Isotopic Correlation (δ18O versus δ13C) of Otoliths in Identification of Groundfish Stocks

Abstract

AbstractThe management of many marine fish stocks suffers from a lack of genetic data or insignificant genetic differentiations, particularly for the commercially important groundfish along the U.S. Pacific coast. In this study, we investigated a large number of otoliths of various groundfish species from the coasts of Washington and Oregon and analyzed them for stable oxygen (18O/16O, or δ18O) and carbon isotope ratios (13C/12C, or δ13C). The isotopic results and correlation of δ18O versus δ13C of Pacific hake Merluccius productus, sablefish Anoplopoma fimbria, Pacific halibut Hippoglossus stenolepis, and Pacific cod Gadus macrocephalus indicated that most of the groundfish we examined had two or more spawning stocks or subpopulations; the only tested species that might belong to a single coastwide stock was yelloweye rockfish Sebastes ruberrimus. Compared with genetic methods of stock identification, the isotopic signatures of otoliths have distinct advantages in determining (1) a time series to separate the different life stages of marine fish and (2) the oceanographic and environmental conditions to which fish are exposed. Thus, stable isotopic signatures in otoliths appear to be an alternative for marine fish stocks when there is little genetic differentiation between populations or no genetic data are available.