Hydrological disturbance and the changing quality of refuge habitats for displaced fishes: Coastal natural vs. wetland artificial?

Background/Question/Methods

Disturbance regimes can regulate the flux of organisms across the landscape. Mobile organisms can avoid or minimize the negative effects of disturbance by emigrating to more bening habitat patches or 'refuge; habitats. Anthropogenic modifications can alter the quality or value of these refuge habitats, yet with increasing global change understanding the role of refuge habitats to population persistance is pressing. In tropical pulsing systems such as the Florida Everglades, seasonal hydrology creates a temporally-variable habitat mosaic that influences patterns of fish abundance and distribution across both coastal and freshwater habitats. In response to this seasonal variation in habitat availability and quality, fish move into deeper or refuge habitats, but little is known about their relative quality. Their relative quality may also be variable in both space and time as a function of water management and other anthropogenic alterations. We compared the quality of coastal mangrove creeks and inland manmade canals as refuge habitats for key wetland mesoconsumers displaced in the dry season: Largemouth bass, Florida gar and bowfin. In mangrove creeks, we compared the performance of these mesoconsumers to that of resident common snook. We assessed variation in patterns of abundance, size distribution, body condition, and extent of the habitat use using electrofishing and tagging techniques.

Results/Conclusions

Largemouth bass and gar were more abundant in canals, but were larger and in better condition in creeks. In creeks, freshwater mesoconsumers were two to five times more abundant than snook. Results suggests tradeoffs in habitat quality that likely influence the movement decisions of fishes, and highlight the importance of refuge habitats to population and recolonization dynamics in pulsing systems. We discuss results in the context of climate change and implications for recreational fisheries. We expect the importance of these refuge habitats to population persistence to become increasingly important with climate change and predictions of lower rainfall and increased frequency of extreme climate events (droughts).