Estimates of maximum population growth rate and steepness for blue sharks in the north and south Atlantic ocean

Maximum population growth rates and steepness values of the Beverton-Holt stock-recruitment relationship were computed for North and South Atlantic stocks of blue shark (Prionace glauca) based on the latest biological information available gathered at the 2015 Blue Shark Data Preparatory meeting. To encompass a plausible range of values, uncertainty in the estimates of life history inputs (reproductive age, lifespan, fecundity, von Bertalanffy growth parameters, and natural mortality) was incorporated through Monte Carlo simulation by assigning statistical distributions to those biological traits in a Leslie matrix approach. Estimated productivity was high (rmax=0.31-0.44 yr-1 for the North Atlantic stock; rmax=0.22-0.34 yr-1 for the South Atlantic stock) as previously found for these and other populations of this species. Consequently analytically derived values of steepness were also high (h=0.73-0.93 for the North Atlantic stock; h=0.55-0.84 for the South Atlantic stock). These estimates can be used as inputs into both surplus production (rmax) and age-structured (steepness) stock assessment models.