Evaluation of shrimp polyculture system in Thailand based on stable carbon and nitrogen isotope ratios

To quantify the contribution by cocultured animals to waste assimilation in an intensive shrimp farm in Thailand, the food web structures of the macrobenthos in a reservoir pond, a shrimp culture pond and water treatment ponds were examined using the stable C and N isotope ratio technique. Seawater for aquaculture was drawn from a creek, and stored in a reservoir pond, used for farming the banana prawn Fenneropenaeus merguiensis in culture ponds, and then recycled through treatment ponds where the green mussel Perna viridis was cultured to remove organic wastes discharged from the farming. The clam worm Nereididae sp. and the mud creeper Cerithideopsilla cingulata in the culture pond had delta(13)C values of -21.0parts per thousand and -18.4parts per thousand, respectively, suggesting that shrimp feed (mean delta(13)C=-20.7parts per thousand.) was the main food source for these species. The delta(13)C analysis also suggested that sediments (-23.7parts per thousand) in the reservoir pond and particulate organic matter (POM) (-24.0parts per thousand) and/or sediments (-25.0parts per thousand) in the treatment pond supplied carbon for most macrobenthic animals. However, green mussels in the treatment pond had a mean delta(13)C value of -20.5parts per thousand, suggesting that shrimp feed was the main food source for this species.