Invertebrate predation in Lake Michigan: Regulation of Bosmina longirostris by Leptodora kindtii

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110049/1/lno19913630483.pd

The North American invasive zooplanktivore Bythotrephes longimanus is less hypoxia tolerant than the native Leptodora kindtii

The predatory cladoceran, Bythotrephes longimanus (spiny water flea), has been invading lakes and damaging food webs across the central part of North America since the early 1980s. To understand its niche and that of the taxonomically related and native predatory cladoceran Leptodora kindtii, we investigated species survival after 12-hour exposures to low dissolved oxygen (D.O.) concentrations in the laboratory. B. longimanus (n = 690) exhibited a hypoxia tolerance limit (LC50) of 1.65 mg LThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Foraging mechanisms of age-0 lake trout (Salvelinus namaycush)

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/m 2 /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/m 2 ), age-0 lake trout could quickly satisfy their energetic demands in a benthic setting