AQUACULTURE DEPENDENCY ON THE WILD SEED

Wild versus hatchery produced seed

Eel aquaculture is 100 percent dependant on wild seed and the supply of glass eels is decreasing. Some harvest areas seem to be declining more rapidly than others, but, as the European eel population must be considered as a whole, the overall supply is at risk. The collected seed material in Europe exceeds the needs of the aquaculture industry, and the excess supply is consumed in Spain as an expensive seafood delicacy (Table 4). If artificial breeding of the European eels becomes possible, it could still take many years before the necessary quantity of seed required for farming becomes available and can be economically produced.

During the 2004/2005 season, purchases from Asia started late when the glass eel supply was no longer available in sufficient quantity to meet the demand. This caused prices to rapidly increase and peak to an unexpected level of €1150/kg. At this price the European farmers could no longer buy any glass eels to stock their facilities, as they could only afford to pay €700/kg (approximately US$1100/kg) and still remain profitable. If this situation had persisted for several seasons, European eel farming would have closed down.
The Asian eel farming industry is based on two species, i.e. Anguilla anguilla and Anguilla japonica. The local species is much preferred to the imported one especially in Japan as they perform better in terms of growth and survival rates. However, the supplies of Anguilla japonica had decreased considerably forcing eel farmers to find other supplies and the European eel began to be imported into Asia. The supplies of Anguilla japonica have started to increase again in recent years for unknown reasons, rising from the low catch of 15 tonnes in 2002 to over 100 tonnes in 2006.

 

 

Future of eel aquaculture

The European eel farming industry is stable and the production meets the current market demand. The industry however is not expanding; no new farms are being constructed, and the existing ones are in a reasonable to good economic situation.
The Chinese industry, on the other hand, has undergone a serious crisis over the last two years, as the intensive use of prohibited products, such as malachite green, was disclosed and all exports were banned from China to Europe, Japan, China Hong Kong Special Administrative Region (SAR), Republic of Korea and other Asian countries. Many eel farms had to cease operation as they no longer could sell their products. The import of European glass eels decreased in 2005–2006 and is likely to decrease even further (Table 4). The Asian eel market has suffered from this crisis as well, with customers being afraid of “potentially carcinogenic products” in the farmed eels. The Chinese eel farmers claim to have succeeded in raising eels without using such products. The market confidence will have to be bought back at high cost for the farmers, meaning that the Chinese eel farming industry is not likely to grow significantly in the coming 2–3 years. European glass eels, as long as they do not decrease further, will be able to supply aquaculture demand for at least the next 2–3 years.
If the Chinese eel farming industry had not faced this problem, the collection of European glass eels would not have been sufficient to meet demand. The Chinese importers would have turned their attention to the American species (Anguilla rostrata), and taken the available quantities there as well. Even with this new supply the shortage would not have been addressed and other eel species would have been tested.

Table 4
Glass eel harvest (in tonnes) and their use in aquaculture and direct human consumption

Economic and technical implications of wild caught versus farmed seed As there is no farmed seed available, comparison between wild and farmed seeds can only be estimated. If artificial reproduction of eels is achieved, it will still be questionable if the mass production can be realized and at what cost, compared to wild caught glass eels.

FISH FEED

Wild caught food

Eel farming in Europe relies entirely on wild-caught food: cod roe is used to wean the glass eels while artificial dry food, based on fishmeal and fish oil, is used for on-growing. In China, glass eels are weaned on cultured Tubifex worms for about one month, until they reach an average weight of one gram. They are then gradually adapted to an artificial pasty food for the rest of the farming process. Eels seem to be very sensitive to alternate protein sources and none of the tests conducted so far with non-animal protein sources have succeeded (Dana Feed, personal communication, 2007). Thus this species is still totally dependent on feed derived from wild-caught fish.
Cod roe – Most of this product is supplied by Danish fishmongers, who estimate the total quantity supplied to the eel farming industry at 20–40 tonnes per season. The cod (Gadus morhua) fishing industry easily supplies this quantity of roe and the price is less than €5/kg (approximately US$7.9/kg). The product is supplied in frozen blocks of 20 kilograms. If the cod quota drops in the future, and insufficient roe supplied, this feed source can be replaced with blended mussels which is available in large quantity. Initial natural food supply for glass eels is available without a problem.
Fish oil used in Europe – Although information is not available on the fish species from which the oil is extracted, the feed industry indicates that supplies are plentiful and not at risk over the next 10–15 years (Dana Feed/Provimi, personal communication, 2007). Fishmeal used in Europe – As with fish oil, this source is apparently not at risk in the near future. The species used are exploited “at a sustainable level” (Dana Feed, personal communication, 2007).
Fish oil used in China – China imports fish oil from Chile, Iceland and the United States of America. One of the species used to produce the oil is the Pacific cod (Gadus macrocephalus). With an annual harvest of around 400 000 tonnes this oil supply can be considered steady and reliable.
Fishmeal used in China – Fishmeal imported in China originates from many countries, e.g. Chile, Russia, Singapore and the United States of America. The supply is plentiful and local feed plants do not expect any shortage, with various fish sources are used as raw material. As the eel farming industry has been profitable, eel farmers can afford higher feed prices than other fish farmers, assuring their access to feed supplies.

Artificial food

As the initial food used to wean the glass eels has a high water content (?70 percent) it is important to rapidly switch over to a more nutritive food in order to obtain better growth. Artificial feeds for glass eels do exist, and tests have been conducted to compare efficiency of feeding and growth on eels started on natural food compared to eels directly fed with artificial food. The tests show that a higher percentage of elvers weaned on natural food start eating the artificial feed, resulting in better growth and survival rates. Use of natural food for on-growing is unsuitable for the farming techniques in both Europe and Asia. Even in Japan, where eel farming has the longest history, the natural food items used to grow eels (fresh fish, silk worm pupae, fish waste, etc.) have been entirely replaced by artificial feeds (Matsui, 1980).
The artificial food used in Europe is mainly extruded pellets, distributed via self feeders or automatic feeding machines. Feeding may also be completely automatic and managed by computer programmes. In Asia, most eel farms use a pasty feed prepared twice daily in kneading-machines. The paste is made available to the eels on floating frames or trays attached to the sides of the culture tanks.

Food resources

None of the feeds used to produce eels, apart from the cod roe, was previously used for human consumption.
Cod roe – The quality of roe sold to eel farmers is “pierced and damaged roe” plus “small roe” as large and whole roe is sold as a delicacy. The quality used for eel was previously sold to the canning industry or exported for production of tarama (a traditional appetizer – roe mixed with either bread crumbs or mashed potato with addition of lemon juice, vinegar and olive oil) in Mediterranean countries.
Fish oil used in Europe – This was previously used for other fish or animal feeds. Fishmeal used in Europe – This was previously used for other fish or animal feeds. Tubifex worms used in China – These were previously used for the aquarium food industry as both frozen or dried.
Fish oil used in China – This was previously used for other fish or animal feeds.
A significant increase of global eel production is not anticipated due to the limited supply of glass eels. Hence the supply of wild-caught feed is sufficient to meet the current eel farming demand.