Bomb dating and age determination of large pelagic sharks

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 59; no. 3; pp. 450 - 455
• Main Authors: Campana, Steven E, Natanson, Lisa J, Myklevoll, Sigmund
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.03.2002; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Age; Agnatha. Pisces; Animal, plant and microbial ecology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Isurus oxyrinchus; Lamna nasus; Marine; Methods and techniques (sampling, tagging, trapping, modelling...); Predators; Sexual maturity; Sharks; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; West Atlantic; Atlantic Ocean; North Atlantic; AN, North Atlantic; Marine environment; Vertebrata; Isotope labelling; Growth; Pelagic organism; Pisces; Interspecific comparison; Determination; Technique; Chondrichthyes; Cervical vertebra; Age
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f02-027

Despite their notoriety and role as apex predators, the longevity of large pelagic sharks such as the porbeagle (Lamna nasus) and shortfin mako (Isurus oxyrinchus) is unknown. Vertebral growth bands provide an accurate indicator of age in young porbeagle, but age validation has never been reported for any large shark species past the age of sexual maturity. Here, we report the first application of bomb radiocarbon as an age validation method for long-lived sharks based on date-specific incorporation of radiocarbon into vertebral growth bands. Our results indicate that porbeagle vertebrae recorded and preserved a bomb radiocarbon pulse in growth bands formed during the 1960s. Through comparison of radiocarbon assays in young, known-age porbeagle collected in the 1960s with the corresponding growth bands in old porbeagle collected later, we confirm the validity of porbeagle vertebral growth band counts as accurate annual age indicators to an age of at least 26 years. The radiocarbon signatures of porbeagle vertebral growth bands appear to be temporally and metabolically stable and derived mainly from the radiocarbon content of their prey. Preliminary radiocarbon assays of shortfin mako vertebrae suggest that current methods for determining shortfin mako age are incorrect.