Modeling Size Dependent Interactions of a Juvenile Piscivore: Implications for Growth and Survival
Galarowicz, Tracy Lyn
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Permalink
https://hdl.handle.net/2142/87012
Description
Title
Modeling Size Dependent Interactions of a Juvenile Piscivore: Implications for Growth and Survival
Author(s)
Galarowicz, Tracy Lyn
Issue Date
2003
Doctoral Committee Chair(s)
Wahl, David H.
Herendeen, Robert A.
Department of Study
Ecology, Ethology, and Evolution
Discipline
Ecology, Ethology, and Evolution
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Language
eng
Abstract
The influence of size-specific interactions on foraging and mortality has consequences for growth and recruitment of juvenile fish. Many juvenile piscivores, such as walleye (Stizostedion vitreum), undergo ontogenetic diet shifts switching from zooplanktivory to benthivory and, finally, piscivory. These foraging shifts ultimately impact growth given the discrepancies in energetic gain from different prey types. Age-0 fish are also susceptible to size-dependent mortality including predation, starvation, and, potentially, size-related stress. To address the importance of size-related processes, I developed and tested an individual-based model (IBM) comprised of three submodels (foraging, growth, and mortality) to predict growth and survival of young-of-year walleye in Illinois. To develop the foraging submodel, I first conducted a series of laboratory experiments to examine the influence of prey type and availability on young-of-year walleye foraging patterns. When walleye were offered different prey types (zooplankton, benthic invertebrate, or fish) separately, consumption was influenced by walleye size and prey density. However, foraging patterns varied with relative prey availability when all three prey types were available simultaneously. Small juveniles (20 mm) selected zooplankton and fish, whereas larger walleye (40--100 mm) selected benthic invertebrates and fish. The foraging submodel successfully predicted diet composition when compared to diets of walleye in an experimental pond. Growth of walleye as a function of prey type was examined in the laboratory. Small walleye exhibited the highest growth on fish and moderate growth on either zooplankton or benthic invertebrates. For walleye larger than 40 mm, growth was highest on zooplankton or benthic invertebrates. For walleye larger than 40 mm, growth was highest on fish, intermediate on benthic invertebrates, and lowest on zooplankton. The growth submodel was based on published bioenergetics parameters. I also compared metabolic rates, food consumption, growth, and conversion efficiency among juvenile walleye as a function of latitude. Geographic origin, in addition to size, may influence walleye growth. The mortality submodel was built with data compiled from laboratory experiments and field observations. Simulated walleye mortality resulted from thermal stress, starvation, or predation. Simulations were performed for several reservoirs in Illinois. The IBM successfully predicted growth and survival for several systems and years and supports the hypothesis that size-specific interactions can shape an age-0 fish cohort.
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