Killifish habitat suitability as a measure of coastal restoration performance: Integrating field data, behavioral trials and simulation

One of the goals of the Comprehensive Everglades Restoration Plan (CERP) is to restore more natural salinity regimes to the coastal bays of South Florida (USA) with the aim of improving their degraded estuarine function (e.g., as productive feeding and nursery areas). Here, we examined the occurrence (presence–absence) and concentration (presence-only fish density) of goldspotted killifish (Floridichthys carpio) observed in an ongoing fish survey as potential indicators of restoration performance in Biscayne Bay, Florida. To determine F. carpio salinity affinity, we applied regression analyses to field data and performed behavioral choice trials in the laboratory, whereby individuals were exposed to a salinity gradient (10–50). Analysis of field data indicated a parabolic relationship between killifish occurrence and salinity, where occurrence is maximized at salinity ∼22. Killifish concentration was unrelated to salinity. Experimental salinity choice results tended to agree with field observations of occurrence and demonstrated a preference for intermediate salinity levels (10–30). Finally, we performed a simulation exercise to compare seasonal changes in habitat suitability within our study domain over the course of one year. Seasonal comparisons were performed as a proxy for assessing different freshwater management alternatives. We applied the relationship between killifish occurrence and salinity that resulted from analyses of field data to the output of a published hydrodynamic salinity transport model. This exercise provided areal estimates of suitable habitat gained or lost, as well as maps indicating the geographic distribution of habitat quality by season. We conclude that: (1) continued field monitoring of goldspotted killifish occurrence is warranted for its utility as a biological indicator of nearshore salinity conditions in an ecosystem-based management framework and (2) the regression relationships revealed by the present study may be useful in habitat suitability modeling exercises, especially those that compare impacts of different freshwater flow scenarios via simulation.