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MACROSCOPE

Crawfish and Water Birds

Jay Huner

Farming Crustaceans

Adult crawfish stocked into new ponds in the spring burrow into the enclosing mud levees before the shallow pools are drained for the summer. There is no real control of how many crawfish survive, so there is no way to regulate the number of young crawfish that appear when these impoundments are refilled in the autumn. Because the growth of the animals slows when their density is too high, a given pond may have so many crawfish that they do not reach sizes that are desirable to market. In such cases, allowing birds to reduce the density of crawfish seems a logical method to assure adequate growth.

Thus many environmentalists contend that crawfish farmers should be happy that water birds thin their crawfish crops. The rub is that when small crawfish are culled in experimental ponds, there is no substantial compensatory growth in those remaining. Only when these same small crawfish are moved to underpopulated ponds do they thrive and attain large size. It would appear that some unidentified environmental factor in the original pond must limit the ability of small crawfish to grow there. In any event, computer simulations support the position of the farmers: Heavy predation from birds, regardless of the species involved, probably hurts crawfish production.

Louisiana crawfish aquaculture is also threatened by another increasingly common phenomenon: globalization. The problem is that the importation of frozen crawfish products from China has depressed market prices. Many crawfish farmers, disappointed by the loss of income, are instead trying to raise other crops, such as sugar cane, that do not require them to flood the land. As a way to make ends meet, some have begun leasing the right to hunt the many ducks and geese that visit their ponds.

If Louisiana crawfish aquaculture disappears, it is not only the farmers that will be displaced. Consider one well-known rookery for wading birds at Lake Martin, just east of Lafayette. This vast breeding ground—a breathtaking site to visit—undoubtedly takes this spectacular form because it is situated within 25 miles of some 30,000 acres of crawfish ponds, which support, in large part, these nesting birds and their offspring throughout most of the year. Losing too much crawfish acreage in that vicinity would thus devastate the rookery, which would be an environmental tragedy.








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