Adaptations in salt marsh teleosts to life in waters of varying salinity

Salt marsh environments are stressful, partially because of regular or unpredictable variations in ambient salinities, limiting habitability to a few teleost fish species. This study reviews capabilities of physiological response to ambient salinity in 10 teleost species of Florida Gulf coast salt marshes, nine permanent residents, and one a seasonal inhabitant. Two additional species found in marshes elsewhere in Florida, but absent from the study site, were also included. We examined salinity tolerances and osmotic regulatory capabilities among these teleosts, and related differences in their physiological responses to patterns of utilization of salinity-habitat zones, fresh to hypersaline waters. Lower salinity tolerance varied from fresh water to dilute brackish water, while upper salinity tolerance varied From 25 ppt to >100 ppt within this group. Osmotic regulatory capabilities also varied within the group, with the ambient salinity zone of most consistent plasma osmotic regulation varying in width, and in position at lower or higher ambient salinities, and varying among species. This was also true of the levels at which plasma osmotic concentrations were maintained. Several patterns of physiological responses to ambient salinity were found, with these roughly correlated with ranges of ambient salinity inhabited by the various species.