This study is aimed to compare stock assessment models which are effective in assessing Red snow crab resources and to select and apply an effective stock assessment model in the future.
In order to select an effective stock assessment model, a Process-error model, Observation-error model, and Bayesian State-space model were estimated. Analytical results show that the least error is observed between the estimated CPUE and the observed CPUE when using the State-space model. For the State-space model, the 95% confidence interval range for the maximum sustainable yield (MSY), carrying capacity (K), catchability coefficient (q), and intrinsic growth (r) are estimated to be 10,420 47,200 tons, 185,200-444,800 tons, 3.81E-06-9.02E-06, and 0.14-0.66, respectively. The results show that the State-space model is estimated to be most reliable among the models.
Using the results of the Bayesian State-space model, internationally widely utilized bioeconomic models were used to make a comparison between and analyze the effectiveness of Red snow crab fisheries management policies. As a specific effect analysis, biological and economic effects were analyzed separately for the analysis on both the TAC policy and effort reduction policy. The biological effectiveness analysis of the TAC policy estimates that if the TAC is set to and maintained at the current level of 26,000 tons, the Red snow crab biomass after 10 years would decrease from 106,000 tons to 73,076 tons. However, it was estimated that the amount of biomass would increase to 125,316 tons in the future if the level of TAC was set to 22,000 tons. In the case of reduced fishing efforts, a 10 % decrease from the current level would result in greater biomass, and NPV was also estimated at the highest level. In addition, a sensitivity analysis of changes in market prices was conducted to analyze the minimum TAC level of the Red snow crab offshore pot fishing industry, which was estimated at 10,673 tons as of 2018. The minimum TAC level was analyzed to be 8,210 tons if the market price increased by 30% and the minimum TAC volume level to 15,247 tons if the market price decreased by 30%. In addition, the sensitivity analysis result of the change in fishing costs showed that the TAC level at which the fishing profit is nil based on the fishing cost in 2017 was 10,673 tons. The minimum TAC level was analyzed to be 13,857 tons if the fishing cost increased by 30% from the current level, 18,114 tons if increased by 70%, and 21,345 tons if increased by 100%.
Lastly, economic impact of the ITQ system which is widely adopted through the world was analyzed. If the fishing effort for the crab was limited to the 21,131 hp, which is equivalent to EMEY, the potential benefit would be 66,496,752 thousand Won which is bigger than that of the current TAC system (60,935,752 Won). Also, even though the catch amount was decreased by 1,233 tonnes, return of fisheries vessels would increase.