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Explaining a fish kill

The image of a massive fish die-off—so thick it made a canal near Venice, La. look like a gravel road –was first broadcast by a television station in New Orleans on Tuesday, and then quickly made its way around the Internet. Given the recent history of that area, many observers immediately jumped to the conclusion that the fish were killed by exposure to oil or dispersants from the Deepwater rig disaster offshore.

Plaquemines Parish President Billy Nungesser called for testing to determine the precise cause. However, Fish and Wildlife officials say that the dead fish likely succumbed to low oxygen levels when the tide went out, leaving thousands—mostly a bait fish known as menhaden—stranded in shallow bayou waters. Click here to watch an NBC News video on the fish kill.