Population Dynamics

Most adult female crawfish emerging from the burrow after the fall flood-up will be releasing young-of-the-year crawfish that have hatched out during the summer. These young-of-the-year crawfish will immediately begin to forage about the pond and begin to grow to become market size in the spring. A fewer number of adult female crawfish will be flooded out of their burrows and still have eggs attached to the underside of their tails. These crawfish may or may not reburrow to hatch their eggs. The young hatched from these females will become market size in the very late spring to early summer.

Finally, there will be a few adult female crawfish that will be flooded out of their burrows that had not yet laid their eggs to be attached to the underside of their tails. These crawfish will reburrow into the high ground at the water level to hatch their eggs through the fall. The young crawfish hatched out by these females will typically be released into the pond in late December, January and February. These young crawfish will become market size in June or later, and in many cases will be held over and not reach market size until the next year.

The majority of recruitment of crawfish into the pond occurs at flood-up. That is why it is of utmost importance that dissolved oxygen levels be maintained during this period of time. Elimination of this wave of recruitment would result in the severe reduction and possible elimination of the year's potential profits. Should an oxygen depletion occur during the early flood-up period, there is a chance to recoup some costs late in the crawfish harvest season by harvesting the second wave of recruitment that would enter the pond during the winter to early spring. However, the numbers of crawfish recruited at this time are greatly reduced from the fall numbers.

Crawfish ponds should be checked for population density beginning approximately 4-6 weeks after the initial pond flood-up in the fall. A dip net made with 1/8 to 3/16 inch netting attached to a long handle is very effective in sampling the young-of-the-year and juvenile crawfish, with an occasional capture of an adult. The net should be 14-18 inches wide with at least an 8 inch depth or bag to it. It should be attached to the handle with a sturdy metal frame. The ideal pond population is 5-10 crawfish per square yard throughout the entire pond. Less than 5 crawfish per square yard indicates a less than optimum population and the pond's yields may suffer, but the crawfish harvested will probably be very large (greater than 15 per pound). A population of more than 10 crawfish per square yard indicates an over population causing most crawfish to be very small (smaller than 25-30 per pound) and many cases too small to be marketable. Should an over population situation occur, the only rememdy is to reduce the numbers of crawfish in the pond. One way to accomplish this is to drain the pond rapidly, flushing many crawfish out of the pond with the discharge water and stranding many others with the quick draining. An additional heavy application of urea to the pond bottom after it has been drained quickly has shown good effectiveness in additional reduction of the crawfish population. The pond can then be reflooded within a few days after the draining or urea application, depending on which method was used.

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