With air temperatures expected to plummet statewide tonight, including into the upper teens and lower 20s all the way to the coast, the possibility exists for localized fresh- and saltwater fish kills, according to biologists with the Louisiana Department of Wildlife and Fisheries.

“Any time we get sub-freezing temperatures for any period of time there is a potential for localized cold weather fish kills or stuns,” said Jason Adriance, Finfish Program Manager for LDWF.  “Any kills may not be apparent for two to three days after the kill occurs, as that's how long it may take for dead fish to float to the surface.”

This afternoon, the buoy at Shell Beach showed a water temperature of 43.5, while information from Southwest Pass at Vermilion Bay indicated water temperatures slightly over 44 degrees. Water temps at Big Lake also were reported at 44 degrees by mid-afternoon.

Speckled trout usually have no issues until water temperatures drop below 40 degrees, and redfish are even a bit hardier than that, he said. 

“Typically water temperatures below 40 degrees Fahrenheit for any more than a day begin to cause problems for spotted sea trout, whereas red drum are slightly more tolerant and will begin to experience problems in the mid-30s,” he said. “How quickly the water cools down is also important. If fish have had a chance to acclimate and move, and do not get caught in shallow colder water, the potential for survival is better.

“The freezes of 1983 and 1989 saw below-freezing air temperatures for several days to one week. With this Arctic system, below freezing air temperatures are expected to be of a much shorter duration.”

Highs Tuesday in the western part of the state are forecast for the mid-40s, while New Orleans is looking at a high of 39, with Venice only getting into the mid-30s.

Mike Wood, director of Inland Fisheries, said north Louisiana’s cold temperatures could also cause problems for some freshwater species, but might also put a dent in the growth of problem aquatic vegetation.

“Localized fish kills are possible in north Louisiana as a result of extremely cold conditions.  Potential kills would most likely be comprised primarily of threadfin shad,” Wood said. “Threadfin shad are sensitive to very cold water, but they are a very prolific species, and long-term negative effects are unlikely.

“Any negative effects resulting from the upcoming cold weather will be offset by beneficial control of aquatic vegetation.  Our worst problem plants, like giant salvinia, water hyacinth and alligator weed, are all non-natives of tropical origin.  They all have less tolerance for cold weather than native plants.  Long term effects of the cold weather are expected to be positive.”

If you observe a fish kill or stunned fish, Adriance said to contact LDWF at 1-800-256-2749 with your specific location so it can be investigated.