Science Centres: Fisheries

An eel lift at Waitaki dam.

Longfin and shortfin eels support an important fishery in New Zealand, but numbers, especially of large longfins, have declined since the fishery’s heyday in the 1970s.

Among the many factors that may have contributed to this decline is the proliferation of obstacles such as weirs and dams, which block the upstream migration of juveniles from the sea where they are spawned.

Māori traditionally transferred juvenile eels (e lvers) above natural barriers, such as waterfalls, to enhance eel numbers. Since the early 1980s, this technique has been applied to hydro dams.

NIWA has been monitoring these operations for the Ministry of Fisheries since 2000-01, with the help of power companies, iwi, regional councils and various other private and public bodies.

A staggering 4.4 million elvers were transferred at 12 dams around New Zealand in 2005-06. About 920 000 of those were longfins – the largest number ever recorded, and the first increase in longfins since accurate records began 10 years ago.