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(70-35) Retention of selected metals and radionuclides in two tropical fish after a pulse-chase feeding. Warnau, Michel*,1, Teyssié, Jean-Louis1, Cotret, Olivier1, Fowler, Scott1, Rouleau, Claude2, 1 IAEA-Marine Environment Laboratory, Principality of, Monaco2 National Water Research Institute, Burlington, Canada ABSTRACT- Two fish species commonly found in tropical waters (Monodactylus argenteus and Scatophagus argus) were selected to investigate retention of metals and radionuclides ingested with food. Both species are euryhaline but have contrasting trophic habits: M. argenteus is a pelagic predator whereas S. argus is an omnivorous/detritivorous fish. High quality aquarium maintenance, required to keep stable tropical conditions in the experimental microcosms, was successfully achieved and fish were maintained in the laboratory for 6 to 12 months with nearly no mortality. Juvenile and adult fish were reared in 400 and 3000L aquaria, respectively (10 % water renewal hr-1; temperature: 25±0.3°C; salinity: 35 p.s.u.). Adult Artemia salina were exposed for 15 days to inorganic salts of 57Co, 65Zn, 109Cd, 110mAg, 134Cs, and 241Am. Fish (80 juveniles and 15 adults of each species) were then allowed to feed ad libitum on these radiolabelled prey for 1.25 hr. Whole-body loss kinetics of ingested radioisotopes were followed for 45 days in juveniles (n = 20) and the fine tissue distribution of the contaminants was determined at different times in juveniles and adults. Among these elements, only 134Cs was efficiently assimilated and retained (AE = 55-63 %; Tb Key words: tropical fish, trophic transfer, metals, radionuclides |
= 27-48 days). In contrast, ingested 109Cd and 241Am remained totally associated with the faeces and were not absorbed. Results suggest that assimilation efficiency (AE) and organ targeting of metals and radionuclides depend more on the element considered than on fish species or age. However, retention efficiency of 57Co, 110mAg and 65Zn was significantly higher (factor 1.5-2) in S. argus (Tb