Nonnative Fishes in Freshwater Canals of the Florida Everglades: Implications for Management

Nonnative species pose a serious threat to the ecological integrity and biodiversity of natural ecosystems, including those found within protected areas. Presently in Everglades National Park (ENP), fourteen nonnative fishes are established, yet we know little about how they interact with native biota, their response to hydrological disturbance including restoration efforts, and their overall impact. A subset of these nonnative fishes are new invasions since 2000, several of them accompanying restoration projects. Additional invasions of nonnative fishes may be expected as the number of nonnative fishes established outside of the protected natural areas continues to increase. Ongoing research examines the impact of nonnative fishes on lower trophic levels and ecosystem processes, how their impact is mediated by hydrology, the potential for new invasion threats from bordering canals, and the alternatives for their containment.

This study is focused on examining the spatiotemporal dynamics of fish communities, both native and nonnative, in canals bordering ENP.  Our research questions include the following:

1. What factors drive community structure in canals?
2. How do canals function as conduits for nonnative fishes?  
3. How does the inclusion of nonnative fish species alter fish community structure?
4. How do we control & contain nonnative fishes that have invaded canals, but are not yet present in ENP marshes?

Fish communities in canals bordering ENP marshes are sampled via boat-mounted electrofishing. Fish communities appeared distinct among canals, with nonnative fishes composing between 8% and 70%. Habitat complexity and other abiotic factors seem to be influencing natives and nonnatives differently (e.g., littoral habitat structure). Because restoration efforts in this region will impact water management, there is a strong need to better understand how these canals function as habitat.  In addition, canals are being used by restoration projects to deliver water to Everglades marshes often with little consideration of their role in the spread of nonnative taxa.  Our research findings suggest a need for more effective management of these nonnative fishes while they are confined to the canal systems and should serve as a useful tool for restoring Everglades marshes.