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A theory for a general equilibrium ecosystem model that can include large number of interacting species is presented. The theory is applied using simulations of an eight-species Alaskan marine ecosystem for which a 'natural' equilibrium is calculated.

Pacific salmon (Oncorhynchus spp.) are exposed to increased environmental change and multiple human stressors. To anticipate future impacts of global change and to improve sustainable resource management, it is critical to understand how wild salmon populations respond to stressors associated with human‐caused changes such as climate warming and ocean acidification, as well as competition in the ocean, which is intensified by the large‐scale production and release of hatchery reared salmon. Pink salmon (O. gorbuscha) are a keystone species in the North Pacific Ocean and support highly valuable commercial fisheries. We investigated the joint effects of changes in ocean conditions and salmon abundances on the productivity of wild pink salmon. Our analysis focused on Prince William Sound in Alaska, because the region accounts for ~50% of the global production of hatchery pink salmon with local hatcheries releasing 600–700 million pink salmon fry annually. Using 60 years of data on wild pink salmon abundances, hatchery releases, and ecological conditions in the ocean, we find evidence that hatchery pink salmon releases negatively affect wild pink salmon productivity, likely through competition between wild and hatchery juveniles in nearshore marine habitats. We find no evidence for effects of ocean acidification on pink salmon productivity. However, a change in the leading mode of North Pacific climate in 1988–1989 weakened the temperature–productivity relationship and altered the strength of intraspecific density dependence. Therefore, our results suggest non‐stationary (i.e., time varying) and interactive effects of ocean climate and competition on pink salmon productivity. Our findings further highlight the need for salmon management to consider potential adverse effects of large‐scale hatchery production within the context of ocean change. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the nature of rational expectations equilibria for economic epidemiological models, with a particular focus on the behavioral origins and dynamics of epidemiological bifurcations. Unlike mathematical epidemiological models, economic epidemiological models can produce regions of indeterminacy or instability around the endemic steady states due to endogenous human responses to epidemiological circumstance variation, medical technology change, or health policy reform. We consider SI, SIS, SIR and SIRS versions of economic compartmental models and show how well-intentioned public policy may contribute to disease instability, uncertainty, and welfare losses. [ABSTRACT FROM AUTHOR]

Widespread testing is key to controlling the spread of COVID-19. But should we worry about self-selection bias in the testing? The recent literature on willful ignorance says we should – people often avoid health information. In the context of COVID-19, such willful ignorance can bias testing data. Furthermore, willful ignorance often arises when selfish wants conflict with social benefits, which might be particularly likely for potential 'super-spreaders' – people with many social interactions – given people who test positive are urged to self-isolate for two weeks. We design a survey in which participants (n = 897) choose whether to take a costless COVID-19 test. We find that 70% would take a test. Surprisingly, the people most likely to widely spread COVID-19 – the extraverts, others who meet more people in their daily lives and younger people – are the most willing to take a test. People's ability to financially or emotionally sustain self-isolation does not matter to their decision. We conclude that people are selfless in their decision to test for COVID-19. Our results are encouraging – they imply that COVOD-19 testing may succeed in targeting those who generate the largest social benefits from self-isolation if infected, which strengthens the case for widespread testing. [ABSTRACT FROM AUTHOR]