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Modeling human, climate, and habitat impacts on Pacific Northwest groundfish: a project proposal. Melissa A. Haltuch, UW School of Aquatic & Fishery Sciences This project will develop multispecies simulation models within which changes in west coast groundfish population trends and expected rebuilding rates for overfished species can be considered on two time scales: (a) short-term changes in population size due to anthropogenic effects such as fishing, and (b) decadal or interdecadal changes in population size due to low frequency environmental variation. Simulation modeling of the dynamics of groundfish stocks off the Pacific Northwest will be conducted at appropriate spatial and temporal scales following a review of the available data. Environmental variability and climate change will be included as forcing variables in the model, which will be structured to answer questions related to the distribution of fish stocks and expected rebuilding rates under different levels of future catch. Alternative model structures representing different hypotheses regarding the nature of the relationship between environmental variation, climate change and groundfish population dynamics will be fitted to existing data to assess whether the data can discriminate among these hypotheses. Both quantitative methods, such as meta-analysis, as well as qualitative approaches will be used to analyze and synthesize historical data on groundfish populations. These data will be used to develop hypotheses regarding the impacts of oceanographic processes, such as El Nino, on groundfish population and community dynamics.
Stock Assessments and Emerging Fisheries: Population dynamics of Pacific Northwest nearshore fishes. Jason M. Cope, UW School of Aquatic & Fishery Sciences Declines in and restricted access to many traditionally targeted marine resources have produce rapidly emerging fisheries that lack basic information and appropriate controls to assess and manage newly targeted stocks. The nearshore fishery along the west coast of the United States is an example of an emerging fishery currently under mandate from state and federal levels to ensure long-term sustainability and conservation of the resources while simultaneously maintaining or improving socio-economic status, all using "the best possible science", though very little data exists. I will present a recent history of the development of the US west coast nearshore fishery and the challenges of assessing it with little information. I will discuss a general operational model for the nearshore fishery and suggest and solicit ideas that may improve our ability to assess populations in data-poor situations.
Status and Future Prospects for the Cabezon (Scorpaenichthys marmoratus) as Assessed in 2003 Jason M. Cope, UW School of Aquatic & Fishery Sciences The cabezon (Scorpaenichthys marmoratus) assessment represents the first stock assessment performed on cabezon and the first for a nearshore fish. Data was very limited and results were highly dependent on length composition and recreational fishery-dependent data, but we also considered the incorporation of spawning and recruitment indices. The ability to perform an assessment with stock structure in a data-poor situation was also considered, while we used a Bayesian approach to characterize assessment uncertainty. This presentation will offer a look at the data available, how decisions were made, and presents assessment results.
Minimum Stock Size Thresholds: How well can we detect whether stocks are below them? Teresa A'mar & André E. Punt, UW School of Aquatic & Fishery Sciences Management of marine fisheries in U.S. waters is based on the Sustainable Fisheries Act. In particular, Rebuilding Plans need to be developed for fish stocks that have been depleted to below a Minimum Stock Size Threshold, MSST. Whether a stock is below MSST or not is based on the results from a stock assessment. Two types of error can arise when a stock is assessed relative to MSST: (a) it can be assessed to be above MSST when it is not, or (b) it can be assessed to be below MSST when it is not. The probability of making these two errors depends on the quality of the data and the suitability of the population dynamics model underlying the stock assessment. Simulation is used to assess the likelihood of making these two types of errors as a function of the true status of the resource, the stock assessment method applied, and the quality and quantity of the data available for assessment purposes.
The Impact of Recruitment Projection Methods on Forecasts of Rebuilding Rates for Overfished Marine Resources André E. Punt, UW School of Aquatic & Fishery Sciences
Under the U.S. Sustainable Fisheries Act, Rebuilding Plans have to be developed for fish stocks that are determined to be overfished, i.e. are found to be below the Minimum Stock Size Threshold, irrespective of whether they are data-rich or data-poor. Rebuilding Plans have to include analyses to determine the minimum time, TMIN, to recover to a BMSY proxy and the target level of fishing mortality, FREC, that is consistent with recovery to this proxy within a pre-specified timeframe and with an agreed probability. Key factors that determine TMIN and FREC are the methods used to forecast future recruitment and to estimate the size of the unfished reproductive output of the population. Several approaches to modeling future recruitment are available. For example, Monte Carlo draws from previous recruitments, from previous recruits per spawner, and from a parametric probability distribution around an estimated stock-recruitment relationship have been used for groundfish resources off the U.S. west coast. The results of rebuilding analyses are sensitive to this choice of modeling approach. The performance of alternative approaches to modeling future recruitment, in terms of providing unbiased and precise estimates of TMIN and FREC, are explored by means of simulation. [The impacts of uncertainty in the estimates of historical recruitment and spawning stock size, and of the number of years for which stock and recruitment data are available on the ability to make reliable predictions of the quantities required by the Sustainable Fisheries Act are quantified. The results of these analyses are used to identify the most robust approaches for predicting future recruitment in data-rich and data-poor situations.]
The Use of Reproductive Potential to Compare Age-Structured Models to Surplus Production Models Ian G. Taylor & Vincent F. Gallucci, QERM & School of Aquatic & Fishery Sciences Surplus production models have been applied to elasmobranch populations due to a shortage of age-specific data. This is despite knowledge that many of these species have long life-spans and a late age of maturity, traits that would be better described by age-structured models. The data limitations have suggested the exploration of alternative methods to better assess these populations. Reproductive potential, a concept developed by R.A. Fisher, is a sum of the expected future contributions of all individuals to the population as a whole. By incorporating the probabilities of surviving to spawn in future years and differences in fecundity-at-age values it represents more accurately a population's capacity for growth than does biomass.
What is it in fisheries data that tells us about population abundance? Arni Magnusson, UW School of Aquatic & Fishery Sciences The goal of this study is to identify what kinds of stock assessment data are informative about current abundance. Besides working through real and simulated datasets, a general method will be developed for quantifying how much information comes from each data component in a statistical catch at age model. This method will improve our understanding about the uncertainty in each stock assessment, and indicate what kind of data sampling effort would be particularly valuable for a given fishery. With experience, stock assessment scientists acquire a "feeling" for what kind of data are informative about population abundance. In broad terms, these include (1) contrasted catch history, (2) consistent age data showing high recruitment variability, and (3) an index of abundance that corresponds to fluctuations catch history. The uncertainty also depends on the overall amount of data available, and how heavily the stock has been fished.
Reference Points and Decision Rules in US. Federal Fisheries: West Coast Groundfish Experiences Jody Little, UW School of Aquatic & Fishery Sciences At the core of the nascent field of sustainability science is evaluation of dynamic interactions between nature and society - the aim being to better understand how to 'meet fundamental human needs while preserving the life-support systems of planet Earth'. Moving from a global scale to a regional one, how can we explore the nature-society system of the US West Coast coastal marine ecosystem, fisheries, and coastal communities? This question is the focus of my doctoral research. As I am in the beginning stages of my project, in this workshop I will present a research outline, outputs from recent ecosystem valuation work, and seek feedback on these approaches and results.
Reference Points and Decision Rules in US. Federal Fisheries: West Coast Groundfish Experiences André Punt, Jason Cope*, and Melissa Haltuch The management goals for Federally-managed fisheries in the US are implicitly defined by the 10 National Standards of the Sustainable Fisheries Act of 1996. National Standard 1 states that 'Conservation and management measures shall prevent overfishing while achieving on a continuing basis, the optimum yield from each fishery for the United States industry'. The need to satisfy this standard has led to the development of harvest control rules that assess whether overfishing is occurring or a stock is an overfished state. If a stock is an overfished state, it is necessary to develop a rebuilding plan so that the stock is recovered to BMSY within a pre-specified number of years. The control rules therefore include reference points related to fishing mortality and biomass. The rebuilding plans need to include quantities such as when recovery is expected to occur. The existence of these control rules leads to a well-defined structure within which management decisions can be made. However, simulation testing and empirical evidence for the US west coast groundfishery suggests that the catch limits based on these control rules will vary substantially from one year to the next due to assessment imprecision, the mathematical structure of the control rules, and difficulties predicting future recruitment. Other control rules may perform adequately in terms of allowing resource recovery but do not provide all the quantities required under US legislation. These results emphasize the need for scientists and decision makers to both have input into the choice of management goals and reporting requirements.
Size, Configuration and the Impacts of Boundary Infringements In Marine Protected Areas Richard Little, Tony Smith, Francis Pantus, André Punt*, Bruce Mapstone, and Campbell Davies, and David McDonald, CSIRO Marine Research Designing Marine Protected Areas (MPAs) inherently involves spatial issues in arranging areas gazetted for different uses. From a fisheries management perspective, MPAs involving no-take zones might serve to enhance exploited stocks, provide harvest refugia, and conserve vulnerable biota. An explicit assumption of such closures is that they are adequately enforced against infringements, or that their features, such as size and arrangement, have been designed to minimise infringement. In most systems, the number of possible arrangements of closed areas is large, but information with which to evaluate their efficacy is scarce. To overcome this paucity of information, we have developed a spatially structured simulation model of the population dynamics, and line fishing exploitation of common coral trout (Plectropomus leopardis) on the Great Barrier Reef. In this paper, we use this tool, called the Effects of Line Fishing Simulator (ELFSim), to evaluate the effects of different MPA arrangements on fish biomass and catch rates both inside and outside closed areas. Our model, which involves a detailed spatially structured model of the full life-history of common coral trout, and a multiple sector (commercial, charter and recreational) line fishing harvest model, allows us to explore these effects over decadal periods.
The role of bias-correction when combining equilibrium and stochastic recruitment models Richard D. Methot, NOAA Northwest Fisheries Science Center When annual recruitment is freely estimated in population assessment models, it is most common to find a right-skewed distribution that appears lognormal. In this situation, most of the numbers of fish in the population, and their accumulated biomass, comes from the infrequent large recruitments. Simulations confirm that the long-term mean population biomass follows arithmetic mean recruitment, not median recruitment or geometric mean recruitment. This has implications for calculation of the initial, virgin population abundance in population models that start with equilibrium age composition. Application of a standard bias correction to the geometric mean recruitment produces an initial equilibrium biomass that is indistinguishable from that obtained by resampling from lognormal distribution of recruitments over a long time period. This has implications for rebuilding calculations and Bmsy calculations. Rebuilding targets typically are 40% of Bzero, a mean-based calculation. However, rebuilding to this target is calculated in terms of probabilities derived from resampling lognormal recruitments. There is a small conservative bias in requiring a 50% Pr of rebuilding to a level that would be achieved less than 50% of the time under perfect knowledge and management. This bias is probably smaller than the potential difference between the proxy target (40% of Bzero) and the true Bmsy. Bmsy itself probably should be calculated as a median-based quantity derived through simulation of the pop dyn and management procedures. This log-bias consideration also can cause a difference between maximum likelihood and MCMC results when some early recruitments have little constraint by data, so their ML values drift to the expected valued from the spawner-recruitment relationship. Because the S-R is defined for log(recruitment), the expected values it produces are for median recruitment. However, when resampling through MCMC, the values of those recruitments will take on the full lognormal distribution, so will have a different mean than occurs in the ML case. This difference could account for the observed difference in ML v. MCMC results for some assessments.
Are bias-correction factors biased? André E. Punt, UW School of Aquatic & Fishery Sciences Use of the log-normal distribution when modelling recruitment implies that the expected recruitment differs from the median recruitment. Account can be taken of this when fitting assessment models. However, the bias-correction factor is usually based on the assumption steepness = 1. This talk explores the consequences of using this bias-correction factor when steepness < 1.
Issues in Metapopulation Modeling Ian Taylor, UW QERM and School of Aquatic & Fishery Sciences Tagging studies of spiny dogfish in the Northeast Pacific are characterized by primarily local recaptures with some very long distance migrations. These patterns, combined with the lack of larval dispersal for this species and strong regional differences in fishing effort make the population a strong candidate for metapopulation modeling. I will briefly present a metapopulation model for spiny dogfish in the Northeast Pacific and then discuss (and seek feedback on) some issues I'm dealing with which need to be faced in metapopulation models in general, including: 1. methods of incorporating movement, 2. the interaction between movement rates and equilibrium population sizes, 3. the estimation of sustainable harvest rates, and 4. the interaction between movement rates and sustainable harvest rates.
Information about stock abundance: Data, models, and assumptions Arni Magnusson, UW School of Aquatic & Fishery Sciences Fisheries stock assessment models provide estimates of population abundance and management reference points, as well as the uncertainty about these estimates. This perceived uncertainty reflects the information contained in the available data, but also depends in a complex way on the choice of model and implicit assumptions that are made. In this study, I identify what kinds of data are informative in stock assessments, and how this is influenced by model assumptions. A statistical catch-at-age model is used to analyze a large number of simulated datasets. These scenarios involve different fishing histories, where the population is either decreasing, steady, or increasing. Some model runs have all data available to them, but in others the abundance index or catch at age is excluded. This is useful to distinguish whether the information is coming from one data component in particular, or whether the abundance index and catch at age are mainly informative when analyzed together. Model runs also vary with respect to whether parameters are fixed or estimated. The key findings will be presented and discussed at the workshop.
Good and ugly multispecies fisheries: ITQs in British Columbia versus retention limits on the U.S. West Coast Trevor Branch, UW School of Aquatic & Fishery Sciences Can we devise a set of regulations for multispecies fisheries so that productive species are not undercaught (resulting in economic loss) while preventing overfishing of unproductive species? The groundfish fisheries of British Columbia and the U.S. West Coast offer some insights. They were managed by individual trip limits (with all their associated problems) until 1996, but thereafter diverged. The B.C. fishery implemented a 100% on-board observer system, permitting individual accountability of catch and discard mortality, followed in 1997 by the introduction of Individual Transferable Quotas (ITQs). The West Coast fishery, forbidden to consider ITQs by the Sustainable Fisheries Act, continued on the path of increasingly restrictive retention limits, and ever-increasing regulatory-induced discarding, as additional species were declared overfished. By almost any measure, the B.C. fishery is now in a better state of health: ITQs have resulted in greater flexibility, increased profitability, reduced overcapitalization, compliance with TACs, and the reduction of marketable discards to near zero. The reduction in discards alone provides additional income sufficient to cover the costs of observer coverage. A model of fishermen's location choice highlights the benefits of accounting for catches and discards under 100% observer coverage and the benefits of increased flexibility under ITQs.
Examining the screenplay: the myth of the free market and the consequences for economic efficiency in American fisheries Lucy Flynn, UW School of Aquatic & Fishery Sciences The "tragedy of the commons" phenomenon has been understood for centuries, and discussions of modern economic theory with respect to fisheries have been commonplace in the scientific literature since the early 1950s. However, instead of addressing these issues, management agencies have traditionally been required to regulate solely to perpetuate, restore, or enhance a fishery resource, without regard to the economic impacts of their policies. I will argue that this tradition is perpetuated by what I call the "myth of the free market," a culturally important myth that an unregulated free market is the only path to continually increased efficiency and a higher standard of living for all. Although in fact the early function of government fisheries agencies was to aid industry with research and development, and current subsidies and enforcement costs are paid by the general public, the simultaneous popular acceptance of the "no-government-intervention-is-best" ethic prevents policy makers from controlling investment and capacity (and therefore economic efficiency) in fisheries. I will seek to explain the source of the myth of the free market, the constraints it imposes on fishery management agencies, and the implications for future directions in fisheries policy, including the recent trend toward privatization with individual quota systems.
Moving beyond MSY: making Alaska's salmon fisheries socially and economically sustainable Ray Hilborn, UW School of Aquatic & Fishery Sciences Many of Alaska's salmon fisheries are models of biological success, with management structures that have maintained biomass, stock diversity and biological yield. At the same time the fisheries face severe challenges due to low price for the product, and the fisheries have been declared formal "economic" disasters by state and federal agencies in recent years. From many perspectives these fisheries are in crisis. I explore how the governance system for Alaskan salmon has led to biological success and economic failure. I review a range of alternative governance structures that are in place or being considered that might provide for social and economic sustainability. I also demonstrate that the basic biological principal that has guided management, Maximum Sustainable Yield, is a serious impediment to social and economic sustainability.
Progress towards rebuilding André E. Punt, UW School of Aquatic & Fishery Sciences The Pacific Fishery Management Council adopted rebuilding plans for eight groundfish species in 2004 in the form of Amendments 16-2 and 16-3 to the groundfish FMP. Each of these eight stocks will be re-assessed during 2005 and, as a consequence, there will be an opportunity to determine whether or not they have responded to recovery efforts and are on track to rebuild as previously projected.
It is to be expected that the results of the 2005 groundfish assessments with not conform exactly with the results expected based on the previous assessments. The question that arises then is whether the fishing mortality rate used to set harvest guidelines specified as part of the rebuilding plan should be changed, and if so how. A further consideration is that data now available may show that the original basis for the rebuilding plan is no longer valid (e.g. because the values assumed for natural mortality or stock recruitment steepness have changed markedly). Although guidelines exist regarding how rebuilding analyses are to be conducted, there no guidelines to determine whether (and to what extent) rebuilding plans are to be updated given new information.
The objectives of this presentation are to outline: a) a set of possible "rebuilding revision rules" which could be used to measure progress towards rebuilding (and make appropriate adjustments to rebuilding plans as needed), and b) a framework which uses simulation to provide a quantitative means to compare alternative rebuilding revision rules in terms of their effectiveness at correctly (and adequately) making adjustments to rebuilding plans.
Analysis of survey data using GLMMs: dealing with the "complete survey" Tom Helser, NOAA Northwest Fisheries Science Center A generalized linear mixed model (GLMM) that treats year and spatial cell as fixed effects while treating vessel as a random effect is used to estimate biomass and variances for 11 slope species in the NMFS bottom trawl surveys on the upper continental slope of U.S. West coast. A Bernoulli distribution is used to model the probability of a non-zero haul and we examine alternative error distributions from the exponential family using AIC to model the non-zero catch rates.
Measuring uncertainty in age-structured fisheries stock assessment models using MCMC, bootstrap, and Hessian methods Arni Magnusson, UW School of Aquatic & Fishery Sciences Uncertainty is a fundamental part of fisheries stock assessment, that needs to be quantified to successfully manage the resource. Among the statistical methods that are used to measure uncertainty are Markov chain Monte Carlo (MCMC) simulations, bootstrap, and Hessian delta-method approximation. In this study, a large number of stochastic datasets is generated, where the true parameter values are known. Confidence bounds are then estimated using the different methods, and the claimed uncertainty is compared with how often they contain the true value. The findings from this simulation study are reviewed, as well as theoretical and practical differences between the methods.
CAN WHALING BE MANAGED TO PROTECT WHALES AND WHALERS? Judith E. Zeh, UW Department of Statistics The International Whaling Commission (IWC) was established in 1946 by the International Convention for the Regulation of Whaling, signed by 14 whaling nations, “to provide for the proper conservation of whale stocks and thus make possible the orderly development of the whaling industry”. Part of the Convention is a Schedule that contains the actual regulations regarding species and numbers of great whales that can be caught, times and places in which whaling is allowed, etc. Amendments to the Schedule, which require a 3/4 majority vote for adoption, must be “based on scientific findings”. Thus, since its inception, the intent of the IWC has been to base management on science, and one of its standing committees has been the Scientific Committee (SC). The SC meets annually, just before the Commission meets, and the Chair of the SC presents SC findings to the Commission. I will talk about successes and failures of this management process before, during, and since my 1999-2002 term as SC Chair. Successes have come when the Commission obtained and followed good scientific advice. Failures have sometimes occurred because of inadequate scientific advice, but more often because economics or politics got in the way of following good advice. Both successes and failures occurred in the 1960s, when a committee of three scientists appointed by the Commission recommended immediate protection of Antarctic humpback and blue whales from whaling and drastic reductions in fin whale catches. The Commission did protect humpback and blue whales, but delayed reductions in fin whale catches because of pressure from whaling nations. Eventually greater reductions in fin whale catches had to be made to allow the stock to recover. The management procedure developed by the SC during the 1970s proved unworkable because it required classifying whale stocks on the basis of quantities that were difficult to estimate. Meanwhile, some whaling nations stopped whaling and other nations joined the IWC. It now has 66 members, the majority of which are non-whaling nations and many of which could be characterized as anti-whaling nations. This adds a complicating dimension to the “science and policy interface”. During the 1980s, the Commission imposed a moratorium on commercial whaling that is still in effect. However, the Convention allows whaling in spite of the moratorium by nations that objected to its adoption and by any nation under Special Permits for scientific research. Meanwhile, the SC has developed a revised management procedure (RMP) that requires only regular estimates of abundance of a stock and the known catch history. The RMP was tested by simulations of 100 years of catches using it. These simulations took into account uncertainties in a wide range of factors. In my view, whales and whalers would be better protected by use of the RMP to manage whaling than by the moratorium. The SC currently provides advice on aboriginal subsistence catch limits for bowhead whales using a similar management procedure.
External and internal estimates of age reading errors Bill Clark1, and Rick Methot2
Current efforts to conserve Pacific salmon (Oncorhynchus spp.) rely on a
variety of information sources including empirical observations, expert
opinion, and models. I will outline a framework for incorporating
detailed information on density-dependent population growth, habitat
attributes, hatchery operations, and harvest management into conservation
planning in a time-varying, spatially explicit manner. The model relies
on a multi-stage Beverton-Holt model to describe the production of salmon
from one life stage to the next. We used information from the literature
to construct relationships between the physical environment and the
necessary productivity and capacity parameters for the model. As an
example of how policy makers can use the model in recovery planning, we
applied the model to a threatened population of Chinook salmon (O.
tshawytscha) in the Snohomish River basin in Puget Sound, Washington,
USA. By incorporating additional data on hatchery operations and harvest
management for Snohomish River basin stocks, we show how proposed actions
to improve physical habitat throughout the basin translate into projected
improvements in four important population attributes: abundance,
productivity, spatial structure, and life history diversity. I will also
describe how to adapt the model to a variety of other management
applications.
Geostatistical conditional simulation of the distribution of schooling fish based on acoustic survey data: two approaches Charlotte Boyd and Mathieu Woillez
Geostatistical conditional simulations are a useful tool for capturing the full range of variability in spatial data. The distribution of schooling fish is inherently patchy – this patchiness may be lost in kriging which presents a best local estimate at each point and tends to smooth over local variability. In contrast, stochastic geostatistical simulations reproduce the variability of a variogram model. Simulations can be conditioned on the observed data values, and, on average, reproduce the statistical properties and spatial pattern of the sample data. Multiple simulations can therefore be used as the basis for estimating uncertainty at given locations. Geostatistical simulation is thus relevant to analyses of spatial sample data in which measurement error, local variability, or sampling uncertainty are important (such as risk assessment and decision analysis).
In the Gaussian case, geostatistical conditional simulation can be achieved relatively easily by adding a simulated error term to the kriging. However, in the case of acoustic surveys of schooling fish, where the acoustic backscatter is often characterized by a high proportion of zeroes and skewed positive values, some transformations are necessary. Here, we present and discuss two contrasting approaches to perform geostatistical conditional simulation in this context – one based on transformed Gaussian simulations and on a Gibbs sampler to handle the numerous zero acoustic values within a classical geostatistical framework, and the other based on a binomial/ lognormal hurdle model within a generalized linear mixed modeling framework.
Reconciling uncertain and conflicting trends in petrale sole abundance Melissa Haltuch
Petrale sole are a commercially important flatfish that migrate seasonally between feeding and spawning grounds, and have recently been declared overfished. The summer trawl survey shows a decline in petrale sole abundance since 2005 similar to the unstandardized summer catch-per-unit-effort (CPUE) from the fishery. However, many stakeholders disagree that petrale sole abundance has been declining, instead choosing to focus on the unstandardized winter CPUE that shows a strong increase beginning in 2000. The assessment attributes the increasing trend in winter CPUE to management actions that forced the fleet to 1) increase fishing effort during the winter, and 2) conduct winter fishing in locations with high historical catch rates. Standardized fishery CPUE was not used in the assessment due to changing management regulations beginning in the late 1990s and the high likelihood of a winter CPUE index showing hyper-stability due to the fishery focusing on the aggregated spawning stock. Given the potential discrepancy between the assessment results and the experience of the groundfish fleet, particularly during the winter fishing season, and the limited conclusions that can be drawn from unstandardized CPUE, this work explores the utility of the summer and winter fishery CPUE series as indices of abundance for the petrale sole stock assessment. The ultimate goals are to determine if an adequate index of abundance can be created using fishery CPUE, and to address the uncertainty due to the discrepancy between the fishery independent and fishery dependent data sources and therefore the perceived stock assessment uncertainty.
Modeling fish in a vertically integrated model, from climate to MSE Ivonne Ortiz1,2, and Kerim Aydin2
The Bering Sea Integrated Research Program (BSIERP) is a 5 year program designed to test hypotheses regarding the ecosystem's response to climate change. Both historical and BSIERP field data are used to put together a vertically integrated model that includes 5 modules: i) Climate (specific to the Bering Sea), ii) ROMS (Regional Ocean Modeling System) , iii) NPZ-benthos (Nutrient-Phytoplankton-Zooplankton-benthos), iv) FEAST (Forage/Euphausiid Abundance in Space and Time), and v) Economics (fleet movement model). The vertically integrated model in turn, will be used as the "real world" model in a Management Strategy Evaluation for the Bering Sea pollock, and Pacific cod fisheries. We will start with a presentation of the vertically integrated model structure and feedbacks, summarizing some of the challenges of working across multiple scales, units and objectives. We will then discuss the development, ongoing tuning and validation of the fish module FEAST, highlighting transitions from original to current formulations of bioenergetics, movement and reproduction through several rounds of meetings with field biologists. Finally, we'll detail what processes in the model are expected to respond to climate change, where we expect them to be buffered, and where they are non-sensitive.
FEAST runs on a grid of ~10 km resolution and models size-based, two way interactions between 13 fish species (walleye pollock, Pacific cod, arrowtooth flounder, salmon, capelin, herring, eulachon, sandlance, myctophids, squids, shrimp, crabs and other), and the 7 zooplankton groups in the NPZ model (small/large microzooplankton, small/large copepods, euphausiids, jellyfish, and benthic infauna). Both temperature and advection from ROMS are used in the bioenergetics and movement components. The operating hypothesis in FEAST is that forage fish and macrozooplankton are tightly coupled in a two-way interaction, and the dynamics of this interaction under different climate scenarios is a strong structuring element for the ecosystem as a whole.
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