EEL CULTURE

EelLifeCycle

1. Leptocephalus ~ 0.2”

(glass eels ~ 1 – 2”)

2. Elver

3. Adult

A. japonicus –growth optimum = 25 – 28oC

A. rostrata & A. anguilla = 20 – 23oC

Elver fishery -

• As the leptocephalus larvae sense freshwater,they undergo a metamorphosis to the classicaleel shape but remain transparent.

• These late larvae are called "glass eels" (~ 2” inlength).

• As they begin to move into the mouths of riversand bays in East Asia, the eastern coast of NorthAmerica as well as the coastal regions of bothNorthern and Southern Europe, the glass eelsbecome darkly pigmented and are referred to as“elvers”.

Black gold

Part of this elver harvest is exported to Japan as wellas China and Taiwan, two other significantproducers of cultured eels in Asia.

– price varies dramatically from year to yeardepending on natural supply.

– recent years, the price of a single glass eelhas risen from as little as 3 cents to asmuch as 60 cents.

– cost of glass eels can account for 40% ofproduction costs.

– Asian culturists prefer Anguilla japonicaglass eels

Japanese eel farms are typically small(~ a half of football field in total tank area)

• A series of tanks, gradedin size from 100 ft2 to1,000 ft2 in area and 3 -4 feet deep are used asthe eels grow to marketsize.

• production cycle 6 months - 1 year

• paddle wheels and water exchange used to maintainacceptable DO (dissolved oxygen) levels

Training -

• Paste costs around

US $ 45 cents/lb.

• Food conversion on

modern formulated paste

superior to traditional feeds.

• Formulated paste is fed at a rate of 2 - 6% bodyweight per day until the fish are about 1.5 oz. andthen 1 - 3%

• Large eels finish feed in 15 - 30 minutes.

• Total feed cost represents about 30 - 40% ofoperating costs in eel culture.

Culture density -

• Water exchange rate of 40% per day yields canbe up to 8 tons/acre/yr. No water exchangeyields are limited to ~ 2 tons/acre/yr.

• Initial stocking density of 10/ft2 –

• thinned and sorted two or three times prior toharvesting

• fast growing eels (females) reach market size(1/3 - 2/3 lb) in 6 months

• final density about 1 - 2 (100g animals) per ft2

• slow growers may take up to 18 months

Disease – lots!!

• Antibiotic sulfa drugs used forbacterial infections of the gills,fins and epidermis

• Stains, malachite green &methylene blue, baths used forfungal infections (prevalent < 22oC )

• Formalin via bath or added topond water for treatment ofciliates on skin and gills (“Ich”),trematodes, and parasiticcopepods.

• Illegal in the U.S.

Eel Production – 265,000 mtFAO 2008 (< 1% all fish)

Japanese eel (Anguillia japonica) = 254,000 mt

China = 205,000 mt

Taiwan = 21,000 mt

Japan = 21,000 mt

Korea= 7,000 mt

Fishery = 300 mt

Eel market in Japan

• Estimated to be 120 – 140,000 mt/yr

– Japanese eel aquaculture declining

• Late 1980’s – early 1990’s = ~ 40,000 mt

• 2008 = 21,000 mt

– Chinese production soaring to meet bothJapanese market and emerging domestic market

• 1989 = 60,000 mt (1st yr reported production in China

• 2008 = 205,000 mt

– Change is primarily to lower production costs inChina

Eel production costs - 1999Lee et al 2003 Aquaculture 221:115-124

6.091.360.510.420.331.781.69China

9.444.900.591.981.783.522.80Japan

TotalMain

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Other

InterestUtil.LaborFeedSeed