Large fish kill underway in Mobile Bay, Gulf of Mexico, USA

A widespread fish kill is underway across Mobile Bay. It appears to be affecting primarily filter-feeding fish such as menhaden, sardines, alewives and shad.

 

Dead fish are present in the shallows and on beaches on both sides of the bay, from Point Clear to Daphne on the eastern shore and from Arlington Point south to Fowl River on the western shore. Dead and dying fish also dot the surface of the bay, from one side to the other.

 

The kill does not appear to be related to a red tide bloom occurring in the Gulf of Mexico and around Dauphin Island. Instead, the bloom in the upper bay appears to be another species of algae with a similar neurotoxic effect on fish.

 

Fish affected by the algae swim in a markedly erratic fashion, zipping straight ahead for a time, then falling into lazy circles, often swimming on their side or even upside down.

 

AL.com collected samples of sick fish and the water where they were found during trips across the bay, from Fairhope to the mouth of Fowl River, on both Tuesday and Wednesday. Those fish were provided to the Dauphin Island Sea Lab for analysis. In addition, AL.com measured oxygen levels and salinity where the samples were collected using a YSI meter, a standard tool for environmental sampling.

 

“There does not appear to be a correlation with oxygen or salinity,” said Andy Depaola, a microbiologist with the U.S. Food and Drug Administration lab on Dauphin Island. Depaola participated in the AL.com sampling trip. “Those oxygen levels were not low enough to kill fish.”

 

Alison Robertson, who specializes in harmful algal blooms with the Dauphin Island Sea Lab, said she had ruled out red tide, which is caused by an organism called Karenia brevis, in the bay. The red tide algae prefers the high salinity found in the Gulf of Mexico. It does not do well in lower salinity, particularly the low levels of salt measured in the AL.com sampling.

Courtesy of al.com

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