Recirculating aquaculture systems (RAS) are a land-based production technology for aquatic organisms and high-value finfish. They utilise simple water treatment technologies (mechanical and biological filtrations) to minimise water use and maintain a tightly controlled environment. These can range from very open systems that use only basic treatment technologies to reuse some of their water resource, to fully closed systems which reuse 100% of the water and only add new water to account for splashing and evaporation. RAS vary in their design and functionality depending on the species being produced, the local conditions and the cost/access to a local water resource.
Advantages of using RAS
Reduced water requirements
Water is treated and recirculated, significantly reducing water requirements.
Water can be heated/cooled, high oxygen can be maintained, pH adjusted, pathogens treated, and waste products removed to maximise health, growth rates, and the welfare of the stock.
Increase in long-term production
Stock are unaffected by seasonality, periodic disease events and adverse weather, allowing continuous and reliable production.
Reduced environmental footprint
Waste streams are treated and recycled to ensure they have the least impact on the environment as possible. Being land-based, there is also no risk of fish escaping and interbreeding with wild populations.
The system can easily be customised for different species, locations and consumer preferences.
A video about The world's most mysterious fish. NIWA researchers are working with iwi to try to unlock the secrets of New Zealand tuna—freshwater eels. Every year tiny, glass eels wash in on the tide at river mouths along our coast. But where do they come from and how do they get there?
As a young child growing up on an Irish farm, one of Eimear Egan’s chores was to regularly clean out the well from where her family drew its drinking water. In the well lived a large eel that, no matter how many times it was shifted, just kept coming back.
The Fish Passage Assessment Tool has been developed to provide an easy to use, practical tool for recording instream structures and assessing their likely impact on fish movements and river connectivity.
We have prepared a breakdown of the different guidelines that are available for sampling freshwater fisheries. The overview provides links to key documents that explain what should be considered when designing fish monitoring studies and how to implement the various sampling techniques.