The Generalised Yield Model was used to estimate fishing mortality and spawning stock biomass reference points for the krill fishery in CCAMLR Area 48 consistent with the catch trigger level of 620,000 tonnes. Projections were run with various increased levels of recruitment variability to analyse the sensitivity of the estimates of the reference points to recruitment variability.
The estimates of F and SSB reference points for the krill stock in Area 48 consistent with the catch trigger level are 0.0159 (95 % CIs: 0.00750 – 0.0357) and 97.7 % SSB0 (80 % CIs: 71.6 – 135 %) respectively. In comparison, the F and SSB reference points for the precautionary catch limit of 5.61 million tonnes are 0.186 (95 % CIs: 0.0762 – 0.630) and 75.0 % (47.9 – 113 %) respectively.
The probability of stock depletion increases substantially with increased recruitment variability, though in absolute terms remains negligible. The uncertainty surrounding median estimates of F and SSB reference points for the catch trigger level increases with increased variability in recruitment, though the median estimates are unaffected.
The model terminated prematurely with a 40% increase in recruitment proportion SD. It is likely that this is due to a design feature of the Generalised Yield Model in place to prevent projections from running with potentially significant bias in projected recruitment resulting from poor parameterisation of the beta function.