Are hydroscapes landscapes? A behavioral landscape-ecology framework for functional connectivity in aquatic ecosystems

Background/Question/Methods

Behavioral responses to landscape structure, such as habitat edges, area, and configuration, and subsequent emergent patterns of connectivity are mostly known from terrestrial environments. In particular, the application of this conceptual framework to submerged landscape structure has only been applied to a limited range of aquatic ecosystem types. We used a conceptual model of behavioral landscape-ecology as a framework for analyzing functional connectivity from fish movement in a hydroscape where structural connectivity varies seasonally from annual droughts. The Florida Everglades is a spatially extensive wetland with hydroscape structure from artificial elements, such as canals, and local to regional scale variation in topography that shapes spatiotemporal patterns of hydrology. How the natural and artificial hydroscape structure in this wetland affects connectivity from fish movement is not well known, adding uncertainty to outcomes of proposed restoration measures. We used radio telemetry techniques to quantify the movement patterns of three species of large-bodied piscivorous fishes within areas characterized by different hydroscape patterns. Statistical models of hydroscape structure at multiple scales was extracted from an integrated network of monitoring gauges and hydrology models and confronted with empirical data on movement scales and directions, including movement between canals and marshes.

Results/Conclusions

Florida Gar, the most abundant predatory fish, made longer, more directed movements when structural connectivity was decreasing during droughts than during the increased connectivity characterizing the rainy season. During receding water, Florida Gar movement patterns were shaped by the distance and direction they needed to move to reach drought refuge habitats. Scale, timing, and direction of functional connectivity between marshes and canals were influenced by spatial patterns of hydrology bordering each canal. Permeability of the borders between canals and marshes to fish movement and the scale of hydroscape structure affecting connectivity distances and directions were both greater for an invasive species, the Mayan Cichlid, than for Florida Largemouth Bass, a commercially important native predator. These quantified links between fluctuating hydroscape structure and functional connectivity scale up to metapopulation and metacommunity dynamics at annual and long-term time scales. A major goal of Florida Everglades restoration is to recreate more natural hydrological patterns, including reconnecting regions where flow is currently blocked by canals and levees. A hydroscape perspective on connectivity provides a framework for predicting the impacts of climate- and water management-related changes to hydrology in the Florida Everglades.