Age-reading error matrices for Merluccius paradoxus and M. capensis

The revised methodology for hake assessments currently under development requires inputs on the relative biases amongst different readers of hake ages from otoliths, and the extent of variability of these readings. This document details the methodology applied to determine these ageing error matrices

Taking account of the new longline data in the updated Reference Case for the South African hake resource

This paper summarises the assumptions that have been made in previous hake assessments concerning the longline data and makes suggestions for the updated Reference Case

Management procedures for the South African hake resource in the 2000s

Includes bibliographical references.The two-species South African hake fishery (deep-water Merluccius paradoxus and shallow-water M. capensis) has been managed using Operational Management Procedures (OMPs) since 1990. This thesis summarises the development of two OMPs: OMP-2007, which was the basis for the 2007 to 2010 Total Allowable Catch (TAC) recommendations, and OMP-2011, which was first used for the 2011 TAC recommendation and which is intended to extend to 2014. The Operating Models (OMs) used for simulation testing of OMP-2007 were based on the first fully species-disaggregated coast wide assessment of the South African hake resource

Some comments on "Illustration of the role of the pre-1978 species splitting assumptions in hake assessments"

OLRAC (2009) notes the importance of the assumption for the pre-1978 species split of the offshore trawl catches in the assessment results and suggests that the changeover from a mainly capensis fishery to a mainly paradoxus fishery occurred later than what is assumed in the Reference Set

An initial attempt at a spatially structured stock assessment for the South African hake resource including movement based on a gravity model.

The movement model for assessing the South African hake populations which was presented to last year’s review workshop is simplified by applying the “gravity” method to model movement. This reduces the numbering of movement parameters estimated from 234 to 68. This results in recent biomass estimates which are slightly more precise and somewhat lower in both absolute terms and relative to estimated pre-exploitation levels. Areas for possible future research are discussed briefly

2012 Routine update of the South African hake reference case assessment

This paper presents a routine update of the South African hake Reference Case assessment (RS1) (Rademeyer and Butterworth, 2010), including new commercial (catches and CPUE) and survey (abundance estimates and length distribution) data. This analysis does not include post-2009 commercial length distribution data whose finalisation is still in progress

Refinements of the BR CMP as of April 2022

The BR CMP is adjusted in a few respects, most importantly by allowing limited temporal dependence in the values of the control parameters over the first few years of management, to allow for smoother transitions in the TACs from 2022 to 2023. This was necessitated especially by the now higher West area TAC for 2022 included in the updated package. Results are provided for the four basic development tunings, plus one variant for one of those tunings where the default maximum TAC decrease constraint is reduced from 30% to 20%. Suggestions are made of areas for possible improvement in performance, which would require some further refinements of this CMP

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

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