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Economics & Social Sciences Research Program

Bio-economic Model to Forecast Effects of Ocean Acidification on Bristol Bay Red King Crab

figure 1, see caption
Figure 1.  Outline of the linked bio-economic model.

A comprehensive bio-economic model for Bristol Bay red king crab is under development with support from NOAA's Ocean Acidification Program. Increases in atmospheric CO2 concentrations, caused primarily by fossil fuel emissions and deforestation, has led to corresponding increases in oceanic CO2 concentrations and, hence, changes in carbonate chemistry of the oceans and decreases in ocean pH. As CO2 levels continue to rise over the coming decades, the pH in the ocean will fall even further.

This trend could have substantial physiological effects on marine organisms, affecting growth, survival, reproduction, and behavior. Calcifying organisms may be particularly affected because the reduction in pH makes it more difficult to excrete and sustain a calcified shell or exoskeleton.

Most of the management strategies developed for fish and invertebrate species in the United States and elsewhere are predicated on the assumption that the productivity of the resources remains constant over long time periods. This assumption is likely to be violated by the impact of ocean acidification. However, the impact of such violation is poorly understood generally and for North Pacific crab fisheries in particular.

The ideal tool to explore the biological and economic impacts of ocean acidification is a bio-economic modeling framework which a) integrates predictions regarding trends over time in ocean pH; b) separates life-history stages for growth and mortality of juveniles and adults; and c) includes fishery impacts by analyzing catch and effort in both biological and economic terms
(Fig. 1 above).

In this model, a size-structured population dynamics model component for larger animals is coupled to a stage-structured model component for smaller animals that have not been recruited into the fishery (i.e., "pre-recruits"). Including an explicit pre-recruit component is unusual in population dynamics models, and it is used in the new king crab bio-economic model to represent the impacts of ocean acidification on pre-recruit life-history stages.

These impacts are the subject of ongoing laboratory experiments with juvenile crabs, and data from these experiments will be used to parameterize the pre-recruit component of the new bio-economic model.

By Michael Dalton, Dusanka Poljak (UW-SAFS), André Punt (UW-SAFS)

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