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Tuna on a trip

Name: New Zealand longfin eel

Māori name: Tuna

Scientific name: Anguilla dieffenbachii

Looks like: A long, almost-tubular fish with a head that starts smooth but becomes bulbous as they grow − tuna are the largest freshwater eels in the world. The longfin eel is so named because its top or dorsal fin is longer than its bottom fin (in shortfin eels, the dorsal and anal fins are the same length). Another way to tell the difference between the longfin and shortfin eel is that when a longfin eel bends its loose skin wrinkles, whereas a shortfin’s skin remains smooth. Females are larger and can grow up to two metres in length. In one Māori myth, Māui fought Tuna after it frightened his wives, cutting it clean in half. One part became the sea-dwelling conger eel (ngōiro or kōiro), and the other a freshwater eel.

Habitat: Longfin eels are endemic to New Zealand (meaning they are found nowhere else) and lurk in freshwater waterways all around the country. They are great climbers, climbing up vertical surfaces to heights of about 30metres when young, and will sometimes be seen travelling long distances over wet grass in search of another lake, pond or river to pop into. They are diadromous, meaning they spend portions of their life cycles partially in fresh water and partially in salt water.

Feeds on: Longfin eels are carnivores and once they are big enough will feed mainly on crustaceans and small fish. They will also eat larvae, snails, dead animals, birds and whatever meat curious humans throw into their river.

Did you know? At the end of their lives, longfin eels travel thousands of kilometres to deep, warm trenches in the Pacific Ocean to spawn, then die. Their appearance changes for the journey − their head flattening and body streamlining, and their eyes becoming bigger to aid their vision. Their tiny offspring travel back to New Zealand, swept along on ocean currents.

If it were human it would be: A keen observer of the great Kiwi tradition ­– the OE. Though with the dramatic twist of dying while away, then having its babies turn up in New Zealand not long after.

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