Corridors and Habitat Connections for Native and Exotic Fishes in a Modified Landscape

Landscape structure affects fish movement in ways that alter the outcome of environmental disturbance, rate of invasive species spread, and overlap between competitors, predators, and prey.  The Florida Everglades landscape is heavily modified by addition of levees and canals that alter hydrology and can act as barriers, corridors, and habitat for native and exotic species.  We conducted a 3-year, radio telemetry study of native (largemouth bass) and nonnative (Mayan cichlid) fish movement in three canals in order to measure spatial scale of movement within canals, frequency of movement between canals and adjacent marshes, and scale of movement into bordering marshes.  Tracking occurred in both the wet season, when rising water levels connect canals and marshes, and in the dry season, when water levels are declining.  In most years, largemouth bass moved greater distances within canals than Mayan cichlids, with movement significantly decreasing in the dry season.  A higher percentage of Mayan cichlids dispersed from canals to marshes than largemouth bass, with Mayan cichlids also dispersing from canals earlier in the wet season and moving further into adjacent marshes than largemouth bass.  These patterns illustrate how human-altered landscapes influence animal movement and provide avenues of dispersal for native and nonnative species.