not the Gulf of Mexico oil spill.

Between 5,000 and 15,000 dead fish were found Sunday, collected in pockets of spill boom near the Mississippi River Gulf Outlet.

Species included crabs, sting rays, eel, drum, speckled trout and red fish.

An investigation and samplings by the Louisiana Department of Wildlife & Fisheries show the area was hypoxic.

Long before the oil spill, the northern Gulf has suffered from a persistent "dead zone" of low-oxygen water blamed on nutrient-rich runoff from the Mississippi River.