The reaction distance, angle of attack, and foraging success were determined for siscowet lake trout (Salvelinus namaycush siscowet) during laboratory trials under lighting conditions that approximated downwelling spectral irradiance and intensity (9.00×108-1.06×1014photonsm-2s-1) at daytime depths. Siscowet reaction distance in response to golden shiners (Notemigonus crysoleucas) was directly correlated with increasing light intensity until saturation at 1.86×1011photonsm-2s-1, above which reaction distance was constant within the range of tested light intensities. At the lowest tested light intensity, sensory detection was sufficient to locate prey at 25±2cm, while increasing light intensities increased reaction distance up to 59±2cm at 1.06×1014photonsm-2s-1. Larger prey elicited higher reaction distances than smaller prey at all light intensities while moving prey elicited higher reaction distances than stationary prey at the higher light intensities (6.00×109 to 1.06×1014photonsm-2s-1). The capture and consumption of prey similarly increased with increasing light intensity while time to capture decreased with increasing light intensity. The majority of orientations toward prey occurred within 120° of the longitudinal axis of the siscowet's eyes, although reaction distances among 30° increments along the entire axis were not significantly different. The developed predictive model will help determine reaction distances for siscowet in various photic environments and will help identify the mechanisms and behavior that allow for low light intensity foraging within freshwater systems.
Bibliographical noteFunding Information:
For assistance and expertise with fish collection and husbandry, the authors thank the crew of the RV Kiyi. Funding for this project was provided by Minnesota Sea Grant (Sea Grant Research Project R/F 35), the United States Geological Survey , National Science Foundation Grants IOS-1354745 and DBI-1359230 (AFM), Lake Superior Biological Station and the University of Minnesota Duluth Biology Department . The authors would also like to thank M. Joyce for his great knowledge of all things statistical as well the continued help and support from K. Harrington, K. Olson, R. Mahling, E. Heald, B. Vetter, G. Hanson, M. Sorenson, M. Sizer, T. Arhenstorff and the McNair Scholars Program at the University of Wisconsin-Superior.
© 2015 International Association for Great Lakes Research.
- Angle of attack
- Lake Superior
- Light attenuation
- Reaction distance