proceeding.

For the best visual results, prioritize video over still photos. The undulating, serpentine swimming motion of the Longfin Eel is its most striking feature and is best appreciated in motion. Set your camera to record 30-second clips with a short trigger interval. During the summer months, water clarity is usually better, and eels are more active due to warmer temperatures. However, avoid filming immediately after heavy rain, as suspended sediment and 'river 'snow' can cloud the water and trigger false motion alerts on your camera.

Similar Species

Species that look similar or are commonly confused with New Zealand Longfin Eel.

New Zealand Shortfin Eel

The dorsal fin is almost the same length as the anal fin, and the skin is generally smoother and more silvery-white on the belly.

Australian Longfin Eel

This species has distinct black blotches or 'marbling' all over its back and sides, whereas the NZ Longfin is a uniform dark color.

Frequently Asked Questions

New Zealand Longfin Eels are primarily nocturnal. They usually emerge from their hiding spots under banks or logs at dusk to hunt throughout the night, though they may become active during the day if food is sensed nearby or if the water is highly turbid.

If you have a stream on your property, you can attract New Zealand Longfin Eels by providing natural cover like large rocks or sunken logs. For camera observation, placing a weighted mesh bag of oily fish or meat in the water is a highly effective way to draw them out of hiding.

Their diet varies by age. Young eels eat insect larvae and snails. As they grow into 'top predators,' they shift to eating larger prey including small fish, freshwater crayfish (koura), and occasionally even small water birds like ducklings.

Yes, they are surprisingly common in urban and suburban environments. They can be found in city park ponds, golf course water hazards, and small suburban streams, provided the water quality is decent and there is enough cover for them to hide during the day.

The easiest way is to look at the fins. On a New Zealand Longfin Eel, the top (dorsal) fin starts much further forward toward the head than the bottom (anal) fin. On a Shortfin Eel, the two fins are roughly the same length. Longfins also have more wrinkled skin when they turn.

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