Publication
Age validation of Black Rockfish, Copper Rockfish, and Cabezon using secondary ion mass spectrometry (SIMS) to elucidate seasonal patterns in otolith stable oxygen isotopes
Publisher:
Springer Science and Business Media LLC
Date:
13-02-2023
DOI:
10.1007/S10641-023-01392-3
Abstract: Stock assessors commonly use models that incorporate biological data such as fish length and age to determine the status of fish stocks and how different management scenarios affect stock size. Ages used in assessment models need to be accurate and precise because ageing error can affect many model inputs and potentially result in stock mismanagement. Despite the requirement for sound age data, few studies have investigated accuracy of ages for groundfish captured in coastal nearshore waters off Oregon, USA. In this study, we validate otolith ages for Black Rockfish ( Sebastes melanops ), Copper Rockfish ( Sebastes caurinus ) and Cabezon ( Scorpaenichthys marmoratus) , three species with recreational and commercial importance to Oregon. Ages obtained by traditional break-and-burn methods were validated using secondary ion mass spectrometry (SIMS) to examine otolith stable oxygen isotope ratios (δ 18 O) over a fish’s lifetime. This technique relies on the inverse relationship that exists between otolith δ 18 O and ambient water temperature, and independent counts of δ 18 O maxima should be comparable to ages obtained by visual counts of otolith growth marks laid down during cold water periods. Locations of δ 18 O maxima in otolith chronologies matched well with locations of visual growth marks in otoliths of all three species, maxima counts were strongly positively correlated with age, and variation in otolith δ 18 O decreased with age. However, significant variability in the δ 18 O chronologies caused by variability in intra-seasonal upwelling and resulting water temperature variations made maxima counts difficult in several s les. Correct interpretation of chronologies required knowledge of location of the first annulus, the compression of growth zones with age, and an assumption of the seasonal litude of the ambient water δ 18 O.