Temperature-dependent fractionation of stable oxygen isotopes in otoliths of juvenile cod (Gadus morhua L.)

Abstract

2004. Temperature-dependent fractionation of stable oxygen isotopes in otoliths of juvenile cod (Gadus morhua L.). e ICES Journal of Marine Science, 61: 243e251.Analysis of stable oxygen isotopes in otoliths is a promising technique for estimating the ambient temperature experienced by fish, but consistent equations relating temperature and fractionation of stable oxygen isotopes in otoliths among different fish species are lacking. Juvenile cod were reared at constant temperatures from 6 to 20(C and the sagittal otoliths were analysed for oxygen isotope values. We determined that temperature-dependent fractionation of oxygen isotopes in the otoliths was close to that reported for inorganic aragonite at low temperatures, but there were deviations from oxygen isotope fractionation equations for otoliths of other species. The linear relationship between oxygen isotope value in the cod otoliths and temperature was determined to be: 1000 Ln a ¼ 16:75ð10 3 TK ÿ1 Þ ÿ 27:09. Temperature estimates with 1(C precision at the 95% probability level require a sample size of R5 otoliths. Only an insignificant amount of the variance in the data was due to variance between left and right otolith, and due to repeated measurements of otolith subsamples. This study confirms that stable isotope values of cod otoliths can give precise and accurate estimates of the ambient temperature experienced by fish.

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

“…However, our estimated values of δ c -δ w are consistent with previous studies on different fish species carried out in laboratory conditions (Kalish 1991b, Thorrold et al 1997, Gao et al 2001, Høie et al 2004b). All those investigations concluded that deposition occurs at or near equilibrium in fish otoliths.…”

“…Since no oxygen isotope fractionation relationship has been established for the European hake, temperature was estimated using the equation resulting from a robust study on another gadoid, Atlantic cod Gadus morhua L. (Høie et al 2004b), with a 0.95 ‰ prediction limit range:…”

“…During the night, large numbers of hake larvae gather at 60 to 80 m depth, while during the day vertical distribution can extend up to 10 m from the surface (Sabatés 2004). The temperature estimates from the otolith edge for fish caught in SO were systematically higher than for fish caught in CA, and these significant differences stand irrespective of the error of measurement (between 1.1 and 1.3°C; Høie et al 2004b). Values and seasonal variability of estimated temperatures in SO are consistent with temperature variation above the thermocline, whereas temperatures estimated for fish from CA seem more closely associated to the limited temperature variations that characterise the depths below the thermocline (Fig.…”

“…Studies estimating temperature-dependent fractionation of oxygen isotopes in otoliths have so far concluded that deposition occurs at or near equilibrium; that is, only temperature explains variation in isotopic fractionation between the water and the carbonate of the otolith (Høie et al 2004b). Moreover, 13 C/ 12 C ratios (δ 13 C) measured in fish otoliths have been used to study metabolic rates and are relevant in the study of ontogenetic changes of trophic levels in the food chain (Schwarcz et al 1998, Gao & Beamish 2003.…”

Otolith geochemistry indicates life-long spatial population structuring in a deep-sea fish, Coryphaenoides rupestris

“…Høie et al 2004b) and the relative metabolic activity (Sherwood & Rose 2003) of the individual (Kalish 1991a,b, Thorrold et al 1997, Campana 1999, Høie et al 2004a, Shephard et al 2007). As the otolith aragonite grows, oxygen isotopes are precipitated in equilibrium with the endolymph fluid, which is itself in isotopic equilibrium with ambient seawater (Kalish 1991a, Thorrold et al 1997, Campana 1999, Høie et al 2004a.…”