Economic Impacts of Changes in Bristol Bay Red King Crab Fishery from Ocean Acidification
Fossil fuel emissions and deforestation have increased atmospheric CO2 concentrations, which have led to corresponding increases in oceanic CO2 concentrations, and hence, changes in carbonate chemistry of the oceans and decreases in ocean pH. Due to the increase in oceanic CO2 concentrations, the surface ocean pH has decreased on average by 0.1 units compared to pre-industrial levels. This is equivalent to a 30% increase in acidity of the surface waters. As CO2 levels continue to rise over the coming decades, the pH in the ocean will fall even further. A standard emissions scenario predicts that average pH in surface waters will fall from the current level of 8.1 to 7.8 before 2100.
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. This will slow the growth of many marine fish species including crabs. As a result, the harvests of and, therefore, the revenue from harvests of fish species will decrease. The decrease in the revenue implies the reduction in the number of jobs in fish harvesting and processing sectors, and decrease the income of the stakeholders engaged in the fisheries. This will generate a wide range of economic impacts on fishing-dependent communities.
We used bioeconomic models and data on survival of juvenile red king crab from ocean acidification experiments conducted at the AFSC Kodiak Laboratory to estimate the linear and nonlinear effects of ocean acidification on survival parameters in stage structured pre-recruitment dynamics model; coupled the pre-recruitment dynamics model with a post-recruitment population dynamics model; and derived a sequence of Bristol Bay Red King crab (BBRKC) yield curves for an ocean acidification scenario from 2009 to 2100, using the coupled model. Using the sequence of BBRKC yield curves, we calculated the temporal and cumulative regional economic impacts of the reduction in BBRKC yields on the Alaska economy within a recursive dynamic computable general equilibrium (CGE) model for Alaska. We compared the CGE model outcomes computed with yield projections based on two different assumptions about the form of ocean acidification effects in the bioeconomic model, which represent linear and nonlinear effects on the survival of juvenile red king crab, to a baseline without ocean acidification effects.
Results demonstrate considerable uncertainty in future projections of yields and economic effects, and show that outcomes including regional economic impacts, welfare changes, and temporal changes in quota share lease rates for BBRKC are sensitive to the linear versus nonlinear form taken in the yield projections, and to changes in the world price for BBRKC.
