Aquaculture is the farming of aquatic organisms: fish, molluscs, crustaceans, aquatic plants, crocodiles, alligators, turtles, and amphibians. Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. Farming also implies individual or corporate ownership of the stock being cultivated.
Aquaculture is a fast-growing food production industry in most parts of the world. While commercial aquaculture only arose some 30 years ago, aquaculture now produces more than half of the world fish supply for human consumption.
The Netherlands, as a small country surrounded by the seas, has always been given great importance to a modern, economical profitable and sustainable fishing and aquaculture industry. It has nowadays obtained a major position on the international market in fishing, aquaculture and fish processing. Along with the industry the Netherlands has excellent research institutes in this field, of which Wageningen University and Research Centre (http://www.wageningenur.nl/en.htm) is the most well-known.
Innovative new aquaculture developments in the Netherlands include the land-based outdoor integrated production of marine aquatic organisms (fish, shell fish, worms, algae and marine vegetables) in which the residues of one production component are used as input for the next, the on-land shellfish production, the integration of fish culture and horticulture (aquaponics), and the outdoor cultivation of marine algae as food source for shell fish. In addition, pilots for off-shore mussel production are being developed.
The Netherlands finfish aquaculture sector is unique in Europe and worldwide. This innovative sector is based solely on recirculation aquaculture systems (RAS).
Innovative RAS system
RAS are land based fish production systems in which water from the rearing tanks is re-used after mechanical and biological purification to reduce water and energy consumption and to reduce nutrient emission to the environment. The water consumption in RAS is entirely based on water exchange to compensate for evaporation, incidental losses and to control water quality. Because of its controllability, water temperatures in a RAS are kept constant at the optimal rearing temperature for the species under concern. Compared to cages, flow-through systems or ponds, RAS present several advantages: water and energy savings, water quality control, low environmental impacts, high biosecurity and an easier control of waste production.
The Dutch fish aquaculture sector developed with the application of RAS in the 1980’s. The industry is the only one consequently and nearly exclusively applying RAS technology in indoor farming systems for several species, such as catfish, eel, tilapia, sturgeon, pikeperch, turbot, yellowtail kingfish and other species. The current fish production is approximately 7000 MT produced at circa 15 farms.
A net with mussel seed
The Netherlands is a major producer of shellfish (mussels and oysters). Three species of bivalve shellfish are farmed: the blue mussel (production of approximately 38,000 MT annually), the Pacific oyster (production of 19 million pieces ≈ 1,500 tonnes annually) and the European oyster (production of 1 million pieces ≈ 100 tonnes annually).
The main production method is farming on bottom plots, although some companies are using suspended culture methods. Especially seed collection is more and more done using nets or ropes that are placed in the water. Since 2005, two shellfish hatcheries have been established in the Netherlands. They produce seed of mussels, oysters and clams. Efforts are put into improving shellfish hatchery technology with recirculation systems and large-scale outdoor continuous algae production to decrease the costs. Hatchery production offers opportunities for product improvement through selective breeding, for example of oyster strains that are tolerant to diseases.
the Test location the Wierderij
Seaweed cultivation is worldwide a fast growing economic opportunity. With an annual turnover of 7.5bn$, it offers a unique novel feedstock for the biobased economy. In order to make seaweed cultivation a new sector, Wageningen UR has developed the concept of sustainable seaweed-based seafarms thus combining economic benefits with the conservation of marine ecosystems and societal support. This concept has been tested under Dutch conditions for three years in the Eastern Scheldt region and as the results are promising a private seafarm cultivating seaweeds has been started. Besides the traditional application of emulsifiers (agar, carrageenan and alginate), we have discovered that seaweeds are an interesting new source of plant proteins with at least similar quality as soy protein, an array of interesting sugars. Furthermore, seaweed biomass contain interesting polyunsaturated fatty acids and a vast array of anti-oxidants.
Sea lettuce growing at the Wierderij
Wageningen UR has developed a cultivation system that under Dutch conditions produces throughout the year seaweeds that implies a mixture of green (Ulva lactuca – Sea Lettuce) and brown seaweeds (Saccharina latissima – Sugar Kelp and Laminaria digitata – Finger Kelp). Seaweed cultivation may well be combined with shellfish cultivation and Wageningen UR has started experiments to optimise such cultivation systems.
Seaweed biomass is a novel feedstock for a sustainable biobased economy and may lead besides the above mentioned food and feed opportunities to novel chemical compounds to be applied in green chemistry.