Comparative Overview of Western Atlantic Bluefin Tuna Growth and Catch-at-Age Composition, a 30 Year Perspective

Growth of Atlantic bluefin tuna has been studied for more than fifty years in both the eastern and western Atlantic.  Age estimates have been generated using a variety of different structures and protocols resulting in a set of growth parameters with a high variance.  Asymptotic length, for example, ranges from 266cm to 455cm.  We hypothesize a large degree of this variability is due to different methodologies, structures used, interpretation of annuli and potential sampling bias.  The current growth curve used for the western assessment estimates uses both otolith aging and length frequency data, some of which was collected more than forty years ago.  Given the substantial changes in growth observed with southern bluefin tuna, an updated assessment of growth is warranted.  Here, using a large collection of otoliths (n>1000) sampled from bluefin tuna from 2010-2012 in the Gulf of Maine (100cm – 310cm), we construct a new growth curve and compare these growth parameters to historical studies.  Furthermore, we estimate catch at age composition using these different growth parameters, compare results across years and evaluate the implication of these different catch at age compositions for assessment.