The increasing number of depleted, overexploited and recovering world marine stocks, together with increasing demand for fish and need for sustainable management of aquatic resources has led to a gradual shift to inland intensive aquaculture with water reuse. Intensive recirculating systems are becoming a rapidly developing sector of aquaculture, with the objectives to increase production and minimize environmental impact. However, transfer of technologies from original sites to locations of different climate is not always successful. The present study evaluates the use of an open recirculating system in a temperate climate. The 3-year study showed successful production with better fish growth and feed utilization than in a flow-through facility at the same site, but presented significant issues necessitating changes in technology as well as physical adaptations. A positive effect of the technology with respect to the environment is possible, but systems must be adapted to temperate climatic conditions.

Aquaculture is currently one of the fastest growing food-producing sectors, accounting for around 50% of the world's food fish. Limited resources, together with climatic change, have stimulated the search for solutions to support and sustain the production of fish as a nutritious food. The integration of a constructed wetland (CW) into a recirculating hatchery (RHS) was evaluated with respect to its economic feasibility and environmental impact. The outcome of eight production cycles showed the potential of CW integration for expanded production without increased operation costs or environmental load. Concretely, the use of constructed wetland allows the rearing about 40% more fish biomass, resulting in higher production and profitability. The low requirements for space, fresh water, and energy enable the establishment of such systems almost anywhere. Constructed wetlands could enhance the productivity of existing small scale facilities, as well as larger systems, to address economic and environmental issues in aquaculture. Such systems have potential to be sustainable in the context of possible future climate change and resource limitations.

Aquaculture, as the fastest growing agriculture sector, is currently focused on exploring the development of effective intensive recirculating systems (RAS). The use of intensive RAS requires a stable supply of fingerlings throughout the year. Salmonids are a highly important aquaculture species, with rainbow trout Oncorhynchus mykiss often reared in freshwater RASs. The dominant position of rainbow trout has triggered the investigation of a wider diversification of species, including brook char Salvelinus fontinalis. Brook char has the potential to be reared in facilities similar to those used for rainbow trout, but it is not known if brook char is suitable for hatching in an intensive recirculating hatchery system (RHS) to provide a consistent supply of fingerlings to an associated RAS roughly every three months. The present study evaluated the feasibility of producing brook char fingerlings in an RHS and compared results to those obtained with rainbow trout. A production cycle from eyed egg to fingerling was completed separately for rainbow trout, brook char, and parallel rearing of both species for the comparison of growth rate, feed conversion ratio, and the time to reach individual fingerling weight of 2 g. The results showed slower growth rate of brook char compared to rainbow trout reared under the same conditions and a significantly longer production cycle (~108 days), compared to rainbow trout (~74 days). Results suggest that brook char is not suitable for parallel rearing in facilities with primary rainbow trout production. The main practical problem is disruption of the production cycle which requires fingerling stocking at 3-month intervals.