Age Validation of the Common Thresher Shark (Alopias vulpinus) in the Northeastern Pacific Ocean

Abstract

The purpose of this study was to validate the vertebral band pair deposition rate for Common Threshers (Alopias vulpinus) in the northeastern Pacific Ocean (NEPO). Vertebrae of 37 Common Threshers marked with oxytetracycline (OTC) were collected from tag-recapture efforts and used in this study. OTC tagging occurred off southern California from 1998 through 2013, and time at liberty of the 37 sharks ranged from 0.53 to 3.81 years with an average of 1.27 years (± 0.15 standard error, SE). Shark size at time of injection with OTC ranged from 63 to 128 cm fork length (FL) and from 83 to 168 cm FL at recapture. Vertebral band pair counts distal to the OTC marks indicate one band pair (1 translucent and 1 opaque) form annually for Common Threshers of the size range examined in the NEPO. This finding supports previous age and growth assumptions that have formed the basis of management decisions for the Common Thresher, and will support population dynamics data analyses moving forward.