MEPS prepress abstract  -  DOI:

Reconstruction of the salinity history associated with movements of mangrove fishes using otolith oxygen isotopic analysis

Kotaro Shirai*, Futa Koyama, Naoko Murakami-Sugihara, Kusuto Nanjo, Tomihiko Higuchi, Hiroyoshi Kohno, Yoshiro Watanabe, Ken Okamoto, Mitsuhiko Sano


ABSTRACT: Recent degradation and loss of tropical estuaries due to human impact have made necessary the protection of essential habitats for estuarine fishes. A better understanding of estuarine use patterns contributes greatly in identifying essential habitat conditions. This study presents quantitative reconstruction of the salinity history experienced by individual estuarine fishes using an otolith oxygen isotope. δ18Ootolith was determined from the kuhliid Kuhlia rupestris and pomacentrid Chrysiptera cyanea for use as freshwater and marine end-member references, respectively. The salinity history of three species of estuarine mangrove fishes, often dominant in tropical East Asian estuaries, viz. the apogonid Fibramia amboinensis, pomacentrid Neopomacentrus taeniurus and terapontid Terapon jarbua, were examined. The δ18Ootolith ranges of −5.4 to −2.3‰ for F. amboinensis and −3.7 to −2.3‰ for N. taeniurus corresponded to 6 to 30 psu and 19 to 30 psu, respectively, when converted to salinity, based on the two salinity extreme values of the reference fishes. T. jarbua, on the other hand, exhibited δ18Ootolith variation range (−1.8 to −3.0‰) corresponding to 25 to 34 psu. Field observations in other studies have indicated that F. amboinensis and N. taeniurus may be resident species, hovering near mangrove roots and tolerating a variable salinity environment, whereas T. jarbua may be a vagile species which can move to areas of preferred higher salinity conditions. Such behavioral ecologies are largely consistent with the reconstructed salinity histories from δ18Ootolith. These results suggested that F. amboinensis and N. taeniurus may be estuarine resident fishes, whereas T. jarbua may be a marine migrant.