[StBernard] LDWF reports fish kill in the MRGO tied to low oxygen levels

Westley Annis Westley at da-parish.com
Tue Aug 24 23:41:56 EDT 2010


Biologists from the Louisiana Department of Wildlife and Fisheries conducted
a thorough investigation of a fish kill found in the Mississippi River Gulf
Outlet (MRGO) over the weekend. They found low oxygen levels to blame and
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 have 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. The
dead fish found appeared 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

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