Sustainable farming of Arctic charr (Salvelinus alpinus)
Sammanfattning: Arctic charr (Salvelinus alpinus L.) is a salmonid that is well adapted to cold waters and is commonly farmed in open net cages. A breeding program has enabled a relatively large production in Sweden, providing a continuous supply of fresh fish to the market. Despite expansions and improvements of the Arctic charr farming industry during the last decade, there are still sustainability challenges to overcome. This doctoral thesis explores various methods for improving the sustainability of Arctic charr farming, such as alternative protein sources in the feed, a shortened production cycle through selective breeding and an adaptive feeding management model. A new feed composition, containing a protein mixture with ingredients that are not attractive for human consumption, was evaluated for Arctic charr. The feed consisted of Baltic Sea decontaminated fishmeal (Sprattus sprattus and Clupea harengus), Baltic Sea blue mussel meal (Mytilus edulis) and baker’s yeast (Saccharomyces cerevisiae). The new feed resulted in lower growth compared with fish fed a commercial-type control feed, likely due to a reduced digestibility caused by the baker’s yeast. However, a self-selection study revealed a preference for the new feed over the control feed. Additionally, consumers could not distinguish between fish that had been fed the new feed or the control feed. Possible family effects that the new feed may have on growth were also investigated, showing that selection for high growth on a commercial-type feed would also benefit a higher growth capacity on the new feed. Selective breeding of Arctic charr had clear positive effects on growth. After adjusting for changes of environmental factors within the hatchery, the growth improvement from the first generation to the current seventh generation was 11 % per generation and production time has been shortened by ten months. Selective breeding also affected seasonal growth patterns and Arctic charr from the seventh generation grew more during winter than previously, although the largest weight improvement between generations occurred during summer. A new growth capacity, and pattern, demands an adaptive feeding management model so that feed waste and environmental impacts can be minimized. A new model on the digestible energy need of Arctic charr and a seasonal growth capacity factor were developed and can together be used to calculate the daily feed allowance during different periods of the growth season.
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