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interpretation of vertebral growth marks as annuli in the sandbar shark carcharhinus plumbeus: analysis of vertebrae of captive specimens

Published online by Cambridge University Press:  06 October 2005

borja torres
Affiliation:
l'oceanogràfic, ciutat de les arts i de les ciències, grupo parques reunidos, junta de murs i valls, s/n, 46013, valencia, spain
gabriel morey
Affiliation:
csic/uib—institut mediterrani d'estudis avançats, miquel marquès 21, e-07190 esporles (illes balears), spain, e-mail: gabriel.morey@uib.es; javier.tomas@uib.es
javier tomás
Affiliation:
csic/uib—institut mediterrani d'estudis avançats, miquel marquès 21, e-07190 esporles (illes balears), spain, e-mail: gabriel.morey@uib.es; javier.tomas@uib.es
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Abstract

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four captive specimens of sandbar shark carcharhinus plumbeus from the l'oceanogràfic aquarium (valencia, spain) were studied: one adult female (192 cm total length [tl]) reared for five months, her two new born pups (a female, 61 cm tl and a male, 60 cm tl), and one juvenile female, born in captivity, dead at nine months of age (90 cm tl). comparative measurements of length and diameter of vertebrae from three different regions of the vertebral column showed that vertebrae above the pelvic fins (nos. 59–63) are the biggest in this species. consequently, these vertebrae are preferred for age estimation given that growth marks are easier to identify. the only present mark in the vertebrae of the two neonate specimens was at the edge and was interpreted as the birth mark. a mark at a similar distance was present in the vertebrae of the juvenile and adult females.

adult female vertebrae analysis shows 23 marks without any variation in the banding pattern distribution during free-range growth and short period of captivity. the juvenile individual shows two clear growth marks developed after birth. the presence of these marks in a 9-month old individual suggests that the counting of all vertebral growth marks as annuli may result in the overestimation of age for this shark species.

Type
research article
Copyright
© 2005 marine biological association of the united kingdom