Sarah Gaichas

National Oceanic and Atmospheric Administration | NOAA · Northeast Fisheries Science Center

Dynamic food web models are increasingly used to investigate the ecosystem effects of fishing; however, key unknown functional response parameters describing predator-prey interactions strongly influence model behavior. We explored functional response parameter uncertainty and its effect on fishing simulation results using a dynamic food web model...

We apply graph theory and network analysis to the food web of the Gulf of Alaska marine ecosystem to classify its structural properties, which suggest how the ecosystem as a whole may respond to heavy fishing pressure on its components. Three conceptual models of network structure, random, small-world, and scale-free, each have different implicatio...

Ecosystems have been viewed both as chaotic, untamed nature, and as mechanical systems with predictable equilibrium states. A developing concept of ecosystems as “complex adaptive systems” lies between these extreme concepts, with recognizably patterned but not fully predictable behavior. Sustainability has also been redefined as humans have exploi...

Fish community biomass is generally thought to decline with increasing temperature due to higher metabolic losses resulting in less efficient energy transfer in warm-water food webs. However, whether these metabolic predictions explain observed macroecological patterns in fish community biomass is virtually unknown. Here we test these predictions b...

Marine population modeling, which underpins the scientific advice to support fisheries interventions, is an active research field with recent advancements to address modern challenges (e.g., climate change) and enduring issues (e.g., data limitations). Based on discussions during the ‘Land of Plenty’ session at the 2021 World Fisheries Congress, we...

A R T I C L E I N F O Keywords: Atlantis marine ecosystem models end-to-end models biogeochemical forcing primary production global reanalysis ocean color lower trophic levels A B S T R A C T The northeast United States Atlantis model (NEUSv2) is an end-to-end ecosystem model that can simulate biogeochemical, ecological, fishery, management, and so...

China's 13th Five-Year Plan elevated the national mandate for environmental sustainability. Chinese fisheries are characterized by full retention of high diversity catch harvested using unselective gears, creating ecological risks. Therefore, China launched pilot projects in management by Total Allowable Catch (TAC) in five coastal provinces in 201...

Management strategy evaluation (MSE) is a simulation approach that serves as a “light on the hill” ( Smith, 1994 ) to test options for marine management, monitoring, and assessment against simulated ecosystem and fishery dynamics, including uncertainty in ecological and fishery processes and observations. MSE has become a key method to evaluate tra...

States in the Northeast United States have the ambitious goal of producing more than 22 GW of offshore wind energy in the coming decades. The infrastructure associated with offshore wind energy development is expected to modify marine habitats and potentially alter the ecosystem services. Species distribution models were constructed for a group of...

Emergent properties of ecosystems are community attributes, such as structure and function, that arise from connections and interactions (e.g., predator–prey, competition) among populations, species, or assemblages that, when viewed together, provide a holistic representation that is more than the sum of its individual parts. Climate change is alte...

Managers, stakeholders, and scientists recognize the need for collaborative, transparent, integrated approaches to complex resource management issues, and frameworks to address these complex issues are developing. Through the course of 2019, the Mid-Atlantic Fishery Management Council developed a conceptual model of ecosystem linkages and risks for...

As ecosystem-based fisheries management becomes more ingrained into the way fisheries agencies do business, a need for ecosystem and multispecies models arises. Yet ecosystems are complex, and model uncertainty can be large. Model ensembles have historically been used in other disciplines to address model uncertainty. To understand the benefits and...

Management Strategy Evaluation (MSE) is an effective tool to gauge the relative performance of fishery management options. For the most part, MSEs have been applied to single-species management procedures. However, to be more inclusive of all the biological and technical interactions occurring within a system, ecosystem-based strategies are emergin...

Integrated ecosystem assessments (IEAs) compile and use indicators, risk assessments, and other analyses to address regional policy needs at varying spatial scales. Although approaches to implementing IEAs are context-specific, challenges in data acquisition, management, processing, analysis, and communication are universal. By embracing open scien...

Resource managers worldwide are being asked to consider the ecosystem while making management decisions. Integrated Ecosystem Assessment (IEA) provides a flexible framework for addressing ecosystem considerations in decision making. The US Mid-Atlantic Fishery Management Council (Council) adapted the IEA approach and implemented a structured decisi...

Ecosystem models are important tools for conducting ecosystem-based management. A particularly useful method of characterizing the flow of energy through an ecosystem and the subsequent direct and indirect implications of management actions is mass balance modeling. Here we outline the equations as utilized in Rpath, an R implementation of the mass...

Climate change is a pervasive and growing global threat to biodiversity and ecosystems. Here, we present the most up-to-date assessment of climate change impacts on biodiversity, ecosystems, and ecosystem services in the U.S. and implications for natural resource management. We draw from the 4th National Climate Assessment to summarize observed and...

The increasing need to account for the many factors that influence fish population dynamics, particularly those external to the population, has led to repeated calls for an ecosystem approach to fisheries management (EAFM). Yet systematically and clearly addressing these factors, and hence implementing EAFM, has suffered from a lack of clear operat...

Worldwide fisheries management has been undergoing a paradigm shift from a single-species approach to ecosystem approaches. In the United States, NOAA has adopted a policy statement and Road Map to guide the development and implementation of ecosystem-based fisheries management (EBFM). NOAA’s EBFM policy supports addressing the ecosystem interconne...

Management strategy evaluation (MSE) is an increasingly popular tool for developing, testing, and implementing fisheries management regimes, oftentimes utilizing participatory modeling. This special issue, “Under pressure: addressing fisheries challenges with Management Strategy Evaluation”, includes eleven articles highlighting cutting edge MSE ap...

In the United States, implementation of strong legislative mandates and investments in scientific programmes have supported sustainable fisheries management for seafood production, marine ecosystems, and maritime communities and economies. Changing climate and ocean conditions present new and growing challenges that affect the ability to manage fis...

Management strategy evaluation (MSE) is a simulation-based approach to examine the efficacy of management options in achieving fishery-, ecosystem-, and socioeconomic-related objectives while integrating over system uncertainties. As a form of structured decision analysis, MSE is amenable to stakeholder involvement, which can reduce implementation...

The New England Fishery Management Council used management strategy evaluation (MSE) to evaluate possible harvest control rules for Atlantic herring (Clupea harengus), the first MSE in the US and perhaps globally to use open-invitation, public workshops for input. Stakeholder inclusion can increase both realism and likelihood of use by managers, bu...

Fishery managers worldwide are evaluating methods for incorporating climate, habitat, ecological, social, and economic factors into current operations in order to implement Ecosystem Approaches to Fishery Management (EAFM). While this can seem overwhelming, it is possible to take practical steps toward EAFM implementation that make use of existing...

Atlantic herring (Clupea harengus) in the Northwest Atlantic have been managed with interim harvest control rules (HCRs). A stakeholder-driven management strategy evaluation (MSE) was conducted that incorporated a broad range of objectives. The MSE process was completed within 1 year. Constant catch, conditional constant catch, and a biomass-based...

Ecosystem-based management (EBM) of the ocean considers all impacts on and uses of marine and coastal systems. In recent years, there has been a heightened interest in EBM tools that allow testing of alternative management options and help identify tradeoffs among human uses. End-to-end ecosystem modelling frameworks that consider a wide range of m...

Quantitative models for marine ecosystem-based management are often constrained by availability of observations. Uncertainty about the underlying system structure can affect model estimates and conclusions about the consequences of management actions. Qualitative models can augment model development for decision-making and may provide an alternativ...

The NOAA-National Marine Fisheries Service (NMFS) held its 4th National Ecosystem Modeling Workshop (NEMoW 4) on February 28-March 2, 2017 at the NMFS Southeast Regional Office in St. Petersburg, FL. Ten years ago, scientists and administrators at NMFS established the first NEMoW in response to needs to more formally review, evaluate, and project t...

Marine ecosystems are complex, and there is increasing recognition that environmental, ecological, and human systems are linked inextricably in coastal regions. The purpose of this article was to integrate environmental, ecological and human dimensions information important for fisheries management into a common analytical framework. We then used t...

Between 2014 and 2016 an interdisciplinary team of researchers including physical oceanographers, biologists, economists, and anthropologists developed a working example of an Integrated Ecosystem Assessment (IEA) for three ecologically distinct regions of the Northwest Atlantic; Georges Bank, the Gulf of Maine, and the Grand Banks, as part of the...

Risk assessments quantify the probability of undesirable events along with their consequences. They are used to prioritize management interventions and assess tradeoffs, serving as an essential component of ecosystem-based management (EBM). A central objective of most risk assessments for conservation and management is to characterize uncertainty a...

The application of ecosystem considerations, and in particular ecosystem report cards, in federal groundfish fisheries management in Alaska can be described as an ecosystem approach to fisheries management (EAFM). Ecosystem information is provided to managers to establish an ecosystem context within which deliberations of fisheries quota occur. Our...

We explored alternative status determination criteria and reference points that could simplify fisheries management using a simulated multispecies/ecosystem-based operational management procedure. There are four components to the procedure: (i) limit total removals from the ecosystem; (ii) allocate the total removals limit among aggregate species g...

Marine ecosystems are characterized by many complex interactions. Fisheries managers face the challenge of maintaining or restoring sustainability for individual living resources which are affected by both ecological and economic interactions with other species, through processes like predation and fishing fleet interactions. These species interact...

Ecosystem models can be used to understand the cumulative impacts of human pressures and environmental drivers on ecosystem structure and dynamics. Predictive modeling can show how management can influence those dynamics and structures and the ecosystem services these systems provide. Many nations and intergovernmental organizations are advocating...

Need to assess the skill of ecosystem models: Accelerated changes to global ecosystems call for holistic and integrated analyses of past, present and future states under various pressures to adequately understand current and projected future system states. Ecosystem models can inform management of human activities in a complex and changing environ...

Decadal model skill metric analysis. (DOCX)

The Eastern Bering Sea (EBS) and Gulf of Alaska (GOA) continental shelf ecosystems show some similar and some distinctive groundfish biomass dynamics. Given that similar species occupy these regions and fisheries management is also comparable, similarities might be expected, but to what can we attribute the differences? Different types of ecosystem...

In setting fisheries management quotas, fish interactions with marine mammals are seldom considered. Even less often considered are indirect effects from fishing and species interactions or potential changes to ecosystem structure as marine mammal populations rebuild. To explore these interactions, we used a multi-species production model to evalua...

Risk assessment methods are used worldwide to evaluate threats posed by fisheries and other impacts on living marine resources, and to prioritize management of these threats. We derive a simplified risk analysis for aggregate fish communities as a preliminary tool to identify priorities for further detailed assessment. Because some of the largest o...

Just over fifteen years ago in their seminal work, Pauly and his colleagues coined the phrase “fishing down the food web”. That phrase describes how fisheries systematically target fish species sequentially down the food web as the higher trophic levels are depleted. This behavior, measured by the mean trophic level of the catch, can have dramatic...

The commercial fishing fleet targeting Pacific halibut (Hippoglossus stenolepis) was unobserved until 2013. Prior to that, catches of non-halibut species (bycatch) were not accounted for unless the bycatch was landed. State of Alaska and Federal fishery managers and scientists have long recognized the need for bycatch estimation in this fishery....

End-to-end models were constructed to examine and compare the trophic structure and energy flow in coastal shelf ecosystems of four US Global Ocean Ecosystem Dynamics (GLOBEC) study regions: the Northern California Current, the Central Gulf of Alaska, Georges Bank, and the Southwestern Antarctic Peninsula. High-quality data collected on system comp...

Similarly structured food web models of four coastal ecosystems (Northern California Current, Central Gulf of Alaska, Georges Bank, southwestern Antarctic Peninsula) were used to investigate competition among whales, fishes, pinnipeds, and humans. Two analysis strategies simulated the effects of historic baleen and odontocete whale abundances acros...

Executive Summary The NMFS held a National Ecosystem Modeling Workshop (NEMoW) on August 25-27, 2009. The workshop was held at the Chesapeake Bay Foundation, Merrill Center, in Annapolis, MD. This 2nd NEMoW was held as a national workshop analogous to National Stock Assessment Workshops and National Economists Meetings for the purpose of engaging t...

To better manage living marine resources (LMRs), it has become clear that ecosystem-based fisheries management (EBFM) is a desired approach. To do EBFM, one of the key tools will be to use ecosystem models. To fully use ecosystem models and have their outputs adopted, there is an increasingly recognized need to address uncertainty associated with s...

Ecosystem Based Fisheries Management (EBFM) is a holistic, place-based method for managing fisheries resources. In the Northeast United States, steps are being taken to adopt EBFM. One of the first steps was creating spatial ecological productions units (EPU) that contain similar biological and oceanographic features. These EPUs are the foundation...

Exploring Dynamic Variability and Interactions of Marine Fish Populations Hui Liu, Jason Link, Mike Fogarty, Caihong Fu, Sarah Gaichas, George Sugihara We compared the dynamics and underlying interactions of marine fish populations across 11 Large Marine Ecosystems in the northern hemisphere using a nonlinear time-series approach. The study inc...

Background/Question/Methods Much scientific advice for fisheries management is based on results from single species population assessment methods. However, as fisheries management becomes increasingly ecosystem-based, models that consider multispecies and environmental interactions are required, as are effective ecological indicators and referenc...

Metrics representative of key ecosystem processes are required for monitoring and understanding system dynamics, as a function of ecosystem-based fisheries management (EBFM). Useful properties of such indicators should include the ability to capture the range of variation in ecosystem responses to a range of pressures, including anthropogenic (e.g....

Understanding the drivers of the productivity of marine ecosystems continues to be a globally important issue. A vast body of literature identifies 3 main processes that regulate the production dynamics of fisheries: biophysical, exploitative, and trophodynamic. Here, we synthesize results from international workshops in which surplus production mo...

The MEPS Theme Section on 'Comparative Analysis of Marine Fisheries Production' is dedicated to Dr. Bernard Megrey. Dr. Megrey was well known for comparative studies of ecosystems, but his contributions to science were far broader. His pioneering of comparative marine ecosystem studies began long before they achieved a high profile in the field. He...

This paper introduces the MEPS Theme Section (TS) 'Comparative Analysis of Marine Fisheries Production'. The unifying theme of the studies in the TS is the relative influence of a 'triad of drivers' - fishing, trophodynamic, and environmental - on fisheries production. The studies were developed during 2 international workshops held in 2010 and 201...

Marine ecosystems are influenced by drivers that operate and interact over multiple scales, resulting in nonlinear or abrupt responses to perturbation. Because of the inherent complexity of marine ecosystems, progress towards an understanding of factors that affect fisheries production will be most efficient if researchers adopt a comparative appro...

A key aspect of ecosystem-based fisheries management is assessing sustainability at multiple levels of organization beyond single target species. For this, appropriate biological reference points (BRPs) for aggregated groups of species need to be developed. But what are the potential risks and benefits of applying aggregate management measures to t...

Ecology Letters (2011) 14: 1288–1299 Predator–prey interactions are a primary structuring force vital to the resilience of marine communities and sustainability of the world’s oceans. Human influences on marine ecosystems mediate changes in species interactions. This generality is evinced by the cascading effects of overharvesting top predators on...

Federal mandates have been established in US law that demand consideration of ecosystem effects (reauthorized Magnuson-Stevens Act, National Environmental Protection Act, Marine Mammal Protection Act, Endangered Species Act) when making fishery management decisions. Likewise, coastal states, interstate fishery commissions, and fishery management co...

An Eastern Bering Sea Ecosystem Synthesis Team was assembled in 2010 to bring together a multidisciplinary group of experts to choose ecosystem indicators that could form as the basis of a new ecosystem assessment for the eastern Bering Sea (EBS). The goal of this assessment was to provide current and relevant scientific advice for fisheries manage...

Mathematical modeling of marine food webs has been an area of active research in Alaska, particularly with respect to the fisheries management. Food web analyses have played a role in managing some single species fisheries, in estimating overall yields that may be sustainably extracted from ecosystems, and more recently in modeling and predicting f...

We define extended single-species production models (ESSPMs) as single species production models that incorporate time series of principal prey and/or predator species as biological covariates. One advantage to ESSPMs over single species production models without biological covariates is that these models can be used to test the existence and direc...

Two international workshops have been held that focused on the production modeling approach, at various levels of aggregation and with various covariates. How the outputs from such models could be used to estimate management-relevant metrics and ecosystem attributes was examined. The objectives were to A) use comparative analyses to build a methodo...