Age, growth, and reproduction of spotted seatrout in Barataria Bay, Louisiana

Spotted seatrout Cynoscion nebulosus (604 males, 1,453 females) were collected from Barataria Bay, Louisiana, from January 1994 to November 1995 for analyses of age, growth, and reproduction. It was confirmed that opaque annuli in sagittal otoliths accrete once a year during the period from November to April. Age among both sexes varied from 0 to 5 years; females dominated the population at age 2 but had disappeared from it at age 5. Females were significantly larger than males at all ages. Instantaneous mortality, annual mortality, and survival were, respectively, 1.40, 0.75, and 0.25 for females and 0.60, 0.45, and 0.55 for males. Spotted seatrout spawn over a 6-month period beginning in April and continuing through September, as indicated by elevated gonadosomatic index values and the recrudescence of oocyte maturation. Essentially all male and female spotted seatrout become reproductively mature the first summer after hatching. The presence of multiple oocyte maturation stages during the spawning season, the sporadic occurrence of postovulatory follicles, and the complete lack of spent females during the spawning season confirms the occurrence of batch spawning among spotted seatrout in Barataria Bay. The batch fecundity of 25 females aged 2-4 years (341-515 mm total length, 342-1,502 g total weight) ranged from 102,369 to 511,859 (mean, 250,483) ova per spawning event. Spawning frequency was estimated as one spawning event every 4 or 5 d. Given the above, on average, female spotted seatrout will spawn between 9 and 11 million ova each spawning season.