Sigurd Handeland and Bendik Fyhn Terjesen participated in the OPP project. (Photo Credit: Reidun L. Kraugerud/Nofima)
NORWAYFriday, November 07, 2014, 23:10 (GMT + 9)
It may be possible that all farmed salmon can survive in the facilities used for postsmolt production in the future. The key is careful control of the salmon’s environment as it grows, according to research led by Nofima scientists.
In current salmon aquaculture, the fish are kept in closed freshwater facilities on land until they weigh approximately 80 g and are ready to be transferred to sea water (smolts). They are then moved to open cages in the sea.
The term “postsmolt” is used to describe the fish from the time it has acquired sea water tolerance and the initial part of the growth phase in salt water.
An average of 84 per cent of the salmon in Norwegian aquaculture survive the seawater phase, according to the Norwegian Food Safety Authority.
When salmon are exposed in open cages in the sea, they face a changing environment, disease and sea lice. Many small salmon smolts are not sufficiently robust to deal with these threats.
This is one part of the problem that scientists and the aquaculture industry have been closely working together to solve for the past three years. They have discovered that it is possible to reduce the time that the salmon spend in the sea by increasing the time on land, or in closed facilities in the sea. The scientists have also investigated the consequences for the performance, physiology and production costs of the fish.
“We have achieved 99 per cent survival in repeated experiments using our method, in which the fish are not transferred to cages in sea until they are postsmolts. The results show that some fish cannot cope with the transfer from land-based facilities to the sea if this is carried out when they are immature. It is exactly these fish that are more robust, and can cope with the stress that they experience in the sea when they are instead transferred as young adults, weighing well over 250 g,” says Bendik Fyhn Terjesen.
The senior scientist at Nofima is the technical project leader in Optimized postsmolt production (OPP), which is supported by the Research Council of Norway. The project is a collaboration with several R&D institutes and stake holders in the aquaculture industry.
The project group believed that in addition to allowing the smolts to grow more than usual before being set out into the sea, the salinity of the water and the water velocity in the tank, would be crucial factors in increasing survival.
After experiments with various combinations and using large-scale experiments, Fyhn Terjesen and his colleagues carried out an experiment in a recirculation plant using the solution that the project group believed would be the best.
The solution involved, among other things, a lower salinity of the water, exercise, and gentle handling of the fish in the closed facility on land, right up until the salmon weighed 600 g. The fish were subsequently transferred to normal cages in the sea. When the salmon had reached 2.5 kg, 99 per cent survived.
Sigurd Handeland at Uni Research has the same experience from other experiments in the OPP project. He did an experiment with fish that were kept to 1 kilo in a semi-closed containment system in the sea, and obtained similar results as Fyhn Terjesen obtained on land.
“It will be more difficult in everyday aquaculture to achieve the 99 per cent survival that we achieved in our carefully monitored experiments. But we have shown that the potential is there. What remains is to develop innovative solutions in technology and biology in order to get results that can be seen in statistics from the aquaculture industry,” says Terjesen.
“We want to continue research into culture of postsmolts in closed systems, in order to contribute to solving the challenges that are limiting growth in salmon production, up to 2050,” he concludes.
In current salmon aquaculture, the fish are kept in closed freshwater facilities on land until they weigh approximately 80 g and are ready to be transferred to sea water (smolts). They are then moved to open cages in the sea.
The term “postsmolt” is used to describe the fish from the time it has acquired sea water tolerance and the initial part of the growth phase in salt water.
An average of 84 per cent of the salmon in Norwegian aquaculture survive the seawater phase, according to the Norwegian Food Safety Authority.
When salmon are exposed in open cages in the sea, they face a changing environment, disease and sea lice. Many small salmon smolts are not sufficiently robust to deal with these threats.
This is one part of the problem that scientists and the aquaculture industry have been closely working together to solve for the past three years. They have discovered that it is possible to reduce the time that the salmon spend in the sea by increasing the time on land, or in closed facilities in the sea. The scientists have also investigated the consequences for the performance, physiology and production costs of the fish.
“We have achieved 99 per cent survival in repeated experiments using our method, in which the fish are not transferred to cages in sea until they are postsmolts. The results show that some fish cannot cope with the transfer from land-based facilities to the sea if this is carried out when they are immature. It is exactly these fish that are more robust, and can cope with the stress that they experience in the sea when they are instead transferred as young adults, weighing well over 250 g,” says Bendik Fyhn Terjesen.
The senior scientist at Nofima is the technical project leader in Optimized postsmolt production (OPP), which is supported by the Research Council of Norway. The project is a collaboration with several R&D institutes and stake holders in the aquaculture industry.
The project group believed that in addition to allowing the smolts to grow more than usual before being set out into the sea, the salinity of the water and the water velocity in the tank, would be crucial factors in increasing survival.
After experiments with various combinations and using large-scale experiments, Fyhn Terjesen and his colleagues carried out an experiment in a recirculation plant using the solution that the project group believed would be the best.
The solution involved, among other things, a lower salinity of the water, exercise, and gentle handling of the fish in the closed facility on land, right up until the salmon weighed 600 g. The fish were subsequently transferred to normal cages in the sea. When the salmon had reached 2.5 kg, 99 per cent survived.
Sigurd Handeland at Uni Research has the same experience from other experiments in the OPP project. He did an experiment with fish that were kept to 1 kilo in a semi-closed containment system in the sea, and obtained similar results as Fyhn Terjesen obtained on land.
“It will be more difficult in everyday aquaculture to achieve the 99 per cent survival that we achieved in our carefully monitored experiments. But we have shown that the potential is there. What remains is to develop innovative solutions in technology and biology in order to get results that can be seen in statistics from the aquaculture industry,” says Terjesen.
“We want to continue research into culture of postsmolts in closed systems, in order to contribute to solving the challenges that are limiting growth in salmon production, up to 2050,” he concludes.
The results from OPP were presented at the Smolt production in the future conference organised by Nofima and Sunndal Næringsselskap at Sunndalsøra in October.