Abstract Age estimation is an issue for the shortfin mako, Isurus oxyrinchus, because of dis-agreement on vertebral band-pair deposition periodicity. In the 1950s–1960s, thermonuclear testing released large amounts of radiocarbon into the atmosphere, which diffused into the ocean through gas exchang...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.610.9147 http://nefsc.noaa.gov/nefsc/Narragansett/sharks/refpdfs/Ardizzone et al 2006.pdf |
| Summary: | Abstract Age estimation is an issue for the shortfin mako, Isurus oxyrinchus, because of dis-agreement on vertebral band-pair deposition periodicity. In the 1950s–1960s, thermonuclear testing released large amounts of radiocarbon into the atmosphere, which diffused into the ocean through gas exchange. This influx created a time-specific marker that can be used in age val-idation. Annual band-pair deposition in the por-beagle, Lamna nasus, was validated in a previous study and indicated preliminary annual deposi-tion in the shortfin mako, using four samples from one vertebra. In the present study, age estimates from 54 shortfin mako vertebrae collected in 1950–1984 ranged 1–31 years. Ageing error be-tween readers was consistent, with 76 % of the estimates ranging within 2 years. Twenty-one D14C values from eight shortfin mako vertebrae (collected in the western North Atlantic in 1963– 1984) ranged –154.8 & to 86.8&. The resulting conformity with the D14C timeline for the por-beagle supported annual band-pair deposition in vertebrae of the shortfin mako. |
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