Chum Salmon Research Articles

Relationship between in-river return rate of hatchery-origin chum salmon Oncorhynchus keta and coastal water temperature and body weight at release on the Japan Sea side of Honshu, Japan

Relationship between in-river return rate of hatchery-origin chum salmon Oncorhynchus keta and coastal water temperature and body weight at release on the Japan Sea side of Honshu, Japan

First Report of Bacterial Kidney Disease (BKD) Caused by Renibacterium salmoninarum in Chum Salmon (Oncorhynchus keta) Farmed in South Korea

In 2021, a prominent increase in mortality was observed in juvenile and subadult cultured chum salmon (Oncorhynchus keta) on a mariculture farm in Jeollanam-do Province, South Korea. The affected fish displayed distinct symptoms: pale gills, petechial hemorrhages in the muscles, and white nodules on the kidneys. Infectious pancreatic necrosis virus (IPNV) was cultured from some fish samples using fish cell lines. Bacteria were isolated from various fish tissues using kidney disease medium-two (KDM-2) culture medium. By detecting and sequencing the 16S rRNA gene using DNA extracted from the kidneys of the infected fish via PCR, the isolated bacteria were identified as Renibacterium salmoninarum. Histopathological examination primarily focused on hematopoietic tissues of kidneys and revealed clear evidence of severe necrosis and granulomatous changes. Additionally, nuclei with peripherally displaced chromatin were abundant in the kidneys of affected fish. These findings suggest that mass mortality of chum salmon was caused by R. salmoninarum, which induced typical bacterial kidney disease (BKD) symptoms, without IPNV infection. This represents the first outbreak of BKD attributed to R. salmoninarum infection in farmed chum salmon in South Korea.

Guidance of fish to the fishway by gate release and confirmation of induction effect

A fishway is a structure that aids fish migration by preventing the blockage of migration paths by dams. However, excessive water through a dam’s gate prevents fish from reaching the fishway. We hypothesized that fishways are sensitive to dams, especially those with independent gates to release water downstream in different spatial patterns. To test this, the sensitivity of fishways to the coordinated operation of multiple gates was investigated via controlled systematic gate manipulation. By manipulating dam gates, we aimed to obtain hydraulic phenomena that circumvent the obstacles to fishways. Numerical model simulations and actual dam discharge experiments showed that releasing water from a gate near fishways facilitated continuity between the downstream regions and fishways, eliminating circulating eddy flows at the fishway entrance. For biovalidation, Oncorhynchus keta was radio-tagged and released ∼1 km downstream of the dam after applying the existing (circulation flow) and new operation methods (no circulation flow). The arrival rate to the fishway was only 40% in the presence and 100% in the absence of circulating flow; this corroborates our hypothesis by showing that changing the dam’s flow release pattern to eliminate circulating flow ensured hydraulic continuity between the mainstream river region and fishways, benefiting fish passage.

Exploring Fish Parvalbumins through Allergen Names and Gene Identities

Parvalbumins are the main source of food allergies in fish meat, with each fish possessing multiple different parvalbumins. The naming convention of these allergens in terms of allergen codes (numbers) is species-specific. Allergen codes for parvalbumin isoallergens and allergen variants are based on sequence identities relative to the first parvalbumin allergen discovered in that particular species. This means that parvalbumins with similar allergen codes, such as catfish Pan h 1.0201 and redfish Seb m 1.0201, are not necessarily the most similar proteins, or encoded by the same gene. Here, we aim to elucidate the molecular basis of parvalbumins. We explain the complicated genetics of fish parvalbumins in an accessible manner for fish allergen researchers. Teleost or modern bony fish, which include most commercial fish species, have varying numbers of up to 22 parvalbumin genes. All have derived from ten parvalbumin genes in their common ancestor. We have named these ten genes “parvalbumin 1-to-10” (PVALB1-to-PVALB10), building on earlier nomenclature established for zebrafish. For duplicated genes, we use variant names such as, for example, “PVALB2A and PVALB2B”. As illustrative examples of our gene identification system, we systematically analyze all parvalbumin genes in two common allergy-inducing species in Japan: red seabream (Pagrus major) and chum salmon (Oncorhynchus keta). We also provide gene identifications for known parvalbumin allergens in various fish species.

Special Features of Chum Salmon Oncorhynchus keta (Salmonidae) Stock Formation in the South-Western Sakhalin Fish Hatcheries as Identified Using the Otolith Marking Method

Special Features of Chum Salmon Oncorhynchus keta (Salmonidae) Stock Formation in the South-Western Sakhalin Fish Hatcheries as Identified Using the Otolith Marking Method

Fish Diversity of East Sea Streams in Nakdong River Region

Fish surveys were conducted near artificial structures installed in eight streams flowing from the Nakdong River region to the east coast of Korea. As a result of the survey, a total of 20,000 individuals belonging to nine orders, 17 families, and 47 species were found. The dominant species was Zacco koreanus, and the subdominant species was Pungtungia herzi. Among the surveyed fish species, endangered species were Pseudobagrus brevicorpus (rank I) and Cottus hangiongensis (rank II). In addition, migratory fish species were Oncorhynchus keta, Plecoglossus altivelis, and Tribolodon hakonensis. As a result of community analysis, the highest diversity, dominance, richness, and evenness indices were Wangpi, Chuksan, Gokgang, and Janggi Stream respectively. The highest number of species was surveyed in Gokgang Stream (25 species). Alpha diversity, the number of species at each survey point in each stream, was the highest at a survey point in Wangpi Stream (20 species), and beta diversity, species at each stream survey point that does not overlap with nearby survey point, was the highest at survey points in Gokgang Stream (12 species). As a result of the similarity analysis, surveyed streams were divided into four groups: group 1 (Chuksan, Baeknok Stream), group 2 (Uljinnamdae, Wangpi, Yungdeokosip Steam), group 3 (Gokgang Stream), and group 4 (Janggi, Hoeya Stream). This study is expected to serve as basic data for managing the aquatic ecosystem of streams flowing from the Nakdong River region to the east coast.

Towards a method for determining the age of chum salmon

The purpose of the work is to perform a quantitative comparative analysis of the structure and size of annual rings of chum salmon scales to prepare a methodological manual for determining age. The research material included scale preparations from 493 chum salmon producers of different ages, on which sclerites were counted and the diameter of annual rings was measured.Methods used: comparative data analysis, descriptive statistics methods.Results: it was found that the size of the scales, the size of each of the annual rings, as well as the number of sclerites in the annual rings of male and female chum salmon within each age group do not differ. The number of sclerites forming each annual ring, as well as the radius of the rings, varies significantly among different individuals. With age, as the length and mass of fish increase, the size of the scales naturally increases. Moreover, an acceleration in the growth rate is observed during the year preceding puberty. As a result, the number of sclerites in the last annual ring, as well as the size of this ring in fish that reach sexual maturity is always greater than in fish of the same age, but remaining in the sea to continue feeding.Practical significance: the presented article is a scientific accompaniment of a methodological manual for the practical determination of the age of chum salmon by scales.

Body size- and temperature-related metabolic traits of juvenile chum salmon during northward migration

Due to rapid ocean warming at higher latitudes, northward habitat shifts of the dominant anadromous fish in the Northern Hemisphere, chum salmon ( Oncorhynchus keta), have recently been reported. Physiological development is considered to be a trigger for habitat shifts during early life. However, the possibility of physiological adaptations to future ocean warming is not fully understood, because data on the physiological traits of juveniles, such as metabolic rate and swimming performance, are limited. Using swim tunnel respirometers, we identified the metabolic traits of different-sized chum salmon juveniles originating from the Sanriku coastal river, Japan, which is far from the northern feeding grounds. The weight gain of >2 g steeply increased the prolonged swimming performance, and the metabolic cost of swimming against the southward current in the Sanriku coast decreased with weight gain under the sea water temperature range of 8–12 °C. These findings indicate weight gain and inhabiting areas with temperatures < 13 °C might provide potential benefits for northward migration. These results will be valuable when assessing the increased costs associated with changing ocean conditions.

In-season monitoring of harvest and effort from a large-scale subsistence salmon fishery in western Alaska

In-season management of salmon harvest requires real-time data. Specifically, following a brief period of open fishing, knowledge of harvest outcomes is useful when deciding the nature of subsequent fishing periods. This in-season management strategy is relatively new to the lower Kuskokwim River of western Alaska, where depressed salmon runs have caused restrictions to the subsistence fishery. We have developed an in-season monitoring program to rapidly inform managers about fishery outcomes from short-duration (6-24 hours) fishery openings. Completed trip information and one or more aerial surveys are combined to estimate daily effort and harvest from drift gillnet fishers spanning 11 communities and ~130 river kilometers. We present a re-analysis of the 40 monitored openers in June-July 2016-2023, and validate harvest estimates of Chinook, chum, and sockeye salmon by comparing them to post-season estimates derived from an independent long-term monitoring program. Our results indicate that the program has produced estimates of sufficient quality to inform in-season managers, although it will likely need alterations to be successful in years with less restricted fishing.

БОЛЕЗНИ ПРОХОДНЫХ ЛОСОСЁВЫХ РЫБ ПРИ ИСКУССТВЕННОМ ВОСПРОИЗВОДСТВЕ В УСЛОВИЯХ КРАЙНЕГО СЕВЕРА ДАЛЬНЕГО ВОСТОКА

Replenishment of fish stocks by increasing the release of juveniles during artificial fish farming is currently an urgent problem in the Far North of the Far East. In 1995-2003; 2021, an epizootological survey of natural spawning grounds and fish farming enterprises located in the northern part of the Okhotsk Sea basin was conducted: Ola, Arman, Taui, Yana, Iret, Ola experimental production acclimatization base, Armansky, Taui, Yansky salmon hatcheries. The aim is to study bacterial and protozoal diseases of passing salmonids in artificial fish farming. The novelty of the research is that for the first time in the waters of the northern part of the Okhotsk Sea basin, bacterial and parasitic diseases were detected in passing salmon fish in natural reservoirs during anadromous migration and artificial fish farming. In pink salmon, chum salmon, coho salmon, sockeye salmon, Aeromonas hydrophila culture isolated from blood and internal organs turned out to be virulent. Aeromonosis was established for the first time in passing salmon fish of natural populations. As a result of bacteriological studies, Aeromonas hydrophila bacteria were isolated from different batches of fertilized eggs, yolk sac of larvae, ascitic fluid of the abdominal cavity of juveniles. Due to the detection of the invasion of juvenile fish Trichodina truttae and Myxosoma cerebralis, which amounted to 10.0-46.5%, trichodyniosis and myxosomiasis were registered. The ways of transmission of infection to fish farms have been established. Fertilized eggs are infected from producers on spawning rivers during the selection of sexual products. The epizootological situation of aeromonosis, trichodyniosis and myxozomiasis is recognized as unfavorable. The method of diagnosis of bacterial diseases of salmonids at fish-breeding enterprises of the region has been improved.

How safe are wild-caught salmons exposed to various industrial chemicals? First ever in silico models for salmon toxicity data gaps filling

Salmons are crucial to ecosystems and economic activities like commercial fishing and aquaculture, while also serving as an important source of nutrients, underscoring their ecological significance and the need for sustainable management. To better understand the toxicity and biological interactions between the salmon and industrial chemicals in the aquatic environment, we utilized the ToxValDB database to develop first ever computational toxicity models for six salmon subspecies (covering Atlantic and Pacific salmon) across two genera, employing Quantitative Structure-Activity Relationship (QSAR) and quantitative Read-Across Structure-Activity Relationship (q-RASAR) methods. For three smaller datasets (Oncorhynchus nerka, Oncorhynchus keta, and Oncorhynchus gorbuscha), we created mathematical models using the entire datasets where QSAR models demonstrated superior statistical quality compared to q-RASAR. Conversely, the three larger datasets (Oncorhynchus kisutch, Oncorhynchus tshawytscha, and Salmon salar) were divided into training and test sets, the q-RASAR models yielded better results compared to QSAR models. Mechanistic interpretations of these models revealed that descriptors such as Burden eigenvalues (BCUT), autocorrelation of topological structure (ATSC), and molecular polarizability were significant predictors of toxicity. For instance, higher polarizability and certain topological features were associated with increased toxicity as per the developed models. Statistically superior models for each subspecies were used to predict the aquatic toxicity of 1085 untested organic chemicals for toxicity data gap filling and risk assessment considering the applicability domain (AD). These insights are pivotal for designing safer chemicals and emphasize the need for sustainable management of salmon populations.

Messenger RNA transcription levels of neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex components in the olfactory nerve system of the anadromous Pacific salmon, masu salmon Oncorhynchus masou.

Anadromous Pacific salmon (genus Oncorhynchus) are known for homing behavior to their natal rivers based on olfactory imprinted memories during seaward migration. The SNARE complex is a regulator of vesicle exocytosis from the presynaptic membrane. Our previous study suggested that its component genes (Snap25, Stx1, and Vamp2) are more highly expressed in the olfactory nervous system (ONS) during the migration stages associated with olfactory imprinting in the evolutionary species of Pacific salmon, such as chum (O. keta) and pink (O. gorbuscha) salmon. Masu salmon (O. masou) has a significantly different life history from these species, living longer in rivers and being a more primitive Pacific salmon species. In this study, the transcription of snare mRNAs in the ONS was analyzed using mainly male wild masu salmon. Five cDNAs encoding masu salmon SNAREs, which are well conserved among vertebrates, were isolated and sequenced. Each snare mRNA was highly expressed in age 1+ (yearling) parr prior to smoltification, particularly in the olfactory bulb. Their transcription status was significantly different from that of chum and pink salmon, which showed high expression in earlier under-yearling juveniles. The present results and our previous studies indicate that snare mRNAs are highly transcripted until the seaward migration, reflecting neural development and neuroplasticity of the ONS for olfactory imprinting.

Comparison of Juvenile Pacific Salmon abundance, distribution, and body condition between Western and Eastern Bering Sea using spatiotemporal models

Recent changes in climate have had generally negative impacts on salmon stocks in the eastern and positive effects in the western Bering Sea (WBS). Eastern Bering Sea (EBS) salmon stocks have periodically experienced reduced productivity, size, and survival, whereas salmon stocks in the western Bering Sea (WBS) have tended to be more stable, with some stocks increasing in abundance. This difference could be partially attributed to the different habitats that juvenile salmon occupy during their first marine year, which often determines recruitment. Here, we used salmon surveys in the EBS and WBS to compare the status of juveniles in these two large marine ecosystems. We applied spatio-temporal vector autoregressive spatio-temporal (VAST) models to adjust for differences in timing, vessels and trawl gear used, and to compare the relative abundance and body condition indices (length, weight, and Fulton's condition factor) of three juvenile salmon species pink, chum and sockeye salmon (Oncorhynchus gorbuscha, O. keta, and O.nerka respectively) between the WBS and EBS from 2002 to 2022. Juvenile salmon in WBS exhibited a consistent trend of larger size and higher Fulton's condition factor, with greater abundance compared to EBS in even years. A clear even-odd year pattern, which is believed to be driven by pink salmon, occurred in all species’ relative abundance and body condition in the WBS, with a limited impact of interannual temperature changes. Conversely, temperature had a significant impact on EBS salmon, with much of the variation in relative abundance and body condition occurring between warm and cold periods, and even/odd patterns were found only in pink salmon relative abundance and body condition. We detected different WBS-EBS migration patterns, with EBS juveniles dispersing from nearshore habitats earlier than WBS juveniles but migrating offshore later that is connected to bathymetry and the broad shelf in the EBS.

Food base of nekton in deep-sea areas of the western Bering Sea: dynamics, current state and its consumption by pacific salmon

Long-term dynamics of the food base for nekton in the deep-sea waters of the western Bering Sea are analyzed on the data of ecosystem surveys in 1986–2022. The main patterns of species composition and structure are determined for the main taxonomic groups of zooplankton and their production is evaluated. These features are influenced by climateoceanographic and biocenotic factors, with priority of the climate-oceanographic ones, whereas the biocenotic factors are conditioned by them. As an example of biocenotic impact, the effect of chaetognats on copepods is considered. Trophic characteristics of the most abundant species of pacific salmon (chum salmon Oncorhynchus keta and pink salmon O. gorbuscha) and their consumption of zooplankton production were estimated for 2020–2022. Comparing productivity and grazing of the main zooplankton groups, there is concluded that pacific salmon consume a small portion from seasonal production of their prey, therefore, food competition between the species of pacific salmon is absent in the deep-sea waters.

Oxidative processes in the immunocompetent organs of pink salmon Oncorhynchus gorbuscha and chum salmon Oncorhynchus keta (Salmonidae) during the marine period

The influence of various factors on the fish body is reflected in changes in metabolic processes, including an imbalance of redox processes. The study of the level of oxidative processes and antioxidant protection in the tissues of aquatic organisms is often used in ecological and ecologicaltoxicological studies to assess the environmental conditions. Obtaining such data when conducting comprehensive ichthyological studies makes it possible to assess the features of adaptation to various habitat conditions, as well as the health status of fish. Mature pink salmon Onchorhynchus gorbuscha and chum salmon O. keta were caught in the summer of 2018 in the open waters of the northwestern Pacific Ocean (east of the Kuril Ridge) using a mid-water trawl during a trawl survey. Immediately after catching, liver, kidney and spleen samples were taken from the fish. Test tubes with organ tissue samples were frozen at –20 °С. Homogenates were prepared from thawed organ samples under laboratory conditions. The level of lipid peroxidation products and antioxidant activity was evaluated. As a result, intertissue and interspecific similarities and differences in the studied parameters of pink salmon and chum salmon during the marine period of life were established. The detected differences in indicators are presumably related to the structural and functional organization of the tissues and organs studied, as well as species characteristics. The results can be used to monitor population health and compare with closely related species.

A complete study of neuroendocrine regulation of fish reproduction. 4. Migration impulse as a starting mechanism of spawning

The participation of the hypothalamo-hypophysial neurosecretory system (NS) in the initiation of anadromous fish spawning migration was established on the basis of ecological-histophysiological analysis the results of histomorphological, immunohistochemical and electron microscopic studies for the first time. Activation of the neurosecretory products synthesis in the neurosecretory cells perikaryons and their excretion into the cerebrospinal fluid of the III brain ventricle in anadromous migrants forms at the beginning of the river spawning migration, spring-spawning: Russian sturgeon, stellate sturgeon and autumn-spawning: pink salmon and chum salmon, was shown. Transport and mass accumulation of neurosecretory products in the neurohypophysis were discovered at the same time. It is concluded, that the NS impacts a complex synchronous effect, which consists: firstly, in the neurotropic effect of nonapeptide neurohormones (NPh) on behavioral centers, which causes a dominant state of CNS excitation corresponding to the “Migration impulse”; secondly, in the violation of the long-term adapted marine “Pastured” level of osmoregulation; and thirdly, in the cessation of the well-known antigonadotropic effect of NPh, which contributes the organism transition to the energyconsuming energy type of metabolism. A comparative analysis (cross-analysis) of our own and literature data confirms the commonality and points to the universality of this metabolic mechanism for different forms of migration in fish ontogeny, which allows us to consider it as the most important aromorphosis type of phylogenetic adaptations, aimed at the species biological progress achieving. In the subsequent navigational mechanisms of homing, widely covered in the world literature, the leading role is played by the luliberinergic centers of the hypothalamus. The ecological diversity of these population-level mechanisms and the presence of straing in fish allow us to consider them as specializations of microevolutionary origin. The most promising direction for the further neuroendocrinological research development seems to be the analysis of the mechanisms of imprinting in connection with the enhancement of growth and survival of juveniles in the critical salinity medium, and for the purpose of homing control (development of the commercial fish-return biotechnology management) — the mechanisms of interaction between the NS and the luliberinergic centers in the neuroendocrine complex of CNS.

Pacific salmon monitoring results in Sakhalin Bay in 2023

The purpose: getting up-to-date information about the summer anadromous migration in 2023 and the qualitative indicators of Pacific salmon in the Sakhalin Bay (Khabarovsk Territory).Methods used: the work was carried out in accordance with the methods generally accepted in fisheries research.Result: Up-to-date information about the beginning of spawning approaches of pink salmon and chum salmon in the Sakhalin Bay has been obtained. The number of fishing areas and the dynamics of pink salmon catch in the southern, central and northern parts of the Sakhalin Bay are indicated. It is noted that the commercially significant approaches of pink salmon began from the southern part of the bay. The main biological characteristics of pink salmon and chum salmon suitable for the rivers of the Sakhalin Gulf in 2023 are given.Practical significance: Information on the migration of Pacific salmon in the Sakhalin Bay and their qualitative indicators will be used in the preparation of materials justifying the projected catch volumes in subsequent years, as well as in the regulation of Pacific salmon fishing in the Sakhalin Bay area.

Correction: Exploring predators of Pacific salmon throughout their life history: the case of Japanese chum, pink, and masu salmon

Correction: Exploring predators of Pacific salmon throughout their life history: the case of Japanese chum, pink, and masu salmon

The state of spawning grounds, a study of the biology and population dynamics of pacific salmon on Kunashir Island (Southern Kuril Islands) in 2023

The purpose: formation of scientific foundations for improving the efficiency of salmon management on Kunashir Island (South Kuril zone) to ensure the sustainable exploitation of the commercial stock of Pacific salmon, maintain the necessary level of their reproduction, preserve the habitat, as well as improve scientific approaches to forecasting commercial catches.Methods used: the work was carried out in accordance with the methods generally accepted in fisheries research.Result: information was obtained on the dynamics of Pacific salmon entry, the filling of spawning grounds and the state of reservoirs on Kunashir Island. The collection of materials characterizing the biological indicators of chum salmon producers was carried out. Statistical information was obtained on catches of chum salmon and artificial reproduction of salmon fish on Kunashir Island.Practical significance: information on the filling of the spawning grounds of Pacific salmon on Kunashir Island and the quality indicators of their producers will be used to substantiate fishing regulation measures. Data on the state of artificial and natural reproduction of Pacific salmon are intended to develop a strategy for the development of artificial reproduction on Kunashir Island.

On monitoring the downstream and spawning migrations of Pacific salmon on the Paramushir Island (Northern Kuriles) in 2023

The purpose: The main goal of the work is to study the conditions of migration of juveniles on the control Savushkina River and describe the state of Pacific salmon migrating off the coast of the Paramushir Island in 2023.Methods used: Research work was carried out using standard generally accepted methods.Result: During the research work, data were obtained on the timing and dynamics of migration of juvenile Pacific salmon. The results of monitoring the approaches of Pacific salmon producers are presented. Shown are data on the size-mass characteristics and age composition of chum salmon, sockeye salmon, coho salmon and pink salmon.Practical significance: The results of the research work carried out will be used in the preparation of materials for the projected volume of production (catch) of Pacific salmon for 2024 and subsequent years for the North Kuril subzone.