X-rays of vertebral half-centra, and X-rays and transmitted white light examination of caudal thorns, were used to estimate the ages of Amblyraja georgiana from the Ross Sea. Caudal thorns viewed with transmitted white light provided the clearest growth bands, but reading precision was low, producing uncertain age estimates. Furthermore, annual deposition of thorn bands has not been validated. The maximum age was 14 years, but this should be regarded as a conservative estimate of longevity because of the possibility that thorn growth ceases in large individuals. Von Bertalanffy growth curves are provided for females, males, and both sexes combined. There was no obvious difference between the sexes, so the curve for both sexes provides the best available representation of growth in the species: Lt = 70.8(1-e-0.308[t+1.10]), where Lt is the pelvic length (PL) in centimetres at age t. Applying this growth curve to the estimated lengths at maturity for males and females (64 cm and 66– 69 cm PL respectively) produced estimated ages at maturity of 6–7 years for males and 8–11 years for females. These estimates are near the middle to upper end of the range of ages at maturity for skates worldwide.
Document Number:
WG-FSA-04/29
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Abstract