Eel

NIWA has knowledge and experience in the development and sustainability of commercial and cultural eel fisheries, as well as expertise in wild eel biology and distribution.

Scientific name: Anguilla australis, Anguilla dieffenbachii

Māori name: tuna

Description

Freshwater eels are found in many river systems and lakes throughout New Zealand. The two native species, the shortfinned and the endemic longfinned eel, are distinguished by the length of their dorsal fin, which is roughly equal to the anal fin in shortfins but extends well forward towards the head in the longfin. Historical records report eels of up to 2 m being caught, but it is rare to find eels longer than 1.5 m nowadays. Eels spend part of their life cycle in seawater and part in freshwater, with the spawning grounds of our native eels thought to lie hundreds of kilometres away in deep ocean trenches near Tonga. The delicate leptocephalus larvae ride on oceanic currents back to New Zealand, where they turn into tiny glass eels just before entering freshwater. Eels are well adapted to upstream migration, being good climbers. They have an important ecological role as top predators in our freshwater once they grow beyond a metre, feeding on koura, insects and fish. In the wild, eels reach sexual maturity after 20–50 years and they then migrate back to the tropics to spawn, after which they die.

Why are eels farmed?

Worldwide eel aquaculture is estimated to be worth over US$1 billion, accounting for 65% of the total eel production. Asia and Europe are the largest eel markets, but a decline in glass eel stocks in both regions has opened up opportunities for exploitation of species in other areas. New Zealand has the potential to reap large commercial benefits by supplying international eel markets through aquaculture. Eels are a traditional food source for Māori, with high cultural and spiritual significance. Aquaculture can help replenish wild eel populations, allowing cultural harvesting to continue without the threat of over-exploitation.

How are eels farmed?

Eel farming involves catching juvenile (glass) eels when they enter freshwater and on-growing them to a marketable size. Glass eels can be grown to maturity in 2 years in captivity. Eel aquaculture requires knowledge of upstream glass eel migration patterns together with effective collection methods, and appropriate water quality and temperature conditions for culture. The three main culture techniques are:

  • pond culture, by size grading eel stocks and placing them in separate outdoor ponds (a popular technique used worldwide)
  • accelerated temperature culture, using solar heating, geothermal sources, or heat pumps to achieve faster growth and easier stock management, and
  • recirculation system culture, to maintain optimum water quality through intensive filtration and purification.

How is NIWA research helping eel aquaculture?

NIWA has knowledge and experience in the development and sustainability of commercial and cultural eel fisheries, as well as expertise in wild eel biology and distribution. NIWA’s eel aquaculture research is focused on developing techniques to make eel farming economically viable, and includes studies on feeding habits, rearing techniques for juvenile eels, weaning of glass eels from natural to synthetic foods, and short-term fattening of wild-caught shortfinned eels. Trials to be conducted at Bream Bay Aquaculture Park will assess the growth of glass eels in saltwater versus freshwater, and examine potential advantages of seawater eel culture, such as suppression of fungal and disease problems.

Who to contact for more information

Aquaculture development, commercial and cultural fisheries

Don Jellyman
NIWA Christchurch
Ph 03 343 7846
don.jellyman@niwa.co.nz

Fattening

Mike Martin
NIWA Hamilton
Ph 07 856 1768
mike.martin@niwa.co.nz

Business development opportunities

Dr Michael Bruce
Ph 09 375 2035
michael.bruce@niwa.co.nz