Spatiotemporal distribution of the endangered fishery target species Leucopsarion petersii in the shallow sea of Obama Bay, Japan

Abstract

The ice goby Leucopsarion petersii is decreasing in abundance and was recently classified as a vulnerable species by the Ministry of the Environment of Japan. Although most of its life history is spent in the ocean, L. petersii is an anadromous fish that ascends rivers during the spawning season and spawns downstream. Much information on L. petersii has been collected from its river habitats; however, its ocean habitats remain poorly understood. Therefore, in this study, we investigated the spatiotemporal distribution of L. petersii at five survey sites in Obama Bay, Japan. Surveys were conducted in early summer (7 June, 2018), summer (26 July, 2018), autumn (18 October, 2018), winter (31 January, 2019), and early spring (21 February, 2019). Beam trawling was conducted from a ship, for periods of a few minutes; a total of 274 individuals were caught throughout the study period. A generalised linear model was used to detect seasonal and site effects, with number of individuals as an objective variable, and season and sampling location as explanatory variables. A negative binomial distribution was assumed, and we corrected for differences in sampling effort. The maximum catch per unit effort occurred in autumn, with significant differences among sampling sites; however, we detected no significant effect of environment or distance from the river mouth, due to the limited number of sampling sites used in this study.