By Mike Urch, SeafoodSource contributing editor
Published on 12 May, 2013
If we are going to be able to increase food production as much as we need to in the future, it is time to look to the ocean to create large scale fish farming. This is the view of fisheries consultant, Erik Hempel, who spoke at the fourth International Symposium on Cage Aquaculture in Yeosu, Korea, at the end of last month.
Global aquaculture production is soaring, Hempel said. “In 2011 total production of aquatic animals and plants increased to more than 60 million metric tons (MT).” However, he added, marine aquaculture is relatively modest. “Only 30 percent of the total volume came from marine operations. This is in spite of the fact that the ocean offers the greatest potential for aquaculture by far.”
Cage culture enables fish to be reared in the open sea where the water quality is better than close to shore, said Hempel, and if the cages are large enough the living conditions are close to what they are used to in the wild.
Although fish have been farmed in cages in a primitive fashion, probably since the end of the last century, the development of modern cage culture is commonly attributed to the emergence of salmon farming, particularly in Norway, from the 1960s. Since then cage culture technology has developed tremendously and is now a very advanced, science-based activity.
Modern cages can be enormous structures with circumferences of up to 160 meters and a single cage can hold as many as 500,000 fish, or about 1,000 MT. Made from plastic or steel, they can withstand very harsh weather conditions.
In modern salmon farming, these large cages are connected to a feed barge, which also serves as a command center for the operation.
As well as floating cages, other types include submersible cages, closed and semi-closed systems, and tension leg cages.
A lot of research is being done on what Hempel terms tomorrow’s marine fish farming. “Researchers and technology suppliers are working on finding the best solutions for floating cages to be secured in exposed areas — ways to improve fish welfare, cages that allow the fish to roam freely and that allow full control over feeding. There will be ever more automated systems with increased monitoring of the fish in the cages, and surveillance of the condition of the nets [surrounding the cages].”
Traditional floating operations have, until now he said, used stationary cages moored to the seabed in relatively shallow waters. But many observers envisage free-floating cages in large structures propelled by onboard motors and with sophisticated GPS systems.
One of the reasons this development might happen, “is that one needs to keep the fish in clear, pollution-free waters, and also to be able to move the fish rapidly in case of environmental threats like algae invasions or water temperature changes.”
Automation has already been introduced to some extent, he added. “In Norway, it is no exaggeration to say that most farms are already semi-automated. Basic operations like fish monitoring and feeding have already been taken over by automatic systems.”
Hempel foresees there may be a need to be close to the final market. “With floating, self-sustained farms this may be a possibility, although there are problems of pollution, access to water bodies close to markets etc. But one can envisage the possibility of farming fish offshore outside major markets (cities).
“Tomorrow’s floating cages to be used in marine environments will be large, very robust, highly automated and very capital intensive, and perhaps self-propelled.
“Although not all species, for example bottom-dwellers or coral fish, will thrive in large, open cages, there is the potential to massively increase our aquaculture production from the sea.”