An experimental evaluation of transgenerational isotope labelling in a coral reef grouper
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ORIGINAL PAPER
An experimental evaluation of transgenerational isotope labelling in a coral reef grouper David H. Williamson · GeoVrey P. Jones · Simon R. Thorrold
Received: 6 February 2009 / Accepted: 31 July 2009 / Published online: 22 August 2009 © Springer-Verlag 2009
Abstract Transgenerational isotope labelling (TRAIL) using enriched stable isotopes provides a novel means of mass-marking marine Wsh 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 Weld applications must be preceded by larval rearing studies that validate the geochemical marking technique, determine appropriate concentrations and demonstrate that larvae are not adversely aVected. 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 eVects on reproductive performance, egg size, condition and larval growth due to injection of adult female Wsh. The injection of barium isotopes at both 0.5 and 2.0 mg Ba/kg body weight into the body cavities of gravid female Wsh was 100% successful in the geochemical tagging of the otoliths of larvae from the Wrst spawning after injection. The low-dose rate produced no negative eVects 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
Communicated by U. Sommer. D. H. Williamson (&) · G. P. Jones ARC Centre of Excellence for Coral Reef Studies and School of Marine and Tropical Biology, James Cook University, Townsville, QLD 4811, Australia e-mail: [email protected] S. R. Thorrold Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
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 aVect larval growth or survival. Hence, enriched Ba isotope injections will provide an eVective means of mass-marking grouper larvae.
Introduction The establishment of marine parks, including networks of no-take reserves (NTRs), has been widely advocated to stem global declines of Wshery resources and marine biodiversity (Agardy 1994; Dayton et al. 2000; Russ 2002; Roberts et al. 2005; Mora et al. 2006). The beneWts of NTR protection have been well documented for exploited species within reserve boundaries (Halpern and Warner 2002; Russ 2002; Williamson et al. 2004; Roberts et al. 2005; Russ et al. 2008); however, estimates of the degree to which reserves contribute to sustaining Wsh stocks in surrounding Wshed areas have remained elusive (McClanahan and Mangi 2000; Gell and Roberts 2003; Sale et al. 2005; Abesamis et al. 2006). For Wshes whose numbers increase within NTR areas, the potential for augmenting Wsh populatio
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