Quantitative protocols for exploring the optimal measurement points for estimating body length and weight from otolith information using the blackthroat seaperch in the western Sea of Japan

The accuracy of the back-calculation method to estimate past individual growth based on the relationship between otoliths and body length is important. However, limited studies have examined the variation in accuracy by measurement site used for estimation, and little has been done to evaluate its effectiveness. Currently, effective utilization of juvenile fish in the blackthroat seaperch fishery in the Sea of Japan does not always take place, so it is necessary to investigate the complex relationship between population density and growth rate. This study estimates body length and weight from otolith length, weight, and area of blackthroat seaperch, analyzes variations in estimation accuracy at each measurement site, and provides a general quantitative protocol for evaluating the performance of each measurement site. The conversion models for body length and body weight indicate that models using otolith weight and area are more accurate than those using otolith length. There were no significant differences in the estimation accuracy of these models, and the estimation errors were all less than 0.7% of the original body length and weight means. Searching for the best model, verifying the estimation accuracy quantitatively, and selecting the model to use is important when performing back-calculations.