Temporal and Spatial Patterns of Non-Native Fishes in the Florida Everglades

In 2001 we evaluated the distribution of non-native fishes in freshwater ecosystems of South Florida, focusing on the Everglades.  Ten years later, we re-visit that analysis to assess changes in the distribution and abundance on non-native fishes in the region, and to evaluate the impact of hydrological management on those changes.  In the original analysis, we concluded that non-native fish were most abundant in the mangrove zone at the border of Florida Bay and the Everglades, and were also abundant in short-hydroperiod wetlands on the eastern boundary of Everglades National Park, as well as in canals crossing the Everglades.  While all non-native fishes found in these habitats were also present in the largest freshwater habitat of the region, wet prairies of the Everglades, none were particularly abundant there.  Non-native fishes generally comprised fewer than 2% of the fish or biomass in the Everglades, with seven species comprising the bulk of non-native fishes observed.  Ten years since that summary, four new species have expanded into the Everglades and become locally abundant, including brown hoplo (Hoplosternum littorale), African jewelfish (Hemichromis letourneuxi), swamp eel (Monopterus albus), and spiney eel (Macrognathus siamensis).   The relative abundance of non-native fishes remains low in wet prairies, but has increased in many locations, particularly in alligator ponds.   Everglades restoration has included increased connections of canals to marshes of the Everglades in an effort to regain historical patterns of sheetflow that yield beneficial physical impacts on the landscape, but which may facilitate invasion of non-native fishes from canals.   Decompartmentalization of the Everglades (filling canals and removing levees) is a major goal of the Comprehensive Everglades Restoration Plan, but may facilitate the spread of non-native aquatic animals, notably fishes.  A major cold front crossed South Florida in January, 2010, which produced a marked decline in most species of non-native fishes.  However, recovery of these is already apparent in 2012, indicating a resiliency of these invaders that creates challenges for their management.