Bomb Dating and Age Estimates of Big Skate (Beringraja binoculata) and Longnose Skate (Raja rhina)

Directed fisheries for big (Beringraja binoculata [formerly Raja binoculata]) and longnose (R. rhina) skates have re-emerged in the Gulf of Alaska, but due to their life history traits (i.e. extreme low fecundity, long life span, slow growth, late age at maturity) these species may be at risk of population declines and overexploitation. While age and growth estimates have been produced for skate populations in the Gulf of Alaska, British Columbia and California, studies have not produced similar results, highlighting the need for age validation. Using archived specimens of big and longnose skates collected in 1980 and 1981 we conducted an age validation study using bomb radiocarbon (¹⁴C). Although longnose skates were not as old as originally estimated (birth years 1967-1976) the Δ¹⁴C values overlapped the mid to top portion of the reference curve. Age estimates based on vertebral band counts appear to be accurate with low inter-reader bias and improved precision for unstained sections (APE=5.99) versus (APE=10.17) for stained. Archived big skates were born post-bomb signal so the age methodology cannot be validated with this approach.