| Scale (tonnes) | 500 |
| Investment ($ millions) | $13.3 |
| 10 YR NPV - 14% discount rate ($ millions) | $(4.5) |
Freshwater eels (tuna) 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.
Eels spend most of their life in freshwater but return to sea to breed. Eel spawning grounds are believed to be located hundreds of kilometres away in deep ocean trenches near Tonga. Shortfin males migrate in February–March, and longfin males in April. The females soon follow, and both males and females die after spawning. Studies show the species also migrate at different ages:
From the spawning grounds, the delicate eel larvae (leptocephalus) drift with oceanic currents back to New Zealand, metamorphosing into tiny glass eels just before entering fresh water in spring.
Short finned eel (Anguilla australis)
Worldwide eel aquaculture is estimated to be worth over US$1 billion, accounting for 65% of the total eel production. China, Taiwan and Japan are the largest eel producing countries, but significant quantities of eels are also farmed in Europe and America. Eel culture is based on the wild capture and on-growing of glass eels as they return from the sea and enter rivers. Whilst the Japanese have managed to close the life cycle and produce a few individual eels, hatchery culture of eels has yet to be reliably achieved. Due to the long larval phase and delicate nature of the larvae, eel hatcheries are unlikely to become a commercial reality in the near future. Consequently a massive demand for glass eels for Asian farms has resulted in high prices being offered for glass eels, and over exploitation of glass eel stocks in some countries.
Commercial eel farms use a variety of tank and pond based systems for rearing eels. Whilst tanks and ponds are used in Taiwan, in Europe the requirement to heat water for eel farming has led to the increasing use of RAS for eel production.
Eels are highly robust in culture and are well suited to farming using RAS technology. With regular grading and good husbandry FCRs better than 1.2 can be achieved in well run systems. A number of large (>200 t per year) modern systems operate overseas, particularly in Denmark and the Netherlands. Farmed eels are harvested for market from 150 g upwards, depending on the market. Smaller eels are sold to Asian markets while larger eels are better suited to European markets.
The largest market for eels is Japan. The price of imported live eels has risen consistently in recent years and currently sits at around $NZ45 /kg landed into Japan.
Live eel prices reported at customs in Japan.
|
Origin |
Jan / Nov 2012 |
Jan / Nov 2013 |
||||
|
|
Volume (MT) |
Value (million NZD) |
Value (NZD/kg) |
Volume (MT) |
Value (million NZD) |
Value (NZD/kg) |
|
China |
2,884 |
$ 125 |
$ 43 |
3,471 |
$ 157 |
$ 45 |
|
Taiwan |
1,327 |
$ 55 |
$ 41 |
828 |
$ 36 |
$ 43 |
|
Others |
115 |
$ 4.4 |
$ 38 |
111 |
$ 3.6 |
$ 32 |
|
Total |
4,326 |
$ 184 |
$ 43 |
4,410 |
$ 196 |
$ 45 |
In New Zealand, early attempts at eels farming during the 1970s and 80s, were unsuccessful. The failure of the farms was attributed to a variety of reasons which included; poor economic conditions, escalation in food costs, depressed export prices, problems with culturing the New Zealand eel species and some instances of disease. The irregular supply of glass eels was also considered a constraint to production.
In 2003 NIWA undertook trials on weaning and on-growing of eels in fresh and brackish water recirculation units, and achieved acceptable growth and survival rates under intensive culture. Glass eels were grown to maturity in less than 2 years in captivity. Details on growth rates and FCR can be obtained from NIWA (see contacts below). The Queensland Govt. has published FCR’s of 1.5 – 2.0 for short finned eel culture in recirculation systems.
The eels from this project were used to undertake product evaluation that demonstrated that intensively-farmed New Zealand shortfin eel is acceptable in Japanese cuisine.
The major bottleneck in eel aquaculture in New Zealand is the availability of wild glass eels. It is currently illegal to possess eels weighing less than 220 g except under a special permit. Any commercial access to glass eels will require legislative change, and any future regulatory change which is likely to enable glass eel collection will require the fishery to be demonstrably sustainable and socially acceptable. A key element of this will be the ability to separate longfin and short fin eels at an early stage and return longfins to the wild. A project to investigate the sustainability of harvesting glass eels for culture is currently being undertaken and should be completed by 2015.
New Zealand has the potential to reap commercial benefits by supplying international eel markets through aquaculture. The short finned eel (Anguilla australis) is the preferred species for culture in New Zealand, but further work on husbandry protocols, such as managing differential growth rates, controlling disease and developing suitable feeds for intensive culture, is required.
The three main culture techniques are:
Intensive RAS farming of eel (Denmark)
The following generic model simulates the production of eel in an intensive RAS system. The assumptions entered in the model are based on the best information available to NPFL at the time. They will give a general picture of the likely economics and financial viability with this species.
The key outputs from the 10 year generic eel model are:
Based on your specific location, RAS system design and performance specified by the supplier the assumptions may need to be altered for your particular situation. Additionally you may wish to manage production differently i.e. grow the fish to a larger size before sale.
NPFL strongly advise that you seek advice from experts in setting up your own assumptions for your model runs.
NIWA Christchurch
Ph 03 343 7846
NIWA Hamilton
Ph 07 856 1768
