Social Welfare Impacts of Alternative Recruitment Specifications: Implications for Pacific Whiting Management using Bioeconomic Analysis

Sherry Larkin, Department of Agriculture and Resource Economics, OSU. j1 \I specifications on recommended yields and social benefits, a 3-year bioeconomic model is employed. This management-level, optimal control model integrates population dynamics, intrinsic product quality (via proximate analysis) and industry economics to develop optimal intraand interseason harvest patterns (i.e., short-term property rights allocations). This age-structured (14 cohort) model tracks the stock over time (across months and into successive years) and between geographic regions (U.S. and Canada). In addition, the optimal temporal allocations depend on the harvest sector (onshore or at-sea) and product form (surimi, fish meal, headed and gutted, or fillet) produced. Pacific whiting, Mer/uccius productus, is ecologically and commercially one of the most important fish species on the North American west coast. The stock is exploited by both the U.S., which captures approximately 75% of the allowable catch, and Canada. The stock is managed triennially in the U.S.; every three years biologists with the National Marine Fisheries Service recommend the total allowable catch for each of the upcoming three years assuming recruitment (number of age-2 fish) remains constant at the historical median. Like the gadoids, however, recruitment. variation is a major component of stock .dynamics for this pelagic specie; it can have ,a. greater impact on production than either variability in mortality or growth. c:onsequently, fluctuations in stock .~bundance caused by interannual recruitment 'o'ariation can significantly impact social 'Nelfare. Results of the sensitivity analysis reveals that using a constant level of recruitment can mask the importance of a large year-class. When a constant level of recruitment is changed, the change in social welfare (i.e., net present value based on a 5% real discount rate) will be proportionately equal to the change in average annual yield (MSY). If recruitment is variable, both the existence and magnitude of a large year-class can significantly impact welfare and total yield. More importantly, these figures depend on when the large cohort entered the model; for example, welfare and yields each increase by approximately 50% if a large cohort occurs in the second year, as opposed to the third, in this 3-year model. In terms of the existing management structure, these results suggest significant potential benefits from incorporating recruitment estimates. These estimates could be obtained from either (1) prediction (which is possible given the 2-year lag between spawning and recruitment) or (2) survey methods. These results were also supported using a 15-year planning horizon. In addition, discounting only affected the net present value and not the MSY (when measured in thousands of metric tons). These results are, therefore, robust to changes in the both the time horizon and use of discounting. f