Ecological Archives M083-005-A1

Pamela L. Reynolds, John F. Bruno. 2013. Multiple predator species alter prey behavior, population growth, and a trophic cascade in a model estuarine food web. Ecological Monographs 83:119–132. http://dx.doi.org/10.1890/11-2284.1

Appendix A. Predator efficiency of prey capture.

To assess how efficiently our predators consumed A. longimana, we conducted a feeding trial in September of 2008 at the University of North Carolina at Chapel Hill’s Institute of Marine Science (IMS) in Morehead City. The experimental setup was the same as in the community experiment except predators were not caged (n = 6). After 6 hours we removed all predators and counted the remaining A. longimana. Lower recovery indicated greater predator efficiency. We compared the number of amphipods recovered across predator treatments using a one-factor ANOVA with LSM planned comparison of the 3 predator polyculture to the average predator monoculture in JMP.

Predator identity affected A. longimana survival (one-factor ANOVA: F3,20 = 7.896, P = 0.0011, Fig. 2). Almost all amphipods were recovered in the no-predator replicates, which on average lost 2.8% of prey. Fish and shrimp were the most efficient predators in monoculture, consuming on average 53.8 and 46.7% of prey respectively during the feeding trial, while crabs only consumed 24.4%. These results are similar to those of Bruno and O’Connor (2005) and Nelson (1979). The fewest prey were recovered in predator polycultures, which consumed on average 57.8% of prey during the trial. These conclusions should be interpreted with caution as predator efficiency and richness effects may change under more natural conditions with open prey populations (O'Connor and Bruno 2009).

Table A1. Sizes of predators used in the community experiment. Lengths are true length for fish and shrimp, carapace width for crabs. Values are means + 1 SE. n = 32.

Predator

Wet Mass (g)

Length (cm)

Panopeus herbstii (mud crab)

2.5 + 0.1

1.8 + 0.1

Penaeus aztecus (brown shrimp)

4.2 + 0.2

5.8 + 0.1

Lagodon rhomboides (pinfish)

2.6 + 0.1

4.3 + 0.1

Literature cited

Bruno, J. F., and M. I. O'Connor. 2005. Cascading effects of predator diversity and omnivory in a marine food web. Ecology Letters 8:1048–1056.

Nelson, W. G. 1979. Experimental studies of selective predation on amphipods: Consequences for amphipod distribution and abundance. Journal of Experimental Marine Biology and Ecology 38:225–245.

O'Connor, M. I., and J. F. Bruno. 2009. Predator richness has no effect in a diverse marine food web. Journal of Animal Ecology 78:732–740.

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