Effects of Smallmouth Bass on Atlantic Salmon Habitat Use and Diel Movements in an Artificial Stream

Abstract

Invasive smallmouth bass Micropterus dolomieu have been introduced to some of the last remaining watersheds that contain wild anadromous Atlantic salmon Salmo salar, yet little is known about the interactions between these species. We used an artificial stream equipped with passive integrated transponder tag antenna arrays to monitor habitat use and movements of age-0 Atlantic salmon and age-0 smallmouth bass in sympatry and allopatry. We used additive and substitutive designs to test for changes in habitat use, diel movements, and diel activity patterns of prior-resident Atlantic salmon or smallmouth bass resulting from the addition of conspecifics or heterospecifics. Atlantic salmon prior residents did not change their habitat use in the presence of conspecific or heterospecific invaders. However, Atlantic salmon invaders did lessen riffle habitat use by smallmouth bass prior residents during daytime. Atlantic salmon and smallmouth bass displayed different diel activity patterns of movement (Atlantic salmon were more nocturnal; smallmouth bass were more diurnal), which were affected by heterospecific introductions. Because the two species tended to favor different habitat types and displayed different diel activity patterns, we suggest that under the conditions tested, the level of interspecific competition for habitat was low. Age-0 Atlantic salmon and smallmouth bass may be able to avoid intense interspecific competition through spatial and temporal habitat partitioning. These data do not, however, predict the potential for competition under different seasonal or ontogenetic circumstances.

Received October 5, 2010; accepted July 7, 2011

ACKNOWLEDGMENTS

We thank Wes Ashe, James Osenton, Scott Ouellette, Megan Patridge, Janice Hubner, and Silas Ratten for their assistance in the laboratory. We are also grateful to Dimitry Gorsky for his help data organization and analysis. We thank Paul Santavy, Scott Craig, and staff at the Craig Brook National Fish Hatchery for providing Atlantic salmon fry and logistical support. This project benefited from the logistical and professional support of Neil Greenburg and Douglas Reed (University of Maine) and Peter Ruksznis (Maine Department of Marine Resources). We thank Jeff Johnson and Pat Connolly for reviewing an earlier version of this manuscript and Fred Utter and three anonymous reviewers for providing valuable suggestions that improved the manuscript. Funding was provided by the University of Maine, the Maine Agricultural and Forest Experiment Station, the U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, the Outdoor Heritage Fund, and the Maine Department of Marine Resources. This paper is Maine Agricultural and Forest Experiment Station Publication Number 3166. All experimental fish were handled in accordance with Protocol A2005-08-01, which was approved by the Institutional Animal Care and Use Committee, University of Maine. Mention of trade names does not imply endorsement by the U.S. Government.