Masa‐aki Fukuwaka

Japan Fisheries Research and Education Agency

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Shigehiko Urawa

Japan Fisheries Research and Education Agency

Kentaro Morita

The University of Tokyo

Tomonori Azumaya

Japan Fisheries Research and Education Agency

Nancy D. Davis

University of Washington

Tôru Nagasawa

Takasaki University of Health and Welfare

Yutaka Watanuki

Hokkaido University

Shunpei Sato

Japan Fisheries Research and Education Agency

Masahide Kaeriyama

Hokkaido University

Hironori Ando

Niigata University

Akihisa Urano

Hokkaido University

Cooperative Institutions

Hokkaido University

Japan Fisheries Research and Education Agency

The University of Tokyo

University of Washington

NOAA National Marine Fisheries Service

Tohoku University

National Oceanic and Atmospheric Administration

National Agriculture and Food Research Organization

Osaka University

Kyushu University

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Variation in prey size selectivity of fingerling chum salmon (Oncorhynchus keta) in sea life: effects of stomach fullness and prey abundance

Masa‐aki Fukuwaka

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Variation in Body Size, Fecundity, and Egg Size of Sockeye and Kokanee Salmon, Oncorhynchus nerka, Released from Hatchery

Masahide Kaeriyama Shigehiko Urawa Masa‐aki Fukuwaka

Adult sockeye salmon (Oncorhynchus nerka) returning to the Bibi River, which were orig- inally derived from LakeShikotsu kokanee salmon,and adult kokanee salmon in Lake Shikotsuwere exam- ined for variation in body size, fecundity, and egg size. Both groups of adults originated from hatchery- released juveniles. Larger adult females had higher fecundity. Fecundity and fork length fitted allometric formula within each population. There was no relationship between fork length and egg size in Lake Shikotsu kokanee salmon or in age-I.1 sockeye salmon from the Bibi River although the sockeye salmon were approximately 65% larger in fork length than the kokanee salmon. Age-1.2 sockeye salmon, how- ever, had eggs about 12% larger than did kokanee and age-1.1 sockeye salmon. We suggest fecundity in hatchery-released sockeye salmon vary with body size influenced by environmental components, and that their egg size would be affected by both environmental and genetic components such as polygene model within a cohort or population because of exclusion from the breeding competition and parental care.

Hatchery

Fish measurement

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Intraspecific variation in the swimbladder occurrence and possibility of acoustic discrimination of the dominant mesopelagic fish Diaphus garmaniioff western Kyushu, Japan

The Journal of the Acoustical Society of America (2016)

Hiroki Yasuma Shinya Ohshima Tohya Yasuda Masa‐aki Fukuwaka Kôki Abe

Diaphus garmanii (Family, Mictophidae) is the most abundant mesopelagic fish in the continental slope off western Kyushu. For the application of acoustic monitoring, we have observed the swimbladder morphology of this species to estimate the target strength (TS). In this session, we show the intraspecific variation in the occurrences and shapes of swimbladder in D. garmanii, and propose the acoustic discrimination of the swimbladder morphology for accuracy improvement in biomass estimates. Acoustic data and biological samples were collected in the summer of 2012 to 2014. Both of fishes with (30% in all samples) and without (70%) swimbladder were observed by the soft X-ray method, and frequencies of the swimbladder occurrence were significantly different between male and female fishes. Theoretical scattering models showed that the TS difference between 38 kHz and 70 kHz was the most preferable parameter to discriminate the swimbladder occurrence of D. garmaniiin field acoustic data. Field acoustic data analyses implied different patterns of vertical distribution between swimbladder and swimbladderless (male and female) fishes.

Mesopelagic zone

Target strength

Variation (astronomy)

10.1121/1.4970515

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Ⅱ-1. Status of Pacific salmon production in the North Pacific Ocean

NIPPON SUISAN GAKKAISHI (2018)

Toshihiko Saito Masa‐aki Fukuwaka

10.2331/suisan.wa2555-3

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EARLY SEA MORTALITY OF CHUM SALMON JUVENILES IN THE JAPAN SEA COAST

Masa‐aki Fukuwaka Toshiya Suzuki

We examined the early mortality of juvenile chum salmon to clarify population dynamics of hatchery-reared chum salmon in the Japan Sea coast. We calculated the survival rate using mark-and-recapture experiments during 10-50 days after release from the hatcheries along the Japan Sea coast of Honshu. Estimated daily survival rate during early sea life was 76.9 approx. 100% day . Mean survival during the whole sea life was 0.258% in 1988-1997. Early sea mortality of chum salmon accounted for 97.4% of the whole sea mortality. Results suggest that early sea mortality soon after release from hatcheries will determined a population level of returning adults of a cohort of chum salmon. INTRODUCTION In anadromous Pacific salmon, mortality is often extensively high soon after the entering into the sea (Pearcy 1992). Hatchery-reared chum salmon juveniles reach coastal waters within several days after release (Mayama et al. 1983; Kaeriyama 1986). Early sea mortality is much higher than subsequent stages in the life history of hatchery-reared chum salmon, thus it may determine adult population level (Bax 1983). Early sea distribution of chum salmon is restricted in nearshore regions in the Japan Sea coastal water (Fukuwaka and Suzuki In press). To clarify the population dynamics of hatchery-reared chum salmon in the Japan Sea coast, we examined early sea mortality of juvenile chum salmon using mark-and-recapture experiments in the coastal waters. METHODS Mark-and-recapture data sets for chum salmon juveniles were provided from the prefectural fisheries experimental stations along the Japan Sea coast of Honshu in 1992-1997 (Hokkaido Salmon Hatchery 1993-1997; National Salmon Resources Center 1998). Over 3 million fin-clipped juveniles were released from several private or prefectural hatcheries in 11 marking experiments in 1992-1997 (Table 1; Fig. 1). Surveys in coastal waters operated by the fisheries experimental stations of Yamagata, Niigata, Toyama, and Ishikawa Prefectures. Fisheries Agency of Japan financially supported these mark-and-recapture experiments. In 1992-1997, 1663 marked juveniles were recaptured by the prefectural fisheries experimental stations or commercial fishermen. Daily survival rate was estimated using the equation: ln (mt / nt)= ln (M / N0) + (t – 0.5) ln S,

Hatchery

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FORl\tIATION PERIODICITY OF INCRElVIENT AND ALLOlVIETRIC GROWTH IN JUVENILE CHUlVl SALMON OTOLITH

Masa‐aki Fukuwaka

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Interception of a PIT-Tagged Columbia River Basin Steelhead in the Central North Pacific Ocean

Nancy D. Davis Megan Atcheson Dave Marvin Masa‐aki Fukuwaka

Interception

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Elevation of the Plasma Level of Insulin‐like Growth Factor‐I with Reproductive Maturation prior to Initiation of Spawning Migration of Chum Salmon

Annals of the New York Academy of Sciences (2009)

Takeshi A. Onuma Keita Makino Masatoshi Ban Hironori Ando Masa‐aki Fukuwaka

When, where, and how oceanic chum salmon initiate spawning migration is unknown although gonadal development and elevation of the activity of the pituitary–gonadal axis (PG‐axis) are essential. Insulin‐like growth factor‐I (IGF‐I) is a somatotropic signal that interacts with the PG‐axis for gametogenesis. We thus examined the plasma level of IGF‐I in immature and maturing chum salmon in the Bering Sea and the Gulf of Alaska. The maturing adults which had maturing gonads left the Bering Sea for the natal river by the end of summer, because almost all fish were immature in September. The plasma level of IGF‐I and corresponding body size in the maturing adults were two‐ to threefold that of immature fish. The plasma IGF‐I level correlated positively with the pituitary contents of follicle‐stimulating hormone and the plasma levels of 11‐ketotestosterone and estradiol‐17β. Therefore, the plasma level of IGF‐I increased with elevation of the PG‐axis activity prior to the initiation of spawning migration from the Bering Sea. Circulatory IGF‐I from visceral organs may inform the status of body growth to the PG‐axis for gonadal development that is inseparable from decision of chum salmon whether to initiate homing behavior from the Bering Sea or not to initiate spawning migration by the coming spawning season.

Plasma levels

10.1111/j.1749-6632.2008.03668.x

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Ocean Condition and Pacific Salmon Stock Assessment in the North Pacific Ocean, 2000

Yukimasa Ishida Masa‐aki Fukuwaka

We summarize results of researches on salmon stock assessment conducted by Japan in summer of 2000. Four Japanese salmon research vessels (Oshoro maru, Hokusei maru, Shoyo maru, and Wakatake maru) conducted oceanographic observations, 56 gillnet (2,717 tans), 40 longline (959 hachi), 3 hook-and-line fishing operations in the western, the central, the eastern North Pacific, and the Bering Sea from June to August. Mean sea surface temperature, abundance and body size of Pacific salmon in 2000 are compared to those from 1992 to 1999. Mean sea surface temperature in 2000 was 12.6 C in the western North Pacific, 8.49 C in the central North Pacific, 7.69 C in the Bering Sea, 9.89 C in the eastern North Pacific. A total of 12,231 salmonids was caught, including 6,758 chum (55.3%), 2,851 pink (23.3%), 1,544 sockeye (12.6%), 612 coho (5.0%), 315 chinook salmon (2.6%), and 151 steelhead trout (1.2%). CPUEs of chum, pink, sockeye, and coho salmon in 2000 were in low levels in 1992-2000 in the North Pacific Ocean. In the Bering Sea, CPUE of pink salmon in 2000 was the lowest in 19922000. In that regions, CPUE of chum salmon was the lowest in even-years in 19922000. CPUEs of chinook salmon and steelhead trout were higher than the mean in 19921999. No common trend in annual changes of mean fork lengths of salmonids was observed.

Chinook wind

Fish measurement

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Japanese Research Plan in the Bering Sea and the Gulf of Alaska

Masa‐aki Fukuwaka Tomonori Azumaya

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