Estuarine fish community changes associated with the Mississippi River Gulf outlet following Hurricane Katrina

The Mississippi River Gulf Outlet (MRGO) is a shipping channel constructed in the 1960s as a short cut between the Gulf of Mexico and the port of New Orleans, Louisiana (USA).  After construction, deterioration of freshwater marshes and forests were exacerbated as the MRGO's deeply dredged channel facilitated the advance of saltwater intrusion and marsh erosion.  In 2005, Hurricane Katrina forced a massive surge of saltwater up the MRGO channel, accelerating marsh erosion to a degree that equalled the total land loss during the previous ten years.  We analyzed standardized fish monitoring data collected by the Louisiana Department of Wildlife and Fisheries (LDWF) from 1988 to 2009 at fixed stations in the marsh and Breton Sound estuary surrounding the MRGO.  We compared fish community changes from otter trawl, gill net and seine data before and after Hurricane Katrina using partial canonical correspondence analysis (pCCA).  Overall, species abundances that decreased significantly (T-value biplots, 499 Monte Carlo randomizations, P < 0.05) in trawls were Brown shrimp, Spot, Atlantic croaker and Gulf menhaden.  Conversely, White shrimp, Bay anchovy and Sand seatrout abundances increased significantly.  In gill nets, Atlantic croaker and Gizzard shad abundances decreased, while White shrimp, Black drum, Blue crab and Gafftopsail catfish abundances increased.  In seine, Atlantic croaker and Gulf menhaden increased, while Sea catfish, Blackcheek tonguefish and juvenile Spotted seatrout increased.