A formulated feed for juvenile sole has increased survival rates from nil to 90% and helps prevent stock depletion.
May 18, 2005
Sole have long been considered an attractive fish for farming and it is easy to rear large numbers of larvae. However, previous attempts to farm this fish on a commercial scale have failed due to the lack of an adequate formulated feed. Until now, the survival rates had been negligible.
To overcome this, EUREKA project E! 1533 ROLF has developed a new formulated feed that has increased juvenile sole survival rates from almost zero to 90%, making large-scale sole farming economically viable.
In the wild, young sole feed on tiny shrimps called artemia but, as supplies of this shrimp cannot be guaranteed, this was not a commercially viable option.
"Unlike salmon or trout, sole hatch very young and their mouths are not mature enough to handle normal fish feeds," explains Einar Nygård, one of the inventors of the feed at Fiskeriforskning, the Norwegian Department for Feed Development and Marine Processing.
"The new feed is not only four times cheaper than expensive larval feed, but has also been specifically developed with a younger fish in mind. The feed particles are soft, making them more easily digested by juvenile fish, and the feed also meets their nutritional needs," says Nygård.
Other factors, such as the speed at which the food particles sink in water and low dispersion rates that keep the particles intact, ensure that the feed is attractive to the young fish.
The partners have achieved impressive results: juvenile sole survival rate has increased from almost nil to 90% and daily growth rates are up from 8 or 10%, to 20 to 50%. They have also determined the smallest size at which the sole can be effectively weaned - 12mm long. This is invaluable information for a commercial sole farmer.
"We combined our expertise to create a new feed and develop commercial sole farming. Only the co-operation of a EUREKA project makes such synergy possible," says Dr Anders Aksnes, project nutritionist at Fiskeriforskning and Norwegian project leader.
The potential market for the feed is worth over 50 million Euro a year, and work is continuing to develop formulated feeds for crustacean species and other fish including cod, whitefish and halibut.