Effect of missing values from the Canadian spring and fall surveys of NAFO Divisions 3LNO on the calculation of the TAC using the Greenland halibut HCR

• Main Authors: Regular, P M, Butterworth, Douglas, Rademeyer, Rebecca
• Format: Report
• Language: unknown
• Published: Department of Mathematics and Applied Mathematics 2022
• Subjects: Greenland halibut; Missing surveys; NAFO; TAC; Greenland
• Online Access: http://hdl.handle.net/11427/38239

To test the impact of ignoring recent missing abundance indices for Greenland Halibut in NAFO divisions 2+3KLMNO on applying the accepted HCR for this population to provide a TAC recommendation for 2023, the impact of similar exclusions in the past is examined and found to be small. To further test of the impact of the missing 2021 index from the Canada Fall 3LNO survey, a range of pessimistic to optimistic abundance index values were assumed to assess the plausible range of impact this one value might have on the TAC computation. The range of the resultant TACs is small, and the difference of the impact of TACs at either end of this range on exploitable biomass projections for the next year is found to be negligible. Hence, it is argued, the minimalist and straightforward approach of simply ignoring the missing 2021 Canadian Fall 3LNO result in the four-survey version of the HCR agreed last year would be a defensible and appropriate approach to the required adjustment of the implementation of this HCR to provide a TAC recommendation for 2023.