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There is a paucity of age data for chondrichthyan fishes owing, in large part, to limitations in traditional age estimation methods. Fourier transform near-infrared (FT-NIR) spectroscopy has shown promise as an alternative, more efficient method for acquiring age data from chondrichthyans. However, studies are limited to sharks in the southern hemisphere. We explored FT-NIR spectroscopy to predict age for a batoid species in the northern hemisphere. The longnose skate (Raja rhina) is one of a small number of batoids for which annual band periodicity in vertebral centra has been validated, allowing for traditional age estimation and making it an ideal candidate for this study. We fit a multivariate partial least-square predictive model between FT-NIR spectra collected from vertebral centra and traditional age estimates, and tested model predictive skill by using external validation. Using FT-NIR spectroscopy, we were able to predict age for longnose skates between the ages of 1 and 14 years with precision and bias near equal to those of traditional methods in less than a quarter of the time. These results support potential for FT-NIR spectroscopy to increase the amount of age data available for assessments used to inform the conservation and management of this sensitive group of species. We evaluated whether we could more rapidly estimate the age of longnose skates using a new approach, namely, shining near infrared light through their vertebrae. This approach produced age estimates comparable to those from traditional methods for most of the included age range, and in a quarter of the time. Findings show promise for increasing the amount of age data available for age-structured population assessments to monitor the status of this species. [ABSTRACT FROM AUTHOR]

Historically, Pacific spiny dogfish (Squalus suckleyi) have been aged using dorsal fin spines, a method that was validated through bomb radiocarbon analysis and oxytetracycline tagging. However, ages generated using this method generally have poor precision and require estimation of missing growth bands in eroded spines, prompting a search for improved age determination methods. In the present study, spiny dogfish were aged using the historical spine method and a new method involving stained thin sections of vertebral centra. Results of an inter-laboratory exchange demonstrated the need for readers to calibrate ageing criteria with a reference collection before reading structures, a practice that yielded significant improvements in between-reader precision of spine band pair counts. After calibration, the primary readers examined the full sample set. The two structures yielded similar age estimates for younger animals, but centrum estimates were consistently younger than spine estimates after age-10. Although further work is necessary to fully explore potential reasons for the observed bias, such as centrum size and location within the vertebral column, at the present time centra are not a suitable alternative to dorsal fin spines for age determination of Pacific spiny dogfish .10 years of age. [ABSTRACT FROM AUTHOR]