Otolith elemental signatures reflect residency in coastal water masses

Abstract

We examined variability in otolith chemistry of wild caught fish in relation to in situ temperature and salinity within the California Current System. Barium, magnesium, and iron from the most recent growth zone in otoliths differentiated pelagic juvenile shortbelly rockfish (Sebastes jordani) residing in water masses with distinct temperature and salinity properties from central and southern California spanning nearly 500 km of coastline. The 3-element signature also discriminated fish that resided in different water masses that were associated with mesoscale cyclonic eddy circulation in the Santa Barbara Channel. Variability in otolith chemistry reflected the spatial patterns of both horizontal gradients and vertical gradients in water mass properties related to circulation. Although we found that the concentrations of particular elements in otoliths were correlated to ambient temperature or salinity, we suggest that these parameters are more useful as an identifying signature of distinct water masses associated with unique otolith signatures rather than as factors directly affecting otolith chemistry. Other factors varying among the water masses or among the fish populations residing in the water masses may also affect otolith chemistry. We discuss how oceanographic phenomena associated with the 1997-1998 El Niño and the persistent, recirculating eddy in the Channel may have affected coastal ocean conditions and variation in otolith chemistry of fish in the study area.

Regional Patterns in the Otolith Chemistry of Juvenile Spotted Seatrout (Cynoscion nebulosus) Differ under Contrasting Hydrological Regimes

“…Variation in salinity is one of the most frequently cited environmental correlates in studies of otolith chemistry [11,13,30,50]. In the present study, the regions were equally discernible in both years despite uncoupling between salinity and otolith chemistry under the drier regime in 2006.…”

Evaluating chemical signatures in a coastal upwelling region to reconstruct water mass associations of settlement-stage rockfishes

“…For instance, it has been estimated that up to 98% of Ba/Ca Otolith is de rived from ambient water (Walther & Thorrold 2006), and relative to other elements, the short turn-over time of Ba in the bodies of fishes indicates a strong potential for Ba/Ca Otolith to reflect short-term changes in the Ba concentration of the ambient water (Sturrock et al 2012). Several studies have recognized the potential for otolith chemistry to evaluate fish associations with upwelling regions or water masses; few studies, however have validated these signatures in otoliths or applied them in ecological research (Patterson et al 2004, Kingsford et al 2009, Nishimoto et al 2010, Lin et al 2013, Woodson et al 2013.…”

Phenotypic plasticity in wild marine fishes associated with fish-cage aquaculture

“…This differentiation was characterised by estimating the canonical discriminant functions of the warp scores, standardised by within-score variances. The classification accuracy of each CDA was evaluated by the leave-one-out cross-validation procedure (Nishimoto et al, 2010). To establish the bias of the analysis, Cohen's kappa (j) statistic was used.…”