New insights into the reproductive biology of the blue shark (Prionace glauca) in the South Atlantic Ocean

The blue shark (Prionace glauca) is one of the most abundant and wide-ranging shark species in the world, and also one of the most heavily fished and traded. However, available information is disproportionately distributed across its range, and many aspects of its biology are still poorly understood, limiting our capacity to assess stock status and develop adequate management strategies. Here, we analyze an extensive data set from the southwestern Atlantic Ocean based on commercial longline fisheries and address several aspects of its reproductive ecology and population structure. We combine our results with an exhaustive literature review to provide new insight into the species' reproductive cycle in the South Atlantic. Male and female blue sharks reach maturity at the same size and reproduce annually, but mating, fertilization, and parturition seasons are loosely defined in time. Migratory behavior, sperm storage, and temperature could affect these seasons, causing time lags among groups of females across the year. Females complete their reproductive cycle with or without performing largescale migrations into equatorial waters, giving birth on average to 37 pups after 9-11 months of gestation. Parturition grounds occur in cold-productive southern waters, which may also act as nursery grounds for young juveniles. This study provides new biological information and raises new and many yet unanswered questions regarding the intricacies of its reproductive cycle, female migration, and stock structure, including the consideration of the southwestern Atlantic region as a potential management unit. Our study can inform future stock assessments and management in the South Atlantic and identifies areas where future research efforts are most needed.