Assessments of species in the Australian South East Fishery can be sensitive to the method used to convert from size- to age-composition data

Information about the age-structure of the catch is one of the primary inpu ts to many of the methods of stock assessment currently applied to SEF spec ies. Two methods for calculating the catch-, mean length-, and mean mass-at -age matrices from the data collected from the fishery are outlined. These methods are illustrated by applying them to data for blue grenadier, Macrur onus novaezelandiae, and eastern school whiting, Sillago flindersi. The ass essment and risk analysis results for blue grenadier are highly sensitive t o the choice of method, whereas those for eastern school whiting are not. I t is recommended that a method that allows for inter-annual variation in me an length- and hence mass-at-age should be the standard for SEF stock asses sments but that sensitivity to alternative methods needs to be examined rou tinely.