Stable isotope analysis was used to determine the sources of dietary nitrogen (N) and carbon (C) for shrimp during the rearing phase in extensive riceshrimp ponds in My Xuyen and Gia Rai districts,Vietnam. Farm-made feed was added as a food source in shrimp ponds in My Xuyen district, and based on stable isotope analyses, was generally a poor dietary source. The commercial formulated feed used in Gia Rai also appeared to contribute little directly to the nutritional needs of the shrimp. In contrast, the natural biota in all ponds appeared to contribute substantially. In particular, biota from beam trawls and benthic organic matter were the most likely sources of nutrition in My Xuyen ponds, while benthic organic matter was the main source in Gia Rai ponds. d 15 N ratios in the natural biota in My Xuyen farms decreased over the growing season, suggesting increased N ¢xation in the case of the benthic organic matter reaching values as low as1m. This suggests Nlimitation in the ponds and that natural biota become increasingly dependent on N ¢xed by algae and/or other microorganisms. There is the potential to promote the growth of the plankton and hence, the other natural biota, by the judicious addition of fertilizer.

No abstract

Contribution/ OriginalityThis study is one of very few studies, which have investigated the impact of climate change on snakehead seed production. The paper's primary contribution is finding that which and how climate phenomenon has effected on seed production as well as suggesting some adaptive methods for them.

No abstract

No abstract