Document: ROB-3-75-12

The role of seasonal hydrology in the dynamics of fish communities inhabiting karstic wetlands of the florida everglades.

KOBZA, R.M.* and J.C.TREXLER

Florida International University, Miami, FL 33199 ¹

Abstract:
We studied the role of hydrological variation and availability of dry-season refugia in shaping the structure of fish communities in karstic wetlands of the Florida Everglades. The Rocky Glades is a wetland region of the extreme southeastern Everglades that is flooded for less than 6 months in most years. Solution holes serve as refugia for aquatic organisms, especially fishes, during the dry season. Our study addressed the following questions: Do fishes accumulate into predictable assemblages in solution holes during the dry season? Do abiotic characteristics of solution holes such as depth, water quality, or habitat complexity determine the assemblage of fishes that persist there? And, how do biotic interactions, especially predation, influence which species survive the dry season to recolonize the marsh surface when the rainy season arrives? To assess relative abundance of fishes, we sampled 19 solution holes in Everglades National Park weekly, between December and June, 1999, with non-destructive activity traps, coupled with mark-release-recapture techniques. We collected over 2,500 fishes in 17 species during the study period. The abundance of fishes increased early in the dry season, followed by intense mortality in mid-April. Principal components analysis indicated that fish relative abundance changed during the dry season with early colonization by bluefin killifish and sailfin mollies, followed by piscivorous species in mid-March with concomitant decline in small-sized species. Over 50% of the piscivorous fish were introduced species, such as walking catfish and two cichlids. Introduced fishes appeared to tolerate the stressful solution-hole environment in the late dry season better than most native species. Our results suggest that secondary production of fishes in the Rocky Glades is reduced by mortality during the annual dry season because solution hole refugia are limited in number and experience poor water quality.

Keywords: karstic wetlands, community structure, fish, Everglades, dry-season refugia

This abstract is being presented at: 3:15 PM in session:
Oral Session #62: Freshwater Fish Ecology.