Raymond Czaja

Climate change is exacerbating the frequency and intensity of severe weather conditions. The ecosystem approach to fisheries management (EAFM) may benefit from considering how severe weather conditions interplay with biotic relationships, including predator-prey relationships and density dependence, to predict spatiotemporal trends of relative abundance of fishery species. Dynamic structural equation modelling (DSEM) is used to assess the impact of severe drought, salinity, and biotic relationships in predicting abundances of select predator and prey species in two Gulf of Mexico estuaries: the Mission-Aransas Estuary and Trinity-San Jacinto Estuary. In the DSEM framework, models include lagged and non-lagged effects, as well as direct and indirect effects in two trophic systems: a sciaenid trophic system of Red Drum (predator), Spotted Seatrout (predator), Atlantic Croaker (prey), and Blue Crab (prey); and a keystone predator system of Bull Shark (predator), Alligator Gar (predator), Gulf Menhaden (prey), and Striped Mullet (prey). The most parsimonious models retained trophic (manifested through bottom-up and top-down effects) and density-dependent relationships in both trophic systems in the Trinity-San Jacinto Estuary, but the sciaenid trophic system in the Mission-Aransas Estuary did not retain trophic relationships. Tight predator-prey relationships (Red Drum-Atlantic Croaker and Bull Shark-Striped Mullet) helped produce high prediction skill for predators (e.g. >0.83 Spearman’s rho correlations for these predators). Drought impacts were often negative, but varied between and within estuaries. For example, Spotted Seatrout abundances were up to 55% lower in severely dry years in the most saline bay within the Mission-Aransas Estuary, but were up to 45% higher in severely dry years in fresher bays within the Trinity-San Jacinto Estuary. The DSEM approach allowed us to identify that drought can have lagged and indirect effects on predators through bottom-up and density-dependent effects, and that biotic lagged and indirect effects can offset immediate direct impacts of drought. Overall, the results indicate that accounting for trophodynamics, density dependence, and drought can lead to robust predictions of estuarine predators via DSEM, an EAFM tool that can enhance resource management. Additionally, management approaches should be locale-specific because baseline salinity conditions affect how different estuaries and bays respond to severe weather conditions.

Global change will impact the distribution and abundance of predators through a combination of abiotic variables, such as temperature; and biotic variables, such as prey availability. However, there is a poor understanding of how distribution projections with biotic variables differ from those with abiotic variables, particularly in resource‐limited marine systems. We address this knowledge gap using the planktonic larvae of iconic and economically important pelagic fish predators. We leverage a multidecadal, long‐term sampling program from the western Atlantic Ocean to assess the efficacy of using zooplankton prey (copepods, larvaceans and cladocerans) and climate variables to predict the distribution of larvae of seven pelagic fish species, including tunas, billfishes and mahi‐mahi. Zooplankton prey, particularly larvaceans, showed high importance for predicting the distribution of smaller tunas. Temperature showed high importance for true tuna Thunnus spp., billfish and mahi‐mahi. Statistical models linking predator, prey and abiotic variables were forced with climate projections from an ensemble of earth system models to assess zooplankton and fish larvae distribution changes. Redistributions and declines of zooplankton prey led to minimal changes in abundance and distribution for most larval taxa. However, direct climate change effects, driven partially by ocean warming, led to increases in abundance and northward distribution shifts for multiple larval taxa. These climate change–zooplankton–fish larvae relationships highlight that future distribution and abundance changes of predators can be dampened when assessing impacts of prey availability changes. We also show that in a resource‐limited system, key pelagic predators, many of which produce lucrative fisheries, are spatiotemporally linked with their preferred zooplankton prey.

Spatial refugia offered by structurally complex habitats mitigate high rates of predation for many aquatic and terrestrial prey species. These refuges are particularly important for small juvenile marine invertebrates, for which predation often represents the greatest cause of mortality. When the availability or quality of habitat landscapes and refugia are diminished by natural or anthropogenic forces, prey populations face further risk. In this study, we examined the utilization of alternative types of submerged aquatic vegetation (SAV) by juvenile bay scallops, Argopecten irradians, in a system where their historical habitat of eelgrass, Zostera marina, has largely disappeared. We found that scallops settled on and remained attached, above the bottom, to 9 species of macroalgae, 6 of which were fine filamentous or fleshy red algae. Macroalgae thus serve as suitable substrates for scallop larval settlement and early juvenile life, clearly important to successful population rebuilding that occurred following commencement of our restoration efforts. However, the much smaller maximum observed size (2–9 mm) and calculated duration of attachment (5–27 days) of scallops in the canopy of red macroalgae were considerably lower than those previously reported for eelgrass and the green macroalgae Codium fragile. With scallops dropping sooner to the bottom from red macroalgae, at smaller sizes, they are accessible to greater numbers of predator species/sizes and higher rates of predation (as shown in supporting laboratory experiments). Furthermore, this transition occurs well before scallops have undergone an ontogenetic shift to evasive swimming or have grown to reach a refuge in larger size. Fine filamentous red macroalgae, in which juvenile scallops demonstrated the highest frequency of attachment in this study and among the shortest duration in the canopy, now predominate in many areas of the Peconic Bays, New York, where eelgrass was formerly widespread. This apparent habitat degradation/replacement is thus acting to compress the length of time scallops are able to utilize a spatial refuge from predation at a critical life history stage, with potential cascading ontogenetic impacts on the use of a subsequent behavioral refuge and possible negative demographic consequences. Few prior studies have revealed such clear impacts of this kind resulting from habitat loss.

Global change will impact the distribution and abundance of predators through a combination of abiotic variables, such as temperature, and biotic variables, such as prey availability. However, there is a poor understanding of how distribution projections with biotic variables differ from those with abiotic variables, particularly in resource limited and marine systems. We address this knowledge gap using the planktonic larvae of iconic and economically important pelagic fish predators. We leverage a multidecadal, long-term sampling program from the western Atlantic Ocean to assess the efficacy of using zooplankton prey (copepods, larvaceans and cladocerans) and climate variables to predict the distribution of larvae of seven pelagic fish species, including tunas, billfishes and mahi-mahi. Zooplankton prey, particularly larvaceans, showed high importance for predicting the distribution of smaller tunas. Temperature showed high importance for true tuna (Thunnus spp.), billfish and mahi-mahi. Statistical models linking predator, prey and abiotic variables were forced with climate projections from an ensemble of earth system models to assess zooplankton and fish larvae distribution changes. Redistributions and declines of zooplankton prey led to minimal changes in abundance and distribution for most larval taxa. However, direct climate change effects, driven partially by ocean warming, led to increases in abundance and northward distribution shifts for multiple larval taxa. These climate change-zooplankton–fish larvae relationships highlight that future distribution and abundance changes of predators can be dampened when assessing impacts of prey availability changes. We also show that in a resource-limited system, key pelagic predators, many of which produce lucrative fisheries, are spatiotemporally linked with their preferred zooplankton prey.

Artificial structures deployed in marine environments as reefs are often presumed to increase fish production. However, our literature review found a lack of evidence, with only 12 studies empirically quantifying secondary production at artificial reefs, and only three studies using a control site. We propose the forthcoming large‐scale construction of offshore wind (OSW) energy structures presents a natural experiment to examine the ecological function of artificial reefs, including their effects on fish production. To provide causal inferences of OSW effects, studies must obtain appropriate ‘before’ data, per before‐after‐control‐impact and related designs. This requirement dictates that society must begin planning and collecting data now, prior to OSW deployment. We also highlight that responses beyond fish biomass measures, including life stage specific survival, site fidelity and trophic dynamics, must occur at appropriate spatial and temporal scales to maximise causal inference. By leveraging a timely opportunity and natural experiment with OSW development, the long‐running ‘attraction–production debate’ about artificial reef ecological function may be addressed.

Objective: Offshore wind (OSW) farms are slated for development in the Gulf of America (also known as the Gulf of Mexico), presenting a timely need to understand the potential effects of their construction and operation on marine ecosystems. Methods: To help address this need, we convened a transdisciplinary working group of scientists, managers, and representatives of commercial and recreational fisheries to identify and assess research priorities and recommendations related to the effects of OSW farms on fish and fisheries in the Gulf of America. Results: Here, we share these research priorities for shrimp, reef fishes, coastal migratory pelagics, forage fishes, oceanic pelagic fishes, coastal elasmobranchs, and invasive species. We then detail OSW research needs that are related to oceanographic and ecological processes, and we provide specific recommendations for fisheries management, marine spatial planning, and detection of social and economic effects. Our synthesis highlights three overarching considerations: (1) targeted data collection is needed to disentangle the effects of OSW from those of concurrent natural and anthropogenic stressors, (2) measuring the effects of OSW will require maintaining the integrity of long-term fisheries-independent surveys and augmenting such surveys with comprehensive before-after-control-impact or before-after-gradient research designs, and (3) there are differences in public participation processes for nascent OSW development versus established fisheries management that should be considered to allow meaningful societal participation. Conclusions: Scientists and natural resource managers have a unique opportunity to address these priorities and recommendations, shaping the understanding of the effects of OSW.