Comparative Life History of Paralichthid Flounders in NW Florida and Assessment of Fishery-independent Monitoring Methods

Specific objectives of this project included estimation of size structure, age/growth and reproductive parameters for flounder populations in St. Andrews Bay and adjacent offshore reefs using trammel-net samples and diver surveys. Two fishery-independent methods for assessing size and age structure were compared, and an evaluation was conducted on whether age-length keys or direct random sampling is the most appropriate method for applying ages to the catch.

Information was needed on southern and gulf flounder (Paralichthys lethostigma and P. albigutta) from the Gulf of Mexico age and growth, sex and size composition, and catch per unit effort (CPUE), in light of the rapid decline of summer flounder stocks in the middle Atlantic bight (Mid-Atlantic Fishery Management Council 1991) and perceptions of spawning-stock declines and closure of the Louisiana southern flounder fishery. There was also a need for information on reproductive parameters - e.g., size/age at maturity, spawning-season duration and reproductive contribution (fecundity) by age. Because, unlike many reef-associated species, flounders can be readily sampled during the spawning season, flounder aggregations may provide a model for measuring reproductive success of reef fishes in the wild. Further, flounders may be typical of fishes that are problematic for fishery-dependent assessments because they show high variation in size at age and sexually dimorphic growth, and may be subject to gear selectivity that is difficult to calculate. Therefore population monitoring may be more cost-effective and accurately performed by fishery-independent methods than by reconstruction of population parameters from fishery-dependent data.