Meeting Abstract
Policies guiding sustainable fisheries require accurate estimates of population size and productivity. Age-based characters such as age at sexual maturity and longevity are crucial to correctly determine a population’s status and susceptibility to over-exploitation. Vertebral centra are most commonly used to age elasmobranchs because the centra grow in proportion with body size and the number of band pairs (a proxy for age) deposited in the centra increases with time. However, if centra in different positions along the vertebral column deposit material at different rates, then band pair counts will vary within an individual suggesting that deposition may be a result of functional demands, e.g. swimming, rather than age. This study examined centrum morphology and number of band pairs along the vertebral column within individuals, between sexes and size classes (immature, near size-at-maturity, mature) and among five batoid species: little skate, Leucoraja erinacea, winter skate, L. ocellata, barndoor skate, Dipturus laevis, Atlantic stingray, Dasyatis sabina, and round stingray, Urobatis halleri. Centrum morphology was measured in three directions (dorso-ventral height, medio-lateral width, and rostro-caudal length) for vertebrae 1 through 80 along the column. Band pair counts were made on every 5th vertebrae. Determining the variation in centrum morphology along the vertebral column and through ontogeny is vital for reliable use of vertebral centra for ageing elasmobranchs and thus for assessing population demographics.
