Intracoastal Waterway (U.S. Army Corps of Engi- 

 neers 1950). It was speculated that the shift in oyster 

 distribution and the drastic reduction in the amount 

 of oysters taken were related to the dredging and 

 channeling activities. The confinement of the Calcasieu 

 River Ship Channel within a constant levee system in 

 1964 may have altered the current circulation of the 

 lake (White and Perret 1973). Between 1966 and 

 1974, there were no reported commercial oyster har- 

 vests from Calcasieu Lake. 



Natural and man-caused alterations in the Chenier 

 Plain drainage basins have profoundly affected oyster 

 distribution and production. Urban and industrial pol- 

 lution (i.e., the menhaden processing plant in Calcasieu 

 Lake) has contributed to oyster contamination and 

 mortality. Oyster beds in Sabine Lake were closed to 

 fishing due to higli coliform bacteria count. Intensive 

 fishing, especially by oyster dredging, has been asso- 

 ciated with the depletion of many natural reefs in 

 Texas and Louisiana (Owen 1955, Hofstetter 1977). 



burrows may range from 61 to 91 cm (24 to 36 in) 

 deep. When the water level is minimal, the female will 

 plug the burrow with mud and remain inside for seve- 

 ral months. A male may live in the burrow of a fe- 

 male near the entrance or in holes formed by tree 

 roots (Gary 1974). Although it is believed that 

 mating sometimes occurs within a burrow, most fe- 

 males carry sperm in receptacles to produce young 

 (LaCaze 1970). 



Spawning typically occurs in September and 

 October inside a burrow or in an open pond, depend- 

 ing upon the water level. The eggs are laid and simult- 

 taneously fertilized. The fertilized eggs adhere to the 

 female's swimming legs by a sticky substance. Red 

 swamp crayfish eggs hatch in 14 to 21 days after lay- 

 ing (de la Bretonne, unpublished), whereas tliose of 

 the white river crayfish require 3 to 8 additional days. 

 There is no larval stage (LaCaze 1970). The young re- 

 main attached to the female for one to three weeks, 

 depending on water characteristics (Comeaux 1972, 

 de la Bretonne, unpublished). 



5.6.3 RED SWAMP CRAYFISH (Procambarus 

 clarkii) and RIVER CRAYFISH 

 {Procambarus acutus) 



Crayfishes reside in rivers, streams, marshes, 

 swamps, lagoons, roadside ditches, and pits excavated 

 for highway fill. As the names indicate, the red swamp 

 crayfish is found primarily in swamps and marshes, 

 while the river crayfish resides mostly in rivers and 

 streams (Gary 1974). 



Both species prefer turbid water (Gary 1975), 

 usually less than 38 cm (15 in) deep. Optimum habi- 

 tats are permanent bodies of water exposed to full 

 sunlight and usually subject to annual spring flooding 

 (Penn 1956, Comeaux 1975). The habitats usually 

 have mud bottoms with a variety of aquatic vegetat- 

 tion for cover (Penn 1956). 



Crayfishes are generally nondiscriminant feeders, 

 eating both living and dead plant and animal tissue. 

 They prefer fresh meat and are not usually attracted to 

 rancid bait. They are not active predators and are un- 

 able to catch most mobile animals. They eat worms, 

 insect larvae (LaCaze 1970), a variety of plants (Gary 

 1974) and, under laboratory conditions, fishes, chick- 

 en liver, shrimp meal, and carrots (Amborski et al. 

 1975). Young crayfish, which are able to forage al- 

 most immediately after hatching, may be attracted to 

 decaying plant material colonized by microorganisms 

 (LaCaze 1970). 



Mating is thought to occur primarily in open wa- 

 ter. The male crayfish deposits the sperm into a re- 

 ceptacle on the female. The female retains the sperm 

 until the eggs are laid several months later (LaCaze 

 1970). Although mating usually occurs in May and 

 June, breeding may occur throughout the year, de- 

 pending upon water conditions (Hill and Cancienne 

 1963, de la Bretonne and Avault 1976). After breed- 

 ing, the female will "dig in" or burrow. Burrowing oc- 

 curs while open water is still present and offers pro- 

 tection both from desiccation and from predation. The 



For an abundant crayfish crop, inundation is 

 needed during September and October to force young 

 from the burrows or to allow for hatching in open 

 water (LaCaze 1970, White 1970). Crayfish normally 

 live fiom 12 to 18 months (Gary 1974). 



Several parameters exercise a controlling influe- 

 ence on crayfish. Although considered a freshwater 

 species, both hatchlings and adults have shown salini- 

 ty tolerances directly proportional to their size 

 (Loyacano 1967, Avault et al. 1970). 



Experiments which were conducted in a marsh 

 over a 2-yr period established that red swamp crayfish 

 prefer salinities from 3% to 8%c (LaCaze 1970). 

 Rapid changes or extremes in salinity, particularly 

 during the egg-laying and hatching period, could result 

 in decreased crayfish production (LaCaze 1970). 



According to a pond study by Loyacano (1967), 

 newly hatched young died in S%o salinity, interme- 

 diates were killed at 30%o^ but adults tolerated 30%o 

 for about a week before significant mortality occurred. 

 Growth may be retarded in areas where salinities are 

 20%o. Populations in brackish waters were more tole- 

 rant of high salinities than freshwater populations 

 (Loyacano 1967). 



Water hardness is also limiting. Crayfish require a 

 minimum of 0.05% water hardness, but no more than 

 0.2%. The optimum hardness is 0.1% (Avault et al. 

 1970). Minerals in hard waters provide the necessary 

 elements for shell hardening after molting. 



Dissolved oxygen and pH also control distribution 

 and productivity of crayfishes. LaCaze (1970) found 

 large populations of marketable size crayfishes in waters 

 ranging from a pH of 5.8 to 8.2. Compared to open 

 ponds, which are used in crayfish culture, natural 

 swamp ponds have relatively low productivity. This is 

 attributed to low oxygen levels and to acidities that are 

 either too high or too low (Avault et al. 1970, Gary 

 1975). Small amounts of forage plants and high or low 



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