No 2017-born Japanese silver pomfret found in Ariake Bay as high salinity causes reproductive failure

Japanese silver pomfret experience reproductive failure when salinity is even slightly elevated. Professor Atsuko Yamaguchi and Researcher Yoshimi Ogino from the Graduate School of Integrated Science and Technology (Fisheries) at Nagasaki University discovered a "missing generation" of Japanese silver pomfret born in 2017, despite stable numbers of spawning adults migrating to Ariake Bay, and clarified that the cause was high salinity. Their findings were published in Estuarine, Coastal and Shelf Science.

As the Japanese saying goes, "no salmon in the west, no silver pomfret in the east"; Silver pomfret has long been regarded as a luxury fish comparable to salmon. It reaches a maximum total length of 57.5 centimeters and a maximum body weight of 3.8 kilograms. It is a migratory species that normally inhabits offshore waters and migrates to inner bay areas for spawning. In Japan, spawning grounds are known only in Ariake Bay, the Seto Inland Sea, and Yatsushiro Sea.

The research group conducted age determination through otolith analysis of silver pomfret individuals caught in Ariake Bay and its adjacent waters, aiming to clarify their longevity and growth. During this process, they discovered a clear bias in the age distribution, with many individuals born in 2016 but none born in 2017. When they examined correlations with environmental factors such as water temperature, salinity, and dissolved oxygen levels, as well as biological factors including spawning stock abundance and jellyfish occurrence, they found that reproductive success was closely related to salinity in Ariake Bay during the spawning season.

Japanese silver pomfret is an important fish species representing Asia, with annual landings exceeding 300,000 tons in China. However, the Japanese species population is small, raising concerns that continued reproductive failures could lead to the disappearance of the resource. In fact, a closely related species, the Korean pomfret, ceased migrating to Japan (Ariake Bay) in the 1990s.

These findings, representing the first research results on growth and recruitment for Japanese silver pomfret, not only enable management and assessment of Japanese silver pomfret resources in Japan but also provide new guidance for coastal environmental conservation. Furthermore, the study revealed that authentic estuarine environments, where seawater and freshwater mix extensively, function not only as nursery grounds for many coastal fish species but also serve as important spawning and nursery areas for fish like Japanese silver pomfret that typically inhabit offshore waters.

In recent years, concerns have been raised about coastal water desalination associated with rising seawater temperatures and concentrated rainfall due to climate change. However, increased coastal salinity can also cause serious problems. While adaptation measures for rising water temperatures are being actively considered, there is still room for countermeasures regarding salinity, which is closely related to terrestrial environments and human activities. In the future, there are expectations for investigations into water temperature in coastal areas, the broader salinity dynamics and factors affecting them, and exploring their relationships with organisms, which will contribute to the recovery of coastal biological productivity.

Journal Information
Publication: Estuarine, Coastal and Shelf Science
Title: Growth and year-class dynamics of the Japanese silver pomfret Pampus punctatissimus: Correlation between salinity and recruitment
DOI: 10.1016/j.ecss.2025.109440