Canadian Science Advisory Secretariat (CSAS) Research Document 2020/059 National Capital Region Assessment of the risk to Fraser River Sockeye Salmon due to Tenacibaculum maritimum transfer from Atlantic Salmon farms in the Discovery Islands area, British Columbia C. Mimeault1, O. Nekouei1, K.A. Garver2, S.R.M. Jones2, S. Johnson2, K. Holt3, P. Aubry4, L. Weber1, I.J. Burgetz1, and G.J. Parsons1 1Fisheries and Oceans Canada Aquaculture, Biotechnology and Aquatic Animal Health Science 200 Kent, Ottawa, ON K1A 0E6 2Fisheries and Oceans Canada Pacific Biological Station 3190 Hammond Bay Road, Nanaimo, BC V9T 6N7 3Fisheries and Oceans Canada Institute of Ocean Sciences 9860 West Saanich Road, Sidney, BC V8L 5T5 4Canadian Food Inspection Agency Animal Health Science Division 1400 Merivale, Ottawa, ON K1A 0Y9 November 2020 Foreword This series documents the scientific basis for the evaluation of aquatic resources and ecosystems in Canada. As such, it addresses the issues of the day in the time frames required and the documents it contains are not intended as definitive statements on the subjects addressed but rather as progress reports on ongoing investigations. Published by: Fisheries and Oceans Canada Canadian Science Advisory Secretariat 200 Kent Street Ottawa ON K1A 0E6 http://www.dfo-mpo.gc.ca/csas-sccs/ [email protected] © Her Majesty the Queen in Right of Canada, 2020 ISSN 1919-5044 Correct citation for this publication: Mimeault, C., Nekouei, O., Garver, K.A., Jones, S.R.M., Johnson, S., Holt, K., Aubry, P., Weber, L., Burgetz, I.J. and Parsons, G.J. 2020. Assessment of the risk to Fraser River Sockeye Salmon due to Tenacibaculum maritimum transfer from Atlantic Salmon farms in the Discovery Islands area, British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2020/059. viii + 49 p. Aussi disponible en français : Mimeault, C., Nekouei, O., Garver, K.A., Jones, S.R.M., Johnson, S., Holt, K., Aubry, P., Weber, L., Burgetz, I.J. et Parsons, G.J. 2020. Évaluation du risque pour le saumon rouge du fleuve Fraser attribuable au transfert de la bactérie Tenacibaculum maritimum à partir des fermes d’élevage de saumon atlantique situées dans la région des îles Discovery (Colombie- Britannique). Secr. can. de consult. sci. du MPO. Doc. de rech. 2020/059. x + 55 p. TABLE OF CONTENTS GLOSSARY ............................................................................................................................. VII ABSTRACT ............................................................................................................................. VIII 1 INTRODUCTION .................................................................................................................1 2 BACKGROUND ..................................................................................................................1 2.1 MANAGEMENT PROTECTION GOALS ...................................................................... 1 2.2 PROBLEM FORMULATION ........................................................................................ 2 2.2.1 Hazard identification ............................................................................................. 2 2.2.2 Hazard characterisation ........................................................................................ 2 2.2.3 Scope ................................................................................................................... 2 2.2.4 Risk question ........................................................................................................ 4 2.2.5 Methodology ......................................................................................................... 4 2.3 FISH HEALTH DATA SOURCES ................................................................................. 9 2.3.1 Industry ................................................................................................................. 9 2.3.2 Fish Health Audit and Surveillance Program ......................................................... 9 2.3.3 Fish Health Events ...............................................................................................10 2.3.4 Mortality events ....................................................................................................10 2.4 REGULATORY REQUIREMENTS ..............................................................................10 2.4.1 Licensing and biosecurity .....................................................................................10 2.4.2 Introduction and Transfer Committee ...................................................................11 2.5 INDUSTRY PRACTICES ............................................................................................11 2.5.1 Fish health management practices ......................................................................12 2.5.2 Surveillance and testing .......................................................................................12 2.5.3 Stocking practices in the Discovery Islands area .................................................12 3 LIKELIHOOD ASSESSMENT............................................................................................ 13 3.1 FARM INFECTION ASSESSMENT ............................................................................13 3.1.1 Question ..............................................................................................................13 3.1.2 Considerations .....................................................................................................13 3.1.3 Assumption ..........................................................................................................16 3.1.4 Likelihood of farm infection ..................................................................................16 3.2 RELEASE ASSESSMENT ..........................................................................................16 3.2.1 Question ..............................................................................................................16 3.2.2 Considerations .....................................................................................................16 3.2.3 Assumptions ........................................................................................................17 3.2.4 Likelihood of release ............................................................................................17 3.3 EXPOSURE ASSESSMENT .......................................................................................19 3.3.1 Question ..............................................................................................................19 3.3.2 Considerations .....................................................................................................19 3.3.3 Assumptions ........................................................................................................24 iii 3.3.4 Likelihood of exposure .........................................................................................24 3.4 INFECTION ASSESSMENT .......................................................................................26 3.4.1 Question ..............................................................................................................26 3.4.2 Considerations .....................................................................................................26 3.4.3 Assumptions ........................................................................................................29 3.4.4 Likelihood of infection ..........................................................................................29 3.5 OVERALL LIKELIHOOD ASSESSMENT ....................................................................31 4 CONSEQUENCE ASSESSMENT .....................................................................................31 4.1 QUESTION .................................................................................................................32 4.2 CONSIDERATIONS ....................................................................................................32 4.2.1 Infection dynamics and virulence of Tenacibaculum maritimum ...........................32 4.2.2 Prevalence of Tenacibaculum maritimum in Sockeye Salmon .............................33 4.2.3 Mortality attributable to mouthrot ..........................................................................33 4.2.4 Tenacibaculum maritimum sublethal infections ....................................................34 4.2.5 Fraser River Sockeye Salmon ecology ................................................................34 4.2.6 Stock-specific susceptibility ..................................................................................35 4.3 ASSUMPTIONS ..........................................................................................................35 4.4 MAGNITUDE OF CONSEQUENCES .........................................................................35 4.4.1 Potential impacts on abundance ..........................................................................36 4.4.2 Potential impacts on diversity ...............................................................................38 5 RISK ESTIMATION ...........................................................................................................39 5.1 ABUNDANCE .............................................................................................................39 5.2 DIVERSITY .................................................................................................................39