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Advances in the aquatic sciences

Age under-estimation in New Zealand porbeagle sharks (Lamna nasus): is there an upper limit to ages that can be determined from shark vertebrae?

Malcolm P. Francis A D , Steven E. Campana B and Cynthia M. Jones C
+ Author Affiliations
- Author Affiliations

A National Institute of Water and Atmospheric Research Ltd, Private Bag 14901, Wellington, New Zealand.

B Bedford Institute of Oceanography, PO Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada.

C Old Dominion University, Norfolk, VA 23529-0456, USA.

D Corresponding author. Email:

Marine and Freshwater Research 58(1) 10-23
Submitted: 28 April 2006  Accepted: 16 October 2006   Published: 30 January 2007


Annual deposition of growth bands in vertebrae has been validated for many shark species, and is now widely regarded as the norm. However, vertebrae are part of the shark’s axial skeleton, and band deposition may stop in old sharks when somatic growth ceases. We aged vertebral sections from New Zealand porbeagle sharks (Lamna nasus) under reflected white light and using X-radiographs. Bomb radiocarbon assays supported vertebral age estimates up to ~20 years, but not at older ages. The results suggest that older porbeagles were under-aged by as much as 50% from vertebral band counts, presumably because band width declined to a point where it became unresolvable. This has important implications for growth studies on other long-lived sharks. Estimated ages at sexual maturity were 8–11 years for males and 15–18 years for females, and longevity may be ~65 years. New Zealand and North Atlantic porbeagles differ in these parameters, and in length at maturity and maximum length, suggesting genetic isolation of the two populations.

Additional keywords: bomb radiocarbon, longevity, maturity, validation.


We thank New Zealand Ministry of Fisheries observers for collecting vertebral samples and associated data from tuna longliners, and Caoimhghin Ó Maolagáin (NIWA) for preparing the vertebral sections, X-radiographs and images. Warren Joyce prepared the samples for radiocarbon assay, and Lisa Natanson and Silver Bishop provided valuable input and advice on reading vertebrae. We thank the staff of NOSAMS at WHOI for their expertise in carrying out the radiocarbon assays. Helpful comments were received from two anonymous reviewers. Funding was provided by the Ministry of Fisheries under project TUN2002/01, and National Science Foundation grant OCE9985884 to SEC and CMJ.


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