PARENT SESSION
Oral Session #55: Predator - Prey Interactions.
Presiding: R. Dueser
Wednesday, August 7. 8:00 AM to 11:30 AM. Cochise Meeting Room, TCC.
Facilitation between herons and bass on common minnow prey: death from above and below.
Steinmetz, Jeff*,1,2, Soluk, Daniel1,2, Kohler, Steven3, 1 University of Illinois, Urbana, IL2 Illinois Natural History Survey, Champaign, IL3 Western Michigan University, Kalamazoo, MI
ABSTRACT- The larger fish in deeper water pattern is attributed to different predation pressures on different sized fish. Smaller fish are vulnerable to large piscivorous fish, thus avoid deeper habitats. Large fish are vulnerable to terrestrial predators, thus avoid shallow habitats. Medium sized fish may be vulnerable to both types of predators. What remains unexplored is how these predators interact with one another. We conducted a cage experiment to test whether avian and aquatic predators compete, facilitate, or are neutral in their interactions. We used a 2x2 factorial design, with avian predator presence/absence, and smallmouth bass presence/absence as the treatments. Cages (3x2m) had the shallow half open to wading birds, while bass were confined to the deep portion with a coarse mesh screen. Two prey species, striped shiners and central stonerollers, were stocked in natural densities. Response variables included number of prey surviving and prey habitat use. We found evidence of facilitation between smallmouth bass and wading birds (ANOVA, BassxBird Interaction, F1,26 = 5.328, p=0.029), with greater than twice as many prey consumed when both predators were present compared to when either prey occurred alone. This work illustrates the potential importance of terrestrial predators in aquatic food webs.
KEY WORDS: Facilitation, Multiple predators, Predator-prey, Bird-fish interaction