Initial Applications of Statistical Catch-at-Age Assessment Methodology to Atlantic redfish ...

• Main Authors: Rademeyer, Rebecca A, Butterworth, Doug
• Format: Report
• Language: unknown
• Published: University of Cape Town 2023
• Subjects: Biological mathematics; Biostatistics; Applied statistics; Atlantic redfish
• Online Access: https://dx.doi.org/10.25375/uct.24545923.v1; https://zivahub.uct.ac.za/articles/report/Initial_Applications_of_Statistical_Catch-at-Age_Assessment_Methodology_to_Atlantic_redfish/24545923/1

Age structured production model assessments are explored for four redfish populations. The reason for introducing age-structure into the models is to allow a sounder reality check of the estimates of the survey catchability coefficients q that result when the models are fit to data. The data fitted are the survey abundance trends plus catch-at-length information from both surveys and the commercial catches. The catches-at-length are used to estimate selectivity-at-age relationships, though some assumptions are required, particularly for the commercial information which is not available in species disaggregated form. Only for S. fasciatus in Unit 3 is the survey trend compatible with the expected impact of past catches in terms of a simple density-dependent population model, and the associated assessment results could be used to inform reference point determination for this population. However for the other three populations considered ( S. mentella and S. fasciatus in Units 1+2 and S. fasciatus in 2J3K) ...