Past and present aquatic habitats and fish populations of the Yazoo-Mississippi Delta

Abstract

The goal of this review and synthesis of the literature, published and unpublished, is to describe the major processes that shape and influence the aquatic habitats and fish communities in the YazooMississippi Delta (YMD) and to outline a program of research. The YMD is influenced by the large geographic and temporal scales of the Mississippi River watershed. It extends over 41 percent of the contiguous United States. The Mississippi River has existed in its current location for more than 1.2 million years, and ancient fish species are still present in the watershed. About 9,500 years BP, the Mississippi River formed into a predominantly meandering channel from which most of the aquatic habitats in the YMD developed. Oxbows formed in the meander belts shape the topography of the YMD and are a fundamental part of the development of the aquatic habitat of the YMD. Seasonal floods are keystone events in the YMD, but the process is altered substantially from its previous natural state. Levees, flood control structures, land use practices, and loss of large wood in river channels have modified natural processes throughout most of the YMD. However, most of the larger fish species present during aboriginal occupation of the YMD are still present. Given the large-scale loss of habitat throughout the YMD and the deterioration of water quality, the abundance and diversity of fish likely have declined. In the past few years, management of aquatic habitats in the YMD has centered on mitigating and preventing some of the adverse effects of anthropogenic disturbance. A program of “naturalization” to move aquatic ecosystem processes closer to natural conditions is possible within the context of socioeconomic constraints. The research approach proposed in this paper provides a model to develop an understanding of the fish and aquatic habitat that can contribute to a sustainable restoration program.