The stomach contents and food sources of Oreochromis niloticus in the mangrove and plantationaquaculture ecological coupling systems were analyzed by stable isotope tracing technology. Microscopic examination of the stomach content (n=120) has shown that the diet of adult O. niloticus is composed of organic detritus

benthic microalgae

plankton

litter fall

gastropods

bivalve and silt. The consumed items were different between the two habitats but consistent with the types of habitats they reside. Based on the stable isotope ratios of O. niloticus and the potential food sources

organic detritus

phytoplankton and litter fall were the most important assimilated food in mangrove decorated pond

and the contributions of them were 5%~55%

10%~40% and 15%~26%

respectively. Whereas

their contributions were 8%~64%

25%~55% and 1%~12%

respectively

in the control pond. Analysis of stomach contents and stable isotope tracing indicate that organic detritus always contributed over 50% of the food for O. niloticus in the two habitats. Our results suggest that O. niloticus are typically detritivores. Mangrove

marsh plants and phytoplankton

which are mostly grown locally in each habitat

were of minor importance in the assimilated food.