About
491
Publications
110,936
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
21,183
Citations
Citations since 2017
Introduction
Additional affiliations
July 1994 - January 2001
June 1994 - January 2001
Publications
Publications (491)
State-space assessment models (SSMs) ha v e garnered attention recently because of their ability to estimate time variation in biological and fisheries processes such as recr uitment, nat ural mort alit y, catchabilit y, and selectivit y. Ho w e v er, current SSMs cannot model time-varying growth internally nor accept length data, limiting their us...
Many mobile marine taxa are changing their distributions in response to climate change. Such movements pose a challenge to fisheries monitoring and management, particularly in systems where climate‐adaptive and ecosystem‐based management objectives are emphasized. While shifts in species distributions can be discerned from long‐term fisheries‐indep...
An assessment of the eastern North Pacific stock of gray whales (Eschrichtius robustus) is conducted using a variant of the Bayesian stock assessment method of Wade (2002). This variant is based on the BALEEN II population dynamics model and uses parameters whose values are more familiar to members of the International Whaling Commission's Scientif...
Gerrodette and DeMaster (1990) conclude that dynamic response analysis indicates that the gray whale population passed through its maximum net productivity level (MNPL, approximately equivalent to MSY level) between 1967 and 1980. Their conclusion is examined using models for population trends which permit a point of inflection; these are fitted gl...
Climate change is projected to affect the productivity of global fisheries. Management based on maximum sustainable yield (MSY) has been effective at eliminating overfishing in many regions. However, continuing to use yield‐maximizing targets under climate‐driven changes in productivity can result in higher anthropogenic pressure on populations sub...
Natural mortality (M) is one of the most influential parameters in fisheries stock assessment and management. It relates directly to stock productivity and reference points used for fisheries management advice. Unfortunately, M is also very difficult to estimate, and hence very uncertain. Representing the uncertainty in M and how this influences es...
The eastern Australian stock of orange roughy (Hoplostethus atlanticus) is a deep-water, long-lived species with a history of considerable exploitation during the late 1980s and early 1990s before being reduced to around 10% of unfished spawning biomass only a few years later, resulting in the closure of the fishery in 2006. Recent assessments have...
Generating accurate data for stock assessments is resource-demanding, necessitating periodic evaluation of survey sampling designs and potential impacts on stock assessments. We developed a framework for bootstrapped resampling of survey age data and calculation of input sample sizes as a function of among-bootstrap variance in age compositions. Da...
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...
Ecosystem Based Fisheries Management aims to broaden the set of factors included in assessments and management decision making but progress with implementation remains limited. We developed a framework that examines the consequences of temporal changes in temperature and ocean pH on yield and profit of multiple interacting stocks including eastern...
The harvest control rules for many fish and invertebrate stocks, managed using stock assessments based on fitting population dynamics models to monitoring data, rely on biological reference points. These reference points are often related to unfished conditions (‘B0’) and are calculated assuming that biological parameters and their associated funct...
Consideration of economic outcomes is commonplace in most fisheries management systems globally, although only a few jurisdictions have adopted an economic objective as the primary target for fisheries management. Such an objective has been adopted for Australia’s federally managed fisheries, with maximum economic yield (MEY) identified as the prim...
There is increasing consensus of the need for ecosystem-based fisheries management (EBFM), which accounts for trophic interactions and environmental conditions when managing exploited marine resources. Continued development and testing of analytical tools that are expected to address EBFM needs are essential for guiding the management of fisheries...
Natural mortality (M) is crucially important for stock assessment since it strongly influences estimates of spawning stock biomass, MSY and fishing mortality. Variation in M can occur between sexes, maturity stages and temporally. Estimates of M are confounded with those of catchability, recruitment, and growth. Previous studies, which focused on a...
Specification of how selectivity (the combination of availability and vulnerability) is modelled in integrated stock assessments is key to avoiding bias in estimates of quantities of management interest. Many “rules of thumb” are common in the community but these have yet to be rigorously tested. This paper uses simulation to compare 12 approaches...
Shifts in the distribution of groundfish species as oceans warm can complicate management efforts if species distributions expand beyond the extent of existing scientific surveys, changing the proportion of groundfish available to any one survey each year. We developed the first-ever model-based biomass estimates for three Bering Sea groundfishes (...
This tool provides a way for managers and other stakeholders to explore bycatch scenarios, based on simple information about marine mammal life history and rough estimates of abundance and bycatch. The tool consists of an R package (R Core Team, 2021) and a Shiny application (Chang et al., 2021). The primary machinery in the package is an age-struc...
The Northern Prawn Fishery (NPF) is one of Australia’s most valuable federally managed fisheries. It has also been a focus for modelling in Australia, with over 40 years of development of bioeconomic, stock assessment and management strategy evaluation models that have been used to varying degrees to inform management. The current management model...
The Gulf of Alaska Integrated Ecosystem Research Program (GOAIERP) supported multi-disciplinary analyses integrating physical and biological oceanography and modeling to examine how the environment influences survival and recruitment of early life stages of select commercially and ecologically important groundfish species. Recruitment is an importa...
Fish populations with spatial structure inherently violate the assumption of a single well-mixed stock, necessitating the use of spatially-structured population dynamics models. Accounting for spatial structure accurately and easily is a major goal for the next generation of stock assessment software development. Reference points (e.g., limit or ta...
Fisheries bycatch is the greatest current source of human-caused deaths of marine mammals worldwide, with severe impacts on the health and viability of many populations. Recent regulations enacted in the United States under the Fish and Fish Product Import Provisions of its Marine Mammal Protection Act require nations with fisheries exporting fish...
The Potential Biological Removal (PBR) level serves as a threshold for management of marine mammal–fishery interactions under the US Marine Mammal Protection Act. The PBR protocol involves classifying fisheries based on the ratio of recent average bycatch mortality to PBR. A simulation-based framework is developed that quantifies the probability of...
Bycatch in marine fisheries is the leading source of human-caused mortality for marine mammals, has contributed to substantial declines of many marine mammal populations and species, and the extinction of at least one. Schemes for evaluating marine mammal bycatch largely rely on estimates of abundance and bycatch, which are needed for calculating b...
There is a paucity of age data for chondrichthyan fishes owing, in large part, to limitations in traditional age estimation methods. Fourier transform near-infrared (FT-NIR) spectroscopy has shown promise as an alternative, more efficient method for acquiring age data from chondrichthyans. However, studies are limited to sharks in the southern hemi...
Motivated by the need to estimate the abundance of marine mammal populations to inform conservation assessments, especially relating to fishery bycatch, this paper provides background on abundance estimation and reviews the various methods available for pinnipeds, cetaceans and sirenians. We first give an “entry-level” introduction to abundance est...
The precautionary approach to fisheries management advocates for risk‐averse management strategies that include biological reference points and account for scientific uncertainty (i.e. process, model and observation uncertainty). In this regard, two approaches have been recommended: (a) biomass reference points to safeguard against low stock biomas...
Within fisheries assessments, selectivity refers to the relative probability of a fish of a particular size or age being caught. Selectivity, typically modelled using a parametric function, is informed primarily by age- and size-composition data. This function can vary annually, and not accounting for this variation can result in biased estimates o...
Climate-enhanced stock assessment models represent potentially vital tools for managing living marine resources under climate change. We present a climate-enhanced stock assessment where environmental variables are integrated within a population dynamics model assessment of biomass, fishing mortality and recruitment that also accounts for process e...
Stock assessments based on fitting age-structured population dynamics models using the integrated approach usually require data on the length-/age-structure of fishery removals and age-length data to estimate key population parameters such as growth rates, recruitment, natural mortality rates and selectivity. The errors in the estimates of these po...
Management strategy evaluation (MSE) is the state‐of‐the‐art approach for testing and comparing management strategies in a way that accounts for multiple sources of uncertainty (e.g. monitoring, estimation, and implementation). Management strategy evaluation can help identify management strategies that are robust to uncertainty about the life histo...
The ability to monitor population dynamics and detect major changes in population trend is essential for wildlife conservation and management. However, this is often challenging for cetaceans as surveys typically cover only a portion of a population’s range and conventional stock assessment methods cannot then distinguish whether apparent changes i...
Abundance indices from scientific surveys are key stock assessment inputs, but when the availability of fish varies in space and time, the estimated indices and associated uncertainties do not accurately reflect changes in population abundance. For example, indices for many semi-pelagic species rely on acoustic and bottom trawl gear that differ in...
Taxa can expand beyond historical scientific survey footprints and into new areas with different survey protocols as they move to track their preferred climate. In global groundfish fisheries, for example, scientists estimate population dynamics within the spatial extent of a fishery‐independent survey using an index known as a design‐based estimat...
Stock assessments are integral to fisheries management, and the demand for stock assessments based on population dynamics models continues to increase. Historically, stock assessments have been based on bespoke methods and software. There is now a trend towards the use of flexible, documented, tested and maintained software packages, because use of...
The effects of human-caused mortality, such as fisheries bycatch, of endangered, threatened and protected (ETP) species of marine mammals can be evaluated using population model-based stock assessments. The information available to conduct such assessments is often very limited. Available data might include fragmented time-series of abundance estim...
Stock status for many medium-and small-scale fisheries is unknown due, for example, to a lack of catch data and the absence of scientific observer programs. However, length-frequency data are often available for such fisheries because they are the cheapest and easiest data to obtain. Various stock assessment methods have been developed that use len...
We describe a first estimate of the potential to increase production from Australia’s commercial fisheries based on the difference between current catches and maximum sustainable yield (MSY). MSY is not being advocated as a target reference point but enables a level of consistency across species and/or jurisdictions with different reference points....
Recent observations of record low winter sea-ice coverage and warming water temperatures in the eastern Bering Sea have signaled the potential impacts of climate change on this ecosystem, which have implications for commercial fisheries production. We investigate the impacts of forecasted climate change on the eastern Bering Sea food web through th...
Natural mortality (M) is often considered to be one of the most important parameters in a fish stock assessment and affects productivity estimates for the population. However, it is also among the most difficult parameters to estimate using commonly available data. The magnitude of error (both bias and variance) when estimating this parameter can b...
Electronic monitoring (EM) systems have become functional and cost-effective tools for the conservation and sustainable harvesting of marine resources. EM is an alternative to on-board observers, which produces video segments that can subsequently be reviewed by analysts. It is currently used in a range of fisheries. There are two major challenges...
Determining acceptable rates of human‐caused mortality in low‐data situations is a concern for many taxa world‐wide. An established approach for determining acceptable levels of human‐caused mortality of marine mammals and other species of conservation concern is the Potential Biological Removal (PBR) framework, but PBR requires near‐unbiased estim...
Spatio-temporal models are increasingly used to develop indices of population abundance from fishery-dependent and –independent data. Developments in spatio-temporal index standardization were discussed at a workshop hosted by The Center for the Advancement of Population Assessment Methodology (CAPAM) titled “Development and application of spatio-t...
The potential biological removal (PBR) formula used to determine a reference point for human-caused mortality of marine mammals in the United States has been shown to be robust to several sources of uncertainty. This study investigates the consequences of the quality of monitoring on PBR performance. It also explores stochastic and demographic unce...
All fish populations and fisheries exhibit spatial structure, but accounting for the spatial patterns is commonly ignored in most stock assessments. The Center for the Advancement of Population Assessment Methodology (CAPAM) hosted a workshop on “Spatial Stock Assessment Models” (La Jolla, CA, USA; October 1-5, 2018), and this special volume includ...
The potential biological removal (PBR) formula used to determine a reference point for human-caused mortality of marine mammals in the United States has been shown to be robust to several sources of uncertainty. This study investigates the consequences of the quality of monitoring on PBR performance. It also explores stochastic and demographic unce...
Ocean management involves monitoring data that are used in biological models, where estimates inform policy choices. However, few science organizations publish results from a recurring, quantitative process to optimize effort spent measuring fish age. We propose that science organizations could predict the likely consequences of changing age-readin...
Integrated analysis (or integrated population modelling) methods have become the preferred approach for conducting stock assessments, and providing the basis for management advice for fish and invertebrate stocks since the publication of a seminal paper by Fournier and Archibald in 1982. Methods to assess fish stocks based on single-species, single...
A multi-species size-structured population dynamics model that can account for spatial structure and technical interactions between commercial fisheries was developed and applied to the snow and southern Tanner crab fisheries in the eastern Bering Sea. The model was then used as the basis for forecasts to calculate reference points related to yield...
A Management Strategy Evaluation is used to estimate success at achieving conservation goals for marine mammals while also aiming to minimize impacts on commercial fisheries. It is intended to improve understanding of US import rules that require nations exporting fish and fish products to the US to adhere to marine mammal bycatch standards “compar...
Characterization of uncertainty (variance) in ecosystem projections under climate change is still rare despite its importance for informing decision-making and prioritizing research. We developed an ensemble modeling framework to evaluate the relative importance of different uncertainty sources for food web projections of the eastern Bering Sea (EB...
Analysis of spawning biomass per‐recruit has been widely adopted in fisheries management. Fishing mortality expressed as spawning potential ratio (SPR) often requires a reference point as an appropriate proxy for the fishing mortality that supports a maximum sustainable yield—FMSY. To date, a single generic level between F30% and F40% is routinely...
Effective conservation and management of animal populations requires knowledge of abundance and trends. For many species, these quantities are estimated using systematic visual surveys. Additional individual‐level data are available for some species. Integrated population modelling (IPM) offers a mechanism for leveraging these datasets into a singl...
Fisheries management systems can utilize probability-based harvest control rules to incorporate scientific uncertainty and manager risk tolerance when setting catch limits. A precautionary buffer that scales with scientific uncertainty is used to calculate the acceptable biological catch from the overfishing limit (OFL) for US West Coast groundfish...
The Alaska Climate Integrated Modeling (ACLIM) project represents a comprehensive, multi-year, interdisciplinary effort to characterize and project climate-driven changes to the eastern Bering Sea (EBS) ecosystem, from physics to fishing communities. Results from the ACLIM project are being used to understand how different regional fisheries manage...
Stock assessment methods for many invertebrate stocks, including crab stocks in the Bering Sea of Alaska, rely on size-structured population dynamics models. A key component of these models is the size-transition matrix, which specifies the probability of growing from one size-class to another after a certain period of time. Size-transition matrice...
Model-based stock assessments form a key component of the management advice for fish and invertebrate stocks
worldwide. It is important for such assessments to be peer-reviewed and to pass scientific scrutiny before they
can be used to inform management decision making. While it is desirable for management decisions to be based
on quantitative asse...
Characterizing population distribution and abundance over space and time is central to population ecology and conservation of natural populations. However, species distribution models and population dynamic models have rarely been integrated into a single modelling framework. Consequently, fine‐scale spatial heterogeneity is often ignored in resour...
Balancing trade‐offs amongst social–ecological objectives is a central aim of natural resource management. However, objectives and resources often have spatial dimensions, which are usually ignored in trade‐off analyses. We examine how simultaneously integrating social–ecological benefits and their spatial complexities can improve trade‐off analysi...
There are many methods available for estimating the current abundance of fish species. Design-based estimators, which assume random sampling within the sampling domain, have conventionally been used to provide relative indices of abundance. More recently, the use of spatiotemporal models has increased because of their ability to explicitly account...
We have examined the estimates in Pramod et al. of IUU Alaskan Pollock imported into Japan. Based on extensive knowledge of this fishery we find that their estimates are not substantiated by any known facts from the fishery. Whereas in a retracted version of the paper the authors estimated that 15–22% of Alaskan Pollock imported into Japan were IUU...
Patagonian grenadier (Macruronus magellanicus) is the most abundant demersal fisheries resource off Chilean Patagonia, and also is a key fisheries species off the south of Argentina and off the Falkland Islands. A Stock Synthesis assessment shows that this stock has declined in abundance off Chile, which has been attributed to a major change in rec...
We explore a "Go With the Older Fish" (GWOF) mechanism of learned migration behaviour for exploited fish populations, where recruits learn a viable migration path by randomly joining a school of older fish. We develop a non-age-structured biomass model of spatially independent spawning sites with local density dependence, based on Pacific herring (...
Many small cetacean, sirenian, and pinniped species aggregate in groups of large or variable size. Accurate estimation of group sizes is essential for estimating the abundance and distribution of these species, but is challenging as individuals are highly mobile and only partially visible. We developed a Bayesian approach for estimating group sizes...
The Center for the Advancement of Population Assessment Methodology (CAPAM) hosted a technical workshop on Recruitment: theory, estimation, and application in fishery stock assessment models in Miami, Florida, USA, from 30 October to 3 November 2017. The recruitment workshop was the fourth in a series organized by CAPAM as part of its Good Practice...
Pest eradication conducted over the years 2010 to 2014 at Macquarie Island successfully eradicated introduced rabbits, rats and mice from this sub-Antarctic island. The initial aerial baiting phase in the winters of 2010 and 2011 resulted in significant mortality of several native seabird species through primary and secondary ingestion of brodifaco...
Ontogenetic diet shifts are pervasive in food webs, but rules governing their emergence and the implications for trophic cascades are only partly understood. Recent theoretical advances in multispecies size spectrum models (MSSMs) predict that the emergence of ontogenetic diet shifts are driven primarily by size‐selective predation and changes in t...
The Australian Victorian Western Zone rock lobster fishery is assessed using standardised catch-per-unit-effort (CPUE). Nominal CPUE declined over 1978–2009, but this underrepresents the estimated decline in abundance, and since 2009 standardised CPUE rose notably less than nominal CPUE. This study identified vessel as a key factor that explains th...
