Mangroves as Fish Habitat

Effects of an Episodic Drought on a Floodplain Subsidy Consumed by Mangrove River Fishes (Extended Abstract)

Ross E. Boucek and Jennifer S. Rehage


Ecosystem connectivity is vital to provisioning mangrove-dependent fishes (Mumby 2006). In mangrove rivers, piscivorous fish populations are often subsidized by seasonal, highly abundant prey that flux into rivers from adjacent floodplain habitats at the onset of the dry season. The magnitude of these floodplain prey subsidies may be dependent on (1) rainfall dynamics and inundation patterns of floodplains during the previous flood season (i.e., the growing season for the forage species), and (2) the population dynamics of floodplain predators that may regulate forage fish population dynamics within the floodplain habitat (Welcomme and Halls 2004). Extreme and episodic droughts can disrupt these seasonal prey subsidies by reducing the duration of the flood season, resulting in changes to the population dynamics of floodplain forage fish, as well as affecting floodplain predators. Thus, in dry seasons following these disturbances, the quantity and composition of these subsidies may change as floodplain communities recover from disturbance. However, the long-term effects of droughts on tropical river fish floodplain subsidies remains understudied.

In the coastal mangrove rivers of the subtropical Everglades (U.S.), seasonal rainfall patterns dictate floodplain prey subsidies to a coastal mangrove river piscivore, Common Snook Centropomus undecimalis (Boucek and Rehage 2013). In 2011, a once-in-10-years drought affected South Florida. The drought caused floodplains to remain dry for 100 d, tripling the average number of dry days per year. This drought had profound impacts on floodplain fishes and likely altered subsidies to Common Snook (Boucek and Rehage 2014). The objective of this study was to determine the impact and legacy of the 2011 drought on floodplain subsidies. We hypothesized that 1 year after the drought, due to the reduced duration of the flood season, the floodplain subsidies would be lessened. Two years after the drought, due to the slower recovery of floodplain piscivores and top-down release of forage fishes on the floodplain, we expected a temporary increase in the magnitude of the subsidy to Common Snook.