Enhancing farmed Atlantic salmon quality through new production techniques

Sustainability related challenges are at the forefront of Atlantic salmon aquaculture, particularly in terms of reducing the use of natural resources. Water abstraction from freshwater sources to rear salmon in conventional hatchery systems can be vastly reduced by utilizing recirculating aquaculture systems (RAS). Having stricter control over environmental parameters, such as water temperature, photoperiod and water chemistry, RAS can offer a more stable growing environment for salmon in the freshwater life stage. This in turn can potentially better assist in the physiological, morphological and behavioral changes that salmon undergo during parr-smolt transformation (PST) or smoltification. While PST is a heavily studied topic, issues surrounding it are continuously faced by the Atlantic salmon aquaculture industry in terms of welfare concerns and economic. This research aimed to characterize the smoltification process with regards to differences in hatchery systems and formulated feed. In an effort to assist the industry and help to improve the understanding of using RAS for smolt production, two commercially available genetic strains were used (Irish and Icelandic). In Chapter 2, these two strains were reared in a RAS and a flow-through (FT) with a common water source and transferred to a sea site. It describes numerous smoltification related variables in these two hatchery systems. Chapter 3 characterizes the microbiome of the distal intestine and of system (tank and sea pen) water during the same 16-week trial as chapter 2. Differences between microbial composition in the RAS and FT reared fish were analysed, as well as functionality and factors (smoltification related variables) influencing microbial composition. Fifteen core phyla were identified to be persistent across all rearing systems and measured continuous variables from Chapter 2. Chapter 4 addressed the unsustainability surrounding aquafeeds, focusing on reduction of wild caught fish used in formulated diets. Plant and insect oils were used to partially replace wild caught fish oil to produce feed pellets during a 13-week experiment in a RAS. Results demonstrated that alternative lipid sources have no adverse effects on the PST, suggesting that it is possible to partially replace wild caught fish oil for the consumption of salmon undergoing this process. A suggestion for future studies would be to replicate these experiments and extend the sampling period to the entire lifespan of the Atlantic salmon. This would have the potential to give a broader view of the smoltification process in RAS and a deeper understanding of the implications or benefits of RAS. Finally, Chapter 5 integrates the findings of this thesis by highlighting how this research contributes to the current understanding and provides insights to support the development of sustainable Atlantic salmon aquaculture.

Funder

Marine Institute

Publisher

University of Galway

Rights

CC BY-NC-ND

cbn

Collections

University of Galway Theses (PhD Theses)