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Alternate Title

The Reproductive Biology of Spotted Seatrout, Cynoscion nebulosus, Along the Mississippi Gulf Coast

Abstract

Spotted seatrout, Cynoscion nebulosus, were collected from the barrier islands, Biloxi Bay and St. Louis Bay areas along the Mississippi Gulf Coast during April-Sep. 1998 and March-Sep. 1999. Female spotted seatrout reached 50% sexual maturity at 230 mm standard length (SL) (age 1), and 80% of age-1 spotted seatrout captured were sexually mature. Spotted seatrout have a 5-mo spawning season in Mississippi, ranging from mid-April to mid-Sep., although the onset of the season may vary annually depending on temperature. Histological analysis showed spotted seatrout are capable of spawning multiple times throughout the reproductive season, and batch fecundity was estimated from 51 fish undergoing final oocyte maturation (FOM). Batch fecundity (BF) was significantly (P < 0.001) positively related to SL and ovary-free body weight (OFBW); the equation best describing the BF-size relationship was BF = (554.2·SL) - 88,398 (r2 = 0.25). Relative BF was significantly different among months (P = 0.041), with June values higher than those in Aug. Overall, mean relative BF was 165.7 ± 13.9 eggs/g OFBW. The FOM and postovulatory follicle methods gave similar estimates of overall spawning frequency of once every 4-5 d. However, there were significant differences (P < 0.001) in spawning frequency among areas; spotted seatrout from the barrier islands and St. Louis Bay areas spawned more frequently (mean, every 4 d) than fish from Biloxi Bay area (mean, every 15-18 d). Salinity, depth, and submerged habitat are not different among the areas, but there is greater shoreline development in the Biloxi Bay area. Differences in the reproduction of spotted seatrout among estuaries need to be considered when developing regional management plans for the species.

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