Age, growth, and sexual maturity of the deepsea skate, Bathyraja abyssicola
Research into the age, growth, and reproductive characteristics of chondrichthyan fishes has increased substantially over the past couple of decades. This study set out to estimate age deepsea skate, Bathyraja abyssicola, using vertebral centra and caudal thorns, estimate length at age, and determine length at maturity. Sixty-three specimens of B. abyssicola (n=29 males; n=34 females) were taken on National Marine Fisheries Service bottom trawl surveys between 2001 and 2012. Information derived and structures collected from these samples included sex, maturity class, total length, caudal thorns, and vertebrae. Ageing methods attempted include histology and gross sectioning (vertebral centra) and surface staining (caudal thorns). Moderate success with centra sectioned using the histological method allowed some inference to be made into life history characteristics. Deepsea skates appear to have slow average growth (26 mm yr-1 ±5.41, 95% c.i.) and mature at a large size (males: TL50 = 1175.4 mm, females: TL50 = 1267.3 mm). Band pair counts were not validated as true ages. Males from which growth bands could be enumerated were smaller (𝑛 = 10, 𝑥̅ = 718 mm, SD = 209 mm) on average than that for females (n = 7, 𝑥̅ = 990 mm, SD = 319 mm). This study provides the first attempt to assess B. abyssicola age, growth rate, and sexual maturity traits – information needed for informed skate management.
Funding for this work was provided by the Pollock Conservation Cooperative via the Alaska Education Tax Credit Program.