Ian G. Taylor

Population dynamics and status of striped marlin (Kajikia audax) in the western and central northern Pacific Ocean

AnewunderstandingofthestructureofstripedmarlinstocksinthePacificOceanwasthebasisforestimating the population dynamics in the western and central northern Pacific (1975-2010). Dynamics were estimated using large- scale spatial data and a fully integrated length-based and age-structured model. The model used fishery-dependent catch, size composition and catch per unit effort (CPUE) as likelihood components. Time-varying selectivity patterns were used inthemodellingtoaccount forchangesinfishing practices.Estimatesoffishing intensityshowedapatternofexploitation generally exceeding the levels associated with maximum sustainable yield (MSY). Estimates of spawning biomass and recruitment described a population that was relatively stable near biomass levels associated with MSY until the 1990s, when recruitment declined and biomass levels fell below those associated with MSY. The reduction in recruitment could beexplainedbyalossofspawningbiomassandpotentiallychangesinenvironment.Thefutureprospectsofrebuildingthe stock will depend on the relative importance of the roles maternal biomass and environment play in determining recruitment strength. Additional keywords: environmental versus maternal effects, integrated modelling, time-varying selection.

Incorporating movement in the modelling of shark and ray population dynamics: approaches and management implications

Abstract The explicit incorporation of movement in the modelling of population dynamics can allow improved management of highly mobile species. Large-scale movements are increasingly being reported for sharks and rays. Hence, in this review we summarise the current understanding of long-scale movement patterns of sharks and rays and then present the different methods used in fisheries science for modelling population movement with an emphasis on sharks and rays. The use of movement data for informing population modelling and deriving management advice remains rare for sharks and rays. In the few cases where population movement was modelled explicitly, movement information has been solely derived from conventional tagging. Though shark and ray movement has been increasingly studied through a range of approaches these different sources of information have not been used in population models. Integrating these multiple sources of movement information could advance our understanding of shark and ray dynamics. This, in turn, would allow the use of more adequate models for assessing stocks and advising management and conservation effort.