Louisiana estuarine and coastal fisheries and habitats: Perspectives from a fish's eye view

Stimulated by nutrients from the Mississippi River, the vast coastal wetlan ds 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 sy stem has yielded annual fishery landings of >453.6 x 10(6) kg (1 billion po unds) since 1969. The Louisiana ecosystem has been heavily exploited and si gnificantly altered over the years to meet the demands for coastal developm ent, seafood production, navigation, oil exploration, flood control, and ot her social, economic, and industrial activities. While not all impacts can be viewed as detrimental to fisheries or their habitat, some of these habit at impacts have contributed to significant ecological problems such as salt water intrusion, loss of coastal wetlands, and development of vast area of hypoxia along the coast. Management strategies to deal with some of these p roblems propose directed manipulations of the coastal environments to stop or reduce rates of degradation. Over the past 46 years, fisheries yields fr om Louisiana waters have remained strong. Although quantitative data are la cking to examine more than a few decades of environmental changes, an analy sis of fishery-independent trends for selected inshore species of nekton ov er a recent 21-yr period suggests that many species have been remarkably re silient to significant changes in their habitats and pressures from exploit ation. Over a longer period (60 yr), more significant changes to inshore de mersal 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 environme ntal impacts affecting the system, we also discuss potential reasons why mo re dramatic changes in nearshore and estuarine fish populations of coastal Louisiana are not apparent.