1. Introduction
Turbot is a much appreciated and relatively high value fish species. Often called the "pheasant of the sea".
It is a true marine species and the fry is considered relatively difficult to produce. However, once the fry has reached a size of approx. 5 g, it becomes a very rough fish and very suitable for Aquaculture.
Maximus A/S was back in 1990 the first company to crack the code to produce juveniles of turbot, without deformities and bad pigmentation, with uniform growth, and with a strong immune response system.
Turbots are most economically produced in RAS systems where the water temperature can be controlled throughout the year. The use of RAS will reduce the footprint of the facility, as a reduced biomass standing stock will produce the same annual production if the temperature can be maintained at around 17 degrees all the year, when the fish will grow faster.
Then both capital investments and operation costs will be reduced
2. Culture Systems
• Advantages of RAS for the culture of Turbot VS other systems
i. Brood-stock can be manipulated for all year production of eggs. - 4 photo/temperature manipulated brood stocks required.
ii. It is recognized that fry produced on copepods (a small crustacean) will perform better on growth, fish quality and in uniformity on size, which is essential for reducing costs for grading.
iii. Copepod hatchery technology was originally developed by Dr. Bent Urup.
iv. Grow-out regime well developed and documented. A size of approx. 2 kg required for obtaining a good price – approx. 18 months in grow out.
v. Systems needs to be designed for minimum labor (Semi automatic grading systems).
vi. Product well established and recognized on the markets in Europe.
vii. A good rough fish for aquaculture, which can be produced at the lowest cost with RAS technology, as growth will be much faster, and so, smaller space is required space for production.
3. Biology
- Family
Turbots, also known by several scientific names such as Psetta maxima and Scophthalmus rhombus, are flatfishes found in the family Scophthalmidae. They are found in shallow sandy and muddy bottom from Norway to the Mediterranean and black sea.
- Life cycle of the species
i. Fertilization
Turbot are gonochoric, meaning that their sexual system is either male or female. Female can spontaneously lay eggs in captivity. The obtention of laying spread all year round is made possible through temperature and day length modification. Each clutch consists of hundreds of thousands of eggs of approx. 1 mm in diameter.
ii. Hatching
The larvae of the turbot will initiate eating after 3-4 days post hatch. They will then be fed on different sizes of calanoid copepods from 50 micron up to approx. 800 microns as they grow in size over the following three weeks. During those 3 weeks, they will develop from a hardly visible larvae of 3-4 mm, hatched from a 1 mm egg, into a little turbot of approx. 60 mg.
Picture of turbot reaching 3 weeks old.
iii. Fry stage
After another 8 weeks the fry will reach a size of approx. 5 grams, and will then have developed a strong immune system, and will be ready for transfer to the grow out facility. From 1990 and up to 2013 the majority of fry produced at Maximus have been shipped to the northwestern part of Spain where the seawater is very suitable in temperature for farming turbot. But with advanced RAS technology the production can be done more economically in closed systems, where Denmark is as good a location for this as anywhere else.
iv. Harvest Size
In Grow out it will take approx. 18 months to grow the fish to harvest Size. Therefore, to reach the desired market size of 1.5-2 kg a minimum of 2 years is needed.
Picture of turbot in grow-out facility in China, with RAs technology delivered by UNI-Aqua, equivalent to the water treatment technology pictured above, designed by Aqua-Partners ApS
This page is being edited and will be uploaded at latest by 15 of October 2021.
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Turbot is a much appreciated, relative high value fish specie. Often called the "pheasant of the sea"
It is a true marine species, and the fry is considered relative difficult to produce. Whereas once the fry has reached a size of approx 5 gram, it becomes a very rough fish and very suitable for Aquaculture.
Maximus A/S was back in 1990 the first company to crack the code to produce juveniles of turbot, without deformities and malpigmentation, and with uniform growth, and with a solid immune response system.
Still of today the copepod technology which was initially developed at Maximus, is the superior technology for production of this specie, even though the majority of turbot now are produced by alternative technologies.
Above turbut fry, at the stage where they are weaned on a pellet diet, from a live feed diet. The fry have then a wet weight of approx 50 mg wet weight.
Photo of adult copepod, the copepods have 12 development stages, typical in size from 50-900 micron, and the fish larvae will initially feed on the smaller naupli stages of 100-200 micron, then on bigger stages as they grow.
Turbot are produced most economically in RAS systems where the water temperatures can be controlled through out the year. Using RAS (Recirculating Aquaculture systems) will reduce the footprint of the facility as a reduced biomass standing stock will produce the same annual production if the temperature can be maintained at around 17 degrees all the year, when the fish will grow faster..
Then both capital investments and operation costs will be reduced.
Picture C-turbot-3
Next, water treatment system from Maximus, build for Seawater. 1998, design by Aqua-Partners ApS.
One of the very first true RAS systems designed for seawater, at a stage when RAS was only applied for production of fresh water fish species. The concept includes an active CO2 stripper, with efficient CO2 stripping.
This design concept was later adopted by UNI-Aqua/ AKVAgroup, and has been installed in many RAS systems now for both marine and freshwater production. And actually still used, as for production of Salmon at the new Danish Salmon facility in Hirtshals, even the technology is now almost 20 years of age.
For the new grow out facilities in Hanstholm, Denmark, Sashimi Royal will use the latest generation of RAS technology, with the new RAS2020 concept configurated with Kruger Kaldnes water treatment technology, which includes the most efficient CO2 stripper in the market, which is essential for the growth performance and welfare of the fish in the RAS systems..
Fish produced with the copepod technology for fry production, developed at Maximus, will cost less to grow to harvest size. Labour costs are reduced in the growout facility, due to a reduced grading frequence, as the turbot fry which have been fed on copepods during the early life stages will have a more uniform growth onwards in life. They will grow faster, and have an improved immune response system.
Billed C-turbot-6
Picture of 5 gram turbots from Maximus A/S ready for transfer to grow out.
In short:
a) Brood-stock can be manipulated for all year production of eggs. - 4 photo/temperature manipulated brood stocks required.
