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From Long-Term Data to Understanding: Toward a Predictive Ecology
2015 LTER ASM Estes Park, CO - August 30 - September 2, 2015

Using large predator fish body condition to predict alligator body condition in response to hydrologic seasonality in the Florida Coastal Everglades

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Virginia Fourqurean
Ross Boucek
Jennifer Rehage
Laura Brandt
Frank Mazzotti
Jeff Beauchamp

The linkages between environmental drivers and top mesopredators are often hard to discern because predators are hard to track. As top predators, American alligators (Alligator mississippiensis) play a crucial role in the Everglades, and their responses to hydrological drivers are of interest to ecosystem restoration. Previous research has shown that other predators in this estuarine system such as common snook (Centropomus undecimalis) and Florida largemouth bass (Micropterus salmoides) are both influenced by hydrologic seasonality in the Florida Coastal Everglades. Yet their responses to hydrologic seasonality may differ. For instance, at the start of the dry season, prey subsidies enter the estuary from upstream marshes, providing an abundance of prey for snook inhabiting the estuary, resulting in improved snook condition. Florida Largemouth bass on the other hand, are displaced from the marsh to the estuary in the dry season. But for bass, conditions in the estuary could be more stressful, due to salinity stress and food competition. In this study we asked, are alligators more likely to be influenced by environmental drivers that affect snook, or bass? Hydrologic seasonality may affect alligators either positively, similarly to snook, or negatively, similarly to bass. We compared alligator body condition, an indication of overall health, to that of bass and snook body condition across wet and dry seasons. If alligators are affected by the same drivers as bass, we expected to see a decrease in body condition during dry seasons. However if they are affected similarly to snook, then alligator condition should have improved in the dry season. Findings suggest that patterns are contingent on the type of hydrological year and severity of drying. We expect alligator foraging behavior, salinity stress, and hence, overall health to be strongly responsive to changes in salinity due to restoration (decrease) and sea level rise (increase).  

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