Flooding the pond in the fall is one of the most crucial times of the entire crawfish season. The crawfish are being flooded out of their burrows and the females are releasing their young to forage in the 10,000 lbs. per acre of vegetation that was planted. This vegetation, for the most part, is not native to the new moist environment of the pond, and much of it will drown and start to decay. This decay process requires a considerable amount of dissolved oxygen and is the cause of the number one killer of crawfish in a pond, low dissolved oxygen.
To reduce the effects of the decay process, the ponds should be reflooded for production purposes in the fall after the temperatures have moderated. The ideal date for flooding is when the average daytime high tempertures are averaging in the low 80's and nighttime lows are averaging in the low to mid 60's. This allows for some crawfish growth prior to the extreme winter temperatures. Producers who do not feel that they can adequately maintain dissolved oxygen levels in the pond during this relatively warm time of the year will opt for a later flood date, usually after the first good frost. The reason for this is that the colder the water is the slower the decay process, which means less dissolved oxygen is required. Also, cold water is capable of holding more dissolved oxygen that warm water. However, by holding off flooding until water temperatures are cooler, you also have less crawfish growth going into the winter resulting in smaller crawfish in the spring. This may cause a delay in the initiation of the harvest season due to the size of the crawfish.
When flooding the pond, an initial flood of 8-10 inches of water is adequate. This is enough water to flood the crawfish out of the burrows, and allow the crawfish to roam the pond for forage. Also, it is easier to flush, circulate or exchange 8-10 inches of water than the full 18 inches of water. Once temperatures cool to the point drastically reducing the chance of a low dissolved oxygen problem, the pond can be filled the to full level. The only disadvantage to a partial flood is that predatory birds will have easier access to the crawfish in the shallower water.
Additional ways to counter the low dissolved oxygen problem is through mechanical aeration
of the water.
Most producers in North Carolina construct their ponds so they can recirculate the pond
water, thus being able
to maintain a current within the pond during periods of low dissolved oxygen. Water is
pumped from a
barrow ditch, or canal, that is dug around the pond during pond construction. The water
then circulates
throughout the pond and overflows back into the barrow ditch. The water then has to flow
from the discharge
point back to the pump pickup point to be relifted back into the pond. The longer the
distance between the
discharge and pickup, the longer the water has to have the opportunity to be "cleaned up"
biologically before
being returned to the pond.
Another method this is utilized in North Carolina is the use of
paddlewheels to
circulate massive amounts of water through the pond economically. One such paddlewheel,
using a 3 hp
electric motor and turning 9 rpm's is pushing approximately 10,000 gpm's of water through
the pond. The
paddlewheel itself is made up of a central shaft with 8 spokes of angle iron to which is
attached 2x8 boards
that are 8 feet long. The paddlewheel is boxed into a baffle, or recirculating levee so that
there is about a 1
to 2 inch clearance for the paddles on the sides and bottom. The theory of using this type
paddlewheel to
circulate large amounts of water economically is that you improve the water quality through
the turbulent
movement of the water. This keeps the water from stagnating and also adds dissolved
oxygen. Paddlewheel
aerators, such as those used the catfish industry to aerate ponds have also been tried in
crawfish ponds to
improve the dissolved oxygen levels. Although they are more efficient in adding oxygen to
the pond, they
are very inefficient at pushing that oxygenated water through a crawfish pond. To date neither
type
paddlewheel has been thoroughly tested by researchers to determine the ultimate impact of
these aerators on
the water quality in a crawfish pond.