USGS NAWQA: The Ecological National Synthesis (ENS) Project

Four Primary Objectives of the ENS Project:

Assess the status and trends of aquatic ecological conditions (invertebrates, fish, algae and habitat) in rivers and wadeable streams.

Relate ecological conditions to chemical stressors (such as nutrients and pesticides), physical disturbances (such as habitat and hydrologic alterations) in the context of different environmental settings and land uses.

Enhance understanding of factors that influence the biological integrity of streams and how these stream ecosystems may respond to diverse natural and human factors.

Develop key ecological indicators of aquatic health.

Relations Between Introduced Fish and Environmental Conditions at Large Geographic Scales

Michael R. Meador¹, Larry R. Brown², and Terry M. Short³

¹U.S. Geological Survey, 12201 Sunrise Valley Drive, MS 413, Reston, Virginia 20192, USA
²U.S. Geological Survey, 6000 J Street, Sacramento, California 95819-6129, USA
³U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA

ABSTRACT.— Data collected from 20 major river basins between 1993 and 1995 as part of the U.S. Geological Survey’s National Water-Quality Assessment Program were analyzed to assess patterns in introduced and native fish species richness and abundance relative to watershed characteristics and stream physicochemistry. Sites (N = 157) were divided into three regions--northeast, southeast, and west--to account for major longitudinal differences in precipitation/runoff and latitudinal limits of glaciation that affect zoogeographic patterns in fish communities. Common carp (Cyprinus carpio) and largemouth bass (Micropterus salmoides) were the most frequently collected introduced fish species across all river basins combined. Based on the percentage of introduced fish species, the fish communities most altered by the presence of introduced fish occurred in the western and northeastern parts of the U.S. Native fish species richness was not an indicator of introduced fish species richness for any of the three regions. However, in the west, introduced fish species richness was an indicator of total fish species richness and the abundance of introduced fish was negatively related to native fish species richness. Some relations between introduced fish species and environmental conditions were common between regions. Increased introduced fish species richness was related to increased population density in the northeast and southeast; increased total nitrogen in the northeast and west; and increased total phosphorous and water temperature in the southeast and west. These results suggest that introduced fish species tend to be associated with disturbance at large geographic scales, though specific relations may vary regionally.