Stimulated by nutrients from the Mississippi River, the vast coastal wetlands of the river's past and present deltas interface with the Gulf of Mexico to form a complex and prolific marine ecosystem. This highly productive system has yielded annual fishery landings of >453.6 × 106 kg (1 billion pounds) since 1969. The Louisiana ecosystem has been heavily exploited and significantly altered over the years to meet the demands for coastal development, seafood production, navigation, oil exploration, flood control, and other social, economic, and industrial activities. While not all impacts can be viewed as detrimental to fisheries or their habitat, some of these habitat impacts have contributed to significant ecological problems such as saltwater intrusion, loss of coastal wetlands, and development of vast areas of hypoxia along the coast. Management strategies to deal with some of these problems propose directed manipulations of the coastal environments to stop or reduce rates of degradation. Over the past 46 years, fisheries yields from Louisiana waters have remained strong. Although quantitative data are lacking to examine more than a few decades of environmental changes, an analysis of fishery‐independent trends for selected inshore species of nekton over a recent 21‐yr period suggests that many species have been remarkably resilient to significant changes in their habitats and pressures from exploitation. Over a longer period (60 yr), more significant changes to inshore demersal trawl assemblages are apparent, but data are lacking to conclusively identify their causes or quantitatively document the magnitude of change. We review some of the major changes that have occurred in habitat believed to be essential to fishes and review other factors likely to be significant in structuring fish populations. Given the significant number of environmental impacts affecting the system, we also discuss potential reasons why more dramatic changes in nearshore and estuarine fish populations of coastal Louisiana are not apparent.

Stimulated by nutrients from the Mississippi River, the vast coastal wetlands of the river's past and present deltas interface with the Gulf of Mexico to form a complex and prolific marine ecosystem. This highly productive system has yielded annual fishery landings of Ͼ453.6 ϫ 10 6 kg (1 billion pounds) since 1969. The Louisiana ecosystem has been heavily exploited and significantly altered over the years to meet the demands for coastal development, seafood production, navigation, oil exploration, flood control, and other social, economic, and industrial activities. While not all impacts can be viewed as detrimental to fisheries or their habitat, some of these habitat impacts have contributed to significant ecological problems such as saltwater intrusion, loss of coastal wetlands, and development of vast areas of hypoxia along the coast. Management strategies to deal with some of these problems propose directed manipulations of the coastal environments to stop or reduce rates of degradation. Over the past 46 years, fisheries yields from Louisiana waters have remained strong. Although quantitative data are lacking to examine more than a few decades of environmental changes, an analysis of fishery-independent trends for selected inshore species of nekton over a recent 21-yr period suggests that many species have been remarkably resilient to significant changes in their habitats and pressures from exploitation. Over a longer period (60 yr), more significant changes to inshore demersal trawl assemblages are apparent, but data are lacking to conclusively identify their causes or quantitatively document the magnitude of change. We review some of the major changes that have occurred in habitat believed to be essential to fishes and review other factors likely to be significant in structuring fish populations. Given the significant number of environmental impacts affecting the system, we also discuss potential reasons why more dramatic changes in nearshore and estuarine fish populations of coastal Louisiana are not apparent.

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.

© 1998 Blackwell Science Ltd. 267 than did sperm thawed at 10, 20, 30, 40, 50 or 60°C in a water bath.

No abstract