Viability of Sacramento River winter-run chinook salmon

Article Abstract:

A model designed specifically for the Sacramento River winter run of chinook salmon (Oncorhyncus tshawytscha) takes into account life-history characteristics that affect viability. The chinook salmon are anadromous and semelparous, requiring a specific definition of quasi-extinction. A lognormal distribution can be used in place of the distribution of cohort replacement rates without affecting extinction rates. Inaccurate estimates result, however, when a determinate semelparous life history is used to approximate an indeterminate semelparous life history. Uncertainty should be taken into account in recovery criteria for endangered species.

Environmental aspects, Natural history, Chinook salmon, Rare fishes, Sacramento River

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Influence of complex sex determination on demographic stochasticity and population viability

Article Abstract:

Demographic stochasticity lowers the viability of small populations with multiple-factor sex determination (MSD). In a simulation involving a population with simple sex determination (SSD) and two MSD systems, no significant difference in survival was found for the MSD systems at any population size. However, small MSD systems were not as viable as the SSD populations.

Demographic aspects, Population genetics, Extinction (Biology), Sex determination, Genetic, Sex determination (Genetics)

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Testing the accuracy of population viability analysis

Article Abstract:

A suite of methods that can be used to test the predictive ability of models used in population viability analysis (PVA) is discussed. A framework for using model testing to improve the predictive performance of PVA models, through an iterative process of model development, testing, subsequent modification and re-testing is provided.

Models, Population research

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