Chum Salmon Oncorhynchus Keta 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.

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

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.

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.

Biological characteristics for the spawners of chum salmon Oncorhynchus keta caught in the Indigirka River in 2023

Biological characteristics for the spawners of chum salmon Oncorhynchus keta caught in the Indigirka River in 2023

Characteristics of adult chum salmon Oncorhynchus keta from the commercial stock at Iturup Island in 2023

Characteristics of adult chum salmon Oncorhynchus keta from the commercial stock at Iturup Island in 2023

Efficacy of Topical Application of Chum Salmon (Oncorhynchus keta) Skin-derived Collagen Extracts in Improving Oral Traumatic Ulcer Healing

Background: Traumatic ulcer is a wound on the oral mucosa that often causes pain and impaired eating function. Healing of these wounds takes a long time and can interfere with an individual’s daily activities. One therapeutic approach that is being developed is the use of topical application of chum salmon skin-derived collagen extract. Collagen is the main component of the extracellular matrix and plays a major role in wound healing. The skin of chum salmon (Oncorhynchus keta) contains collagen that is effective for the treatment of wounds. Aim: The aim of this study was to evaluate the effectiveness of topical applications of chum salmon (O. keta) skin-derived collagen extracts in improving the healing of traumatic ulcers through analysis of neutrophil and macrophage numbers and collagen density. Materials and Methods: Twenty-four male Wistar rats were randomly divided into four groups consisting of six rats each. The labial mucosa of the lower lips of the rats was injured with heated amalgam stoppers to create oral traumatic ulcers. Group 1 was a control group; in Groups 2, 3, and 4, 25%, 50%, and 75% of collagen extracts from chum salmon (O. keta) skin were applied topically once a day for 7 days, respectively. The neutrophil and macrophage numbers were observed by hematoxylin and eosin staining. Masson’s Trichrome staining was used to analyze the collagen density. Data were analyzed using one-way analysis of variance and continued with post hoc least significant difference tests. Significance is considered if P < 0.05. Results: The oral traumatic ulcers gradually healed until day 7. The number of neutrophils and macrophages was significantly decreased in the treatment groups, and collagen density was increased, compared to the control group (P < 0.05). The decrease of neutrophil and macrophage numbers occurred significantly with the increased collagen extract concentrations (P < 0.05). Collagen density also increased significantly with the increased collagen extract concentrations (P < 0.05). Conclusion: Topical applications of chum salmon (O. keta) skin-derived collagen extracts accelerate the healing process of oral traumatic ulcers by decreasing neutrophil and macrophage numbers and increasing collagen density.

Tide impacts the dispersion of eDNA from nearshore net pens in a dynamic high‐latitude marine environment

AbstractEnvironmental DNA (eDNA) is increasingly used to detect animals in aquatic habitats, but uncertainty remains about the relationship between the present location of an animal relative to eDNA detections. In marine environments, physical characteristics—such as tides and currents—can influence the distribution of eDNA. In this study, we make use of hatchery net pens containing >46 million juvenile chum salmon (Oncorhynchus keta) in nearshore Southeast Alaska to test for dispersion of eDNA and the effects of tide. Initially, we collected and filtered surface water every 80 m along a 2 km transect to test eDNA attenuation over surface distance during incoming and outgoing tides on a single day. The following year, we sampled at three depths (0 m, 5 m, and 10 m) every 500 m along the same transect as well as along a perpendicular transect, to understand dispersion by depth and in additional directions. Chum salmon eDNA was quantified using species‐specific qPCR. We found that surface samples showed a consistent signal of decreasing chum salmon eDNA across the 2 km transect (R2 = 0.665), with the majority of eDNA detections within 1.5 km of the net pens. Tide had a significant effect, resulting in higher concentrations of chum DNA throughout the transect during incoming tide and a steeper decline in eDNA over distance during outgoing tide (R2 = 0.759). Depth affected chum salmon DNA concentration, with the majority of eDNA at the surface and a decreasing amount of DNA with increasing depth. This study addresses one of the critical knowledge gaps in applying eDNA to marine fisheries management by providing empirical evidence of eDNA dispersion and demonstrating that most eDNA detections are likely from nearby individuals that are either currently or recently present. Yet even at close proximity, eDNA signal strength fluctuates and depends on the physical environmental variables during a given sampling event.

Complete genome sequence and potential pathogenic assessment of Flavobacterium plurextorum RSG-18 isolated from the gut of Schlegel's black rockfish, Sebastes schlegelii.

Flavobacterium plurextorum is a potential fish pathogen of interest, previously isolated from diseased rainbow trout (Oncorhynchus mykiss) and oomycete-infected chum salmon (Oncorhynchus keta) eggs. We report here the first complete genome sequence of F. plurextorum RSG-18 isolated from the gut of Schlegel's black rockfish (Sebastes schlegelii). The genome of RSG-18 consists of a circular chromosome of 5,610,911 bp with a 33.57% GC content, containing 4858 protein-coding genes, 18 rRNAs, 63 tRNAs and 1 tmRNA. A comparative analysis was conducted on 11 Flavobacterium species previously reported as pathogens or isolated from diseased fish to confirm the potential pathogenicity of RSG-18. In the SEED classification, RSG-18 was found to have 36 genes categorized in 'Virulence, Disease and Defense'. Across all Flavobacterium species, a total of 16 antibiotic resistance genes and 61 putative virulence factors were identified. All species had at least one phage region and type I, III and IX secretion systems. In pan-genomic analysis, core genes consist of genes linked to phages, integrases and matrix-tolerated elements associated with pathology. The complete genome sequence of F. plurextorum RSG-18 will serve as a foundation for future research, enhancing our understanding of Flavobacterium pathogenicity in fish and contributing to the development of effective prevention strategies.

Correction: Growth rate characteristics of juvenile chum salmon Oncorhynchus keta originating from the Pacific coast of Japan and reaching Konbumori, eastern Hokkaido

Correction: Growth rate characteristics of juvenile chum salmon Oncorhynchus keta originating from the Pacific coast of Japan and reaching Konbumori, eastern Hokkaido

Critical periods in the marine life history of juvenile western Alaska chum salmon in a changing climate

Recent precipitous declines in western Alaska chum salmon Oncorhynchus keta returns followed unprecedented warming in the northern Bering Sea ecosystem. To better understand the role of anomalous events on the early marine ecology of juvenile chum salmon in the northern Bering Sea, we utilized time-series observations over a 17 yr period (2003-2019) of sea surface temperature (SST) and juvenile chum salmon size (length and weight), diet, energy density, and relative abundance. Particular attention was paid to more recent (2014-2019) years in which there was unprecedented loss of sea ice in the northern Being Sea in comparison to previous warm (2003-2005) and cold (2006-2013) periods. Our findings indicate significant correlations between SST and juvenile chum salmon relative biomass (positive) and energy density (negative). We found that juvenile chum salmon were larger during warm periods than during cold periods; however, there was no significant difference in their length and weight between the warm periods. Juvenile chum salmon fed on lower quality prey during warm periods than during cold periods, with an increase in the proportion of lower quality prey during the recent warm period. Consequently, the energy density of juvenile chum salmon was also lower during warm periods than during cold periods, with the lowest values occurring during the recent warm period (2014-2019). These results identify a shift in energy allocation and/or prey quality of juvenile chum salmon with temperature and illustrate how marine ecosystems have altered the nutritional condition of juvenile chum salmon prior to winter, when energy reserves are considered critical to survival.

Massive stocking of chum salmon (Oncorhynchus keta) fry fattens non-native brown trout (Salmo trutta) in Hokkaido, Japan.

In Japan, stocked chum salmon (Oncorhynchus keta) fry may have become the perfect prey for non-native brown trout (Salmo trutta), which are popular targets of anglers. If this is the case, fry stocking which is intended to boost commercial fishing may be helping to sustain the populations of an invasive predator. We used dietary and biochemical analyses to examine whether brown trout quickly restore their nutritional status following wintertime declines by preying upon chum salmon fry that are stocked in spring. We targeted six rivers in Hokkaido, Japan, three with fry stocking and three without. Changes in brown trout condition factor, triglyceride contents in muscle and serum, serum insulin-like growth factor-1 (IGF-1; an indicator of short-term growth), and docosahexaenoic acid (DHA; an essential fatty acid abundant in fish) content in muscle were examined between before stocking and during the stocking period in the six rivers. Dietary analysis showed that brown trout preyed on fry during the stocking period in all stocked rivers. Their nutritional status tended to be higher during the stocking period than before stocking in stocked rivers, but not in unstocked rivers. These results suggest that the massive stocking of chum salmon fry provides brown trout with the perfect prey to quickly restore their nutritional status and fuel increased growth; this may therefore be a controversial issue among stakeholders.

On fecundity of chum salmon <i>Oncorhynchus keta</i> in the commercial herd at Iturup Island

Absolute fecundity of chum salmon Oncorhynchus keta is investigated for the commercial herd dwelled at Iturup Island. Currently, the herd is formed mostly by fish of hatchery origin but has retained the same species and regional features that distinguished it when it was formed mainly due to natural spawning. The value of absolute fecundity is determined for 3833 females and ranges from 769 to 4400 oocytes. For the fish of two dominant age groups (3+ and 4+), this number usually decreases with age, with the exception of particularly large older fish with greater fecundity. Same factors that promote abundance of hatchery fish in the herd also contribute to decreasing of abortive processes in the ovaries, therefore the absolute fecundity correlates closely and positively with the catch of chum salmon in the coastal waters.

Gametogenesis of pacific salmon. 2. Chum salmon <i>Oncorhynchus keta</i>

All available information on gametogenesis of chum salmon Oncorhynchus keta cited in scientific literature is summarized. The phases of indifferent development and sex differentiation are overviewed, specific features of the testes and ovaries development are noted, forming of fecundity is analyzed.

Influence of Salinity on the Survival Rate of Fertilized Chum Salmon (Oncorhynchus keta) Eggs

Chum salmon (Oncorhynchus keta) exhibit a remarkable ability to adapt to changes in salinity during their life cycle. However, the fertilized egg stages are sensitive to salinity, affecting ontogeny and hatching. This study investigated the effect of salinity (0, 1, 3, and 5 PSU) on the survival of two developmental stages (<1 day after fertilization and <1 day after the eyed-egg stage) of fertilized eggs. Based on the experimental results, we assessed the spawning ground environment using the in situ salinity data of the Namdae River from 1997 to 2002, where the largest number of salmon in Korea migrate to spawn. Survival of the <1-day-old fertilized eggs decreased sharply at 3 PSU or more, and all eggs died at 5 PSU. Hatching of the eyed-egg stage occurred under all environmental conditions. After 2010, the salinity of the layer of water in contact with the sediment in the lower reaches of the river increased (>6.9 PSU) with the frequency of high waves. Overall, the function of the lower river in spawning and hatching is weakening. This study enhances our understanding of the effects of climate change, including increased wave activity, on salmon spawning grounds.

Juvenile feeding of pacific salmon in the lower part of the Pymta River in May–September, 2019–2020

Comparative analysis of feeding in the lower part of the Pymta River (West Kamchatka) is carried out for juvenile Pacific salmon individuals of different age representing four species with a short or long freshwater period of their life cycle (chum salmon Oncorhynchus keta, sockeye salmon O. nerka, coho salmon O. kisutsch and Chinook salmon O. tschawytscha) for the period from May to September in 2019–2020. Spectra of food, stomach fullness indices and degree of food similarity between juveniles of different species and age classes are demonstrated. The feeding in all mentioned species was biotop-dependent. There were frequent changes in the composition of the forage consumed in the course of observations of Pacific salmon juveniles in the Pymta River basin, and the indices of stomach fullness varied extensively. The results of the analysis indicate extensive trophic adaptability in juvenile Pacific salmon in the ecosystem of the Pymta River.

The Status of the Chum Salmon (Oncorhynchus keta) Commercial Stock and Prediction of its Size off Iturup Island

The Status of the Chum Salmon (Oncorhynchus keta) Commercial Stock and Prediction of its Size off Iturup Island