Individual-specific transgenerational marking of common carp, Cyprinus carpio L., using Sr-86/Sr-84 double spikes

Transgenerational isotopic marking has been recognised as an efficient tool for mass marking of high numbers of fish larvae by injecting female spawners with enriched isotope solutions. So far, mainly enriched stable barium isotopes have been applied for this purpose. Here, we present an alternative approach for individual-specific transgenerational marking using strontium Sr-86/Sr-84 double spikes. Four isotonic double-spike solutions with different molar fractions of Sr-86 and Sr-84 and different total Sr concentrations were administered to four female spawners of common carp, Cyprinus carpio, L., by intraperitoneal injection, and one additional female spawner was injected a blank isotonic solution as control. Otoliths (lapilli) were sampled from juvenile offspring and analysed for their Sr isotopic composition by laser ablation-multi collector-inductively coupled plasma-mass spectrometry. Central otolith regions of the progeny of female carps treated with concentrations of at least 0.45 mg Sr-84 kg(-1) bodyweight and 2.28 mg Sr-86 kg(-1) bodyweight showed a significant shift of the absolute Sr-88/Sr-86 and Sr-88/Sr-84 isotope ratios from the natural baseline. Isotope pattern deconvolution was successfully applied for the identification of the originally injected Sr-86/Sr-84 molar fraction ratios of the individual double spikes. Enriched stable Sr isotope double spikes represent an important alternative to enriched stable Ba isotopes for transgenerational marking, especially in freshwater systems.