Abstract
Abstract Southern Flounder Paralichthys lethostigma is the most commonly harvested flatfish in the north-central Gulf of Mexico (GOM), yet knowledge of this species’ growth and reproduction is limited for the Mississippi region. Given the offshore spawning migrations and likely mixing between state-managed units of the GOM Southern Flounder stock, small-scale environmental influences may constitute a major driver of life history dynamics during early life residency in nearshore estuaries. Therefore, estimates of local demographic characteristics are needed for effective fishery management. Here, we describe critical life history traits of Southern Flounder, including estimation of growth rates and maturity. The three-parameter von Bertalanffy growth function best described female-specific growth: mean asymptotic length L∞ was 514 mm TL, mean growth coefficient k was 0.67 year–1, and mean theoretical age at zero length t0 was –0.50 years. The estimated female-specific mean length at 50% maturity (L50) was 303 mm TL, and the female-specific mean age at maturity was 0.96 years. Although we observed significant differences between L50 estimates in the GOM, length-at-age parameter estimates were similar to those reported for other areas of the GOM. Both individual growth and length-at-maturity estimates were significantly different from those reported for the Atlantic, suggesting basin-level differences in population characteristics, with faster growth and earlier maturation in the GOM. Histological indicators and gonadosomatic index data indicated that the spawning season in the north-central GOM occurs from November to January and that Southern Flounder are batch spawners with asynchronous oocyte development. Our study provides a description of growth and spawning dynamics that will contribute to future stock assessment efforts focused on the Southern Flounder fishery in Mississippi and the GOM.
Highlights
Other characteristics of Southern Flounder spawning, including seasonality and reproductive strategy, have not been recently described for the Gulf of Mexico (GOM) or Mississippi
Our study provides a description of growth and spawning dynamics that will contribute to future stock assessment efforts focused on the Southern Flounder fishery in Mississippi and the GOM
Southern Flounder constitute the majority of harvest for the state-managed flounder fishery in the GOM (>10% of flatfish collected in our sampling were identified as Gulf Flounder), yet life history information is currently lacking for Southern Flounder in the Mississippi region
Summary
Other characteristics of Southern Flounder spawning, including seasonality and reproductive strategy, have not been recently described for the GOM or Mississippi. The presence of different oocyte stages throughout the spawning season was indicative of batch spawning in Southern Flounder collected from Louisiana waters (Fischer 1995). We (1) estimate female-specific growth parameters for the length-at-age relationship of Southern Flounder by using four candidate models, (2) estimate the length and age at maturity by using logistic models, (3) define the spawning season duration, and (4) characterize the Southern Flounder reproductive strategy.
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