Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 4300
Title: Spine-based ageing methods in the spiny dogfish shark, Squalus suckleyi: how they measure up
Author: Ian G. Taylor, V. V. Gertseva, Sean E. Matson
Publication Year: 2013
Journal: Fisheries Research
Volume: 147
Pages: 83-92
Keywords: Spiny dogfish shark,Northeast Pacific Ocean,dorsal spine,ageing method,stock assessment,

The second dorsal spine has historically been used for age determination in the spiny dogfish shark. The dorsal spines are located on the external surface of the body and are subjected to natural wear and breakage. Two methods have been developed to account for the worn portion of the spine and extrapolate the lost annuli. We compared the performance of these methods using a large data collection assembled from multiple sources, and evaluated their utility for stock assessment and management of the spiny dogfish shark Squalus suckleyi in the Northeast Pacific Ocean. Our results showed that the two methods produced very different age estimates for older fish with worn spines. Both methods raised significant questions about some aspects of the age estimates produced, and further exploration of techniques to account for worn spine annuli is needed. It is therefore important to develop alternative methods for shark age determination, including those using stained vertebrae.