Details of Status Assessment for North Atlantic Minke Whales

The assessment of North Atlantic common minke whales is based on the models and methods used for Implementation Simulation Trials for the Aboriginal Whaling Management Procedure for West and East Greenland (IWC, 2019).  For assessing status, two different sets of stock structure assumptions are included among the base-case trials.  These models posit either two or three distinct stocks found in the sub-areas in Figure 1. The stock structure hypotheses are:

   1) There are three stocks 'W', 'C', and 'E'. The 'W' stock consists of two sub-stocks ('W-1' and 'W-2') and the 'E' stock consists of two sub-stocks ('E-1' and 'E-2').

   2)  There are two stocks 'W*', and 'E'. The 'W*' stock consists of two sub-stocks ('W' and 'C*') where the 'C*' stock is the same as the 'C' stock for hypothesis 1 except that the whales that occur primarily in the 'WG' sub-area are also part of this stock. The 'E' stock is defined as for stock hypothesis I.

Figure 1: Map of the North Atlantic showing the sub-areas defined for the North Atlantic Minke whales.

For each stock structure model, there are two base-case trials using different levels of MSYR.  Trial specifications are given in Table 1, extracted from the full set of trials specified by IWC (2017). 

Table 1: Trials used for assessing North Atlantic common minke whales.

Notwithstanding the stock structure definitions used for assessment modelling (including stock mixing parameters), there are many choices for how to summarize the results in a manner that best addresses Commission interests.  For this assessment, results are summarized by Medium Area, namely W (WC+WG), C (CG+CIC+CIP+CM), and E (ESW+ESE+EB+EW+EN).

Table 2 summarizes summary statistics by trial for the base-case trials. The following statistics are shown:

·       current (2022) 1+ abundance;

·       current (2022) depletion (number of animals aged 1+ and older relative to 1+ carrying capacity);

·       20-year total change in 1+ abundance, 2002-2022, expressed as a percentage.

Results include the median value and 5^th and 95^th percentiles for each trial.

Table 3 provides the overall assessment estimates, i.e., the average medians across trials, and the pooled 90% intervals for each statistic, where values are pooled over trials and simulations within trials.

 Table 2: Summary statistics, by Medium Area and overall, for each trial

Table 3: Summary statistic medians averaged over trials, and upper and lower bounds for pooled 90% intervals for the summary statistics

References

IWC. 2019. Report of the Scientific Committee, Annex E: Report of the Standing Working Group on Aboriginal Subsistence Whaling Management Procedures, Appendix 4: The AWMP/RMP Implementation Simulation Trials for the North Atlantic Minke Whales. J. Cetacean Res. Manage 18(Suppl.): 152-168.