Water depth modifies relative predation risk for a motile fish taxon in Bahamian tidal creeks |
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Authors: | Andrew L Rypel Craig A Layman D Albrey Arrington |
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Institution: | 1.Department of Biological Sciences,University of Alabama,Tuscaloosa;2.Department of Biological Sciences,Florida International University,North Miami |
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Abstract: | We evaluated the influence of water depth on relative predation risk for mojarra (Eucinostomus spp.) in six tidal creeks on Andros Island, Bahamas. Relative predation risk was determined using a tethering protocol combined
with underwater visual census. In one experiment, we found that relative predation risk increased predictably with water depth
(r2 = 0.83), and survival of tethered mojarra decreased with water depth (r2 = 0.71). We identified three depth zones containing differing levels of predation threat: refugia (0–19 cm), transition (20–69
cm), and predation (> 70 cm). Predation on mojarra rarely occurred within the refugia zone (2% eaten) and always in the predation
zone (100% eaten). Additional factors not examined in this study (e.g., mangrove complexity, predator density) likely drive
variability of relative predation risk within the transition zone. In a second experiment, we directly examined influence
of water depth on relative predation risk at fixed locations from high tide to low tide in a single creek. Mean relative predation
risk was significantly higher during higher tides at deeper water depths. Results provide experimental evidence that exploitation
of shallow water refugia by motile prey can significantly reduce predation risk. We expect the distribution of motile fishes
is at least partially influenced by spatially-dynamic shallow water refugia. |
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