Reaction distances under various light intensities (0-19 uE/m2/s), angles of attack, swimming speeds, and percentage of overall foraging success were measured. Extensive efforts have been invested in restoring lean lake trout (Salvelinus namaycush) populations in the Laurentian Great Lakes, but successful natural recruitment of lake trout continues to be rare outside of Lake Superior and parts of Lake Huron. There is evidence of high mortality during the first several months after eggs hatch in the spring, but little is known about the foraging mechanisms of this age-0 life stage. We developed a foraging model for age-0 lake trout (S. namaycush) in response to amphipods (Hyalella azteca) and mysids (Mysis diluviana) by simulating underwater environmental conditions in the Great Lakes using a temperature-controlled chamber and spectrally matched lighting. Reaction distances under various light intensities (0-19 uE/m2/s), angles of attack, swimming speeds, and percentage of overall foraging success were measured. Intake rates under different light intensities and prey densities were also measured. Age-0 lake trout were non-responsive in the dark, but were equally responsive under all light levels tested. Age-0 lake trout also demonstrated a longer reaction distance in response to moving prey, particularly mysids, which had an escape response that reduced overall foraging success. We determined that prey intake rate (numeric or biomass) could be modeled most accurately as a function of prey density using a Michaelis-Menton equation and that even under low mysid densities (3 individuals/m2), age-0 lake trout could quickly satisfy their energetic demands in a benthic setting.
Bibliographical noteFunding Information:
We thank the Minnesota Department of Natural Resources Lake Superior Area Fisheries, the United States Geological Survey Lake Superior Biological Station, and the Trout Lake Research Station for providing ship time and/or equipment for capturing mysids. Dustin Wing provided assistance setting up lighting and foraging arenas, Ron Regal provided advice regarding data analysis, and John Sandberg provided field assistance capturing mysids. This project was funded in part through a summer grant provided by the University of Minnesota Duluth Visualization and Digital Imaging Lab . This work is the result of research sponsored by the Minnesota Sea Grant College Program supported by the NOAA office of Sea Grant, United States Department of Commerce , under grant No. NA03OAR4170048 . The U.S. Government is authorized to reproduce and distribute reprints for government purposes, not withstanding any copyright notation that may appear hereon. This paper is journal reprint No. JR 599 of the Minnesota Sea Grant College Program.
- Intake rate
- Lake trout
- Reaction distance