An experimental evaluation of transgenerational isotope labelling in a coral reef grouper |
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Authors: | David H Williamson Geoffrey P Jones Simon R Thorrold |
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Institution: | (1) ARC Centre of Excellence for Coral Reef Studies and School of Marine and Tropical Biology, James Cook University, Townsville, QLD, 4811, Australia;(2) Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA |
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Abstract: | 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. |
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