Using stable CNS isotopes to evaluate estuarine fisheries condition and health.

Humans are modifying estuaries of the coastal zone and ecologists have begun measuring ecosystem responses in an attempt to preserve natural ecological conditions and health. Traditional approaches to assessing structural and functional responses of coastal systems include measures of species composition and water quality, but fisheries assessments are often left out because of the perception that fisheries species are too mobile and cannot easily be linked to local conditions. Stable isotopes have emerged as a new and useful way to understand movements and productivity of mobile shrimp and fish species across estuarine seascapes. Two case studies from Louisiana, USA, suggest that estuaries with healthy fishery food webs might be identified using isotope indicators that show low anthropogenic N inputs, strong benthic contributions, and moderate to high fisheries residency and productivity in marsh and mid- salinity areas.