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. There are two main types of reference points: limit reference points (LRPs, or Blim and Flim), and target reference points (TRPs, or BTARGET and FTARGET), which are typically based on fishing mortality rate (F-based) or population abundance (B-based).
Types of reference points:
- Limit reference points (LRPs, or Blim and Flim): define the danger zone, the point beyond which fishing is no longer considered sustainable
- Target reference points (TRPs, or BTARGET and FTARGET): define the ideal fishery state
- Trigger/threshold reference points: typically set between the TRP and LRP to prompt additional management response in order to help ensure that the fishery remains close to the target and/or avoids breaching the limit
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.”
Maximum Sustainable Yield
What is MSY?
Reference points have most often been tied to maximum sustainable yield (MSY), defined as the largest average catch that can be taken continuously from a stock under existing environmental conditions.
Unfortunately, managing for MSY often leads to unsustainable fisheries and suboptimal economics. By definition, MSY is an average, which is to say there is a 50 percent chance of violating it in any given year. This 50 percent failure potential applies to both BMSY and FMSY. That is, fishing at FMSY only gives a coin flip’s chance of being at or above BMSY and is therefore known to lead to fluctuations around BMSY that can be unsustainable. As a result, many fisheries experts advocate for MSY-based limits, not targets, at least for fishing mortality, based on the precautionary approach, the UNFSA, and other international agreements.
Choosing Candidate Reference Points
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)
- Most common reference point: BMSY: the biomass that enables a fish stock to deliver the maximum sustainable yield
- 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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