A note on the sensitivity of hake assessments to the choice of the central year for the shift from a primarily M. Capensis to primarily M. Paradoxus fishery

Abstract

At the February 18 meeting of the DWG, there was a request from Industry for further assessment runs for different choices for the central year for the switch from a primarily M. capensis to a primarily M. paradoxus deep-sea trawl fishery. This note reports the results from such assessment runs for a set of choices for this central year ranging from 1940 to 1972. Fig. 1 shows time trends of the proportion of M. capensis in the catch for these alternatives. These results are repeated for three different choices for the natural mortality vector assumed: both the high and low options put forward for the Reference Set (RS) in Rademeyer and Butterworth (2010), and also for the intermediate vector chosen for the Reference Case (RC = RS1). All runs show results for a modified Ricker choice for the stock-recruitment relationship, as for the RC