University of Cape Town
ICCAT 70(2).pdf (3.66 MB)

A comparison of initial statistical catch-at-age and catch-at-length assessments of Western Atlantic bluefin tuna.

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posted on 2022-04-25, 08:55 authored by Doug ButterworthDoug Butterworth, Rebecca A Rademeyer

A concern associated with existing Atlantic bluefin tuna age-based assessments using Virtual Population Analysis (VPA) is that the catch-at-age data inputs are obtained by the cohort-slicing method, which is approximate and might introduce appreciable bias into the results. Current custom in such circumstances is rather to fit the assessment model directly to the basic catch-at-length data available, under the assumption of invariance of the distributions of length-at-age of the fish over time, with statistical models used to formulate the likelihoods maximized in the model fitting process. Initial results are presented for a process of comparing the 2012 ICCAT SCRS VPA assessment of the western stock with first a statistical catch-at-age assessment approach which also uses the same cohort sliced catch-at-age inputs, and then a statistical catch-at length method which fits instead to catch-at-length distributions.



Department of Mathematics and Applied Mathematics, University of Cape Town