Evaluating the impact of buffers to account for scientific uncertainty when setting TACs: application to red king crab in Bristol Bay, Alaska

Abstract

Punt, A. E., Siddeek, M. S. M., Garber-Yonts, B., Dalton, M., Rugolo, L., Stram, D., Turnock, B. J., and Zheng, J. 2012. Evaluating the impact of buffers to account for scientific uncertainty when setting TACs: application to red king crab in Bristol Bay, Alaska. – ICES Journal of Marine Science, 69: 624–634. Increasingly, scientific uncertainty is being accounted for in fisheries management by implementing an uncertainty buffer, i.e. a difference between the limit catch level given perfect information and the set catch. An approach based on simulation is outlined, which can be used to evaluate the impact of different buffers on short- and long-term catches, discounted revenue, the probability of overfishing (i.e. the catch exceeding the true, but unknown, limit catch), and the stock becoming overfished (i.e. for crab, mature male biomass, MMB, dropping below one-half of the MMB corresponding to maximum sustainable yield). This approach can be applied when only a fraction of the uncertainty related to estimating the limit catch level is quantified through stock assessments. The approach is applied for illustrative purposes to the fishery for red king crab, Paralithodes camtschaticus, in Bristol Bay, AK.

Handle with Care: Establishing Catch Limits for Fish Stocks Experiencing Episodic Natural Mortality Events

“…This conclusion is supported elsewhere, both in the use of buffers to account for uncertainty in setting catch limits and in the frequency of decision making as a means to avoid undesirable stock depletion (Punt et al. ; Li et al. ).…”

Is risk consistent across tier‐based harvest control rule management systems? A comparison of four case‐studies

“…; Prager and Shertzer ; Punt et al . ; Shertzer et al . ).…”

“…Punt et al . () evaluated alternative choices for the buffer between the OFL and the ABC for a range of Alaskan crab stocks using an MSE‐like process. They provided trade‐offs between the probability of overfishing and catch given uncertainty in stock size.…”

“…The buffer is a function of the extent of uncertainty and the risk tolerance given uncertainty (i.e. pðABCðOFLÞ [ OFLÞ ¼ P Ã ; Prager and Shertzer 2010; Punt et al 2012;Shertzer et al 2008). This is implemented for the west coast groundfishery by the PFMC SSC quantifying uncertainty in terms of coefficient of variation for the OFL (r) and the Council selecting the percentile of the resulting probability distribution at which to set the ABC (P*).…”

“…P* is assumed to be 0.49, while the variance of the OFL is set based on the results of the stock assessments. The uncertainty levels in the assessments are considered unrealistically small (Punt et al 2012), and consequently, the buffer between the OFL and the MaxABC is much smaller for Alaskan crab stocks than for west coast groundfish stocks. However, the buffer imposed by the NPFMC SSC is larger than that implied by the agreed P* value.…”