Oral Presentation Australian Society for Fish Biology Conference 2017

Novel methods to assess long-term trends in size and age at maturity in fished stocks (#51)

Henry Wootton 1 , John Morrongiello 1
  1. University of melbourne, University Of Melbourne, VIC, Australia

Age and size at maturation play key roles in determining the fitness of individuals and underpin population demography. Evidence is growing, however, that fishing and climate change can cause dramatic reductions in these key life history parameters by increasing overall mortality and imposing size selectivity on populations. Declines in size and age at maturity can in turn impact on stock productivity as well as result in the loss of valuable phenotypic variation that could buffer populations against environmental perturbations. Age and size at maturity are key parameters in fisheries models, but are currently assumed to be constant through time. Despite the importance of understanding change in maturity schedules, to date studies have largely been restricted to northern-hemisphere, high-value stocks where large observational datasets are recorded. Change in age and size at maturity is currently unassessed in Australian fisheries. However, recent developments in ontogenetic growth-modelling techniques potentially allow us to accurately model age and size at maturity from length-at-age datasets commonly collected by fisheries agencies. This new approach could facilitate the recreation of age and size at maturity over many decades, and drivers of any change then be investigated. I will present the modelling framework and explore its applicability to Australian fisheries. An understanding of current and past trends in maturity is important if we are to accurately estimate population dynamics and recommend future catch limits.