Stable carbon isotope variations in otoliths of Atlantic cod (Gadus morhua)

Abstract

Stable carbon isotope ratios (13C) were measured in annual layers of otoliths of Atlantic cod (Gadus morhua) from the northeastern Scotian Shelf, Atlantic Canada. Layers deposited during the first 4-6 years of otolith growth increased in 13C from minimum values between -5‰ and -2.5‰ to a maximum near 0‰. This pattern of increase was independent of the years in which the fish was collected. Layers formed after reaching the maximum 13C value displayed decreasing or nearly constant isotopic ratios. Early rise in 13C may be a combined result of (i) decrease in the fraction of metabolic oxidized carbon in the fishes' blood as they mature, relative to the proportion of seawater-derived carbon, and (ii) dietary shift to higher trophic-level foods with higher 13C values. Age of maximum in 13C may be indicative of age of maturity of cod. The maximum 13C value attained by otoliths decreased steadily between 1983 and 1993, while cod stocks in Atlantic Canada were declining. Drop in age of attainment of maximum 13C between 1984 and 1985 coincides with changes in population dynamics of the 4Vs stock. This decrease, as well as the post maximum decrease in 13C values of the mature cod otoliths may represent movement of the fish to deeper waters of the shelf, where 13C of dissolved inorganic carbon is lower.

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

“…δ 13 C values in the otoliths showed a clear pattern of ontogenetic change, as has been observed in other species (Schwarcz et al 1998, Gao & Beamish 2003, Gao et al 2004. Together with the aforementioned increase associated with settlement, significant differences in carbon isotopes in the 12 to 15 cm fish size range compared to the larger size groups further indicate changes in feeding behaviour.…”

“…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. The combination of both analyses provides an insight into the changes experienced by fish related to metabolism, food intake and environment.…”

Age verification, growth and life history of rubyfishPlagiogeneion rubiginosum

“…Carbon isotopes are generally understood to be deposited under non-equilibrium conditions, largely controlled by the endolymph from blood plasma (e.g. Kalish 1991;Schwarcz et al 1998). Hence the metabolic rate of the fish, the diet of the fish and the dissolved inorganic carbon (DIC) of marine waters influence carbon isotopes.…”

“…Approximately 30% of carbon is metabolically derived (Kalish 1991), with the remainder influenced by DIC in seawater (e.g. Schwarcz et al 1998;Solomon et al 2006). The d 13 C changes recorded by the otoliths fall into two intervals: an initial period of rapid enrichment prior to growth zone 10, followed by a period of relatively constant d 13 C. The recorded values and the patterns of d 13 C with increasing age are consistent with that seen in other studies (e.g.…”

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

“…Both DIC and MDC have distinct isotopic signatures and their proportions incorporated into the otolith are a function of the daily metabolism of the fish (Kalish 1991a, Thorrold et al 1997, Schwarcz et al 1998, Weidman & Millner 2000, Solomon et al 2006. Therefore, δ…”