Risk assessment of the environmental impact of Norwegian Atlantic salmon farming

Ørjan Karlsen,H. Craig Morton,Karin Kroon Boxaspen,Bengt Finstad,Terje Svåsand,Abdullah Sami Madhun,Egil Karlsbakk,Geir Lasse Taranger,Kevin Alan Glover,Vivian Husa,Bjørn Olav Kvamme,Pål Arne Bjørn,Raymond John Bannister

doi:10.1093/icesjms/fsu132

Abstract

Abstract Norwegian aquaculture has grown from its pioneering days in the 1970s to be a major industry. It is primarily based on culturing Atlantic salmon and rainbow trout and has the potential to influence the surrounding environment and wild populations. To evaluate these potential hazards, the Institute of Marine Research initiated a risk assessment of Norwegian salmon farming in 2011. This assessment has been repeated annually since. Here, we describe the background, methods and limitations of the risk assessment for the following hazards: genetic introgression of farmed salmon in wild populations, regulatory effects of salmon lice and viral diseases on wild salmonid populations, local and regional impact of nutrients and organic load. The main findings are as follows: (i) 21 of the 34 wild salmon populations investigated indicated moderate-to-high risk for genetic introgression from farmed escaped salmon. (ii) of 109 stations investigated along the Norwegian coast for salmon lice infection, 27 indicated moderate-to-high likelihood of mortality for salmon smolts while 67 stations indicated moderate-to-high mortality of wild sea trout. (iii) Viral disease outbreaks (pancreas disease, infectious pancreatic necrosis, heart and skeletal muscle inflammation, and cardiomyopathy syndrome) in Norwegian salmon farming suggest extensive release of viruses in many areas. However, screening of wild salmonids revealed low to very low prevalence of the causal viruses. (iv) From ∼500 yearly investigations of local organic loading under fish farms, only 2% of them displayed unacceptable conditions in 2013. The risk of eutrophication and organic load beyond the production area of the farm is considered low. Despite several limitations, especially limited monitoring data, this work represents one of the world’s first risk assessment of aquaculture. This has provided the Norwegian government with the basis upon which to take decisions for further development of the Norwegian aquaculture industry.

Highlights

BackgroundThe Atlantic salmon (Salmo salar L.) farming industry was first started in Norway in the early 1970s and has grown to become one of the country’s largest export industries by economic value
We have considered the following elements of risk assessment regarding the viral agents salmonid alphavirus (SAV), infectious pancreatic necrosis virus (IPNV), piscine myocarditis virus (PMCV), and piscine reovirus (PRV); release, exposure, and consequences as follow
To evaluate the effects of salmon and rainbow trout farming on the infection status of wild salmonids, there is a need to increase our knowledge about the complete pathogen repertoire present in wild fish in areas of highand low-intensity fish farming

Summary

Background

The Atlantic salmon (Salmo salar L.) farming industry was first started in Norway in the early 1970s and has grown to become one of the country’s largest export industries by economic value. As part of a national strategy for an environmentally sustainable aquaculture industry (Anon., 2009b), the Norwegian government established the following management goal to prevent genetic interactions of farmed escapees with wild salmon populations: “Aquaculture will not contribute to permanent genetic changes in the genetic characteristics of wild fish stocks” (Table 1). This political target, which forms the basis for the risk estimation, is clearly open for scientific interpretation. The risk for genetic changes as a result of farmed salmon introgression was low, moderate, or high for 13 (38%), 11 (32%), and 10 (29%) surveyed rivers, respectively (Figure 3)

Limitations

Future work

Findings

Discussion

Conclusions and summary of main findings