Dynamics of two sailfin sandfish (Arctoscopus japonicus) stocks in the Sea of Japan, and their management

Abstract

The dynamics of the northern and western Sea of Japan sailfin sandfish (Arctoscopus japonicus) stocks (NSJ and WSJ, respectively) varied simultaneously until the mid-1970s but differently thereafter. To identify the mechanisms underlying these dynamics, we evaluated the impact of environment and harvesting on NSJ by developing a recruitment model and simulating NSJ dynamics. The model was constructed based on egg production, density effect, and water temperatures in winter and spring, which correlated significantly and positively with the estimated surface mixed-layer depth. Winter water temperatures and egg production were variables common to the two stocks. Our results suggest that simultaneous dynamics resulted from similarities in variations in winter water temperatures for each stock and the difference in dynamics resulted from NSJ depletion caused by overfishing. We suggest management strategies to prevent NSJ depletion caused by unfavorable environmental conditions and overfishing, as well as to allow improved biomass recovery while taking advantage of favorable environmental conditions, and avoid further exploitation of previously depleted NSJ.Résumé : Les dynamiques des stocks du toroumoque japonais (Arctoscopus japonicus) du nord et de l'ouest de la mer du Japon (respectivement NSJ et WSJ) ont varié de concert jusqu'au milieu des années 1970 pour différer par la suite. Afin d'identifier les mécanismes sous-jacents à ces dynamiques, nous avons évalué l'impact de l'environnement et de la récolte sur le stock NSJ en mettant au point un modèle de recrutement et en simulant la dynamique du stock NSJ. Le modèle est construit sur la base de la production d'oeufs, de l'effet de la densité, et des températures de l'eau en hiver et au printemps, qui sont en corrélation significative et positive avec la profondeur estimée de la couche de mélange de surface. Les tempé-ratures de l'eau en hiver et la production d'oeufs sont des variables qui s'appliquent aux deux stocks. Nos résultats indiquent que la dynamique simultanée résulte de ressemblances dans les variations dans les températures d'hiver pour les deux stocks et que les différences de dynamique s'expliquent par un déclin du stock NSJ à cause de la surpêche. Nous proposons des stratégies de gestion pour empêcher le déclin du stock NSJ causé par les conditions environnementales défa-vorables et la surpêche, ainsi que pour permettre une meilleure récupération de la biomasse en profitant des conditions environnementales favorables et pour éviter une exploitation supplémentaire du stock NSJ déjà réduit.[Traduit par la Rédaction]

Assessing Northwest Pacific Fishery Stocks Using Two New Methods: The Monte Carlo Catch-MSY (CMSY) and the Bayesian Schaefer Model (BSM)

“…Japanese sandfish, a cold-water species, was one of the most important commercial resources in Japan (Watanabe et al, 2011: Yoon et al, 2018. In the northern and western Sea of Japan, the Japanese sandfish stock decreased sharply after the mid-1970s and was severely depleted during the 1980s (Watanabe et al, 2011). This confirms the results of this study, which showed that Japanese sandfish stock decreased rapidly from 1974 on.…”

“…The variations in demersal fish communities were strongly associated with the oceanographic conditions; the Tsushima Warm Current experienced changes from a colder to a warmer regime in the late 1980s, which had a strong effect on the ecosystems of the region and the fish communities therein (Tian et al, 2006(Tian et al, , 2008(Tian et al, , 2011. Japanese sandfish, a cold-water species, was one of the most important commercial resources in Japan (Watanabe et al, 2011: Yoon et al, 2018. In the northern and western Sea of Japan, the Japanese sandfish stock decreased sharply after the mid-1970s and was severely depleted during the 1980s (Watanabe et al, 2011).…”

Spatial Dynamics of Demersal Fish Assemblages off the Korean Coast in the East Sea

“…The population of this species in Korean waters is mainly distributed in the East Sea; however, a small population is present in the Yellow Sea (western sea area of Korea) [ 42 ]. In addition, although the abundances of walleye pollock ( Gadus chalcogramma ) and Japanese sandfish ( Arctoscopus japonicus ) were relatively low in our study, the two species were only distributed in the East Sea (Sea of Japan), constituting important fishery resources [ 44 , 45 ].…”