Causal analysis of escape of Atlantic salmon and rainbow trout from Norwegian fish farms during 2010–2018

Heidi Moe Føre,Trine Thorvaldsen

doi:10.1016/j.aquaculture.2020.736002

Abstract

Farmed fish escaping into the wild and other environmental concerns have curbed the expansion of the Norwegian aquaculture industry. Detailed knowledge of both direct and underlying causes of previous escape episodes is crucial to ensure successful development of new technology and targeted safety-measures at fish farms. This paper provides detailed descriptions of both technological, human and organisational factors relevant to escape of fish from Norwegian fish farms during 2010–2018.Fish farmers in Norway are obliged by law to report escape incidents to the Norwegian Directorate of Fisheries. A total of 305 reported escape incidents with Atlantic salmon (Salmo salar) or rainbow trout (Oncorhynchus mykiss) were confirmed from 2010 to 2018, involving in total 1.960.000 registered escapees.Analysis of 298 of these incidents shows that most registered escapees came from sea-based fish farms (92%), while 7% were from land-based facilities and 1% from transportation between sites. Most escape incidents were directly caused by technological factors, with holes in the net as the most common cause of escape. Bad weather or handling of weights and net prior to delousing have been associated with increased probability of escape incidents.In addition to direct and contributing causes, mostly technological, escape incidents may also have underlying causes related to human and organisational factors. These causes may have triggered the incidents or prevented barriers from being effective, with technical damage and escape of fish as result. Relevant human and organisational causes were explored through interviews with employees that have experienced escape incidents.

Highlights

Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus my kiss) are the primary species for fish farming in Norway
700,000 around year 2006 to below 300,000 during 2012–2016. This decline is often credited the introduction of new regulations (Norwegian Ministry of Trade, Industry and Fisheries, 2015b), which were introduced in 2005, requiring that technical standards like NS9415 (Standards Norway, 2009) should be followed by all fish farming companies
From 2008, less than 0.11% of the farmed salmon was registered as escaped each year, and the 5-year average trend line indicate that on average 0.04% of the salmon was registered as escaped during recent years (Fig. 3)

Summary

Introduction

Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus my kiss) are the primary species for fish farming in Norway. In 2018, 1.28 million metric tons of farmed salmon and 68 thousand tons of rainbow trout were slaughtered (Statistics Norway, 2020). The Norwegian aqua culture industry is a profitable global exporter, and production numbers have increased considerably since the early days of fish farming in the 1970s. In recent years the industry's ambitions for further growth have been curbed by environmental concerns. Problems with parasites and farmed fish escaping into the wild led to a stagnation in produced biomass between 2013 and 2016 (Norwegian Directorate of Fisheries, 2020a). During 2017–2019, an alleged environmentally sus tainable increased production was allowed in areas given a “green light” (Norwegian Ministry of Trade, Industry and Fisheries, 2015a)

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