Modeling pulse dynamics of juvenile fish enables the short-term forecasting of population dynamics in Japanese pufferfish: a latent variable approach and hindcasting

Abstract

Short-term forecasting of population dynamics of fish stocks is required for scientificmanagement recommendations such as catch quotas but is difficult to perform accurately because of the inevitable time lag between data collection and management implementation. Here, we developed a method using small-scale survey data for juvenile Japanese pufferfish (Takifugu rubripes) to shorten this time lag and achieve accurate short-term forecasting. A survey of juvenile pufferfish at a local sandy beach provides data for the strength of year classes before fisheries recruitment; however, use of the raw data is difficult owing to the small sample size and large observation errors. We found that a random-effects model overcame these problems and more accurately predicted pulse patterns of catch rates to derive a standardized recruitment index than a fixed-effects model. A stock assessment model using the standardized recruitment index outperformed models without the standardized recruitment index with respect to hindcasting bias and prediction skill. This study highlights the applicability of a latent variable approach for standardizing small-scale survey data and thereby for unbiased forecasting of short-term fish dynamics.