Seafood is an important part of global food production, but also a resource that has long been treated negligently. Catches from the sea, lakes and rivers have levelled off, while fish and shellfish farming has become more expansive. In the future, we need more aquaculture – but with less environmental impact. Cultivation in closed ecosystems can eliminate leaching of nutrients and chemicals and unwanted mixing with natural populations. Mobile fish farms in the open sea can be a transition to aquaculture that mimic natural shoals.
Seafood is both an energy efficient and healthy food, An annual production of about 150 million tons of important resources feeds the world’s growing population: providing the primary protein source for over a billion people.
About half of all the fish and seafood we eat is caught in the wild, and the other half is farmed – a rapidly growing sector – coming predominantly from open plantations in Asian rivers and coastal areas.
Both wild catch and cultivation have their respective environmental problems. Industrial fishing can lead to overfishing by larger outlets than stocks, long-term supports. The use of dubious and often indiscriminate trapping increases the risk, and even allows for species other than the target affected. Shrimp trawling, for example, can lead to over 80 % of the catch not being utilized.
According to the UN Food and Agriculture Organization, FAO, only 20% of wild fish stocks have a sustainable capacity, the rest are at or beyond the limit of what they can produce.
Cultivation – a viable option?
Growth in aquaculture has emerged as a more sustainable alternative to traditional fisheries. But the culture has downsides. It doesn’t solve the problem of over-fishing, because farmed carnivorous fish are generally given wild fish as feed. Examples include salmon, which is also farmed.
Another problem is local eutrophication and deterioration of water quality as a result of leaching from the often extremely dense individual farms; density also harm fish directly, and creates a breeding ground for pests and diseases, which also tend to spread to wild stocks.
New feed and closed systems
One hope to make tomorrow’s fish farming more environmentally friendly is to develop fodder for farmed carnivorous fish with a larger percentage raw material from alternative sources. It may involve plant, algae or yeast-based feed – where the yeast, for example, can be grown on waste products from the paper industry.
Another promising development is known as integrated “multitroft” aquaculture. There, several species are cultivated together, in more or less closed, balanced systems or food chains – where crops can be incorporated by the water and circulated in the culture vessels. In the latter case, the system grows without soil – a further development of a hydroponic solution. The balance of the ecosystem is maintained by nitrogen-based bacteria.
A simple example of “multitroft” aquaculture is growing mussels and fish together. The potential is considerably higher: such systems can also be placed on land, and cultivation tanks in an urban environment can be a form of local culture – with decreased food shipments as a possible environmental benefit. The company Swedish Fish farming hopes for instance to launch large-scale walley or gös farming in Stockholm in the near future.
More natural farming
A third idea for the future is based on trying to overcome the problem that the concentration of many individuals in a small area brings. The idea is to replace the static mass cultivation in coastal bags with mobile, autonomous devices like the natural school of fish can move freely on the high seas until they are emptied – you can see it as a cross between today’s culture and living conditions for wild populations. This would impact on local water systems and sensitive coastal areas could be eliminated.
Instead of today’s net bags, it is envisioned large, rigid, motorized cages that are durable enough to withstand high seas and greater depths. One example is Aqua Pods, developed by the company Ocean Farm Technologies. Aquapods is geodesic spheres joined by triangular mesh panels. Hawaii Oceanic Technology develops a structure they call Oceansphere, following similar principles.
In the future, the vision is that the culture cages must be increasingly autonomous, automated and remotely monitored – perhaps connected to buoys with solar panels for propulsion.
Future increased food needs will include the increased use of marine foods and thus an increasingly extensive farming of fish and shellfish. But it is clear that there is considerable scope for environmental improvements. A promising research and development work nonetheless suggests that future fish farms will be able to produce more while reducing their ecological footprint. Then we can also reduce the burden on overworked and depleted wild stocks in the sea, lakes and rivers so that this important resource can be utilized in a sustainable manner.
The article was published in December 2013