The Technical University of Denmark (DTU) has coordinated a EUR 5 million research project called PRO-EEL to reproduce the European eel in captivity. The European Commission (EC) is funding this project to establish a self-sustained aquaculture of eels in the continent in response to dramatically dwindling wild European eel stocks.
Eels in the PRO-EEL project receive hormonal treatment to develop gametes and fertilization is made in vitro, as eels do not reproduce in captivity due to a hormonal inhibition of maturation.
The PRO-EEL project aims to broaden the knowledge on European eel (Anguilla anguilla) reproduction and enable successful maturation and offspring production. This includes choosing appropriate broodstocks, enhancing eggs and sperm quality and fertilization methods and culture conditions favorable for the production of viable eggs and larvae.
|Tiny, green-stained spermatozoa around one eel egg. (Photo: Luz Perez, ICTA-UPV)
Determining suitable feed for the eels and establishing feeding cultures of larvae will be particularly challenging, as scientists do not know what to feed these larvae. Findings show that eel larvae feed on extremely diverse marine organisms.
“The primary bottleneck in a controlled reproduction of eels concerns deficiencies in knowledge about their reproductive physiology and methods applied to induce and finalise gamete development,” stated the coordinator of the project, Jonna Tomkiewicz from DTU Aqua.
Gene technology and molecular methods will help obtain a regular and predictable production of viable eggs and larvae from broodstock eels fed enhanced diets.
Other challenges are 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.
Establishing first feeding and feeding cultures of larvae will constitute key breakthroughs. Still, the eel larval phase lasts one year or more, and eel production will require added research on proper feed and culture techniques to ensure the transformation from larvae to glass eels.
PRO-EEL expounds on the results of the consortium, including those of a series of DTU coordinated research projects that produced larvae of the European eel that lived for up to 21 days. These larvae reached the first yolk sac stage and entered the period where they need feeding.
Japanese researchers recently produced offspring from captive-bred Japanese eel, thereby successfully finalising the life cycle of eel in captivity. As the Japanese eel is closely related to the European one, these results are promising for the success of the PRO-EEL project.
PRO-EEL will replace the use of wild glass eels as stocking material for aquaculture with fry raised under controlled conditions.
The PRO-EEL project launched on 1 April 2010 and ends on 31 March 2014.
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By Natalia Real