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aepunt@u.washington.edu, 206/221-6319

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biomathematics, multispecies modeling, population dynamics, stock assessment

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Research

In addition to descriptions of specific research projects below, please see the website, "Marine Population Assessment & Management Group," for further information on my research program.

Estimation of Steller Sea Lion Population Dynamics Parameters

Collaborators: G Fay (graduate student)
Support: North Pacific Universities Marine Mammal Research Consortium, University of British Columbia

Monte Carlo simulation techniques will be used to evaluate the scientific value of Steller sea lion data to be collected in the future. Such data could be used to estimate key population dynamics parameters, such as the survival rate of juveniles, and to evaluate the utility of experimental management techniques, based on spatial zoning of experimental treatments, to discriminate among alternative hypotheses regarding reason(s) for the decline of the western stock of Steller sea lions (Eumetopias jubatus) in Alaska. The simulations will be based on a spatial and temporal individual-based model of Steller sea lion population dynamics being developed as a part of a current NMFS-funded project, to allow the impact of uncertainties due to demographic and environmental variability, as well as spatial heterogeneity, to be evaluated.

Properties of Assessment Models for North Pacific Gray Whales

Collaborators: G Fay (graduate student)
Support: NOAA National Marine Mammal Laboratory, National Marine Fisheries Service

This project involves the investigation of the properties of assessment models for North Pacific gray whales that include inertia dynamics. The investigator will modify a software package used in stock assessment to include inertia dynamics in the calving rate. The modified software will be used to attempt to replicate the scenarios in a paper presented to the International Whaling Commission in 2001. He will then examine the sensitivity of the results of assessments based on inertia dynamics to data set choices and values for prior distributions.

West Coast Groundfish Stock Assessment (2000-2003)

Collaborators: R. Hilborn; R. Methot and T. Helser (Northwest Fisheries Science Center, NMFS)
Support: National Marine Fisheries Service

This project involves conducting research on the population dynamics and stock assessment of groundfish species occurring off the coasts of Washington, Oregon and California. It involves researching and designing quantitative methods for the analysis of the population dynamics of groundfish species which could form the scientific basis for evaluating the consequences of alternative fisheries management actions, collaborating with National Marine Fisheries Service scientists who are conducting quantitative stock assessments of west coast groundfish species on the implementation of population dynamics and stock assessment methods, and building expertise among NMFS and other scientists in the application of methods for conducting management-related research for west coast groundfish.

Models for Evaluating Harvest Regimes for Small Marine Mammal Populations (2001)

Collaborators: J. Breiwick (National Marine Mammal Laboratory, NMFS)
Support: National Marine Fisheries Service

An individual-based model was developed in collaboration with Dr Jeff Breiwick (National Marine Mammal Laboratory, Seattle) to represent the population dynamics of a small marine mammal population subject to harvest. The model included demographic and environmental variation in the probability of birth and death. It was parameterized in terms of current population size and the productivity of the resource (as measured by the ratio of MSY to the population size at which MSY is achieved), in addition to the expected values for age-specific survival and fecundity. The performances of three decisions rules (constant catch, the Potential Biological Removals method, and a decision rule developed for the Bering-Chukchi-Beaufort Seas stock of bowhead whales) were evaluated for a range of values for the parameters of the population dynamics model.

Population Modeling of North Atlantic Humpback Whales (2001-2002)

Collaborators: N. Friday (National Marine Mammal Laboratory, NMFS), Tim Smith (NEFSC, NMFS)
Support: International Whaling Commission

Humpback whales (megaptera novaeangliae) in the North Atlantic constitute at least two genetically distinct biological stocks with separate breeding grounds. Humpbacks also exhibit strong site fidelity to feeding grounds. Models are being developed in collaboration with scientists from the National Marine Mammal Laboratory in Seattle and the Northeast Fisheries Science Center in Woods Hole to allow an assessment of the current status and trend of humpback whales in the North Atlantic, taking account of spatial structure. The models will allow for site fidelity to feeding grounds, density-dependence and depensation, and will be fit to the variety of data (survey estimates of absolute abundance, indices of relative abundance, and fractions of each biological stock in each feeding ground) available for North Atlantic humpback whales. The results of this project will be presented to the Scientific Committee of the International Whaling Commission in 2002.

Modeling Steller Sea Lion Populations (2001-2002)

Collaborators: G. Fay (gradute student), A. York (National Marine Mammal Laboratory, NMFS)
Support: National Marine Fisheries Service

Methods are being developed in collaboration with scientists from the National Marine Mammal Laboratory in Seattle for determining extinction risk and recovery probability of Steller sea lion populations using age-lumped and individual-based spatial population dynamics models. These models will include density-dependent processes as well as demographic and environmental stochasticity in birth and death processes. The models will be parameterized based on known sources of Steller sea lion mortality, and include survival and fecundity schedules appropriate to Steller sea lions. Scenarios to be considered by the model will include the implications of catastrophic events such as oil spills or epizootics that could greatly depress vital rates for varying lengths of time.

Bluefin Tuna Mixing in Assessments and Risk Analyses (2001-2002)

Support: East Coast Tuna Association

This project will make recommendations regarding aspects that need to be considered in order to adequately include data related to bluefin tuna mixing in assessments and risk analyses and to analyze order research on this subject.