An experimental evaluation of transgenerational isotope labelling in a coral reef grouper
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Transgenerational isotope labelling (TRAIL) using enriched stable isotopes provides a novel means of mass-marking marine fish larvae and estimating larval dispersal. The technique, therefore, provides a new way of addressing questions about demographic population connectivity and larval export from no-take marine protected areas. However, successful field applications must be preceded by larval rearing studies that validate the geochemical marking technique, determine appropriate concentrations and demonstrate that larvae are not adversely affected. Here, we test whether injection of enriched stable barium isotopes (135Ba and 137Ba) at two dose rates produces unequivocal marks on the otoliths of the coral reef grouper Epinephelus fuscoguttatus. We also assess potential negative effects on reproductive performance, egg size, condition and larval growth due to injection of adult female fish. The injection of barium isotopes at both 0.5 and 2.0 mg Ba/kg body weight into the body cavities of gravid female fish was 100% successful in the geochemical tagging of the otoliths of larvae from the first spawning after injection. The low-dose rate produced no negative effects on eggs or larvae. However, the higher dose rate of 2 mg Ba/kg produced small reductions in yolk sac area, oil globule area, standard length and head depth of pre-feeding larvae. Given the success of the 0.5 mg Ba/kg dose rate, it is clearly possible to produce a reliable mark and keep the concentration below any level that could affect larval growth or survival. Hence, enriched Ba isotope injections will provide an effective means of mass-marking grouper larvae.
KeywordsInductively Couple Plasma Mass Spectrometry Standard Length Inductively Couple Plasma Mass Spectrometer Larval Quality Group Larva
This work was made possible through the assistance of the Gondol Research Institute for Mariculture, Bali Indonesia. Special thanks to Dr. Adi Hinafi (Director), Dr. Agus Priyono, Dr. Nyoman Adiasmara Giri, Dr. K. Suwirya, I. Made Sedana, Mohammed Sapri, Agus Supriatna, Katimin. Thanks also to Dr. Mike Rimmer, Adam Reynolds and Anjanette Johnston from the Northern Fisheries Centre (QDPI & F), Cairns, QLD. The primary funding for this work was provided by the Australian Marine and Tropical Sciences Research Facility (MTSRF), with additional support from the ARC Centre of Excellence for Coral Reef Studies, and the US National Science Foundation (OCE-0424688).
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