Trends during development of Scottish salmon farming: An example of sustainable intensification?

Commercial farming of Atlantic salmon in Scotland started in 1969 and has since expandedto produce >179,000 t yr-1. A government department has published annual statistics andinformation on the seawater and freshwater sub-sectors of the Scottish salmon farmingindustry since 1979, and this review collates and discusses metrics covering aspects ofproduction, farm sites and systems, fish performance, socio-economics and environmentalpressures. Trends illustrated in this case study of aquaculture development include: initialincreases in numbers of farms and companies, followed by decreases due to industryconsolidation; increases in average farm size, and productivity of systems and employees;increases in survival, size at age and productivity of fish (yield per smolt, ova perbroodstock); reduced dependence on wild stocks for ova. This case study also illustrates theimportance of disease management, control of biological processes to overcome naturalseasonality (i.e. production of out-of-season smolt), and the international nature ofaquaculture. Improvements in fish survival, growth and productivity are attributed toprogress in vaccination and health management (including fallowing), husbandry, systemdesign, feed formulation and provision, and introductions of technology and mechanisation.Salmon farming is discussed in relation to the challenging strategy of “sustainableintensification”. Improved growth and survival over a period of increasing rearing unit size,farm size and output and decreasing relative staff input counters the common assumptionthat intensification compromises animal welfare. The value of capturing time series data onindustry wide metrics is illustrated as it enables identification of trends, underperformanceand bench-marking, as well as assessment of resource use efficiency, environmental pressures, and ultimately sustainability.
Statement of relevance

This review is an original collation of a comprehensive set of time series of official statistics on an entire, discrete and regionally important sector of commercial aquaculture.