Date of Award
The objectives of this study were to describe the life history patterns of the southern flounder (Paralichthys lethostigma) in Louisiana waters through determination of age, growth, and reproductive biology. A variety of sample sources were included to demonstrate how the southern flounder life cycle is dependent on both the estuary and offshore waters throughout the various stages of its life cycle. Females exhibited greater lengths then males reaching a maximum of 764mm total length and males a maximum of 414mm. Ages were estimated through examination of transverse sections of sagittal otoliths. Annuli were validated to form yearly in the winter months. Females lived longer then males reaching a maximum age of eight years while males reached a maximum of 4 years. Resultant Von Bertalanffy growth equations were shown to be significantly different between males and females. Males displayed a higher growth rate then females but had a much smaller Loo. Histological evidence and gonadosomatic indices indicate that southern flounder spawn in December and January in offshore waters. Southern flounder are batch spawners indicated by the presence of multiple stages of oocytes throughout the spawning season. Mean batch fecundity was estimated for 1991 and 1993 as 62,000 and 44,000 ova per batch. Spawning frequency was estimated using the postovulatory follicle method as 3.6 days and 6.4 days. The time-calibrated method provided estimates of 2.3 days and 3.1 days. Females were found to reach fifty-percent maturity at 229mm and all females were mature above 509mm. Sex ratios indicate that males begin to migrate offshore as early as October in preparation for the spawning season. Female migration offshore takes place in November and December. Both males and females begin to move back into the estuaries as early as February as the spawning season comes to an end.
Fischer, Andrew James, "The Life History of Southern Flounder (Paralichthys Lethostigma) in Louisiana Waters" (1999). LSU Historical Dissertations and Theses. 8286.