Nearshore Salinity and Juvenile Pink Shrimp (Farfantepenaeus duorarum): Integrating Field Observations, Laboratory Trials, and Habitat Suitability Simulations

of a dissertation at the University of Miami. Dissertation supervised by Professors Joseph Serafy and Diego Lirman. No. of pages in text. (252) The pink shrimp Farfantepenaeus duorarum has been selected as one of many ecological indicators to assess implementation of the Comprehensive Everglades Restoration Plan (CERP). One element of CERP, the Biscayne Bay Coastal Wetlands (BBCW) project, intends to reduce salinity conditions along southwestern Biscayne Bay nearshore areas while also redistributing freshwater inflows to expand the spatial extent of reduced salinity (mesohaline [5-18 ppt] and oligohaline [0.5-5 ppt]) conditions. CERP restoration goals for Biscayne Bay juvenile pink shrimp nearshore populations presumed these salinity regimes would benefit pink shrimp abundances. Using this hypothesis as a backdrop, my dissertation was designed to test whether increased area of mesohaline and oligohaline conditions within a 50-m strip of shallow-water shoreline area likely would increase pink shrimp densities. I conducted four studies consisting of a literature review, both field and laboratory studies, and a habitat suitability modeling studies to test this hypothesis. First, I carried out a comprehensive literature review to gather, synthesize, and, where possible, conduct meta-analysis to provide a context for salinity effects on pink shrimp “Essential Fish Habitat” (EFH) metrics (i.e., distribution/occurrence, density/relative abundance, growth, survival, and productivity) and behavior. Polyhaline and/or euhaline salinity regimes generally maximized pink shrimp occurrence, abundance, growth, and survival. However, exceptions to this generalization were noted, such as interaction with benthic aquatic vegetation conditions or limitations with respect to observed salinity ranges. Meta-analysis of survival data yielded a parabolic relationship that maximized at ~30 ppt. Next, I conducted an analysis of field data representing 10 years of pink shrimp density and habitat observations from a monitoring project on southwestern Biscayne Bay nearshore epifaunal communities. Quantile regression detected density limitation by temperature, salinity, total submerged aquatic vegetation percent cover, and water depth. Cluster analysis of pink shrimp spatial density patterns revealed density reductions in a sub-region of the shoreline marked by low mean salinity and higher salinity variation. Temporal clustering indicated low inter-annual and seasonal variability in density patterns. However, wet season densities were more often lower than those of dry season, especially during the 2013 wet season microalgal bloom event. Third, I completed a laboratory study to investigate salinity effects (5, 10, 15, 25, 35, 45, and 55 ppt treatment levels) on pink shrimp growth, in terms of molt increment and intermolt period, and survival. Linear growth in weight and length exhibited parabolic responses to salinity with maximal growth at 34 and 33 ppt, respectively. No statistical relationship between salinity and molt increment nor intermolt period was observed. Pink shrimp survival was reduced at salinities < 15 ppt. This study may have been compromised by an as yet unidentified disease displayed by the shrimp. Lastly, I used quantile regression of 35 d antecedent mean salinity as the basis for a habitat suitability model to simulate salinity effects on pink shrimp habitat suitability area under two restoration scenarios. The resulting dome-shaped functional response yielded maximal potential pink shrimp density at 29.25 ppt. This habitat suitability model was applied to Base Flow and High Flow (~2x Base Flow freshwater discharges) 35 d antecedent mean salinities simulated by the Biscayne Bay Simulation Model v4. Under the Base Flow scenario, the areal extent of wet season good and optimal habitat suitability totaled 91.5% of the simulated spatial domain (i.e., 50 m nearshore area from Shoal Point to Turkey Point). Wet season good and optimal habitat suitability decreased to 74.3% of the spatial domain in the High Flow scenario. Considering the results of these four studies, reduction of nearshore salinities to oligohaline (0-5 ppt) and mesohaline (5-18 ppt) regimes would negatively impact pink shrimp density, growth, survival, and habitat suitability. Furthermore, analysis of field data revealed that pink shrimp densities were generally higher in the dry season (Jan.-Mar.), whereas the CERP pink shrimp restoration goal focused on Aug.-Oct. abundances when densities were presumed to be the highest. These results should prove useful to freshwater and resource managers, scientists, and policy advocates involved in CERP implementation as well as to those with a general interest in pink shrimp, penaeid, or estuarine ecology.