TY - JOUR
T1 - Foraging by a young-of-the-year piscivore
T2 - The role of predator size, prey type, and density
AU - Galarowicz, Tracy L.
AU - Wahl, David H.
PY - 2005/10
Y1 - 2005/10
N2 - Young-of-the-year piscivores undergo ontogenetic diet shifts, but mechanisms influencing prey selection and implications for growth are unclear. We examined foraging and growth of 20- to 150-mm walleye (Sander vitreus) fed either zooplankton, benthic invertebrates, or fish over a range of prey densities in the laboratory. The number of each prey type consumed was influenced by walleye size and prey density. Walleye exhibited type II functional responses on each prey type; attack coefficients were constant across zooplankton and fish densities but decreased with benthic invertebrate densities. Handling time estimates were greater for fish than for other prey types but similar for zooplankton and benthos. Foraging efficiencies on zooplankton and benthic invertebrates increased with walleye size but were variable for fish prey. The smallest walleye size class (20 mm) had similar energy return (J·min-1) and growth (g·day-1) on zooplankton, benthic invertebrates, and fish. For larger walleye, both energy return and growth were highest on fish. intermediate on benthic invertebrates, and lowest on zooplankton. Diet shifts of juvenile piscivores and, consequently, growth can be explained by ontogenetic changes in foraging abilities and prey densities.
AB - Young-of-the-year piscivores undergo ontogenetic diet shifts, but mechanisms influencing prey selection and implications for growth are unclear. We examined foraging and growth of 20- to 150-mm walleye (Sander vitreus) fed either zooplankton, benthic invertebrates, or fish over a range of prey densities in the laboratory. The number of each prey type consumed was influenced by walleye size and prey density. Walleye exhibited type II functional responses on each prey type; attack coefficients were constant across zooplankton and fish densities but decreased with benthic invertebrate densities. Handling time estimates were greater for fish than for other prey types but similar for zooplankton and benthos. Foraging efficiencies on zooplankton and benthic invertebrates increased with walleye size but were variable for fish prey. The smallest walleye size class (20 mm) had similar energy return (J·min-1) and growth (g·day-1) on zooplankton, benthic invertebrates, and fish. For larger walleye, both energy return and growth were highest on fish. intermediate on benthic invertebrates, and lowest on zooplankton. Diet shifts of juvenile piscivores and, consequently, growth can be explained by ontogenetic changes in foraging abilities and prey densities.
UR - http://www.scopus.com/inward/record.url?scp=32644440026&partnerID=8YFLogxK
U2 - 10.1139/f05-148
DO - 10.1139/f05-148
M3 - Article
AN - SCOPUS:32644440026
SN - 0706-652X
VL - 62
SP - 2330
EP - 2342
JO - Canadian Journal of Fisheries and Aquatic Sciences
JF - Canadian Journal of Fisheries and Aquatic Sciences
IS - 10
ER -