Total DDT Derivatives in Fish from the Davis Pond Freshwater Postdiversion Sampling (2007-2009) with a Comparison to Prediversion Levels (2001)

The diversion of freshwater from the Mississippi River is intended to mitigate saltwater intrusion from the Gulf of Mexico and to lessen the concomitant loss of wetland areas. Though effective, freshwater diversion can affect wildlife and habitat; therefore, prediversion and postdiversion data collections are necessary to identify effects. The Davis Pond freshwater diversion area is located between the Mississippi River and Bayou Lafourche and extends to Barataria Bay Basin, Louisiana. Results and interpretations from the prediversion biomonitoring done in 2001- which included data on fish, eagles, and bivalves - are presented in the U.S. Geological Survey (USGS) Scientific Investigations Report 2008-5067, "Davis Pond Freshwater Prediversion Biomonitoring Study: Freshwater Fisheries and Eagles." The postdiversion data generated approximately 6 years later from the sampling of fish whole bodies are presented here in this USGS Data Series. An accompanying log of postdiversion study site photographs was also produced in USGS Data Series 605, "Photographic Images Captured While Sampling for Bald Eagles near the Davis Pond Freshwater Diversion Structure in Barataria Bay, Louisiana (2009-10).

Figure 6A represents the total DDT derivatives detected in largemouth bass, blue catfish and striped mullet samples collected in 2007-2009, approximately six years after the Davis Pond freshwater diversion structure was operational. Figure 6B compares prediversion and postdiversion levels of DDT (not including its derivatives). Figure 6C presents a graphical representation of the ratios of different DDT isomers found in Davis Pond postdiversion testing. It compares the ratios of DDT, DDE, and DDD found in the fish samples collected at Davis Pond from 2007-2009.