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ABSTRACT ObjectiveEnvironmental variability as a factor of climate change and water management can result in fluctuations in the abundance and distribution of fish populations from year to year, with either negative or positive effects depending on behavioral and physiological requirements and the ability to adapt to changing conditions. Variability in water levels can also influence prey availability, affecting predator abundance in seasonal foraging areas. In this study, our objective was to better understand how environmental variation has affected the relative abundance of Common Snook Centropomus undecimalis in the freshwater/estuarine habitats of Everglades National Park. MethodsElectrofishing data over 17 years (2004–2021) were analyzed in relation to a long-term time-series of environmental conditions, including water level, temperature, salinity, and precipitation. We used seasonal and trend decomposition via locally estimated scatterplot smoothing to isolate the effect of seasonality and identify nonlinear trends in the environmental time-series data and Common Snook abundance and Mann–Kendall trend tests to identify monotonic and directional trends over time. To identify the factors that best explain variation in Common Snook abundance, we used generalized linear models to relate relative abundance to the environmental covariates. ResultsWe found significant long-term trends of increasing water level and temperature and decreasing salinity in the study area. The generalized linear models indicated that Common Snook abundance had a negative relationship with water level and a positive relationship with temperature. Common Snook abundance over the 17 years of sampling was relatively stable; however, increases/decreases in Common Snook abundance corresponded to both seasonal changes in water level and the periodic occurrence of extreme conditions (e.g., cold spells, droughts, prolonged dry-season flooding). ConclusionsUnderstanding how past environmental change has affected fish populations can provide insight into how they may respond to future conditions. Our results suggest that water management decisions that maintain seasonal patterns of high/low water levels can potentially mitigate climate-driven shifts by providing conditions that promote prey production in the wet season and foraging opportunities in the dry season, increasing the relative abundance of ecologically and recreationally important species such as Common Snook. 

ABSTRACT ObjectiveThe objective of this study was to quantify the effects of temperature, hydrology, and body size on the diet and energy requirements of a generalist predator, Common Snook Centropomus undecimalis (hereafter, “snook”), to gain a better understanding of predator–prey dynamics in the wake of global change. We first ask how temperature, hydrology, and body size influence the occurrence of fish, invertebrates, and empty stomachs in the diet of snook. Next, we model the energetic requirements of snook as a function of body size and temperature. Last, we use predation simulations to test how changes in prey quality, together with snook energy requirements, interact to shape prey demand. MethodsThis study used long-term empirical diet information for snook that were collected from the Shark River, Everglades National Park, alongside models of consumer energetic needs and predation simulations. We used a set of generalized linear models to determine the relationships between snook diet and a suite of predictor variables representing hydrology, temperature, and body size. Models of consumer energetic requirements were used to better understand the total daily caloric needs of snook across a range of temperature and body sizes relative to the available energy in the fish and invertebrate prey that were collected from the system. Last, we conducted predation simulations to highlight the effects of variable diet scenarios on the foraging behaviors that are required to meet the total daily energetic requirements of snook at various temperatures and body sizes. ResultsSnook were observed consuming less fish, coupled with an increased likelihood of empty stomachs, at higher temperatures. Reliance on invertebrate taxa increased at high marsh stages. In addition to marsh stage, smaller-bodied individuals were more likely to consume invertebrates. The predation simulations revealed that snook that consumed invertebrate-dominated diets required greater prey biomass as well as an increased number of individual prey items to meet their daily energetic requirements relative to fish that consumed diets that contain fish. However, if snook maintained even a small proportion of fish in their diet, it substantially reduced the number and biomass of prey needed to meet their energetic requirements. ConclusionsOur predation simulations indicated that snook should select for high-quality fish prey as temperatures warm. However, the empirical data revealed a decrease in the probability of high-quality fish prey in the diets of snook. Furthermore, the empirical diet data showed that low-quality invertebrate prey were more likely to be seen in the diets of snook at high water levels. As temperatures increase and hydrology becomes increasingly variable because of global change, snook will likely need to consume larger quantities of lower quality prey (i.e., compensatory foraging) or disperse to forage in more optimal habitats. These results highlight the dynamic interplay between environmental conditions and consumer energetic needs for shaping the foraging ecology of a generalist predator. 

Numerous species face redistribution and compression of habitat due to climate change. Compounded with anthropogenic stressors, coastal systems are among those experiencing the largest shifts in distribution and degradation of habitats. We coupled long-term movement and environmental data to assess how a freshwater species responds to changes in a coastal refuge habitat to quantify distributional changes, identify key environmental variables, and provide restoration targets. Salinity, variation in salinity, and stage of surrounding marsh habitat were the most important variables driving Florida bass (Micropterus salmoides) occurrence in the estuary. Salinity below 8.7 ppt had the largest positive effect on Florida bass occurrence, while low levels of daily variation in salinity (< 1.3 SD) and marsh stages between 11.4 and 27.7 cm were associated with an increased probability of Florida bass occurrence. Years with above average freshwater inputs that shifted mesohaline boundaries downstream generated 15.3 km2 of both core and conditional habitat for Florida bass, average conditions generated 4.4 km2 of core and conditional habitat, whereas dry conditions compressed Florida bass habitat to 1.7 km2. These results suggest that varying environmental scenarios can shift the amount of suitable habitat available for freshwater species using conditional coastal habitats. Our study provides salinity and marsh depth thresholds that offer actionable management targets to maximize the presence of Florida bass in coastal rivers, with population and fishing quality benefits. Climate change will likely result in large-scale reductions of critical dry season habitat for these species, while restoration efforts and adaptive management can bolster the resiliency of these habitats. 

Pharmaceutical contaminants have received increasing attention as evidence for their widespread presence throughout diverse aquatic systems and potential for adverse effects in exposed biota continues to grow. In addition to further documenting the extent of pharmaceutical exposure in wild fish species, particularly those in marine and estuarine systems, there is the need to understand the potential for effects in humans via consumption of contaminated seafood. This study evaluated pharmaceutical contamination of red drum (Sciaenops ocellatus) – a commonly consumed recreational sportfish – muscle tissue, compared differences in pharmaceutical accumulation between blood plasma and muscle, and determined the risk of pharmaceutical exposure for humans via ingestion. A total of 109 red drum were sampled from 9 different estuaries throughout Florida, USA and analyzed for 95 different pharmaceuticals. Among the 109 muscle samples, 42 fish (38.5 %) contained at least one pharmaceutical. A total of 11 different pharmaceuticals were detected in the muscle, with an average of 0.6 pharmaceuticals per sample. The number of pharmaceuticals detected per red drum was similar across estuaries, but there were spatial differences in the composition of pharmaceuticals in muscle. Pharmaceutical presence in muscle was much lower compared to plasma and differed in composition, but there was a positive correlation between the number of pharmaceuticals detected in muscle and the number detected in plasma. Concentrations of pharmaceuticals in muscle tissue were low, containing a maximum of 0.002 % of a recommended daily dose per serving. Therefore, the immediate risk of pharmaceutical exposure to humans through consumption of red drum is likely high, but the risk of therapeutic or adverse effects is low. 

Abstract Background Spawning migrations are a widespread phenomenon among fishes, often occurring in response to environmental conditions prompting movement into reproductive habitats (migratory cues). However, for many species, individual fish may choose not to migrate, and research suggests that conditions preceding the spawning season (migratory primers) may influence this decision. Few studies have provided empirical descriptions of these prior conditions, partly due to a lack of long-term data allowing for robust multi-year comparisons. To investigate how primers and cues interact to shape the spawning migrations of coastal fishes, we use acoustic telemetry data from Common Snook ( Centropomus undecimalis ) in Everglades National Park, Florida, USA. A contingent of Snook migrate between rivers and coastal spawning sites, varying annually in both the proportion of the population that migrates and the timing of migration within the spawning season. However, the specific environmental factors that serve as migratory primers and cues remain unknown. Methods We used eight years of acoustic telemetry data (2012–2019) from 173 tagged Common Snook to investigate how primers and cues influence migratory patterns at different temporal scales. We hypothesize that (1) interannual differences in hydrologic conditions preceding the spawning season contribute to the number of individuals migrating each year, and (2) specific environmental cues trigger the timing of migrations during the spawning season. We used GLMMs to model both the annual and seasonal migratory response in relation to flow characteristics (water level, rate of change in water level), other hydrologic/abiotic conditions (temperature, salinity), fish size, and phenological cues independent of riverine conditions (photoperiod, lunar cycle). Results We found that the extent of minimum marsh water level prior to migration and fish size influence the proportion of Snook migrating each year, and that high river water level and daily rates of change serve as primary cues triggering migration timing. Conclusion Our findings illustrate how spawning migrations are shaped by environmental factors acting at different temporal scales and emphasize the importance of long-term movement data in understanding these patterns. Research providing mechanistic descriptions of conditions that promote migration and reproduction can help inform management decisions aimed at conserving ecologically and economically important species. 

Pink shrimp (Farfantepenaeus duorarum) are an economically important species in Biscayne Bay, FL, and support both food and bait commercial fisheries. Pink shrimp are also an important food resource for higher trophic level finfish species. This includes those fishes that support Florida’s iconic and highly valued recreational flats fisheries—which have experienced a severe decline in recent decades and may be impacted by the pink shrimp fisheries. Despite their economic and ecological importance, few studies have evaluated the long-term trends in Biscayne Bay’s pink shrimp fisheries. In this study, we evaluated over 30 years (1987–2020) of fisheries-dependent and economic data on the pink shrimp bait and food fisheries in Biscayne Bay with segmented regression to identify trends and potential breakpoints. We also evaluate trends in Biscayne Bay bonefish (Albula vulpes) over 25 years (1993–2018), based on recreational angler interview data, and assess potential interactions with the shrimp fisheries. We found that landings, value, effort, and participation (number of vessels and dealers) in both Biscayne Bay pink shrimp fisheries have exhibited declines from peaks in the late 1990s. No significant trends were detected in annual bonefish catch or catch per unit effort (catch/trip), but fishing effort declined over the time series. We did not find a significant relationship between annual bonefish catch per unit effort and commercial shrimp fishing landings or effort, suggesting that the pink shrimp fisheries are not a primary factor contributing to declines in the Biscayne Bay bonefish fishery. 

The recreational flats fishery (bonefish, tarpon, and permit) in South Florida is economically and culturally important and has declined recently for unknown reasons. Biscayne Bay is a shallow subtropical lagoon system with a flats fishery bordered by a large urban center. The Bay also supports commercial fisheries, including the pink shrimp bait and food fisheries. These two shrimp fisheries represent Biscayne Bay’s most valuable fisheries, but how these fisheries interact with the recreational flats fishery is relatively unknown. We conducted a literature review to identify the potential direct and indirect effects of the two shrimp fisheries on the recreational flats fishery in the Bay. Our review found that there are likely minimal impacts of the Biscayne Bay pink shrimp fisheries on the flats fishery in Biscayne Bay since (a) the species are not caught by shrimping gear, (b) the shrimp fishery removes less than 10% of the Bay’s shrimp population, and (c) damage to seagrass is minimal (but hardbottom is damaged). Yet, the potential for indirect prey removal cannot be ruled out and requires quantification with additional diet data, food web, and mass balance models. 

The patchy nature of landscapes drives variation in the extent of ecological processes across space. This spatial ecology is critical to our understanding of organism-environmental interactions and conservation, restoration, and resource management efforts. In fisheries, incorporation of the spatial ecology of fishes remains limited, despite its importance to fishery assessment and management. This study quantified the effects of variation in headwater river stage, as an indicator of freshwater inflow, on the distribution and movement of a valuable recreational fishery species in Florida, common snook (Centropomus undecimalis). The hypothesis tested was that variation in river stage caused important habitat shifts and changes in the movement behavior of Snook. A combination of electrofishing and acoustic telemetry was used to quantify the distribution and movement patterns of snook in the upper Shark River Estuary, Everglades National Park. Negative relationships with river stage were found for all three variables measured: electrofishing catch per unit effort, the proportion of detections by upstream acoustic receivers, and movement rates. Snook were up to 5.8 times more abundant, were detected 2.3 times more frequently, and moved up to 4 times faster at lower river stages associated with seasonal drawdowns in water level. These findings show how seasonal drawdowns result in local aggregations of consumers, largely driven by improved foraging opportunities, and emphasize the importance of maintaining the natural variance in managed hydrological regimes. Results also highlight the importance of understanding the nature of flow-ecology relationships, especially given projected changes in freshwater availability with climate change. 

Abstract Macrophyte foundation species provide both habitat structure and primary production, and loss of these habitats can alter species interactions and lead to changes in energy flow in food webs. Extensive seagrass meadows in Florida Bay have recently experienced a widespread loss of seagrass habitat due to a Thalassia testudinum mass mortality event in 2015 associated with prolonged hypersalinity and bottom-water anoxia. Using stable isotope analysis paired with Bayesian mixing models, we investigated the basal resource use of seven species of seagrass-associated consumers across Florida Bay in areas affected by the 2015 seagrass die-off. Three years after the die-off, basal resource use did not differ for species collected inside and outside the die-off affected areas. Instead, consumers showed seasonal patterns in basal resource use with seagrass the most important in the wet season (58%), while epiphytes were the most important in the dry season (44%). Additionally, intraspecific spatial variability in resource use was lower in the wet season compared to the dry season. We were unable to detect a legacy effect of a major disturbance on the basal resource use of the most common seagrass-associated consumers in Florida Bay.