The widespread use of ecological network models (e.g., Ecopath, Econetwrk, and related energy budget models) has been laudable for several reasons, chief of which is providing an easy-to-use set of ...modeling tools that can present an ecosystem context for improved understanding and management of living marine resources (LMR). Yet the ease-of-use of these models has led to two challenges. First, the veritable explosion of the use and application of these network models has resulted in recognition that the content and use of such models has spanned a range of quality. Second, as these models and their application have become more widespread, they are increasingly being used in a LMR management context. Thus review panels and other evaluators of these models would benefit from a set of rigorous and standard criteria from which the basis for all network models and related applications for any given system (i.e., the initial, static energy budget) can be evaluated. To this end, as one suggestion for improving network models in general, here I propose a series of pre-balance (PREBAL) diagnostics. These PREBAL diagnostics can be done, now, in simple spreadsheets before any balancing or tuning is executed. Examples of these PREBAL diagnostics include biomasses, biomass ratios, vital rates, vital rate ratios, total production, and total removals (and slopes thereof) across the taxa and trophic levels in any given energy budget. I assert that there are some general ecological and fishery principles that can be used in conjunction with PREBAL diagnostics to identify issues of model structure and data quality before balancing and dynamic applications are executed. I humbly present this PREBAL information as a simple yet general approach that could be easily implemented, could be considered for further incorporation into these model packages, and as such would ultimately result in a straightforward way to evaluate (and perhaps identify areas for improving) initial conditions in food web modeling efforts.
•Ecopath with Ecosim models are easy to construct and have been for the past 30 years.•We highlight thermodynamic and ecological diagnostics for best practice in Ecopath.•The state of the art in ...Ecosim time series fitting and calibration are elucidated.•Uncertainty is addressed through Monte Carlo calculations.•“Key runs” are highlighted as best practice for ecosystem based management.
Ecopath with Ecosim (EwE) models are easier to construct and use compared to most other ecosystem modelling techniques and are therefore more widely used by more scientists and managers. This, however, creates a problem with quality assurance; to address this we provide an overview of best practices for creating Ecopath models. We describe the diagnostics that can be used to check for thermodynamic and ecological principles, and highlight principles that should be used for balancing a model. We then highlight the pitfalls when comparing Ecopath models using Ecological Network Analysis indices. For dynamic simulations in Ecosim we show the state of the art in calibrating the model by fitting it to time series using a formal fitting procedure and statistical goodness of fit. Finally, we show how Monte Carlo simulations can be used to address uncertainty in input parameters, and we discuss the use of models in a management context, specifically using the concept of ‘key runs’ for ecosystem-based management. This novel list of best practices for EwE models will enable ecosystem managers to evaluate the goodness of fit of the given EwE model to the ecosystem management question.
The discipline and practice of fisheries science and management have had an useful, successful, and interesting history. The discipline has developed over the past century and a half into a very ...reductionist, highly quantitative, socially impactful endeavor. Yet given our collective successes in this field, some notable challenges remain. To address these challenges, many have proposed ecosystem-based fisheries management that takes a more systematic approach to the management of these living marine resources. Here I describe systems theory and associated constructs underlying system dynamics, elucidate how aggregate properties of systems can and have been used, contextualize these aggregate features relative to optimal yield, and note how this approach can produce useful estimates and outcomes for fisheries management. I explore two contrasting examples where this approach has and has not been considered, highlighting the benefits of applying such an approach. I conclude by discussing ways in which we might move forward with a portfolio approach for both the discipline and practice of fisheries science and management.
Overfishing has severe social, economic, and environmental ramifications. Eliminating global overfishing is one of the United Nations' Sustainable Development Goals (SDGs). The SDGs require effective ...policy and progress monitoring. However, current indicators are issue-specific and cannot be utilized to measure fisheries efficacy holistically. This study develops a comprehensive index that takes into account the inputs, outputs, and ecological implications of fisheries. These components are then merged to form a single composite fishing index that evaluates both total fishing pressure on the ecosystem and historical patterns. The global fishing intensity grew by a factor of eleven between 1950 and 2017, and geographical differences emerged. The fishing intensity of developed countries peaked in 1997 and has since fallen due to management, but developing countries' fishing intensity has increased continuously over the whole research period, with quasi-linear growth after 1980. Africa has experienced the most rapid expansion in fishing activity and now has the highest fishing intensity. This index takes a more comprehensive and objective look at fisheries. Its worldwide spatial-temporal comparison enables the identification of similar temporal trends across countries or regions, as well as areas of uneven development and hotspot sites for targeted policy action.
Abstract
Marine capture fisheries in the U.S. are important from a societal, cultural, economic, and ecological perspective. Although fisheries in the U.S. are generally well-managed, they still face ...some challenges as do most fisheries around the world. To address these challenges, a broader, more systematic approach is useful. There is a global need to develop measures of ecosystem overfishing (EOF) that detect overfishing of an entire ecosystem using readily available data and based on widely repeatable patterns. These EOF indicators extend the thinking beyond single stock overfishing to an entire ecosystem and are largely based on well-established trophic theory. Moreover, these EOF indicators need to be germane for both data rich and especially data limited situations, easily interpretable, and relatively simple to calculate. Here, I present the results of several of these indicators—the Ryther, Fogarty, and Friedland indices—as well as indices based on cumulative biomass-Trophic Level curve parameters for eight U.S. Large Marine Ecosystems (LMEs). Significantly, all these EOF indicators also have thresholds beyond which EOF is indicated, particularly when coupled with other evidence. Evidence for EOF is suggested for two of the eight U.S. LMEs. Even apart from EOF thresholds, detecting whether EOF is occurring, or how debatable the proposed EOF thresholds are, there are multiple benefits from monitoring these ecosystem-level indicators. Detecting patterns and trends in overall fishing changes for an ecosystem is chief among them. Additionally, EOF indicators detected changes in these LMEs at least 2–3 years, even up to 5 years prior to major impacts that might not be identified by piecing together fishing impacts on a stock-by-stock basis; thus, the EOF indicators could serve as an early warning signal. I propose that instead of starting with the history of which stocks have been assessed or even with what we deem most valuable, we look at the entire system of fisheries in an LME and if EOF is detected, explore means to address excess fishing pressure systematically before delving into the details of specific stocks. I conclude that EOF measures need to be monitored, EOF thresholds refined, and if EOF is detected then the means to mitigate total fishing pressure in an ecosystem should be explored.
Abstract
Living marine resources (LMRs) contribute considerably to marine economies. Oceans continue to respond to the effects of global change, with environmental factors anticipated to impact ...future seafood production and its associated economic performance. Here we document novel relationships between primary productivity and LMR-based economics for US regional marine ecosystems and 64 international large marine ecosystems (LMEs). Intermediate relationships between production, total biomass, fisheries landings, revenue, and LMR-based employment are also elucidated. We found that all these factors were dependent on the amount of basal production in a given system. In addition, factors including human population, exploitation history, and governance interventions significantly influenced these relationships. As system productivity plays a foundational role in determining fisheries-based economics throughout global LMEs, greater accounting for these relationships has significant implications for global seafood sustainability and food security. Quantifying the direct link between primary production and fisheries economic performance serves to better inform ecosystem overfishing thresholds and their economic consequences. Further recognition and understanding of these relationships is key to ensuring that these connections are accounted for more effectively in sustainable management practices.
The cellular mechanism(s) linking macrophages to norepinephrine (NE)-mediated regulation of thermogenesis have been a topic of debate. Here we identify sympathetic neuron-associated macrophages ...(SAMs) as a population of cells that mediate clearance of NE via expression of solute carrier family 6 member 2 (SLC6A2), an NE transporter, and monoamine oxidase A (MAOA), a degradation enzyme. Optogenetic activation of the sympathetic nervous system (SNS) upregulates NE uptake by SAMs and shifts the SAM profile to a more proinflammatory state. NE uptake by SAMs is prevented by genetic deletion of Slc6a2 or inhibition of the encoded transporter. We also observed an increased proportion of SAMs in the SNS of two mouse models of obesity. Genetic ablation of Slc6a2 in SAMs increases brown adipose tissue (BAT) content, causes browning of white fat, increases thermogenesis, and leads to substantial and sustained weight loss in obese mice. We further show that this pathway is conserved, as human sympathetic ganglia also contain SAMs expressing the analogous molecular machinery for NE clearance, which thus constitutes a potential target for obesity treatment.
Tissue-resident and recruited macrophages contribute to both host defense and pathology. Multiple macrophage phenotypes are represented in diseased tissues, but we lack deep understanding of ...mechanisms controlling diversification. Here, we investigate origins and epigenetic trajectories of hepatic macrophages during diet-induced non-alcoholic steatohepatitis (NASH). The NASH diet induced significant changes in Kupffer cell enhancers and gene expression, resulting in partial loss of Kupffer cell identity, induction of Trem2 and Cd9 expression, and cell death. Kupffer cell loss was compensated by gain of adjacent monocyte-derived macrophages that exhibited convergent epigenomes, transcriptomes, and functions. NASH-induced changes in Kupffer cell enhancers were driven by AP-1 and EGR that reprogrammed LXR functions required for Kupffer cell identity and survival to instead drive a scar-associated macrophage phenotype. These findings reveal mechanisms by which disease-associated environmental signals instruct resident and recruited macrophages to acquire distinct gene expression programs and corresponding functions.
Display omitted
•Myeloid cell diversity in NASH is associated with distinct microanatomical niches•Reprogramming of LXR activity leads to impaired Kupffer cell identify and survival•ATF3 collaborates with LXRs to promote a scar-associated macrophage phenotype•Altered enhancer landscapes enable inference of disease mechanisms
Kupffer cells and recruited myeloid cells contribute to the pathology of nonalcoholic steatohepatitis (NASH), but molecular mechanisms specifying their distinct identities and functions are not known. Seidman and colleagues address this problem by defining cell- and disease-specific enhancer landscapes that enable inference of key transcription factors that drive myeloid cell diversity in NASH.
The shift in marine resource management from a compartmentalized approach of dealing with resources on a species basis to an approach based on management of spatially defined ecosystems requires an ...accurate accounting of energy flow. The flow of energy from primary production through the food web will ultimately limit upper trophic-level fishery yields. In this work, we examine the relationship between yield and several metrics including net primary production, chlorophyll concentration, particle-export ratio, and the ratio of secondary to primary production. We also evaluate the relationship between yield and two additional rate measures that describe the export of energy from the pelagic food web, particle export flux and mesozooplankton productivity. We found primary production is a poor predictor of global fishery yields for a sample of 52 large marine ecosystems. However, chlorophyll concentration, particle-export ratio, and the ratio of secondary to primary production were positively associated with yields. The latter two measures provide greater mechanistic insight into factors controlling fishery production than chlorophyll concentration alone. Particle export flux and mesozooplankton productivity were also significantly related to yield on a global basis. Collectively, our analyses suggest that factors related to the export of energy from pelagic food webs are critical to defining patterns of fishery yields. Such trophic patterns are associated with temperature and latitude and hence greater yields are associated with colder, high latitude ecosystems.
PDF
