Stock identification of Atlantic blue shark (Prionace glauca)

We conducted a review of all available information on genetics, tagging, and movement of blue shark (Prionace glauca) in the Atlantic Ocean since 2015 to evaluate stock structure and inform the upcoming stock assessment. There is evidence of a north-south movement across the equator by larger, older individuals particularly in the eastern Atlantic. However, the observed movement rates between the North and South Atlantic appear to be low enough to consider separate spatial units for stock assessment. When considering genetics, several studies found complete genetic homogeneity across the Atlantic Ocean (and globally in some cases). However, small sample size combined with the pace of drift of genetic traits and population size may impact results. Additional studies have found genetic differentiation within the Atlantic Ocean, and between the Atlantic Ocean and the Mediterranean Sea, which further confounds splitting stocks based on genetics. Outside of the Mediterranean Sea, there is no new evidence to suggest that further splitting of the Atlantic Ocean beyond a northern and southern stock is required at this time.