Estimates of stock status and catch limits can change dramatically with new data or modelling approaches, creating undesirable socioeconomic impacts. This study evaluated strategies for minimizing catch variation while mitigating ecological risk when assessments indicate large changes in stock status. We investigated: 1) harvest control rule (HCR) performance under consistent assessment mis-specification, 2) HCR performance when mis-specification occurs only initially, and 3) impacts of removing the constraint requiring Acceptable Biological Catch (ABC) to be less than the overfishing limit (OFL).
We compared four HCRs using management strategy evaluation for two fish life histories. Assessment parameters (natural mortality, stock-recruitment steepness, catch history, and selectivity) were deliberately mis-specified to create ±25% bias in OFLs. HCR performance was examined under three scenarios: a) correctly specified assessment, b) consistently underestimated parameters (-25% OFL bias), and c) consistently overestimated parameters (+25% OFL bias). We also evaluated scenarios where mis-specification occurred only in the first assessment and was subsequently corrected. Performance metrics focused on catch variation and biological risk.
HCR performance varied with life history and initial depletion. All HCRs maintained stable catches for stocks at the least-depleted level (0.48B₀). The status quo probability-based HCR stabilized catches for 0.28B₀ and 0.34B₀ depletions after several years, and the phase-in HCR performed similarly, preserving total catch while phasing catches in over time. Using a 15% constraint, the ABC constraint HCR was most conservative, increasing catches gradually, while the F constraint HCR produced more stable catch limit changes relative to the status quo HCR.
These HCRs effectively minimized catch variability and biological risk. The F constraint HCR offered the greatest stability and socioeconomic benefit but increased risk for depleted stocks. Flexible HCR frameworks can better balance stability and conservation under assessment uncertainty, and managers should consider life history and stock status when selecting appropriate HCRs.