STABLE CARBON AND NITROGEN ISOTOPE RATIOS OF PENAEID JUVENILES AND PRIMARY PRODUCERS IN A RIVERINE MANGROVE IN GUIMARAS, PHILIPPINES

Stable carbon and nitrogen isotope ratios were analyzed for primary pr oducers and juveniles of four penaeid species (Metapenaeus ensis, Pena eus indicus, P. merquiensis and P. monodon) in a riverine mangrove in Guimaras, central Philippines. delta(13)C values of shrimp (-15.5 to - 19.6 parts per thousand) were closer to phytoplankton (-23.8 parts per thousand) and possibly epiphytic algae (-24.2 parts per thousand) tha n to mangrove leaves (-26.9 to -30.0 parts per thousand) or detritus ( -28.0 parts per thousand). Differences in delta(15)N values suggested 2-3 trophic shifts between phytoplankton (0.6 parts per thousand) and shrimp (6.9 parts per thousand), assuming a 2.4 parts per thousand enr ichment per trophic level. There were no significant differences in de lta(13)C and delta(15)N ratios between green and decomposing leaves, a nd among mangrove species, shrimp species and different size groups of shrimp.