Fish Kill in MRGO Tied to Low Oxygen Levels

Release Date: 08/23/2010


Louisiana Department of Wildlife and Fisheries (LDWF) biologists investigating a fish kill in the Mississippi River Gulf Outlet (MRGO) found low oxygen levels to blame.  LDWF received several reports on Sunday, August 22 concerning a large fish kill around the MRGO, east of Hopedale. 

LDWF biologists have confirmed the kill is a result of natural events and is not associated with the Deepwater Horizon oil spill.  High nutrient content from the Mississippi River in combination with seasonal occurrences has been the cause of hypoxic conditions for years.  Although essential in fertilizing the estuaries, in some cases the nutrient load is too great and hypoxic conditions arise.   Hypoxic events typically occur in late summer to fall and are also associated with processes that bring deep low-oxygen water to the surface. 

Fish need an oxygen level of at least three parts per million to survive.  Measurements taken by LDWF staff at various samples sites showed less than one part per million of oxygen at the bottom of the water. A "borderline" oxygen level of perhaps three parts per million was found at the top.

The only large concentration of dead fish was noted in a bayou immediately adjacent to the MRGO.  An estimated 500 fish were found in the area. Based on the condition of the fish, they appeared to be roughly five days old.  Species observed included large red drum, sheepshead, hardhead catfish, spotted sea trout, croakers and stingray.

Seasonal fish kills are normally found in much of southern Louisiana associated with low oxygen events.  LDWF biologists expect these to be common in areas such as marinas, dead-end canals, and other areas with poor circulation.  LDWF investigates fish kills using long-standing protocols based on the available information. 

To report a fish kill or abnormality, contact the nearest LDWF office during business hours or the Operation Game Thief operator (1-800-442-2511) after hours.

Coastal area offices are listed below:

61384 Fish Hatchery Road
Lacombe, LA 70461
Phone (985) 882-0027

New Orleans
2021 Lakeshore Drive, Suite 407
New Orleans, LA 70122
Phone (504) 284-2030

Post Office Box 189
Bourg, LA 70343
Phone (985) 594-4139

New Iberia
2415 Darnall Road
New Iberia, LA 70560
Phone (337) 373-0032

 Lake Charles
1213 North Lakeshore Drive
Lake Charles, LA 70601
Phone (337) 491-2579

For more information contact Ashley Wethey at or 225-765-5113.