Stolt Sea Farm is the world leader in turbot production, which it markets under the Prodemar brand.

The turbot (Scophthalmus maximus) is a marine flan fish that lives camouflaged in the sandy and stony sea bed at mixed depths in the shallow waters surrounding the European continent. Popularly known as “king of the flat fish” and “pheasant of the seas”, it is one of the most sought-after species thanks to its firm, delicious white meat, and is regarded as a true gastronomic luxury.

There is usually a scarcity of wild turbot in the market, largely due to the difficulties in catching this fish.

The turbot farming industry began in the United Kingdom in the early 70s – but it was soon discovered that the temperature of the waters around the UK were not ideal.

In the 1980s the focus of this activity shifted to Galicia (Spain). Here, the suitability of the region’s estuaries and coast, the ideal temperature and the environmental conditions were a perfect match to the dedication and adaptability of local people to this new occupation.

These factors, along with the growing over-exploitation of seas and oceans, were the main reasons behind establishing cultivation in Galicia, and the move to breeding the Prodemar turbot.

At present, out of the 4,000 tonnes of Prodemar turbot produced annually by the company all over Europe, 3,300 tonnes are produced in Galicia and the rest in Portugal, France and Norway. A spectacular growth, bearing in mind the short time operations have been up and running.

These strong results are the result of state-of-the-art technology and the dedication of highly qualified technical teams who control each phase of the process – reproduction, breeding of larvae, pre-ongrowing, ongrowing and commercialisation – taking the utmost care that throughout the two years that it takes to reach its commercial size, each specimen is developed according to the highest standards.

The hatcheries

The production of young turbot in the hatcheries of Stolt Sea Farm is a complex and fascinating process consisting of several phases: broodstock, incubation, larval rearing and live feed.

The broodstock form the critical base of the whole process, which is why they receive meticulous care. These magnificent specimens always remain under controlled light and temperature conditions.

In its natural habitat, the turbot releases its eggs between spring and summer – but, for an aquacultural company to be profitable, it needs to produce constantly and have larvae and young turbot the whole year round.

One of the advantages of working with the turbot is that its ovulation cycle is related to the hours of light and darkness (photoperiod) it is exposed to. This makes it possible to induce ovulation and therefore obtain eggs, by exposing the broodstock to different periods of light and applying abdominal massages to them in order to encourage the expulsion of sperm by the males and eggs by the females. This ensures the year-round production of eggs.

Once fertilised, the eggs are transferred to the incubation rooms, where they are placed in small tanks with a constant supply of water – at 15º C – of the best quality. After about five days’ incubation, the turbot larvae hatch – measuring only 3 millimetres in length – and will float passively on the surface of the water, blind and with bilateral symmetry. During this period the larvae will still feed from the reserves of their yolk sack.

When they have consumed nearly all of the nutritional substances of their yolk sack, the larvae are transferred to the larvae rearing tanks:large circular tanks with a capacity for 40,000 litres of water and a depth of 4 metres. As they are still very small, they are fed with zooplankton, which is also cultivated on site and fed, in turn, with microalgae or phytoplankton.

After 15 days, the larvae will have grown enough for this food to be too small for them. It is now time to supply them with brine shrimps (live feeding), small shrimps whose young larvae (naupli) are suitable for the feeding of the turbot during this phase of its life. For better handling purposes, the turbot larvae are transferred to smaller tanks for better handling. Extreme care is taken during this process and the water is strictly quality controlled.

Three weeks later, when they reach one centimetre in length, the larvae’s metamorphosis begins. They rotate their head in relation to the body (losing their bilateral symmetry) and the swim bladder disappears, which means that they gradually start going to the bottom of the tank. Once their transformation is over, they acquire the form of a mature turbot and are taken to larger tanks, where they will start to eat dry pellets. At the end of the process, the young turbots will have reached a weight of about 7 grams and will be ready to be transferred to ongrowing farms.

Ongrowing

The central objective of this phase is to keep the fish well fed, clean, healthy and graded so that their growth is as similar as possible within the same production batch.

In the marine farms of Stolt Sea Farm, the small Prodemar turbot specimens are fed several times a day and examined periodically to check their health condition. Environmental conditions are also checked to ensure that they are the most suitable for encouraging growth at the appropriate rate. For more than 20 months the fish will remain in the ongrowing farms, until they reach an average final weight of about 2 kilograms (although the offer to the public, generally speaking, encompasses a wide range of sizes that varies between half a kilo and the 5 kilos that some specimens may eventually reach).

Throughout the whole breeding process within the farms of Stolt Sea Farm, the Prodemar turbot is fed with dry pellets made out of fish flours and oils; this food is analysed regularly to make sure not only that it is in line with legal requirements but also that it meets any additional requirements demanded from the selected suppliers.

The packing

The final phase of the process lies in the preparation of the product for sale. When this moment arrives, the fish are starved for at least 48 hours, before being introduced into a mixture of water and ice that puts them to sleep and avoids suffering. In the packing room, they are classified, marked, gutted (if so required), and washed. They are packed in insulated boxes, so that the Prodemar turbot reaches the consumer in good conditions of freshness and quality.