This video is a student created video abstract to share the findings of a scientific publication from the University of Miami's Shark Research & Conservation Program.
Changes in the movement patterns of predators can cause prey to alter their habitat use, which can subsequently trigger trophic cascades or domino effects to other organisms in the community. In a paper published in the journal PLoS ONE titled, “A Comparison of Spatial and Movement Patterns between Sympatric Predators: Bull Sharks (Carcharhinus leucas) and Atlantic Tarpon (Megalops atlanticus),” our team and collaborators conducted a satellite tagging study to investigate the potential predator-prey interactions between bull sharks and tarpon in Southern Florida waters. SPOT satellite tags were deployed on 18 adult bull sharks and 10 adult tarpon to examine their movement patterns. The tracking data showed that even though bull sharks and tarpon share similar diets and generally occupying similar areas, there was little overlap in their habitat use.
Bull sharks were present in southern Florida waters year-round, but the occurrence of the largest shark (>230 cm) peaked when tarpon abundance was highest. The study revealed that tarpon generally avoided areas of high bull shark density, despite high food availability occurring there. In fact, when moving over deep ocean waters, where shark abundance was highest, tarpon swam at high movement rates, in straight lines, until reaching shallower and more structurally-complex areas (where risk from sharks was lowest), at which point tarpon returned to a normal, slower, swimming speed with behaviors indicative of feeding. The tarpon also occasionally swam up rivers, where tracked bull sharks were absent. Based on these results, we propose that tarpon trade-off energetic costs of food (spending more time in less productive feeding areas) and osmoregulation (moving upstream into freshwater rivers requires extra energy to maintain the correct amount of water inside the fish’s body) to reduce their risk of bull shark predation.
Video by: Gareth Burghes, Lagomorph Films (gburghes.wix.com/lagomorphfilms)