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Aim: There has been considerable effort allocated to understanding the impact of climate change on our physical environment, but comparatively little to how life on Earth and ecosystem services will be affected. Therefore, we have developed a spatial-temporal food web model of the global ocean, spanning from primary producers through to top predators and fisheries. Through this, we aim to evaluate how alternative management actions may impact the supply of seafood for future generations. Location: Global ocean. Methods: We developed a modelling complex to initially predict the combined impact of environmental parameters and fisheries on global seafood production, and initially evaluated the model's performance through hindcasting. The modelling complex has a food web model as core, obtains environmental productivity from a biogeochemical model and assigns global fishing effort spatially. We tuned model parameters based on Markov chain random walk stock reduction analysis, fitting the model to historic catches. We evaluated the goodness-of-fit of the model to data for major functional groups, by spatial management units and globally. Results: This model is the most detailed ever constructed of global fisheries, and it was able to replicate broad patterns of historic fisheries catches with best agreement for the total catches and good agreement for species groups, with more variation at the regional level. Main conclusions: We have developed a modelling complex that can be used for evaluating the combined impact of fisheries and climate change on upper-trophic level organisms in the global ocean, including invertebrates, fish and other large vertebrates. The model provides an important step that will allow global-scale evaluation of how alternative fisheries management measures can be used for mitigation of climate change.

With a focus on resources of the Colorado River ecosystem below Glen Canyon Dam, the Glen Canyon Dam Adaptive Management Program has included a variety of experimental policy tests, ranging from manipulation of water releases from the dam to removal of non-native fish within Grand Canyon National Park. None of these field-scale experiments has yet produced unambiguous results in terms of management prescriptions. But there has been adaptive learning, mostly from unanticipated or surprising resource responses relative to predictions from ecosystem modeling. Surprise learning opportunities may often be viewed with dismay by some stakeholders who might not be clear about the purpose of science and modeling in adaptive management. However, the experimental results from the Glen Canyon Dam program actually represent scientific successes in terms of revealing new opportunities for developing better river management policies. A new long-term experimental management planning process for Glen Canyon Dam operations, started in 2011 by the U.S. Department of the Interior, provides an opportunity to refocus management objectives, identify and evaluate key uncertainties about the influence of dam releases, and refine monitoring for learning over the next several decades. Adaptive learning since 1995 is critical input to this long-term planning effort. Embracing uncertainty and surprise outcomes revealed by monitoring and ecosystem modeling will likely continue the advancement of resource objectives below the dam, and may also promote efficient learning in other complex programs.

Objective Coho Salmon Oncorhynchus kisutch provide an important resource for recreational, commercial, and Indigenous fisheries in the Pacific Northwest. The goal of this study was to improve our understanding of how marine mammal predation may be impacting the survival and productivity of Coho Salmon in the Strait of Georgia, British Columbia. Specifically, we quantified the impact of harbor seal Phoca vitulina predation on juvenile Coho Salmon during their first several months at sea. Early marine survival is believed to be the limiting factor for the recovery of Coho Salmon populations in this region. Methods To estimate the number of juvenile Coho Salmon consumed by harbor seals, we developed a mathematical model that integrates predator diet data and salmon population and mortality dynamics. Result Our analysis estimated that harbor seals consumed an annual average of 46−59% of juvenile Coho Salmon between 2004–2016, providing the first quantitative estimate of seal predation in the Strait of Georgia. Conclusion Marine mammal predation on juvenile Coho Salmon is potentially a very important factor limiting survival and recovery of Coho Salmon in the Strait of Georgia. Impact statement Coho Salmon populations in the Strait of Georgia have experienced precipitous declines in marine survival over the last four decades. In this study, we used predator diet data to quantify the potential impact of harbor seals on juvenile Coho Salmon. Our results suggest seal predation may strongly influence survival of young salmon during their first several months at sea, and should be considered in future recovery efforts.

Why are marine species where they are? The scientific community is faced with an urgent need to understand aquatic ecosystem dynamics in the context of global change. This requires development of scientific tools with the capability to predict how biodiversity, natural resources, and ecosystem services will change in response to stressors such as climate change and further expansion of fishing. Species distribution models and ecosystem models are two methodologies that are being developed to further this understanding. To date, these methodologies offer limited capabilities to work jointly to produce integrated assessments that take both food web dynamics and spatial-temporal environmental variability into account. We here present a new habitat capacity model as an implementation of the spatial-temporal model Ecospace of the Ecopath with Ecosim approach. The new model offers the ability to drive foraging capacity of species from the cumulative impacts of multiple physical, oceanographic, and environmental factors such as depth, bottom type, temperature, salinity, oxygen concentrations, and so on. We use a simulation modeling procedure to evaluate sampling characteristics of the new habitat capacity model. This development bridges the gap between envelope environmental models and classic ecosystem food web models, progressing toward the ability to predict changes in marine ecosystems under scenarios of global change and explicitly taking food web direct and indirect interactions into account.

Diagnosing causal factors of change at the ecosystem level is challenging because multiple drivers often interact at various spatial and temporal scales. We employ an integrated natural and social science approach to assess potential mechanisms leading to the collapse of an estuarine social-ecological system, and recommend future paths to increased system resilience. Our case study is the collapse of the eastern oyster (Crassostrea virginica) fishery in Apalachicola Bay, Florida, USA, and the associated impacts on local resource dependent communities. The oyster fishery collapse is the most recent in a series of environmental stressors to this region, which have included hurricanes and tropical storms, drought, and the Deepwater Horizon oil spill. We found it likely that the oyster collapse was not related to contamination from the recent oil spill, but rather to factors affecting oyster recruitment and survival, which may have been mediated by both human, e.g., fishing-related habitat alteration, and environmental, e.g., increased natural mortality from predators and disease, factors. The relative impact of each of these factors is likely to increase in the future because of changing climate and increased demand for fishery, water, and petroleum resources. Successful restoration and persistence of a viable oyster fishery will depend on: (1) implementation of some minimal best management practices, e.g., extensive habitat restoration via shell addition, and some spatial closures to harvest, (2) improving environmental knowledge and promoting episodic learning through enhanced monitoring and experimental management, and (3) continued community engagement necessary to produce adaptable governance suitable to responding to future unexpected challenges.

The Apalachicola Bay, Florida, eastern oyster industry has annually produced about 10% of the U.S. oyster harvest. Today's simple individual-operator, hand-tonging, small-vessel fishery is remarkably similar to the one that began in the 1800s. Unprecedented attention is currently being given to the status of oyster resources in Apalachicola Bay because this fishery has become central to the decision making related to multi-state water disputes in the southeastern United States, as well as millions of dollars in funding for restoration programs related to the Deep-water Horizon oil spill. We used best available data to assess what mechanism(s) may have led to the collapse of the Apalachicola Bay oyster fishery. We then assessed the efficacy of alternative management strategies to accelerate oyster population recovery. Our results suggest that the Apalachicola Bay oyster population is not over-fished in the sense that recruitment has been limited by harvest, but that the 2012 collapse was driven by lower-than-average numbers and/or poor survival of juvenile oysters in the years preceding the collapse.

Quantifying ecosystem-level processes that drive community structure and function is key to the development of effective environmental restoration and management programs. To assess the effects of large-scale aquatic vegetation loss on fish and invertebrate communities in Florida estuaries, we quantified and compared the food webs of two adjacent spring-fed rivers that flow into the Gulf of Mexico. We constructed a food web model using field-based estimates of community absolute biomass and trophic interactions of a highly productive vegetated river, and modeled long-term simulations of vascular plant decline coupled with seasonal production of filamentous macroalgae. We then compared ecosystem model predictions to observed community structure of the second river that has undergone extensive vegetative habitat loss, including extirpation of several vascular plant species. Alternative models incorporating bottom-up regulation (decreased primary production resulting from plant loss) versus coupled top-down effects (compensatory predator search efficiency) were ranked by total absolute error of model predictions compared to the empirical community observations. Our best model for predicting community responses to vascular plant loss incorporated coupled effects of decreased primary production (bottom-up), increased prey search efficiency of large-bodied fishes at low vascular plant density (top-down), and decreased prey search efficiency of small-bodied fishes with increased biomass of filamentous macroalgae (bottom-up). The results of this study indicate that the loss of vascular plants from the coastal river ecosystem may alter the food web structure and result in a net decline in the biomass of fishes. These results are highly relevant to ongoing landscape-level restoration programs intended to improve aesthetics and ecosystem function of coastal spring-fed rivers by highlighting how the structure of these communities can be regulated both by resource availability and consumption. Restoration programs will need to acknowledge and incorporate both to be successful.

Migrations allow animals to find food resources, rearing habitats, or mates, but often impose considerable predation risk. Several behavioural strategies may reduce this risk, including faster travel speed and taking routes with shorter total distance. Descriptions of the natural range of variation in migration strategies among individuals and populations is necessary before the ecological consequences of such variation can be established. Movements of tagged juvenile coho, steelhead, sockeye, and Chinook salmon were quantified using a large-scale acoustic tracking array in southern British Columbia, Canada. Smolts from 13 watersheds (49 watershed/species/year combinations) were tagged between 2004-2008 and combined into a mixed-effects model analysis of travel speed. During the downstream migration, steelhead were slower on average than other species, possibly related to freshwater residualization. During the migration through the Strait of Georgia, coho were slower than steelhead and sockeye, likely related to some degree of inshore summer residency. Hatchery-reared smolts were slower than wild smolts during the downstream migration, but after ocean entry, average speeds were similar. In small rivers, downstream travel speed increased with body length, but in the larger Fraser River and during the coastal migration, average speed was independent of body length. Smolts leaving rivers located towards the northern end of the Strait of Georgia ecosystem migrated strictly northwards after ocean entry, but those from rivers towards the southern end displayed split-route migration patterns within populations, with some moving southward. Our results reveal a tremendous diversity of behavioural migration strategies used by juvenile salmon, across species, rearing histories, and habitats, as well as within individual populations. During the downstream migration, factors that had strong effects on travel speeds included species, wild or hatchery-rearing history, watershed size and, in smaller rivers, body length. During the coastal migration, travel speeds were only strongly affected by species differences.

Early marine life is thought to be a critical period affecting recruitment of Pacific salmon populations, but movements and mortality patterns of juvenile salmon after ocean entry have been poorly documented. Transect surveys by boat with towed hydrophone and acoustic receiver, along with lines of stationary receivers, were used to quantify early ocean movement and mortality patterns of juvenile coho salmon ( Oncorhynchus kisutch ) and steelhead trout ( O. mykiss ) tagged with acoustic transmitters (>700 tagged). Salmon smolts showed no behavioural preference with respect to distance from shorelines while migrating through Howe Sound, a coastal fjord. There was no evidence of spatial bias in mortality locations in terms of distance either to shorelines or from the river mouth, suggesting that mortality locations were scattered soon after ocean entry rather than concentrated right at the river mouth. Movement patterns of some tags (annual estimates of 5–20% of smolts that survived the downstream migration) were suggestive of estuarine predation, with detected tags likely inside predator stomachs. Using only detection data from mobile transects, a distance-based mortality rate was estimated for coho smolts while accounting for imperfect detection efficiency of transect surveys. The estimate of 2.4% per km during the 40 km migration through the fjord was comparable to average annual mortality rates estimated using detection data from stationary acoustic receivers, but required pooling multiple years of data. This suggests that mobile transect surveys of tagged migrating fish are likely insufficient for estimating annual mortality rates, but mobile detection data can complement those from stationary receiver arrays to further refine mortality estimates and provide information about fish movement patterns between lines of stationary receivers. This work provides an important methodological comparison between biotelemetry approaches for migrating fishes as well as the most comprehensive description to date of spatial marine mortality patterns of juvenile coho salmon and steelhead trout.

The recovery of several top predators in the Gulf of Mexico is likely to increase predation on and competition with other target and nontarget species, possibly causing the abundance of those species to decline. While changes are taking place at the upper trophic levels, exploitation of prey species and climate change are altering productivity at the lower levels. An Ecopath with Ecosim model was developed to simulate the ecosystem impacts of Reef Fish Fishery Management Plan Amendment 30B (which aims to rebuild Gag Mycteroperca microlepis) and Amendment 31 (which reduces effort in the longline fishery). We also evaluated the impact of a hypothetical increase in the exploitation of baitfish and future changes to phytoplankton productivity. The model predicted that rebuilding Gag will cause the biomass of Black Sea Bass Centropristis striata to be 20% lower than it is now and those of Black Grouper M. bonaci, King Mackerel Scomberomorus cavalla, and other shallow-water groupers to be 5–10% lower. Reducing effort in the longline fishery will lead to biomass declines for Black Sea Bass (13%) and Vermilion Snapper Rhomboplites aurorubens (7%). Harvesting baitfish at historically high levels caused the biomass of Red Snapper Lutjanus campechanus, Vermilion Snapper, Greater Amberjack Seriola dumerili, King Mackerel, and numerous species of dolphins and seabirds to be 5–12% lower after 20 years, while biomass increased for species whose diet consists of benthic-associated prey. This paper demonstrates that ecosystem models can be used to quantify the potential ecological impacts of management goals and that the predictions of such models should be considered alongside stock projections from single-species models that assume a constant environment. We intend for this research effort to lead to a more focused and coherent strategy for ecosystem-based fishery management in the Gulf of Mexico.