Characteristics of spatiotemporal distribution of small blackthroat seaperch Doederleinia berycoides in the southwestern Japan Sea and model development for predicting the distribution

Abstract

An offshore trawl fishery within Shimane Prefecture in Japan has introduced mobile protected areas using information from fisheries to manage the resources of the small blackthroat seaperch Doederleinia berycoides since 2012. However, there is an increasing need to understand the distribution of these fish within the entire sea area in advance and to set up efficient protected areas using this information. In this study, we used a random forest method to develop a model for predicting the distribution of these fish in the southwestern Japan Sea using the operating information of the offshore trawl fishery from March to May of 2011–2018 and estimated values of bottom water temperature, salinity, and tidal current. The prediction error against out-of-bag (OOB) data for a model developed in the year of operation was 14.5% and that developed using CPUE in the first half of the fishing year was 14.6%. In addition, the prediction accuracy for test operations by a research vessel was 94%. Based on these results, we elucidated the spatiotemporal distribution of this fish and discussed the characteristics of factors affecting the distribution.