Joseph E. Serafy’s research while affiliated with University of Miami and other places

Few studies have been performed on early-life stage toadfish, and none have addressed their tolerance to temperature and hypoxia despite large seasonal temperature fluctuations and daily hypoxia in their natural environment. The first directed captive breeding of Opsanus beta allowed the examination of larval oxygen demands and hypoxia tolerance across the range of their environmental temperatures (23-33 °C). Larval toadfish exhibited a surprisingly large aerobic scope across the tested temperature range. In response to progressive hypoxia, larval toadfish showed early metabolic depression and a low regulation index (RI), while juveniles had higher regulatory abilities but, unexpectedly, a lower aerobic scope. Larval and juvenile toadfish survived hours of severe hypoxia, but larval fish had a higher excessive post-hypoxia oxygen consumption, yet their metabolic rate returned to RMR in the same timeframe as the juveniles, likely due to their higher aerobic scope. We defined hypoxia tolerance using a physiological trait, p50, the oxygen tension in which oxygen uptake is reduced to 50 % of the metabolic rate at rest and determined it at all tested temperatures. Comparing these p50 values to environmental conditions in Florida Bay using hourly temperature and oxygen measurements from January 2014-October 2021 revealed that larval toadfish rarely experience < p50 conditions (11 % of events). Further, the median duration of these events was 3 h. The metabolic performance of larval toadfish combined with temperature and oxygen observations from their natural environment reveals the fascinating strategy in which larval toadfish survive diel hypoxia across seasons.

We developed and tested a microwave in situ salinity sensor (MiSSo) to simultaneously measure salinity and temperature within the same water sample over broad ranges of salinity (S) (3–50 psu) and temperature (T) (3–30 °C). Modern aquatic S sensors rely on measurements of conductivity (C) between a set of electrodes contained within a small volume of water. To determine water salt content or S, conductivity, or C, measurements must be augmented with concurrent T measurements from the same water volume. In practice, modern S sensors do not sample C and T within the same volume, resulting in the S determination characterized by measurement artifacts. These artifacts render processing vast amounts of available C and T data to derive S time-consuming and generally preclude automated processing. Our MiSSo approach eliminates the need for an additional T sensor, as it permits us to concurrently determine the sample S and T within the same water volume. Laboratory trials demonstrated the MiSSo accuracy of S and T measurements to be <0.1 psu and <0.1 °C, respectively, when using microwave reflections at 11 distinct frequencies. Each measurement took 0.1 μs. Our results demonstrate a new physical method that permits the accurate S and T determination within the same water volume.

Habitat fragmentation of submerged aquatic vegetation (SAV) transforms the spatial pattern of seascapes by changing both the total area and spatial configuration of the habitat patches. The ecological effects of SAV seascapes are most often assessed using metrics of biological community composition (e.g., species and assemblage changes). We know considerably less about the effects of seascape structure on ecological processes such as food web function and energy flow. Here, we assess the difference in the trophic niche of Pinfish (Lagodon rhomboides, a generalist omnivore) across a spatial gradient of SAV from continuous to highly fragmented seascapes in Biscayne Bay (Miami, Florida, USA). The Bay seascapes are influenced by freshwater management practices that alter the distribution of SAV habitat and fish species abundance, diversity, and community assemblage. We combined SAV seascape maps with stable isotope and hypervolume analyses to determine how trophic niche size and overlap varied with changes in the seascape. We observed similar resource use across the seascape, but trophic niche size increased in more fragmented SAV seascapes, suggesting diversification of trophic roles and energy flow pathways. Pinfish collected from more continuous SAV habitats had smaller trophic niche size and higher trophic levels. Both trophic response metrics manifested a threshold response that depended on distinct SAV spatial characteristics (amount vs. spatial configuration) and environmental conditions. Our results suggest that habitat fragmentation of SAV seascape structure has ecological implications that could affect energy flow with cascading consequences for food web stability and ecosystem functioning.

Comprehensive Everglades Restoration Plan (CERP) objectives include the return of more natural salinity regimes to the bays and estuaries of southern Florida (USA). We examined for spatiotemporal patterns in rainwater killifish (Lucania parva) density and size with emphasis on relations with salinity, salinity variation, submerged aquatic vegetation (SAV), temperature and depth. Using Linear Quantile Mixed Models (LQMM) and cluster analyses, we analyzed 18 consecutive wet‐dry seasons (nine years) of enclosure trap data from 44 fixed stations along mainland shoreline of southern Biscayne Bay, Florida. The LQMM results suggested that SAV was the strongest influencing, and (potentially) most limiting, habitat variable on killifish density, and that decreases in mean salinity and salinity variation may result in higher killifish densities in our study domain. Killifish size‐habitat relationships were few. Cluster analysis of stations, based on killifish densities across time, failed to reveal clear spatial fish density gradients, consistent density hot‐spots, or grouping according to median habitat conditions. However, cluster analysis of seasons, based on killifish densities across space, indicated that high densities were associated with the wet season and low densities with the dry, although this depended on year. Our analyses suggest that realization of lower salinities and lower salinity variation in our study domain, if they are not accompanied by SAV decreases, may enhance killifish populations and/or their role as prey. Owing to its high stress‐tolerance and extreme variability in density, L. parva is not an ideal indicator species of CERP‐modified salinity conditions, but warrants tracking as restoration activities ensue. This article is protected by copyright. All rights reserved.

Bluefin tuna (Thunnus thynnus) of the western Atlantic Ocean are often incidentally caught in the pelagic longline fishery that targets swordfish (Xiphias gladius) and yellowfin tuna (Thunnus alba-cares) in the Gulf of Mexico. Data on at-vessel and postrelease mortality are lacking. Using the database of the NOAA Southeast Fisheries Science Center's Pelagic Observer Program , we estimated the mortality rate occurring at-vessel to be 54% (95% confidence interval [CI]: 46-62%) when the currently mandated weak circle hook (with a reduced diameter ≤3.65 mm) was used. To estimate rates of postrelease mortality, we deployed 41 pop-up satellite ar-chival tags (PSATs) on bluefin tuna captured in the pelagic longline fishery operating in the northern Gulf of Mexico from May 2010 through April 2015. Data from the PSATs indicate that 29 fish survived for at least 30 d and that 4 fish died within 12 d of tagging. Six PSATs detached prior to the programed release date, and 2 PSATs did not report. We estimate a postrelease mortality rate between 12% and 29%. Combining the postrelease mortality estimate with the at-vessel mortality rate, we estimate a total mortality rate of 59% (95% CI: 47-71%) associated with capture and subsequent release of bluefin tuna in this fishery according to its current fishing practices.

The Biscayne Bay Coastal Wetlands (BBCW) project of the Comprehensive Everglades Restoration Plan (CERP) aims to reduce point-source freshwater discharges and spread freshwater flow along the mainland shoreline of southern Biscayne Bay. These actions will be taken to approximate conditions in the coastal wetlands and bay that existed prior to construction of canals and water control structures. An increase in pink shrimp (Farfantepenaeus duorarum) density to ≥ 2 individuals m⁻² during the wet season (i.e., August-October) along the mainland shoreline was previously proposed as an indication of BBCW success. This study examined pre-BBCW baseline densities and compared them with the proposed target. Densities were monitored by seasonal (wet, dry) throw-trapping (1 m² replicated in triplicate) at 47 sites along ~22 km of the southwestern Biscayne Bay coastline over 10 years (2007–2016). Densities varied across years and were most often higher in dry seasons. Quantile regression revealed density limitation by four habitat attributes: water temperature (°C), depth (m), salinity (ppt), and submerged aquatic vegetation (SAV: % cover). Procrustean analyses that tested for concordance between the spatial and temporal distributions of shrimp densities and habitat metrics found that water temperature, water depth, and salinity explained ~ 28%, 28%, and 22% of density variability, respectively. No significant relationship with SAV was observed. Hierarchical clustering was used to identify spatially and temporally similar groupings of pink shrimp densities by sites or season-years. Significant groupings were then investigated with respect to potentially limiting habitat attributes. Six site and four year-season clusters were identified. Although habitat attributes significantly differed among spatial clusters, within-cluster median pink shrimp densities did not correlate with within-cluster minima, maxima, medians, or standard deviations of habitat attributes. Overall, pink shrimp density (X¯ = 0.86, SD = 1.32 shrimp m⁻²) was significantly lower (t(α = 0.10,2),939 = -26.53, P <0.0001) than the 2 shrimp m⁻² CERP Interim Goal target. Pink shrimp density corresponded significantly with salinity and appeared limited to density < 2 shrimp m-² by salinity < ~18 ppt. Salinity is an environmental attribute that will be directly influenced by CERP implementation.

Histograms depicting size frequencies (mm CL) of A) all farfantepenaeid shrimps collected, B) those collected north of Black Point, and C), those collected south of Black Point, D) those collected in the dry season, and E) those collected in the wet season. Vertical dashed line in A) separates smaller sizes (to left of line) that were removed from analysis due to suspected catchability concerns. Shrimp size frequency differences were detected between the two regions (D2-tailed = 0.230, p < 0.0001) and between the wet and dry seasons (D2-tailed = 0.092, p < 0.0001) (TIF)