Environmental influences on the recruitment process inferred from otolith stable isotopes in Merluccius merluccius off the Balearic Islands

Abstract

Oxygen (δ 18 O) and carbon (δ 13 C) isotope ratios in sagittal otoliths were analysed in recruits and juveniles of European hake Merluccius merluccius L. caught in the northwest (Sóller, SO) and south (Cabrera, CA) of the Island of Mallorca (western Mediterranean) over 2 consecutive years (2003 and 2004). The analytical method used allowed data to be gathered on both environmental and trophic conditions experienced by fish during the pelagic early life stages (registered in the composition of the inner part of the otolith, core area) and the demersal aggregations of recruits (at the otolith edge). Results on the seasonal variation of oxygen isotope signatures at the edge of fish otoliths captured in SO and CA indicated different vertical migration behaviours of hake between the bottom and the thermocline. δ 13 C showed a clear ontogenetic pattern between the core area and the edge, confirming the differences in diet from the early stages to post-recruits. The seasonal analysis of δ 13 C data from the otolith edge indicated that fish from the early stages in June 2003 encountered poorer trophic resources, which resulted in poor fish condition and subsequent poorer recruitment. The estimated temperature from the core area of otoliths showed lower temperature regimes in the 2002 hatching season compared to the 2003 hatching season, which could be a possible explanation for the observed differences in success of subsequent recruitment.

Development of a species-specific fractionation equation for Arctic charr (Salvelinus alpinus (L.)): an experimental approach

“…They noted differing tendencies in the predictive error of the two equations, which indicated the species-specific fractionation relationship for Patagonian toothfish had a distinctively different slope. Hidalgo et al (2008), however, used the cod-specific fractionation equation estimated by Høie et al (2004) on European hake (Merluccius merluccius (L.)), also a Gadiform, and reproduced temperatures within the range expected from temperature measurements of the water. Høie et al (2004) suggested physiological adaptations to specific environmental conditions might influence the otolith isotopic composition and result in differences in oxygen fractionation.…”

Stock discrimination of European conger eel (Conger conger L.) using otolith stable isotope ratios

“…The relative contribution of these various factors to otolith carbon isotope ratios is likely to vary both in space and in time, and among species. Both isotope ratios have been used successfully as natural tags for fish stock discrimination studies (Edmonds and Fletcher, 1997;Bastow et al, 2002;Gao et al, 2004;Huxham et al, 2007;Dufour et al, 2008;Hidalgo et al, 2008).…”

Age verification, growth and life history of rubyfishPlagiogeneion rubiginosum

“…The initial rapid enrichment in juvenile and young adult fish is believed to result from an increase in the trophic level of the fish with age, probably concomitant with a shift in diet to higher trophic levels (e.g. Schwarcz et al 1998;Begg & Weidman 2001;Hidalgo et al 2008). Subsequently, metabolic rate (and metabolic contribution) would be expected to decrease with age (Schwarcz et al 1998).…”