Stolt Sea Farm, whose Spanish turbot ongrowing facilities are expanding faster than they can produce juveniles, recently extended its Merexo hatchery and bought another at Quilmas.
Merexo was a former Prodemar hatchery, while the hatchery at Quilmas came with the acquisition of Martisanal.
Stolt Sea Farm is about 50% self sufficient in turbot juveniles for stocking its ongrowing farms. This year it will take about 1.4 million juveniles, out of which about 800,000 to 900,000 will be grown at its own facilities.
Juveniles are also bought from France Turbot and Maximus, the Danish company.
Merexo hatchery is a semi-extensive system, doing about 16 to 17 cycles a year. At present, the survival from egg to ongrowing is about 12%, including all the fish that have to be discarded.
Last year Merexo produced about 500,000 turbot juveniles; this year they hope to produce around 700,000.
Stolt Sea Farm believes it can now constantly produce turbot juveniles with a survival rate of between 12 and 15%, and therefore wants more litres of production space to be able to produce more.
Merexo is therefore expanding, with a new nursery phase and larval rearing phase. This is expected to boost the yearly production to one million juveniles a year. Grading and counting will be carried out at one central point.
Quilmas is expected to produce another 500,000 turbot juveniles.
The real change at the Merexo hatchery the last few years has been the switch from intensive to semi-extensive production...
Before they used to put fish in when they were available, stocking very heavily in one part of the year and with very few for the rest.
This made things more difficult for selling because there were periods when they didn't have certain sizes. But now that the hatcheries are more or less giving a constant supply, they can stock and harvest constantly.
Turbot are very much more delicate at the larval stage than seabass or seabream. The early larval rearing stages are much more complicated because the young turbot are much more bacteria-sensitive...
Re-mounting everything would take another three or four months, so the hatchery was actually producing for only half the year.
Quilmas was an intensive production unit when it was bought, but Stolt is now transferring its semi-extensive technology from Merexo.
Although they don't have the same tanks at Quilmas, they are transferring some of the philosophy of the way of producing rotifers and algae so that the systems are much cleaner.
In turbot the big battle is getting around the bacterial bloom that can kill everything.
Stolt has its own selective breeding programme, which has been running for the last five years. It is starting to see the benefits.
It's a family selecting programme, where they spawn selected fish. These are followed and they select their largest offspring.
The programme was being run mainly in Norway, but last year they took the decision to transfer it and now they have it running in both Norway and Spain.
The process for reproducing turbot is completely natural, but requires much time and dedication. Broodstock fish, selected for the production of top quality eggs, are kept in tanks at a low stocking density, with light and temperature carefully controlled to ensure egg production year-round.
Egg spawning and obtaining sperm from these fish involves a form of abdominal massage - "stripping". Each female throughout its egg-production period has a number of ovulations and can lay up to a million eggs per kilogramme of weight.
Fertilisation is external and is carried out directly after stripping. After rinsing, the eggs are placed in incubation tanks.
For their development the fertilised eggs need a supply of purified seawater to avoid bacterial contamination.
Incubation is carried out at 16 C. The hatching of the larvae takes five to six days and the hatched larvae are roughly 3 mm long, living three further days on the egg sac yolk.
During this period they are transferred to the larval rearing tanks.
(from Fish Farming International, Vol. 24, No 10, October 1997)