Retention of a transgenerational marker ( 137 Barium) in tissues of adult female anemonefish and assessment of physiological stress Alexandra-Sophie Roy & Ashley J. Frisch & Craig Syms & Simon R. Thorrold & Geoffrey P. Jones Received: 10 October 2011 / Accepted: 20 April 2012 / Published online: 22 May 2012 Abstract Recently it was shown that female fish injected with enriched stable isotopes maternally trans- mit a chemical signature to larval otoliths. Validation of this larval marking technique requires laboratory experi- ments to determine appropriate injection concentrations and to assess any negative effects on larval and adult condition. This study investigated the temporal profile of 137 barium assimilation and retention in tissues of adult female anemonefish Amphiprion melanopus (Pomacentridae) following intraperitoneal injection with either 2 or 4 μg 137 Ba g -1 body mass. Mean barium isotope ratios ( 138 Ba: 137 Ba) in the two groups of treated fish were not significantly different from each other, but were significantly different from those in the control group up to 56 days post-injection. This pattern of 137 Ba retention was consistent across gonad, muscle, liver and bone tissues. Mean plasma cortisol concentration (an in- dicator of non-specific physiological stress) was not sig- nificantly different among groups and was considered to be representative of unstressed fish. Together, these results indicate that (1) A. melanopus suffer minimal physiolog- ical stress and cope well after treatment with 137 Ba, (2) 137 Ba is retained in female A. melanopus for a pro- longed period (at least 56 days), such that multiple clutches of offspring are likely to be marked with an isotopic signature, and (3) a lower dosage of 2 μg 137 Ba g -1 appears sufficient for transgenerational mark- ing. It is concluded that 137 Ba is suitable for use as a transgenerational marker and is a powerful tool to re- solve long-standing enigmas such as larval dispersal distances and the fishery benefits of marine reserves. Keywords Amphiprion melanopus . Coral reef fish . Larval tagging . Batch marking . Otolith microchemistry . Plasma cortisol Introduction Due to widespread declines in the condition of coral reefs and the fisheries they support (Bellwood et al. 2004; Newton et al. 2007; Knowlton and Jackson 2008), there is burgeoning interest in the development of networks of marine reserves for protecting biodiver- sity and for sustaining fisheries in areas adjacent to marine reserves (Gell and Roberts 2003; Almany et al. Environ Biol Fish (2013) 96:459–466 DOI 10.1007/s10641-012-0029-y A.-S. Roy : A. J. Frisch : 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 C. Syms Institute of Marine and Antarctic Science, Hobart, TAS 7001, Australia S. R. Thorrold Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA A.-S. Roy (*) GEOMAR - Helmholz-Zentrum für Ozeanforschung Kiel, Kiel, Germany e-mail: sroy@geomar.de # Springer Science+Business Media B.V. 2012