Transcript FIGURE 20.2 A food web of Duffin Creek, Ontario, Canada

Chapter 20
Predation and Food Webs
Dodds & Whiles
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FIGURE 20.1
A walleye (Stizostedion vitreum) consuming shiners (cyprinidae). (Photograph courtesy of Bill Lindauer Photography).
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FIGURE 20.2
A food web of Duffin Creek, Ontario, Canada, in December illustrating the high degree of omnivory of the aquatic
invertebrates. (Data from Tavares-Cromar and Williams, 1996).
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FIGURE 20.3
Stable isotope signatures of components of the food web in Lookout Creek, Oregon (A), and Toolik Lake, Alaska
(B). Errors plotted as standard error where data were available. Note that the use of both isotopes allows for clearer
separation of the food web components. The primary consumers in the stream probably rely on periphyton, but
those in the lake likely rely on phytoplankton. (Data from Fry, 1991).
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FIGURE 20.4
Daphnia lumholtzi, an invasive species in the central United States with large spines that protect it from predation.
(Photograph courtesy of K. D. Hambright).
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FIGURE 20.5
Diel vertical migration of young Daphnia longispina in Lake Lucerne. (Data from Worthington, 1931).
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FIGURE 20.6
Selectivity of bluegill (Lepomis macrochirus) on size of prey (Daphnia magna) at two prey densities. At low densities,
all sizes of Daphnia are equally represented in the bluegill guts. At high densities of prey, the larger zooplankton are
preferred (selectivity of 1 means consumption is the same as expected relative to random encounter rates). (Data from
Werner and Hall, 1974).
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FIGURE 20.7
Holling’s three types of functional response curves and the proportion of prey consumed assuming constant predator
numbers.
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FIGURE 20.8
A conceptual diagram of the trophic cascade in the pelagic zone of lakes. When large piscivores are present, smaller
zooplanktivores are uncommon, body size and numbers of zooplankton increase, and phytoplankton decrease.
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FIGURE 20.9
Effects of biomanipulation on fish, chlorophyll, Daphnia, and macrophyte cover in four shallow eutrophic lakes in The
Netherlands. Year 0 is before biomanipulation. Points are means from four lakes and error bars equal 1 standard
deviation. (Data from Meijer et al., 1994).
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FIGURE 20.10
Summary of effects of enclosure (A) and exclosure (B) on predatory fishes (roach (Hesperoleucas symmetricus) and
steelhead (Oncorhynchus mykiss)), roach and stickleback (Gasterosteus aculeatus) fry, invertebrate predators (lestid
damselflies), midge larvae (Pseudochironomus richardsoni), and benthic algae (Nostoc and Cladophora). Size of ovals
represents amount of biomass at each trophic level. (Data from Power, 1990a).
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