Review of the Effectiveness of Recovery Activities for North Atlantic right whales

Appendix B: Defining Risk

Table of Contents

• Complete Text
• 1. Background
• 2. Objective of this Review
• 3. Sources of Information
• 4. Methods for Assessing Effectiveness of Recovery activities
• 5. Review of Recovery activities
  • 5.1. Recovery Objectives
  • 5.2. Threats
  • 5.3. Review of Recovery activities
• 6. Effectiveness of Recovery Activities
  • 6.1. Vessel Strikes
  • 6.2. Fishing-Gear Entanglements
  • 6.3. Disturbance and Habitat Reduction or Degradation
    • 6.3.1. Contaminants
    • 6.3.2. Acoustic Disturbance
    • 6.3.3. Vessel-presence disturbance
    • 6.3.4. Changes in Food Supply
• 7. Indirect Recovery Activities: Monitoring and Stewardship
• 8. Threat-Based Recommendations
  • 8.1. Vessel Strikes
  • 8.2. Fishing-Gear Entanglements
  • 8.3. Disturbance and Habitat Reduction or Degradation
  • 8.4. Required Research and Monitoring
• 9. Conclusions
• 10. Literature Cited
• Appendix A: Acronyms
• Appendix B: Defining Risk
• Appendix C: Summaries of Recovery Activities

Appendix B: Defining Risk

The terms "risk" and "risk assessment" have been widely used in conservation biology (Harwood 1999) and various definitions exist throughout the published literature. Specifically within the North Atlantic right whale literature, various definitions of risk are used, even when quantifying the risk from a specific threat. For example, Fonnesbeck et al. (2008) defined risk as the co-occurrence (in time and space) of whales and vessels. Similarly, Williams and O'Hare (2010) estimate risk by multiplying their predicted whale density estimate by a measure of shipping intensity. Vanderlaan et al. (2008) defined relative risk of a lethal collision as the relative probability that a vessel will encounter a whale (in time and space) multiplied by probability of a lethal collision given an encounter, which was estimated as a function of vessel speed (Vanderlaan and Taggart 2007). Wiley et al. (2011) estimate the risk of lethal collisions as the probability of lethality associated with specific speeds using Pace and Silber's (2005) lethality model. In this report, unless specifically stated otherwise, a specific definition of risk, proposed initially by Kaplan and Gerricks (1981) is used. Kaplan and Gerricks (1981) definition of risk answers three questions or the "set of triplets":

1. What can happen or what can go wrong?
2. How likely is it that it will happen?
3. If it does happen, what are the consequences?

The answer to the first question, what can go wrong, is often referred to as an event. In the context of North Atlantic right whales and the threats that they face, a North Atlantic right whale can be struck by a vessel, or entangled in fishing gear, or can be injured or disturbed from vessel presence, anthropogenic noise, or contaminants. The third question addresses the consequence and in many risk analyses in other disciplines the consequence is usually a monetary value. In this case it can be thought of from the perspective of the whale, i.e., the probability that the whale will die or have decreased health as a result of an event. Therefore, to reduce the risk to North Atlantic right whales from specific threats, the probability of an event must decrease, and/or the probability of death or injury must decrease. In the case of vessel strikes, to reduce the risk to North Atlantic right whales, vessels can be re-routed around the areas occupied predictably by whales to decrease the probability of a vessel striking a whale, and/or decrease the vessel speed thereby decreasing the probability of a lethal injury given that a vessel struck a whale.