User menu
The Kobe Plot has been widely used as a practical, user-friendly method for presenting stock status information and to characterize the status of stocks as “overfished” (B < BMSY) and “subject to overfishing” (F > FMSY). When providing advice on stock status relative to MSY-based reference points, IOTC stocks are currently considered to be overfished and subject to overfishing when the target MSY-based reference points are breached (i.e., SSB < SSBMSY and F > FMSY). However, there is no further change to stock status when the limit reference points are breached; which may not consistent with the intended application of target and limit reference points. For example, when managing stocks to MSY-based target reference points (the agreed/desired state of the stock) it is expected that the stock will fluctuate around that target, sometimes above and sometimes below, due to natural fluctuation in recruitment, stock abundance or other sources of variability.
The adoption of new target and limit reference points (IOTC Res. 15/10), requires a review of the approach used to determine stock status relative to these new reference points. As suchm, the IOTC Scientific Committee recommended to consider alternative formulations of the Kobe plot to indicate an appropriate buffer zone below BMSY to account for natural variations in biomass. In 2019, the TCMP recommended that discussions on potential refinements to the Kobe plots and definitions of “overfished” and “overfishing” in relation to target and limit reference points to be conducted in collaboration with other t-RFMOs. This document discusses and provides possible alternative approaches for evaluating stock status (i.e. “overfished” and “overfishing”) and communicating scientific management advice considering limit and target reference points.
