Bioeconomic assessment of size separators in Pacific saury fishery

In the middle of 1990s, Pacific saury fishery vessels began to install 'size separators' to selectively land large-size class fish with higher price. Contrary to the expectations, it resulted in the complete removal of separators in 2006 because fishers considered that separators had contributed to the price collapses in the 2000s. The intent of this paper is to investigate the effects of separators on both the fishery economy and stock of Pacific saury through simulating population and economic models under a single framework. For this purpose, we specifically developed (i) an age-structured population dynamics model with stochasticity, and (ii) an economic model spanning both price and inventory dynamics with stochasticity, in which each set of model parameters were estimated based on time series data. In ten year simulation, we set the harvest quota as constant covering from 20 to 400 thousand tons, and the effects of separators were incorporated by controlling the catchability of 0 year old fish. We have identified that separators increase the expected yield and decrease the deficit risk when the annual harvest is set smaller than 160 thousand tons. Otherwise, they decrease the expected yield and increase the deficit risk