Stable isotopic comparison in otoliths of juvenile sablefish (Anoplopoma fimbria) from waters off the Washington and Oregon coast

摘要

Genetic methods have been extensively used in the examination of fish population composition and structure. However, it is generally not easy to determine the stock structure of marine fish using the genetic markers, particularly given the large population size and wide spread distribution of long-lived fish. As an alternative, sagittal otoliths of juvenile sablefish (Anoplopotna fimbria) along the Washington and Oregon coast were collected and analysed for stable oxygen and carbon isotope ratios. 5180 values of the otolith nuclei ranged from -1.3 to +0.1 VPDB, whereas delta(13)C of the same otoliths ranged from -8.7 to -6.2%o VPDB. In contrast with the lower isotopic composition in early life, delta(18)O and delta(13)C values of sablefish otoliths at adult stage were levelled at about 2.0parts per thousand VPDB and -1.0parts per thousand VPDB, respectively. From north to south three different spawning stocks or subpopulations were recognized, with a gradual decrease in otolith delta(13)C and trophic level changes in sablefish's diet. Therefore, stable isotopic records of otoliths may be a potential supplement for genetic markers when studying the stock structure of marine fish.