Contributions of the VENFISH program: meso‐zooplankton, Pacific saury (Cololabis saira) and walleye pollock (Theragra chalcogramma) in the northwestern Pacific

Abstract

The comprehensive study of the variation of the oceanic environment and fish populations in the northwestern Pacific (VENFISH) was an interdisciplinary scientific program to enhance our understanding of relationships between the ocean environment and the pelagic fishes, Pacific saury and walleye pollock. As prey of saury and walleye pollock, key species of zooplankton were selected and their life history and production were elucidated. Retrospective analyses were also conducted to investigate the mechanisms of production variation in some zooplankton species. Life history and ecology of Pacific saury and walleye pollock were also investigated and substantial improvements to our understanding of them were achieved. In addition, improved information from VENFISH were used to develop several models to investigate saury growth, and population dynamics, and predatory pressure on zooplankton from walleye pollock. Observational and model results indicate the importance of the Kuroshio and the Kuroshio-Oyashio transition region to saury recruitment and of Oyashio transport to walleye pollock recruitment. Moreover, models developed under VENFISH will become the basis of fisheries management models for saury, walleye pollock, and other fishes in the future.

Comparisons of monthly and geographical variations in abundance and size composition of Pacific saury between the high-seas and coastal fishing grounds in the northwestern Pacific

“…In our study, the monthly distribution pattern (Fig. 6) was consistent with the migration pattern in previous studies from Japan [3,11,15]. Some saury migrated southwestward to the coastal waters in August-September keeping away from the colder intrusive water with SST \10°C, and in November the saury dispersed in the coastal waters around Hokkaido and the Kuril Islands, which had become occupied by cold water with SST \10°C (Fig.…”

“…Annual migratory patterns of Pacific saury in the northwestern Pacific (NWP) have been proposed in several studies [11,15]. Pacific saury migrates extensively between the summer feeding grounds in the Oyashio waters around Hokkaido and the Kuril Islands and the winter spawning areas in the Kuroshio waters off southern Japan [1,2].…”

Food habits of threadfin hakeling Laemonema longipes along the Pacific coast of northern Japan

“…Walleye pollock Theragra chalcogramma (Pallas) was observed only during late summer and autumn (August–November). The fish preyed upon were age-0 fish, born during the preceding spring and settled in late summer and autumn into the Doto area, their most important nursery (Ito et al , 2004). They are distributed mainly over the continental shelves with bottom depths ≤150 m, where threadfin hakeling does not occur (Kooka et al , 2009).…”

Evolution and modulation of a poleward‐propagating anticyclonic eddy along the Japan and Kuril‐Kamchatka trenches

“…The occurrence of nearshore, warm‐core rings off Hokkaido, the western boundary region of the subarctic gyre, could result in a concentrated migration of sauries east of the rings, and thus, fishery grounds farther away from Hokkaido [ Yasuda and Watanabe , ]. The transition region between the Kuroshio Extension and the Oyashio Current is important to both adult fish and their larvae, because the region serves as a nursery ground for larvae that spawned in the subtropical gyre during the spring [ Ito et al ., ; Watanabe , ; Okunishi et al ., ]. The environment of this area critically affects larvae survival and abundance through the recruitment of these fish [e.g., Nishikawa et al ., ].…”