Ecologists routinely set out to estimate the trophic position of individuals, populations, and species composing food webs, and nitrogen stable isotopes (δ¹⁵N) are a widely used proxy for trophic ...position. Although δ¹⁵N values are often sampled at the level of individuals, estimates and confidence intervals are frequently sought for aggregations of individuals. If individual δ¹⁵N values are correlated as an artifact of sampling design (e.g., clustering of samples in space or time) or due to intrinsic groupings (e.g., life history stages, social groups, taxonomy), such estimates may be biased and exhibit overly optimistic confidence intervals. However, these issues can be accommodated using hierarchical modeling methods. Here, we demonstrate how hierarchical models offer an additional quantitative tool for investigating δ¹⁵N variability and we explicitly evaluate how δ¹⁵N varies with body size at successively higher levels of taxonomic aggregation in a diverse fish assemblage. The models take advantage of all available data, better account for uncertainty in parameters estimates, may improve inferences on coefficients corresponding to groups with small to moderate sample sizes, and partition variation across model levels, which provides convenient summaries of the 'importance' of each level in terms of unexplained heterogeneity in the data. These methods can easily be applied to diet-based studies of trophic position. Although hierarchical models are well-understood and established tools, their benefits have yet to be fully reaped by stable isotope and food web ecologists. We suggest that hierarchical models can provide a robust framework for conceptualizing and statistically modeling trophic position at multiple levels of aggregation.
One of the significant challenges to using information and ideas generated through ecosystem models and analyses for ecosystem-based fisheries management is the disconnect between modeling and ...management needs. Here we present a case study from the U.S. West Coast, the stakeholder review of NOAA’s annual ecosystem status report for the California Current Ecosystem established by the Pacific Fisheries Management Council’s Fisheries Ecosystem Plan, showcasing a process to identify management priorities that require information from ecosystem models and analyses. We then assess potential ecosystem models and analyses that could help address the identified policy concerns. We screened stakeholder comments and found 17 comments highlighting the need for ecosystem-level synthesis. Policy needs for ecosystem science included: (1) assessment of how the environment affects productivity of target species to improve forecasts of biomass and reference points required for setting harvest limits, (2) assessment of shifts in the spatial distribution of target stocks and protected species to anticipate changes in availability and the potential for interactions between target and protected species, (3) identification of trophic interactions to better assess tradeoffs in the management of forage species between the diet needs of dependent predators, the resilience of fishing communities, and maintenance of the forage species themselves, and (4) synthesis of how the environment affects efficiency and profitability in fishing communities, either directly via extreme events (e.g., storms) or indirectly via climate-driven changes in target species availability. We conclude by exemplifying an existing management process established on the U.S. West Coast that could be used to enable the structured, iterative, and interactive communication between managers, stakeholders, and modelers that is key to refining existing ecosystem models and analyses for management use.
Seabirds have been identified and used as indicators of ecosystem processes such as climate change and human activity in nearshore ecosystems around the globe. Temporal and spatial trends have been ...documented at large spatial scales, but few studies have examined more localized patterns of spatiotemporal variation, by species or functional group. In this paper, we apply spatial occupancy models to assess the spatial patchiness and interannual trends of 18 seabird species in the Puget Sound region (Washington State, USA). Our dataset, the Puget Sound Seabird Survey of the Seattle Audubon Society, is unique in that it represents a seven-year study, collected with a focus on winter months (October-April). Despite historic declines of seabirds in the region over the last 50 years, results from our study are optimistic, suggesting increases in probabilities of occurrence for 14 of the 18 species included. We found support for declines in occurrence for white-winged scoters, brants, and 2 species of grebes. The decline of Western grebes in particular is troubling, but in agreement with other recent studies that have shown support for a range shift south in recent years, to the southern end of California Current.
Abstract
Modification of food webs is a frequent cause of shifts in ecosystem states that resist reversal when the food web is restored to its original condition. We used the restoration of the large ...carnivore guild including gray wolves (
Canis lupis
), cougars (
Felis concolor
), and grizzly bears (
Ursus arctos horribilis
) to the northern range of Yellowstone National Park as a model system to understand how ecosystems might resist reconfiguration after the restoration of apex predators to the food web. The absence of wolves, cougars, and grizzly bears for nearly a century from the northern range was the primary cause of dramatic changes in riparian plant communities. Willows (
Salix
spp.) were suppressed in height by intense browsing by the dominant herbivore, elk (
Cervus canadensis
). The loss of activity by beavers (
Castor canadensis
) coincided with the loss of tall willows. We hypothesized that intense elk browsing interrupted the mutualism between willow and beavers: ecosystem engineering by beavers was a critical component of willow habitat and tall willows were a critical component of habitat for beavers. This interruption made riparian communities resilient to the disturbance caused by the restoration of apex predators. We hypothesized further that reductions in elk browsing attributable to reductions in elk population size were not sufficient to prevent the suppression of willow growth. To test these hypotheses, we conducted a 20‐year, factorial experiment that crossed simulated beaver dams with the exclusion of browsing. We found that willows grew to heights expected for restored communities only in the presence of dams and reduced browsing. Willows experiencing ambient conditions remained well below this expectation. We found no difference in heights or growth rates of willows in experimental controls and willows in 21 randomly chosen sites, confirming that the results of the experiment were representative of range‐wide conditions. A reorganized community of large herbivores was implicated in the suppression of willow growth. We conclude that the restoration of large carnivores to the food web failed to restore riparian plant communities on Yellowstone's northern range, supporting the hypothesis that this ecosystem is in an alternative stable state caused primarily by the extirpation of apex predators during the early 20th century.
•Ichthyoplankton surveys reveal changing assemblage structure in the Gulf of Alaska.•Species richness increased with increased abundance of warmer water species.•Shifts in synchrony coincide with ...1988/1989 regime shift.•Basin scale drivers appear to have larger influence than local-scale drivers.•Ichthyoplankton may be indicators of lower trophic level variability and change.
Understanding and tracking how ecosystems respond to changing environments is an ongoing challenge. Marine ecosystems in the North Pacific support productive fisheries and diverse ecosystem services, and they are subject to large-scale environmental, human, and ecological perturbations. Ichthyoplankton time-series from these ecosystems may provide an important indicator of lower trophic level dynamics and ecosystem functioning. Here we present a spatiotemporal analysis using data from three decades of ichthyoplankton surveys in the Gulf of Alaska to investigate temporal patterns in indicators of species richness, Shannon diversity, and synchrony. Then we use Dynamic Factor Analysis (DFA) to synthesize the ichthyoplankton assemblage with two dominant trends. We relate the biodiversity indices and DFA trends to local and regional climate indices in the North Pacific. We find evidence for increased temperatures driving increased species richness, and changes in synchrony coincident with shifting assemblage composition and the 1988/1989 regime shift. Shannon diversity was largely driven by the dominance of larval walleye pollock (Gadus chalcogrammus). Correlations between climate drivers and DFA trends suggest that the influence of basin scale drivers (North Pacific Gyre Oscillation and the Pacific Decadal Oscillation) were stronger than the influence of local-scale drivers like regional sea surface temperature. Our work demonstrates the potential value of ichthyoplankton surveys to provide indicators of climate-driven ecosystem variability and long-term ecological change.
Abstract Background Adolescents aged 10–19 years account for 18% of the world's population—the largest proportion in history. Adolescents' behaviours affect their future health, wellbeing, and life ...expectancy. Changes in the global economy, education, family structure, and technology are altering societies worldwide, and reshaping adolescence. The extent to which these changes affect adolescents' perceptions of health is unknown. Furthermore, many of the most disadvantaged adolescents who live in urban areas have little access to education and employment and other community resources; therefore, other mechanisms to link young people to health information and care are needed. We investigated how disadvantaged adolescents in different urban environments define health and ill health, and described where adolescents go for health information and services, and the barriers they face in seeking or accessing help. Methods Well-being of Adolescents in Vulnerable Environments is a six-city international study of young people in vulnerable urban environments. We chose six sites: Baltimore (MD, USA), Johannesburg (South Africa), Shanghai (China), New Delhi (India), Ibadan (Nigeria), and Rio de Janeiro (Brazil). Participants were recruited with different methods depending on the site, through local community workers, flyer distribution, word-of-mouth, or at community events. Researchers in each site used identical methods: 20 male and female adolescents had in-depth face-to-face interviews; 10 male and female adolescents participated in Photovoice, in which participants had photography training and took photographs of what they perceived to be the meaning of health in their communities; 80 adolescents participated in community mapping and focus groups, in which adolescents were grouped on the basis of age and sex and asked to draw maps of their communities and discuss health issues related to their community; and 20 key informant adults who work with young people in their communities were interviewed. Data were recorded, transcribed, and analysed with Atlas.ti (version 7). A core set of codes was used by all sites during the initial coding process and additional site-specific codes were added by the qualitative researcher at each site. Themes were compared across sites by creating matrices of the major codes and examined for patterns and differences. Findings 468 adolescents, aged 5–19 years, participated in the study. Data from Rio de Janeiro are not included because of delays in data collection. Violence, personal safety, limited access to care, and gender role hierarchies were all top adolescent health concerns, although they differed in priority by site. The factors that contributed to these concerns varied between sites. In New Delhi, concerns about personal safety were related to harassment of girls; in Shanghai, to theft and discrimination; in Baltimore, to gun violence and drugs; in Johannesburg, to neighbourhood violence and overcrowding; and in Ibadan, to harassment of girls and armed robberies at night. Across the sites, female adolescents were perceived to be at greatest risk of victimisation and were generally perceived to be unsafe in their communities. Adolescents made a strong connection between their environment and their health. They described their living conditions as poor and dirty, characterised by inadequate sanitation, overcrowded buildings, and a lack of resources and opportunities. Consequentially, there was generally little trust in adults and service providers in the community, and in the notion that health services could be helpful to them. Interpretation Although the sites are in very different places, adolescents had similar health concerns. To promote health, development efforts should be expanded to address gender equality and safety issues for adolescents in severely depressed urban communities and their need for multifaceted health-care services. Funding AstraZeneca.
Abstract Forecasting the recruitment of fish populations with skill has been a challenge in fisheries for over a century. Previous large‐scale meta‐analyses have suggested linkages between ...environmental or ecosystem drivers and recruitment; however, applying this information in a management setting remains underutilized. Here, we use a well‐studied database of groundfish assessments from the West Coast of the USA to ask whether environmental variables or ecosystem indicators derived from long‐term monitoring datasets offer an improvement in our ability to skilfully forecast fish recruitment. A secondary question is which types of modelling approaches (ranging from linear models to non‐parametric methods) yield the best forecast skill. Third, we examine whether simultaneous forecasting of multiple species offers an advantage over generating species‐specific forecasts. We find that for approximately one third of the 29 assessed stocks, ecosystem indicators from juvenile surveys yields the highest out of sample predictive skill compared to other covariates (including environmental variables from Regional Ocean Modeling System output) or null models. Across modelling approaches, our results suggest that simpler linear modelling approaches do as well or better than more complicated approaches (reducing out of sample Root Mean Square Error by ~40% compared to null models), and that there appears to be little benefit to performing multispecies forecasts instead of single‐species forecasts. Our results provide a general framework for generating recruitment forecasts in other species and ecosystems, as well as a benchmark for future analyses to evaluate skill. The most promising applications are likely for species that are short lived, have relatively high recruitment variability, and moderate amounts of age or length data. Forecasts using our approach may be useful in identifying covariates or mechanisms to include in operational assessments but also provide qualitative advice to managers implementing ecosystem based fisheries management.
Building effective fishery ecosystem plans Levin, Phillip S.; Essington, Timothy E.; Marshall, Kristin N. ...
Marine policy,
June 2018, 2018-06-00, Letnik:
92
Journal Article
Recenzirano
Odprti dostop
U.S. fisheries management has made tremendous strides under the current management framework, which centers on single stocks rather than ecosystems. However, conventional management focuses on one ...fishing sector at a time, considers a narrow range of issues, and is separated into individual fishery management plans often leaving little opportunity to consider overarching management goals across fisheries. Ecosystem-based Fisheries Management (EBFM) provides mechanisms to address these but has not been widely adopted. Here, we review and analyze the development of Fisheries Ecosystem Plans (FEPs) as a means to implement EBFM. In doing so, we provide a blueprint for next-generation FEPS that have the potential to translate EBFM to action. We highlight FEPs as a structured planning process that uses adaptive management to operationalize EBFM. This “FEP Loop” process starts by identifying the key factors that shape a fishery system and considering them simultaneously, as a coherent whole. It then helps managers and stakeholders delineate their overarching goals for the system and refine them into specific, realistic projects. And it charts a course forward with a set of management actions that work in concert to achieve the highest-priority objectives. We conclude that EBFM is feasible today using existing science tools, policy instruments, and management structures. Not only that, nearly all of the steps in the proposed “FEP Loop” process are presently being carried out by U.S. fishery managers. The process of reviewing regional experiences in developing and applying the FEP loop will lead to adaptations and improvements of the process we propose.
•Ecosystem-based Fisheries Management (EBFM) addresses shortcomings in fisheries management.•EBFM is not widely practiced.•Fisheries Ecosystem Plans (FEPs) provides a means to translate EBFM into action.•provide a blueprint for next-generation FEPS that have the potential to translate EBFM to action.•FEPs can be a planning process that uses adaptive management to operationalize EBFM.•All steps in the proposed FEP process can be carried out by U.S. fishery managers.
•Impacts of ocean acidification change with latitude in the California Current.•Vulnerable species (e.g., calcifying invertebrates) and their predators decline most.•Decline in revenue projected, ...mainly from lower Dungeness crab catch in the north.
Marine ecosystems are experiencing rapid changes driven by anthropogenic stressors which, in turn, are affecting human communities. One such stressor is ocean acidification, a result of increasing carbon emissions. Most research on biological impacts of ocean acidification has focused on the responses of an individual species or life stage. Yet, understanding how changes scale from species to ecosystems, and the services they provide, is critical to managing fisheries and setting research priorities. Here we use an ecosystem model, which is forced by oceanographic projections and also coupled to an economic input-output model, to quantify biological responses to ocean acidification in six coastal regions from Vancouver Island, Canada to Baja California, Mexico and economic responses at 17 ports on the US west coast. This model is intended to explore one possible future of how ocean acidification may influence this coastline. Outputs show that declines in species biomass tend to be larger in the southern region of the model, but the largest economic impacts on revenue, income and employment occur from northern California to northern Washington State. The economic consequences are primarily driven by declines in Dungeness crab from loss of prey. Given the substantive revenue generated by the fishing industry on the west coast, the model suggests that long-term planning for communities, researchers and managers in the northern region of the California Current would benefit from tracking Dungeness crab productivity and potential declines related to pH.
PDF
