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Researchers Support Future of the Eel

Health Eels Welfare +6 more

DENMARK - The reproduction of eels in captivity has become an important research focus due to the severe decline of the natural stocks.

Leading scientists from European research institutes and the aquaculture industry are determined to reproduce the European eel in captivity.

The result is a €5 million research project: PRO-EEL, coordinated by DTU and supported financially by the European Commission.

Many fish species do not reproduce in captivity and eels are among them.

In the wild, the European eel migrate to the Sargasso Sea to spawn. They do not reproduce in our waters due to a hormonal inhibition of maturation.

In the PRO-EEL project the eels therefore receive hormonal treatment to develop gametes and fertilization is made in vitro.

The objectives of the PRO-EEL project are to expand the current knowledge on European eel reproduction and develop methods for successful maturation and production of offspring.

This includes selecting suitable broodstocks, improving the quality of eggs and sperm, and fertilisation methods and culture conditions conducive to the production of viable eggs and larvae.

A particular challenge will be to find suitable feed and establish feeding cultures of larvae.

The long term perspective of this research – and an indicated goal of the European Commission – is to establish a self-sustained aquaculture of eels in Europe.

Eels are Challenging

"The primary bottleneck in a controlled reproduction of eels concerns deficiencies in knowledge about their reproductive physiology and methods applied to induce and finalize gamete development," said the coordinator of the project, Jonna Tomkiewicz from DTU Aqua - National Institute of Aquatic Resource, Technical University of Denmark.

Researchers will apply gene technology and molecular methods to establish that knowledge base that is crucial to the successful reproduction of the European eel.

These new tools will help obtain a regular and predictable production of viable eggs and larvae from broodstock eels offered enhanced diets.

Further challenges include the identification of suitable larval rearing conditions and initial feed for the larvae.

A particular issue is the step where larvae need to start feeding on their own and the diet is crucial for their healthy development and growth.

The establishment of first feeding and feeding cultures of larvae will be major breakthroughs in European eel research and an important and promising step towards a self-sustained aquaculture of the European eel.

However, the eel larval phase is very long – lasting one year or more – and the production of eels will need further research on suitable feed and culture techniques to assure their transformation from larvae to glass eels.

Promising Results in Reproduction

The PRO-EEL project builds on the cutting edge results of the consortium – including the recent results of a series of DTU coordinated research projects that succeeded in producing larvae of the European eel that survived up to 21 days.

These larvae accomplished the first so-called yolk sac stage and entered the period where they require feeding. These results provide the basis for the present PRO-EEL research team of experts that complement each other within disciplines relating to fish reproduction and aquaculture.

Recently, researchers in Japan succeeded in producing offspring from captive-bred Japanese eel and thereby successfully completing the life cycle of eel in captivity.

The Japanese eel is a closely related species to the European eel, and these promising results bode well for the chances of success for the PRO-EEL project.

Towards a Self-sustained Aquaculture of Eel

The PRO-EEL project will contribute to a shift from capture-based aquaculture towards a self-sustained aquaculture.

This involves replacing the use of wild glass eels as stocking material for aquaculture with fry produced under controlled conditions.

The PRO-EEL technology development and the increasing knowledge about the reproduction of the European eel back up management initiatives to help preserving the species.