Chum salmon (Oncorhynchus keta) are one of the most important species for commercial fisheries in Hokkaido in northern Japan. The Okhotsk coast in eastern Hokkaido is the principal area of salmon production in Japan. Commercial catches of chum salmon have been supported by intensive hatchery programs (Miyakoshi et al. 2013). In Hokkaido, returning chum salmon are fished in coastal waters mainly via set nets that are operated from September to December. Recently, coastal sea water temperatures in autumn have been higher than the historic mean. In years with high coastal sea water temperatures (> 20°C), it has been frequently observed that the peak timing of chum salmon landing was delayed and exploitation rates by coastal set net fisheries were low. In addition, high water temperatures might affect the distribution of chum salmon in coastal areas and the number of fish caught by each set net. In order to determine the effects of sea water temperature on commercial landings, the responses of migrating chum salmon to sea water temperature needs to be elucidated. To understand migration routes, depths, and temperatures experienced by returning chum salmon in the Okhotsk Sea, we caught chum salmon in the coastal waters, applied archival tags to them, and released them in late August or early September from 2016 to 2018. We report the outcomes of the tagging experiment for chum salmon in the Okhotsk Sea. From 5 to 7 September 2016, 28 to 30 August 2017 and 28 to 31 August 2018, tagging experiments for chum salmon were conducted in the Okhotsk Sea from the research vessel Hokuyo maru (237 tonnes, Wakkanai Fisheries Research Institute, Hokkaido Research Organization). At a total of 8 or 9 sites in each year, we visually counted the number of chum salmon and fished for chum salmon at night (Fig. 1). At each site, fishing lights were used, and chum salmon that appeared were fished with a lure with raw bait (a slice of squid or Pacific saury) on the hook. The captured chum salmon were anesthetized, tagged with an archival tag on the base of the dorsal fin, and measured for fork length and weight. After recovery from anesthesia, the tagged fish were released into the sea. At the fishing sites, the vertical distributions of the sea water temperature and salinity were measured using CTD (Seabird SBE9plus, Sea-Bird Electronics, Inc., Bellevue, WA, USA).
Japanese juvenile chum salmon (Oncorhynchus keta) migrate from coastal waters to the Okhotsk Sea during late spring/early summer.The Oyashio current flows southwestward off the Pacific coast of Hokkaido, while the Tsushima warm current flows northward off the Japan Sea coast (Fig. 1a).Thus, the migration direction of juvenile chum salmon is along the current off the Japan Sea coast, but opposite the current off the Pacific coast.In this study, factors affecting the migration of juvenile chum salmon from the Japan Sea coast and the east Pacific coast of Hokkaido to the Okhotsk Sea were investigated using a juvenile salmon migration model.
East Kamchatka pink salmon, West Kamchatka pink salmon, odd and even-year generations, catch, heat content, ice cover Over recent decades Far East pink salmon stocks have undergone considerable variations associated with the strengthening of short-term climate variability in the North Pacific.The last minimum of total pink salmon catch (147,500 metric tons) in 2014 was followed by its growth to a maximum of about 511,000 metric tonnes in 2018.This rise of catches was associated with an increase in heat content of surface waters in the northern North Pacific and Far East Seas in 2014-2019.This presumably created favorable environmental conditions for pink salmon stocks, especially for those spawning in Kamchatka rivers, during their marine period of life.The growth of catches was essentially caused by an unusual increase in catch of even-year generations of East Kamchatka (EK) pink salmon, which were not a dominant stock.From 2012 to 2018, this catch rose more than six times, from 16,730 metric tonnes up to 111,250 metric tonnes, respectively (Fig. 1).In 2018, the share of EK pink salmon in the total Russian pink salmon catch reached almost 22%.
first salmon ceremony, culture of salmon, importance of salmon in communities Salmon inhabit the North Pacific Ocean and are an extremely important food source for people who live around the North Pacific rim.Salmon are not only important to people as a food resource there, but the capture and utilization are very important culturally.The first salmon ceremony is an important cultural event that takes place around the southernmost area of salmon habitat.Gunther's research (1926, 1928) on salmon rituals in the North Pacific region, especially on the American continental side, hardly touches on the Japanese archipelago and the Far East, including Hokkaido.By comparing the beliefs and customs of the Ainu, the people of northern Honshu, the indigenous people of the Amur River basin, and the indigenous people of Sakhalin in relation to salmon hunting, Obayashi proposes that the salmon rituals from Amurland through Hokkaido to northern Honshu be viewed as a single continuum (Obayashi 1992(Obayashi , 1996)).In addition, Suga (2000) and Suzuki ( 2004), among others, have conducted research on salmon rituals around the Tohoku region.The objective of this study is to understand the status of salmon culture in the southern limit of salmon habitat.The target of the research is the MATABE ceremony, the first salmon ceremony in the Tsugaruishi district of Miyako City, Iwate Prefecture.We surveyed rituals related to the MATABE ceremony.The research was conducted by participating in the ritual, interviewing the people involved, and collecting historical data.
We estimated the proportion of hatchery and natural fall spawning chum salmon returning to the Amur River using chemical markers specific to hatchery-origin fry. We used otolith microchemistry technique to identify fish with artificial origin among returning spawners. First, we found that juveniles of artificial origin had higher values of the Sr:Ca molar ratio of the otoliths’ edge zone compared with juveniles of natural origin, what can be related to the use of rearing feed produced from raw materials of marine origin rich in strontium. Then we observed that most of the spawners from Anyuisky Hatchery and from the Amur River mouth at the start of the spawning migration has also the higher value of Sr:Ca molar ratio of the juvenile zone of otoliths. Also, adults with higher values of the Sr:Ca molar ratio are characterized by a skewed right in the peak of the age distribution. Both, the age structure and phenological shift in the time of spawning migration of individuals with higher value of the used chemical marker corresponds to results of studies on hatchery-produced chum salmon completed at different parts on Northern Pacific. The results of this study will be used in the management of Amur fall chum salmon fisheries, and also demonstrates the necessity of the development of specific measures for increasing the survival of juvenile anadromous salmonids released at large rivers and exposed to prolonged freshwater migration to the ocean. As a further application of the methodology, we plan to identify the markers specific to each of the hatcheries and main spawning tributaries belonging to Amur River catchments. This will be an important step in the evaluation of the contribution of different stocks in mixed fisheries and also in the estimation of the effect of hatchery releases on naturally spawning stocks of Amur fall chum.Following to, our results may indicate the applicability of this approach for the determination of artificial-origin fish in a mixed sample of the Amur fall chum salmon.
A decrease in the rate of growth in fish, which is one of the most important characteristics of stock dynamics, can result in a decrease in their abundance, as is widely accepted in classical fisheries ichthyology. A study of growth patterns in pink salmon year-classes with different survival rates during the marine period of their life history has been carried out to elucidate the causes of the sharp reduction in the abundance of this species that occurred recently on the eastern coast of Sakhalin Island. The retrospective analysis of growth rates was based on measurements of scales from pink salmon that returned to spawn on the southeastern Sakhalin coast in 2005–2018. An analysis of the relationship between the growth parameters (body length increase, variability, and skewness of the size structure) with the survival rates of the respective year-classes has shown that these parameters can be used as indicators of survival rate reduction only for feeding juveniles, i.e., during the early marine phase of pink salmon life history. Thus, the hypothesis about a “critical size” for juvenile salmon that, if not reached by the end of the summer–autumn feeding season, significantly decreases its chances to survive the overwintering period, has not been confirmed. The data show that the estimates of size-selective mortality of juvenile pink differ from the actual values not only because of the probable incorrectness of comparing actually observed body lengths (unrepresentative sampling) and those calculated using scales. The unreliability of estimates may also come from the fact that variations in the calculated size structure of surviving fish to some extent reflect the similar processes that occur initially in the entire year-classes.
Chum salmon stock in Hokkaido has been declining since its peak in 2004.In 2017, its stock level reached the lowest level over the past 30 years.In addition, we observed that the stock levels were lower than what we predicted using the sibling regression method.In such a situation, both improving hatchery programs and enhancing the accuracy of the pre-season forecast are essential to managing the chum salmon stock in Hokkaido.We explored factors affecting the variability in-stock level and precision of the pre-season forecast.We calculated the number of chum salmon caught in Hokkaido as the sum of the number of fish caught by the coastal fishery and the number of fish caught in rivers over the period 1986-2020.The number of salmon caught by the coastal fishery is based on data published by the Hokkaido Prefectural Government, and the number of salmon caught in rivers is based on data published by the Hokkaido salmon enhancement association, a public interest incorporated foundation.The return rates of salmon were calculated for 1983-2015 brood years, which were caught during 1986-2020 as three-to five-year-old fish in Hokkaido, using the number of fish released and the number of fish caught described above.The return rates were calculated only for the Pacific coast area, which has had a significant impact on the stock variations of chum salmon in Hokkaido.In order to clarify the relationship between the return rates and coastal sea surface temperatures (SSTs), we conducted regression analyses between monthly average sea surface temperatures from April to June, when chum salmon juveniles enter the ocean and grow in coastal areas (Irie 1990;Seki 2005), at the Pacific coastal areas and return rate of salmon at the Pacific coast.For the calculation of the monthly average sea surface temperatures, we used SSTs for ten areas along the Pacific coast published by the Japan Meteorological Agency (Available at https://www.data.jma.go.jp/gmd/kaiyou/data/db/SP/dbindex_SP.html).Our analyses revealed that the return rate of chum salmon is positively correlated with coastal sea surface temperature (SST) at ocean entry timing.This suggests that the SST during the ocean entry timing of chum salmon juveniles would be a major driver in controlling the year-class abundance and that the decline of the stock level would be caused by the "cold-spring" SST phase around Hokkaido.In 2016, the ocean regime around Hokkaido changed to a warmer condition; however, the 4-year-old fish abundance of the 2015 year-class has not recovered, and a deviation between pre-season forecast and actual abundance has increased, as well.We found that the deviations between pre-season forecast and actual abundance were mainly caused by overestimating the abundance of 4-year-old fish.We analyzed the relationships between age at maturity of year classes and the ratio of 4-year-old fish to 3-year-old fish abundance, known as sibling relationship, to identify the factors affecting these overestimations.Our analyses revealed that the age at maturity had decreased in most areas, and it would affect the sibling relationships.These results suggest that the decline of chum salmon stock levels in Hokkaido would have been mainly caused by cold ocean conditions during spring.In addition, the analysis for the 2015 year-class, which matched favorable ocean conditions in the coastal area, suggests that the survival rate in the Okhotsk Sea and/or farther area might be recently decreasing.The decline of the age at maturity, which affects the sibling relationship, suggests that the survival rate of fish with a slower growth rate might be decreasing.
Adult returns of Japanese chum salmon have shown a decreasing trend since a peak (76 million fish) in 2004, while falling to 19-31 million fish in recent years (2016)(2017)(2018)(2019)(2020).For sustainable management, it is an urgent issue to understand where and why the survival of Japanese chum salmon is decreasing.The Okhotsk Sea is the most important feeding area for juvenile chum salmon originating from Japan and the Russian Far East, except for the coastal area of the Bering Sea (Urawa et al. 2018).Juvenile chum salmon released from Japanese hatcheries migrate along the coastal shelf of northern Japan, heading for the Okhotsk Sea.Genetic and otolith mark studies have indicated that juvenile chum salmon of all regional populations in Japan are distributed in the Okhotsk Sea during their first summer and fall (Urawa et al. 1998(Urawa et al. , 2001(Urawa et al. , 2004(Urawa et al. , 2006(Urawa et al. , 2007;; Chistyakova and Bugaev 2013, 2016).A long-term trawl survey has been conducted by Russian research vessels to estimate the abundance of juvenile chum and pink salmon in the Okhotsk Sea during the fall season (mainly October).The occurrence of otolith-marked juvenile chum salmon caught in the Okhotsk Sea during the fall of 2011-2017 was reported by Bugaev et al. (2019).The abundance of juvenile chum salmon in the Okhotsk Sea was variable: 164-553 million fish in 2011-2017.A total of 9,870 juvenile chum salmon were examined for otolith marks, and 347 otolith-marked fish released from hatcheries in Japan were detected by using the NPAFC otolith mark release database (http://npafc.taglab.org).In the present study, the abundance of Japanese hatchery-released juvenile chum salmon in the Okhotsk Sea was estimated by using the NPAFC otolith mark release database and the recovery data reported by Bugaev et al. (2019).
The Great East Japan Earthquake and Tsunami on March 11, 2011, caused immense damage to marine ecosystems, both nearshore and offshore, on the Pacific coast of northeastern Japan (the Tohoku region).Most fishing vessels and fishery related infrastructure were destroyed by the disaster.In the Tohoku region, salmon hatcheries have been common in many rivers, and every year, released chum salmon have returned to their own rivers.When the 2011 disaster occurred, a lot of juvenile chum salmon were reared in the hatcheries before being released into the sea.Therefore, the salmon production cycle in this region was also severely disrupted by the disaster.In order to reconstruct the devastated human society, scientific investigation was essential to understand the effects of such strong disturbances on not only coastal land areas but marine ecosystems, and to monitor the process of their recovery.The research project of "Tohoku Ecosystem-Associated Marine Sciences (TEAMS)" was established under such circumstances by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) in 2011FY.The purpose of the TEAMS project is to clarify the impact of the earthquake and subsequent tsunami on marine-related ecosystems of the Tohoku coastal areas, highlight the restoration process of the ecosystems based on scientific research, and contribute to the reconstruction of fishery industries in the Tohoku region, including salmon production.The TEAMS project was carried out for a period of 10 years-ranging from coastal to offshore seas and from surface to bottom in the Sanriku region-involving the cooperation and collaboration of a large number of researchers across Japan.Enormous research results obtained on the catastrophe of the earthquake and tsunami on the land and ocean ecosystems will contribute to future crisis management know-how not only in Japan but also overseas (TEAMS 2016).The background and results of this project will be a role model for disaster recovery as it included collaboration between different fields and regions and cooperation between researchers, fishermen, research institutes, and governments both local and national.In addition, the results of this project will be useful for the monitoring and future prediction of marine ecosystem dynamics, the development of sustainable fisheries and aquaculture management, and the establishment of a new marine industry coexisting with marine environmental conservation and landscape (TEAMS 2020).We hope that they will be widely useful in various fields such as the education for conservation of marine ecosystems.
Feeding conditions for juvenile salmon during their early ocean residence have been shown to be critical to their growth and survival, although direct sampling of their food availability has been limited (Brodeur et al. 2011).Increased understanding of prey dynamics during the early marine period of juvenile salmon could help us to better understand when increased competition may be occurring between salmon that eat at similar trophic levels.Juvenile coho (Oncorhynchus kisutch) and Chinook (Oncorhynchus tshawytscha) salmon typically consume age-zero juvenile fish, crab larvae, krill, and amphipods during their early marine residence, many of which are difficult to quantitatively assess using typical plankton gear (Brodeur et al. 2011).In May 2017 and 2018, as part of the National Oceanic and Atmospheric Administration's Juvenile Salmon Ocean and Ecosystem Survey (JSOES), we collected juvenile salmon and their prey concurrently in coastal waters off Washington, USA by adding a fine mesh liner to the surface trawl net that has previously been used to sample juvenile salmon.The primary focus of the JSOES survey is to better understand the early marine period of Endangered Species Act (ESA) listed salmon and how changes in ocean conditions may impact their marine survival (Daly et al. 2013;Burke et al. 2013;Crozier et al. 2021).The goal of our study was to specifically examine prey environment, diet overlap, and how salmon utilized the available prey in 2017 and 2018.Ocean conditions during the winter and spring previous to juvenile salmon outmigration have been correlated with first summer salmon prey community and biomass, salmon diets, and salmon size, growth, body condition, and subsequent adult returns (Pearcy 1992;Daly and Brodeur 2015;Brodeur and Daly 2019).Sea surface ocean temperatures in 2017 were warm, and we observed low catches at every trophic level measured (Wells et al. 2017), resulting in a poor ocean productivity year for salmon.Ocean temperatures were cooler in 2018 than in 2017, although still above the long-term average, and numerous ecosystem indicators in 2018 suggested better conditions than 2017 (fair ocean condition year).Ocean ecosystem indicator rankings for 2017 and 2018 are available at https://www.fisheries.noaa.gov/west
