Workshop on Data-limited Stocks of Short-lived Species (WKDLSSLS)

Concerning faster-growing species, the conclusion was that trend-based management procedures (the ICES 2 over 3 rule, the rfb-rule or any other combination of x over y rules with or without additional elements such as uncertainty caps or biomass safeguards) lead to poor management performance (high risks, low yields) for such species and should be avoided. The only way to comply with precautionary principles for such rules and species is to apply very precautionary multipliers (very low catch advice). Consequently, the recommendation would be to very cautious with trend-based rules for faster-growing species and consider abandoning them. Instead, alternative management procedures (e.g. harvest rate-based rules or escapement strategies) should be explored for faster-growing species.

The operating models were stochastic and uncertainty was included in 500 simulation replicates through a log-normal process (recruitment error σR = 0.6, added to the Beverton-Holt stock-recruitment model) and observation errors (σobs = 0.2, added to the aggregated total biomass and mean catch length indices). Details of the operating models are described in the Supplementary Material. Fischer et al. (2022)

In general, the shorter the lag between observations, advice and management, the bigger the catches and the smaller the biological risks. For in-year management, 1-over-m rules are reactive enough to stock fluctuations as to gradually reduce risks Sánchez-Maroño et al. (2021)

OMs

Figure 1 Operating Model

Abundance Index

Figure 2 Survey devs

Figure 3 Index

Figure 4 Index v OM

Harvest Rate

Figure 5 HR Index

Figure 6 Comparison between \(Catch/SSB\) and OM F.

Figure 7 ROC Curves

Figure 8 ROC Curves Shifted by a year

Length Based Indicators

Figure 9 Length based indicator

Figure 10 Comparison of LBI with OM F.

  year    state label  indicator         TPR FPR TP  TN FP  FN         TSS
1 2021 1.441866  TRUE 0.09904913 0.006802721   0  1 153  0 146 0.006802721
  order     roc.TSS
1    73 0.006802721

Figure 11 ROC Curves

Two over three rule

Figure 12 \(2/3\)

Figure 13 ROC Curve

One over Two rule

Figure 14 \(1/2\)

Figure 15 ROC Curve

Slope

Figure 16 Slope for 5 years

Figure 17 ROC Curve

Figure 18 Slope for 3 years

Figure 19 ROC Curve

Fischer, Simon H, José AA De Oliveira, John D Mumford, and Laurence T Kell. 2022. “Exploring a Relative Harvest Rate Strategy for Moderately Data-Limited Fisheries Management.” ICES Journal of Marine Science 79 (6): 1730–41.
Sánchez-Maroño, Sonia, Andrés Uriarte, Leire Ibaibarriaga, and Leire Citores. 2021. “Adapting Simple Index-Based Catch Rules for Data-Limited Stocks to Short-Lived Fish Stocks’ Characteristics.” Frontiers in Marine Science 8: 662942.