Zinc isotope composition of enameloid, bone and muscle of gilt-head seabreams (Sparus aurata) raised in pisciculture and their relation to diet
Jeremy McCormack, Klervia Jaouen, Nicolas Bourgon, Guy Sisma‐Ventura, Théo Tacail, Wolfgang Müller, Thomas Tütken
Abstract
Abstract The isotope ratios of zinc ( 66 Zn/ 64 Zn expressed as δ 66 Zn), a vital nutrient, increasingly demonstrate trophic discrimination among vertebrates, making δ 66 Zn a valuable dietary proxy for ecological, archaeological, and palaeontological studies. Given the novelty of the methodology, tissue-diet and tissue-tissue zinc isotope fractionation factors remain poorly understood and have so far only been studied in a few terrestrial mammals. Here, we investigate δ 66 Zn compositions of enameloid, bone, and white muscle of seven artificially-fed pisciculture gilt-head seabreams ( Sparus aurata ) from offshore Israel, in comparison to the Zn isotope composition of their diet. In addition, we also analysed δ 66 Zn values in the same tissues of wild-caught S. aurata , bluespotted seabream ( Pagrus caeruleostictus ) and grey triggerfish ( Balistes capriscus ) caught off the coast of Israel. We determine a tissue-diet δ 66 Zn offset for Sparus aurata of − 0.04 ± 0.09 ‰ (2SD) for bone, − 0.29 ± 0.06 ‰ (2SD) for enameloid, and − 0.45 ± 0.07 ‰ (2SD) for white muscle. Wild-caught fish have much higher among-individual δ 66 Zn variability with values distinct from the pisciculture S. aurata , documenting a much more isotopically heterogeneous diet consumed by the wild individuals. Still, tissue–tissue δ 66 Zn differences in wild-caught individuals are close to those observed in the pisciculture ones with progressively lower δ 66 Zn values in the order bone > enameloid > white muscle. Our results demonstrate predictable tissue-diet and tissue-tissue δ 66 Zn differences among fish hard and soft tissues and can be applied to identify the δ 66 Zn values of dietary input, thereby informing trophic (palaeo)ecological reconstructions.