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rash of phone calls in recent weeks about refurbishing fish
ponds after Hurricane Rita is an indication that things
are becoming a little more ormalized. For months following
the storm, area residents were busy dealing with far more
significant issues like a roof over their heads, clothing
on their backs, food on the table and employment. The many
phone calls about fish ponds mean that folks are getting
back to thinking about recreation, aesthetics and enjoying
life.
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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