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Home > Resources & Publications > Newsletters & Magazines > Chenier Ecology > 2006 > 5-06

Resources & Publications:  Chenier Ecology

May 2006

Depending on the location of the pond, damages ranged from being completely filled with debris, carried by Rita’s massive storm surge, to tree and leaf litter causing dissolved oxygen problems.

Most ponds which were inundated by storm surge waters experienced the entire loss of freshwater fish. Salinities were as high as 15-20 parts per thousand in ponds six months after the hurricane. For reference purposes, full strength gulf water is 35 parts per thousand. The storm surge also carried a large volume of clay which settled out into a thick mud layer. Many freshwater fish commonly stocked in ponds can survive in brackish water; however reproduction is limited when salinities go above 5 parts per thousand. What killed most of these ponds, was the quick change from freshwater to very salty, silt and debris laden surge water.

For ponds with debris; the obvious recommendation is to remove it. If at all possible, pump out the remaining water. This is the most efficient way of removing dissolved salt. If the pond is gravity drained or evaporation is allowed, the salt will concentrate and may become bound in the soil.

It also may be necessary to excavate some of the clay layer deposited by the surge water. This could be an opportunity to make changes to the pond shape, bottom contours, add artificial structure, aeration features like fountains, diffused air, etc. Many of the ponds inundated by the storm surge were also filled with a large population of estuarine dependent species such as crabs, shrimp and many saltwater finfish species. If the pond can not be pumped completely, these remaining organisms must be removed or killed so they don’t begin feeding on fingerling fish upon restocking.

Once the pond is dewatered, this may also be an opportune time to add agricultural or dolomitic lime to the bottom. To determine the exact amount of lime needed, a soil sample can be taken to your parish county agent’s office and sent off for a small fee. Most soils in Southwest Louisiana require lime. It is easier to make lime applications to a bare pond bottom than when filled. Lime also helps suppress small clay particles from suspending when water begins refilling the pond.

Refill and stock fish once water reaches fill level and the water clears.

For more information on ponds, visit the LSU aquaculture Web site www.lsuagcenter.com/en/crops_livestock/aquaculture/, or the Louisiana Sea Grant aquaculture site www.seagrantfish.lsu.edu/aquaculture/index.html, or request publication #2573: “Management of Recreational and Farm Ponds in Louisiana” from your parish AgCenter office.

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