Biodiversity Risk and Benefit Assessment for Rainbow trout (Oncorhynchus mykiss) in South Africa Prepared in Accordance with Section 14 of the Alien and Invasive Species Regulations, 2014 (Government Notice R 598 of 01 August 2014), promulgated in terms of the National Environmental Management: Biodiversity Act (Act No. 10 of 2004). September 2019 Biodiversity Risk and Benefit Assessment for Rainbow trout (Oncorhynchus mykiss) in South Africa Document Title Biodiversity Risk and Benefit Assessment for Rainbow trout (Oncorhynchus mykiss) in South Africa. Edition Date September 2019 Prepared For Directorate: Sustainable Aquaculture Management Department of Environment, Forestry and Fisheries Private Bag X2 Roggebaai, 8001 www.daff.gov.za/daffweb3/Branches/Fisheries- Management/Aquaculture-and-Economic- Development Originally Prepared By Dr B. Clark (2012) Anchor Environmental Consultants Reviewed, Updated and Mr. E. Hinrichsen Recompiled By AquaEco as commisioned by Ecosense (2019) 1 | P a g e Biodiversity Risk and Benefit Assessment for Rainbow trout (Oncorhynchus mykiss) in South Africa CONTENT EXECUTIVE SUMMARY ......................................................................................................................... 4 LIST OF FIGURES .................................................................................................................................. 7 LIST OF TABLES.................................................................................................................................... 8 1. INTRODUCTION ............................................................................................................................ 10 2. PURPOSE OF THIS RISK ASSESSMENT ................................................................................... 10 3. THE RISK ASSESSMENT PRACTITIONERS .............................................................................. 11 4. NATURE OF THE USE OF RAINBOW TROUT ............................................................................ 12 5. REASONS FOR FARMING WITH RAINBOW TROUT ................................................................. 13 6. LEGAL CONTEXT ......................................................................................................................... 14 6.1. CATEGORIZATION OF ALIEN AND INVASIVE SPECIES .......................................................... 15 6.2. STATUTORY CLASSIFICATION OF RAINBOW TROUT ............................................................ 16 6.3. LIST OF RESTRICTED ACTIVITIES ............................................................................................. 18 7. TARGET SPECIES: RAINBOW TROUT ....................................................................................... 20 7.1. TAXONOMY ................................................................................................................................... 20 7.2. ORIGINATING ENVIRONMENT .................................................................................................... 21 7.3. KEY PHYSIOLOGICAL CHARACTERISTICS .............................................................................. 22 7.4. REPRODUCTION .......................................................................................................................... 23 7.5. DIETARY ASPECTS ...................................................................................................................... 24 7.6. ENVIRONMENTAL TOLERANCES .............................................................................................. 24 7.7. NATURAL ENEMIES, PREDATORS AND COMPETITORS ........................................................ 25 7.8. POTENTIAL TO HYBRIDISE ........................................................................................................ 25 7.9. PERSISTENCE AND INVASIVENESS ......................................................................................... 25 7.10. HISTORY OF TRANSLOCATION AND CULTIVATION ........................................................ 26 7.11. ABILITY TO CREATE ECOSYSTEM CHANGE .................................................................... 30 7.12. PROBABILITY OF NATURALISATION ................................................................................. 30 7.13. POSSIBLE IMPACTS ON BIODIVERSITY ............................................................................ 31 7.14. POSSIBLE IMPACTS ON OTHER NATURAL RESOURCES .............................................. 33 7.15. RAINBOW TROUT AS A VECTOR OF OTHER ALIEN SPECIES ....................................... 33 8. THE RECEIVING ENVIRONMENT ................................................................................................ 33 8.1. CLIMATE AND HABITAT MATCH ................................................................................................ 34 8.2. TOOLS TO IDENTIFY SENSITIVE AREAS .................................................................................. 36 9. THEORY BEHIND ECOLOGICAL RISK ASSESSMENT ............................................................. 37 9.1. THE PRECAUTIONARY AND OTHER PRINCIPLES................................................................... 38 9.2. METHODOLOGY IN THE RISK ASSESSMENT .......................................................................... 39 9.3. THE RISK PATHWAY ................................................................................................................... 41 9.4. SCALES AND CATEGORISATION OF RISK ............................................................................... 43 9.5. PERCEPTION OF RISK ................................................................................................................ 47 2 | P a g e Biodiversity Risk and Benefit Assessment for Rainbow trout (Oncorhynchus mykiss) in South Africa 9.6. RISK COMMUNICATION .............................................................................................................. 48 10. SPECIFIC FRAMEWORK ASSESSMENT FOR RAINBOW TROUT ........................................... 48 10.1. INVENTORY OF POTENTIAL PATHWAYS AND RISKS ..................................................... 48 10.2. DISCUSSION OF RISK PATHWAYS .................................................................................... 49 10.2.1. THE PATHWAY OF ESCAPE ............................................................................................ 50 10.2.2. THE PATHWAY OF DISEASE ........................................................................................... 54 10.3. DISCUSSION OF RISK ENDPOINTS .................................................................................... 55 10.3.1. PHYSICAL ABIOTIC DAMAGE TO THE ENVIRONMENT ............................................... 55 10.3.2. PREDATOR DISPLACEMENT ........................................................................................... 55 10.3.3. COMPETITION - FOOD, HABITAT & OTHER RESOURCES ........................................... 56 10.3.4. HYBRIDIZATION ................................................................................................................ 57 10.3.5. IMPACT ON PREY SPECIES ............................................................................................. 57 10.3.6. EFFECTS OF DISEASE ..................................................................................................... 57 10.4. ASSESSMENT SCORING OF RISK LEVELS ....................................................................... 58 10.4.1. RISK PATHWAYS .............................................................................................................. 59 10.4.2. RISK ENDPOINTS/IMPACTS ............................................................................................. 62 10.5. SUMMARY OF RISK PROFILE ............................................................................................. 64 11. KEY ECONOMIC, SOCIAL AND SOCIETAL CONSIDERATIONS .............................................. 69 12. BALANCED COST OF ERADICATION ........................................................................................ 72 13. RISK MONITORING ...................................................................................................................... 73 14. RISK CONTROL MEASURES AND MITIGATION ....................................................................... 74 15. BENEFIT / RISK TRADE-OFF....................................................................................................... 77 16. RECOMMENDATIONS .................................................................................................................. 78 17. CONCLUSION ............................................................................................................................... 78 LIST OF APPENDIXES Appendix A: Risk Scoring Methodology for Rainbow trout and guidance supplied by the F-ISK toolkit (Copp et al. 2008). 3 | P a g e Biodiversity Risk and Benefit Assessment for Rainbow trout (Oncorhynchus mykiss) in South Africa EXECUTIVE SUMMARY Internationally, alien species provide a valuable food source and an economic opportunity in both the fisheries and aquaculture sectors (Bartley 2006). In South Africa, aquaculture is composed of a blend of indigenous and non-indigenous species. However, breeding and domestication of indigenous species requires time, technological and financial resources, whilst there are already alien species with proven aquaculture potential that could be utilized for food production and job creation.