Hawaii FEP - Western Pacific Fishery Council

could also be specified in order to trigger changes in F – in other words, the MFMT could haveadditional inflection points.5.2.2 Target Control Rule and Reference PointsA target control rule specifies the relationship of F to B for a harvest policy aimed at achieving agiven target. Optimum yield (OY) is one such target, and National Standard 1 requires thatconservation and management measures both prevent overfishing and achieve OY on acontinuing basis. Optimum yield is the yield that will provide the greatest overall benefits to thenation, and is prescribed on the basis of MSY, as reduced by any relevant economic, social, orecological factor. MSY is therefore an upper limit for OY.A target control rule can be specified using reference points similar to those used in the MSYcontrol rule, such as F TARGET and B TARGET . For example, the recommended default in Restrepo et al.(1998) for the target fishing mortality rate for certain situations (ignoring all economic, social,and ecological factors except the need to be cautious with respect to the thresholds) is 75 percentof the MFMT, as indicated in Figure 20. Simulation results using a deterministic model haveshown that fishing at 0.75 F MSY would tend to result in equilibrium biomass levels between 1.25and 1.31 B MSY and equilibrium yields of 0.94 MSY or higher (Mace 1994).It is emphasized that while MSST and MFMT are limits, the target reference points are merelytargets. They are guidelines for management action, not constraints. For example Restrepo et al.(1998) state that “Target reference points should not be exceeded more than 50% of the time, noron average”).5.2.3 Rebuilding Control Rule and Reference PointsIf it has been determined that overfishing is occurring, a stock or stock complex is overfished orapproaching an overfished condition, or existing remedial action to end previously identifiedoverfishing or to rebuild an overfished stock has not resulted in adequate progress, the Councilmust take remedial action within two years. In the case that a stock or stock complex isoverfished (i.e., biomass falls below MSST in a given year), the action must be taken through astock rebuilding plan (which is essentially a rebuilding control rule as supported by variousanalyses) with the purpose of rebuilding the stock or stock complex to the MSY level (B MSY )within an appropriate time frame, as required by MSA §304(e)(4). The details of such a plan,including specification of the time period for rebuilding, would take into account the bestavailable information regarding a number of biological, social, and economic factors, as requiredby the MSRA and National Standard Guidelines.If B falls below MSST, management of the fishery would shift from using the target control ruleto the rebuilding control rule. Under the rebuilding control rule in the example in Figure 20, Fwould be controlled as a linear function of B until B recovers to MSST (see F REBUILDING ), then heldconstant at F TARGET until B recovers to B MSY . At that point, rebuilding would have been achievedand management would shift back to using the target control rule (F set at F TARGET ). The targetand rebuilding control rules “overlap” for values of B between MSST and the rebuilding target(B MSY ). In that range of B, the rebuilding control rule is used only in the case that B is recovering137