The technology used in aquaculture has developed over many centuries but has done so more rapidly in the last fifty years. Aquaculture systems - and the technology used - vary from very simple facilities that are used for family ponds in tropical countries where production is for domestic consumption to high technology systems, such as intensive closed systems used for rearing striped bass. Herbivorous and filter feeding fish, raised mostly in simple systems of small freshwater ponds account for about half of global aquaculture production.
Much of the technology used in aquaculture is relatively simple often based on small modifications that improve the growth and survival rates of the target species, such as providing additional food, adding seed animals collected elsewhere, managing water exchange to maintain adequate oxygen levels and protecting the stock from predators. A greater understanding of complex interactions between nutrients, bacteria and cultured organisms, together with advances in hydrodynamics applied to pond and tank design, have enabled the development of closed systems. These have the advantage of isolating the aquaculture systems from natural aquatic systems, thus minimizing the risk of disease or genetic impacts on the external systems.
Developments in engineering, some adapted from offshore oilrig construction, increase the possibilities for offshore aquaculture using robust cages. Sea ranching, the release of young fish into the wild to improve the harvest in capture fisheries, has also made a start but its long-term viability is being assessed. Major advances are also being made in the technology of the production of aquafeeds, which generally require the combining of a large number of ingredients into very small feed pellets.