During a drought, everything from leaf litter to fertilizer collects, then when it finally does rain, the debris is washed into retention ponds. As micro-organisms in the water break down the runoff the oxygen level in the water decreases, killing the fish. Shawn College, president of the Fawn Ridge Homeowners Association, theorized that herbicides applied monthly to control exotic weeds in the pond might have been a contributing factor. While this type of fish kill is not dangerous to birds, it is dangerous to ducks and other water fowl because of a bacteria that lives in the gullet of most fish, Lesnett said. The bacteria is transmitted when the fish dies and contaminates nearby vegetation.
Water fowl consume the vegetation and contract a disease similar to food poisoning.
Though harmless to humans it eventually kills the animals, Lesnett said. Lesnett said the problem could also be alleviated by installing a fountain to circulate the water and increase the oxygen level. The county has counted more than 20 fish kills since early January, almost all have been caused by low oxygen levels or cold water. Wildlife officials said it is not unusual for fish to frequently die in retention ponds because the water and nutrient levels fluctuate so frequently. We can't even manage a small retention pond over a couple of acres.