What are reference points?
Reference points are benchmarks used to compare the current status of a fishery management system against a desirable (or undesirable) state. When matched to the management objectives for a fishery, they can be used to assess progress toward meeting those objectives.
Types of reference points:
- Limit reference points (LRPs, or Blim and Flim): A benchmark that defines an undesirable biological state of the stock. To keep the stock safe, the probability of violating an LRP should be very low. However, if an LRP is violated, immediate action—such as a suspension of fishing—should be taken to return the stock or fishery to the target level.
- Target reference points (TRPs, or BTARGET and FTARGET): A benchmark that defines the target fishery state that should be achieved and maintained. Creates a buffer zone to ensure that the limit reference point (LRP) is not breached. Can be based on one or more biological, ecological, social or economic considerations.
- Trigger/threshold reference points: A benchmark that triggers a pre-defined management response to help the fishery remain close to the target reference point (TRP) and avoid breaching the limit reference point (LRP). Typically set between the TRP and the LRP.
Key Reference Point Principles in the U.N. Fish Stocks Agreement (UNFSA):
- LRPs “constrain catches within safe biological limits”; risk of breaching LRP should be “very low”; “if a stock falls below LRP or is at risk of falling below such a reference point, conservation and management action should be initiated to facilitate stock recovery.”
- Design management so that TRPs are achieved “on average.”
- “Fishing mortality rate which generates maximum sustainable yield should be regarded as a minimum standard for limit reference points.”
Choosing Candidate Reference Points
Generally, TRPs and LRPs are divided into two categories: fishing mortality-based (F-based) and biomass-based (B-based). One key question that managers face is whether to use F-based and/or B-based reference points when setting targets and limits. Oftentimes, the answer is to use both because each has its pros and cons, as is further clarified below.
Fishing Mortality Based (F-Based)
- F can be directly managed
- Harder to understand, because F is a mortality rate that is intangible and cannot be directly observed
Biomass Based (B-Based)
- B is the critical point to control from an ecological perspective, cannot be directly managed
- Easy for managers and stakeholders to understand, because biomass is usually expressed as an absolute number that relates physically to the quantity of fish in the water
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