Hawaii FEP - Western Pacific Fishery Council

Source: Restrepo et al. 1998In Figure 20 the dashed horizontal and diagonal line represents a model MSY control rule that isused as the MFMT; the solid horizontal and diagonal line represents a model integrated target(F target ) and rebuilding (F rebuilding ) control rule.The status determination criterion for F is the maximum fishing mortality threshold (MFMT).Minimum stock size threshold (MSST) is the criterion for B. If fishing mortality exceeds theMFMT for a period of one year or more, overfishing is occurring. A stock or stock complex isconsidered overfished when its biomass has declined below a level that jeopardizes the capacityof the stock to produce MSY on a continuing basis (i.e., the biomass falls below MSST). ACouncil must take remedial action in the form of a new FMP, an FMP amendment, or proposedregulations within two years following notification by the Secretary of Commerce thatoverfishing is occurring, a stock or stock complex is overfished or approaching an overfishedcondition, 20 or existing remedial action to end previously identified overfishing or to rebuild anoverfished stock has not resulted in adequate progress.The National Standard Guidelines state that the MFMT may be expressed as a single number oras a function of some measure of the stock’s productive capacity. Guidance in Restrepo et al.(1998:17) regarding specification of the MFMT is based on the premise that the MSY controlrule constitutes the MFMT. In the example in Figure 20 the MSY control rule sets the MFMTconstant at F MSY for values of B greater than the MSST and decreases the MFMT linearly withbiomass for values of B less than the MSST. This is the default MSY control rule recommendedin Restrepo et al. (1998). Again, if F is greater than the MFMT for a period of one year or more,overfishing is occurring.The National Standard Guidelines state that to the extent possible, the MSST should equalwhichever of the following is greater: One-half the MSY stock size, or the minimum stock sizeat which rebuilding to the MSY level would be expected to occur within 10 years if the stock orstock complex were exploited at the MFMT. The MSST is indicated in Figure 20 by a verticalline at a biomass level somewhat less than B MSY . A specification of MSST below B MSY wouldallow for some natural fluctuation of biomass above and below B MSY , which would be expectedunder, for example, an MSY harvest policy. Again, if B falls below MSST the stock isoverfished.Warning reference points comprise a category of reference points that will be consideredtogether with the required thresholds. Although not required under the MSA, warning referencepoints provide warning in advance of B or F approaching or reaching their respective thresholds.For example a stock biomass flag (B FLAG ) could be specified at some point above MSST, asindicated in Figure 20. The control rule would not call for any change in F as a result ofbreaching B FLAG – it would merely serve as a trigger for consideration of action or perhapspreparatory steps towards such action. Intermediate reference points set above the thresholds20 A stock or stock complex is approaching an overfished condition when it is projected that there is more than a 50percent chance that the biomass of the stock or stock complex will decline below MSST within two years (74 FR3178).136