Chum Salmon Oncorhynchus Keta Research Articles

Evaluation of growth status using endocrine growth indices, insulin-like growth factor (IGF)-I and IGF-binding protein-1b, in out-migrating juvenile chum salmon

This study aimed to utilize circulating insulin-like growth factor binding protein (IGFBP)-1b as a negative index of growth to evaluate the growth status of juvenile chum salmon (Oncorhynchus keta) in the ocean. First, rearing experiments using PIT-tagged juveniles were conducted to examine the relationship of circulating IGFBP-1b with growth rate of the fish in May and in June. The serum IGFBP-1b level negatively correlated with fish growth rate in both months, suggesting its utility as a negative index of growth. Next, the growth status of out-migrating juveniles in northeastern Hokkaido, Japan, was monitored for 3 years using the growth indices. Serum levels of IGF-I, a positive index of growth, in fish collected from the nearshore zone were low in May and high in June of all years. Levels of serum IGFBP-1b showed a trend opposite to that of serum IGF-I. However, the IGF-I/IGFBP-1b molar ratios well reflected the seasonal and regional trends. These findings suggest that the juveniles in June left the nearshore area under better growth conditions. The present study also suggests that the use of multiple growth indices would improve the sensitivity and accuracy to evaluate the current growth status of out-migrating juvenile chum salmon.

Chum salmon migrating upriver adjust to environmental temperatures through metabolic compensation.

Ectotherms adjust their thermal performance to various thermal ranges by altering their metabolic rates. These metabolic adjustments involve plastic and/or genetic traits and pathways depend on species-specific ecological contexts. Chum salmon (Oncorhynchus keta) are ecologically unique among the Pacific salmonids as early-run and late-run populations are commonly observed in every part of their range. In the Sanriku coastal area, Japan, early-run adults experience high water temperatures (12-24°C) during their migration, compared with those of the late-run adults (4-15°C), suggesting that the two populations might have different thermal performance. Here, we found population-specific differences in the thermal sensitivities of metabolic rates [resting metabolic rate, RMR, and maximum (aerobic) metabolic rate, MMR] and critical temperature maxima. Using these parameters, we estimated thermal performance curves of absolute aerobic scope (AAS). The populations had different thermal performance curves of AAS, and in both populations high values of AAS were maintained throughout the range of ecologically relevant temperatures. However, the populations did not vary substantially in the peak (AAS at optimal temperature, ToptAAS) or breadth (width of sub-optimal temperature range) of the performance curves. The AAS curve of early-run fish was shifted approximately 3°C higher than that of late-run fish. Furthermore, when the data for RMR and MMR were aligned to the thermal differences from ToptAAS, it became clear that the populations did not differ in the temperature dependence of their metabolic traits. Our results indicate that chum salmon thermally accommodate through compensatory alterations in metabolic rates. Our results imply that metabolic plasticity and/or the effect of genetic variance on plasticity might play a pivotal role in their thermal accommodation.

Comparative Analysis of the Blood Plasma Metabolome of Negligible, Gradual and Rapidly Ageing Fishes

There are a number of different animals that belong to long- and short-lived species and show a various rate of ageing, providing an ideal model to investigate mechanisms of longevity. In this work, a metabolome profiling of blood plasma from fishes with various ageing rates—negligible (Pike Esox Lucius and Sterlet Acipenser ruthenus), gradual (Zander Sander lucioperca and Perch Perca fluviatilis) and rapid (Chum Salmon Oncorhynchus keta and Pink Salmon Oncorhynchus gorbuscha)—was assessed by means of direct infusion to quadrupole time-of-flight mass spectrometry. Of the 2056 distinct m/z features detected by a mass spectrometry metabolic profiling of blood plasma samples, fifteen metabolites in the classes of dipeptides, fatty acids, glycerolipids, phosphoethanolamines and phosphatidylcholines were significantly associated with ageing rate, independent of species differences. This is the first study of the metabolome of fishes with various ageing rate, and this untargeted approach highlighted the metabolic conditions that may serve to assess the ageing process.

Experimental evidence on prevention of infection by the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae in juvenile chum salmon using ultraviolet disinfection of rearing water.

In northern Japan, juvenile chum salmon Oncorhynchus keta (Walbaum) are released from hatcheries to enhance the fishery resource. Infections with ectoparasitic protozoans, particularly the flagellate Ichthyobodo salmonis and the ciliate Trichodina truttae, occasionally cause severe mortality among hatchery-reared juveniles. This study examined the susceptibility of the two parasites to wide-ranging UV irradiation (experiment 1) and then investigated whether UV disinfection of the rearing water using a commercial device was useful for preventing infections among juveniles in a small-scale rearing system over a 28-day period (experiment 2). In experiment 1, parasite mortality reached 100% with UV irradiation doses of ≥9.60×105 μW s/cm2 for I.salmonis and ≥8.40×105 μW s/cm2 for T.truttae. In experiment 2, disinfection of the rearing water at a UV irradiation dose of 2.2×106 μW s/cm2 succeeded in complete prevention of both parasites in the juvenile salmon. These results elucidate the minimum dose of UV irradiation for inactivation of I.salmonis and T.truttae, and demonstrate the usefulness of water disinfection using a commercial UV irradiation device to prevent infections by these parasites in hatchery-reared juvenile chum salmon.

Occurrence of Anisakid Nematodes in Walleye Pollock (Gadus chalcogrammus) Caught off the East Sea of Korea: Their Molecular Identification and Biological Implication

Walleye pollock (Gadus chalcogrammus) is one of the popular fish species in Korea and known to frequently harbor anisakid nematodes. Despite many papers regarding walleye pollock having been published, there is no information on the prevalence and distribution of anisakid nematodes from walleye pollock in Korean waters. We investigated 716 walleye pollock caught from Goseong, the East Sea of the Korean Peninsula during May 2015–December 2016. In total, 1,085 nematodes were collected and subsequently identified by PCR-RFLP analysis of internal transcribed spacer region of ribosomal DNA. The prevalence and mean intensity of anisakid nematodes was 63.6% (68/107) and 4.4 larvae/fish (297/68) in samples of 2015, and 21.5% (131/609) and 6.0 larvae/fish (788/131) in samples of 2016. The most abundantly isolated anisakid nematode was Anisakis simplex (Rudolphi, 1809) (73.5%, 798/1,085), followed by Contracaecum osculatum (Rudolphi, 1802) (3.1%, 34/1,085), Hysterothylacium aduncum (Rudolphi, 1802) (2.9%, 31/1,085), Anisakis pegreffii (Campana-Rouget and Biocca, 1955) (1.4%, 15/1,085), and a hybrid genotype (0.4%, 4/ 1,085). The mitochondrial DNA cox2 gene sequences of randomly selected A. simplex showed the highest similarity (99.5%–98.8%) with those from chub mackerel (Scomber japonicus) in Japan or from chum salmon (Oncorhynchus keta) in Korea. The mtDNA cox2 gene sequences of C. osculatum showed the highest similarity (99.0%) with those from bearded seals in Japan. All of these results give us clues to the geographical distribution, migration route and prey items of walleye pollock caught off Korea. Further extensive analyses will be necessary to get more information on the biology of Korean walleye pollock.

Body condition and reproductive status of chum salmon during homing migration in Otsuchi Bay, Japan, after the 2011 Great East Japan Earthquake and Tsunami

To understand how the earthquake and tsunami on March 11 2011 affected homing chum salmon Oncorhynchus keta in Otsuchi Bay, Japan, we monitored the body condition and reproductive status at the mouth of the bay in October, November, December, and January from 2012 to 2016. The average fork length in 2014 was larger than that in 2012 and 2015, due to the high proportion of 5- and 6-year-old salmon and the low proportion of 3- and 4-year-old salmon, possibly because of the decrease in the salmon fry released by the hatchery program after the disaster. Plasma estradiol-17β (E2) concentrations in females were high in October and November and declined in December and January, whereas plasma 11-ketotestosterone concentrations in males were consistently high throughout the sampling period. Plasma 17α,20β-dihydroxy-pregnen-3-one (17α,20β-P) increased in both sexes in December and/or January. These changes were consistently observed from 2012 to 2016; however, the rise in 17α,20β-P and decline in E2 levels in female salmon in December were conspicuous in 2013 and 2014, reflecting changes in age composition. These results suggest that the earthquake and tsunami temporarily affected the age composition and the physiological condition of chum salmon returning to Otsuchi Bay.

Advances in our understanding of the parr–smolt transformation of juvenile salmon: a summary of the 10th International Workshop on Salmon Smoltification

Advances in our understanding of the parr–smolt transformation of juvenile salmon: a summary of the 10th International Workshop on Salmon Smoltification

Optical and acoustic camera observations of the behavior of the Kuril harbor seal Phoca vitulina stejnegeri after invading a salmon setnet

It has previously been confirmed that Kuril harbor seals Phoca vitulina stejnegeri cause damage to the chum salmon Oncorhynchus keta setnet fishery along the east coast of Hokkaido, Japan, but the level of damage has increased markedly with the recovery of their population in recent years. In this study, we attached an optical camera (Trawl Camera) and a dual-frequency identification sonar (DIDSON) acoustic camera to a setnet to observe the behavior of seals as they invaded the setnet, and to determine the number of salmon inside the net, to help inform the development of modified fishing gear. Salmon were observed at all times during daytime with the Trawl Camera, while seals were only observed once. Observations using the DIDSON in its low-frequency mode confirmed that the behavior of seals became vigorous from around sunset to nighttime within the recording time (1530–2100 hours). Observations using the DIDSON high-frequency mode showed that the overall lengths and body widths of seals ranged from 1.0 to 1.6 m and 0.15 to 0.35 m, respectively, while their swimming speeds ranged from 0.4 to 2.6 m/s, increasing around sunset and declining into the night. These results imply that seals mainly invade the setnet from evening to nighttime to predate on salmon.

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

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

Variation in the numbers of adult returns and released fry for chum salmon Oncorhynchus keta caused by the Great East Japan Earthquake in Miyagi Prefecture

Variation in the numbers of adult returns and released fry for chum salmon Oncorhynchus keta caused by the Great East Japan Earthquake in Miyagi Prefecture

Comparison on Qualities of Chum Salmon (Oncorhynchus keta) Dorsal Muscles Cooked Using Superheated Steam and Other Heating Methods

Comparison on Qualities of Chum Salmon (Oncorhynchus keta) Dorsal Muscles Cooked Using Superheated Steam and Other Heating Methods

First report of growth rate of juvenile chum salmon Oncorhynchus keta captured in the Sea of Okhotsk offshore

The growth rate of 16 juvenile chum salmon Oncorhynchus keta (180–286 mm fork length) captured in the Sea of Okhotsk offshore during autumn 2002 was estimated using daily-incremental analysis of otoliths. The specimens originated from Hokkaido, Japan, and Sakhalin and Kamchatka, Russia. The average (range) of estimated mean daily growth in fork length was 1.19 (1.02–1.54) mm/day through the entire early ocean life and 1.05 (0.84–1.21) mm/day during the first 30 days after sea entry. These growth rates were higher than those reported previously for coastal resident or migrant juvenile chum salmon along the coast of Japan.

Experimental capture and handling of chum salmon reveal thresholds in injury, impairment, and physiology: Best practices to improve bycatch survival in a purse seine fishery

Recommendations and regulations regarding handling of non-target fish (i.e. bycatch) are often vague and subjective in commercial fisheries. Identifying how different components of capture influence the condition of discarded fish can help develop specific guidelines and best handling practices. Using an experimental approach, we modified the severity of capture stressors in commercial purse seine fisheries for Pacific salmon and monitored indices of injury and reflex impairment in chum salmon (Oncorhynchus keta), a species commonly discarded from these fisheries. Study fish were held for 5 or 10 days. Modeling of changes in injury and impairment sought to disentangle the latent effects of capture stressors and the role of sex and maturity. Thresholds in physiological responses to times (i) pursed in the net and (ii) air exposed on deck were also evaluated. Injury progressed throughout holding, was more extensive in females, and accelerated faster in less mature fish. Both crowding severity and set size (i.e. estimated number of fish caught) increased injury and impairment, effects that were exacerbated with time pursed. Physiological indicators of exhaustion also increased with time pursed and 15 min was identified as an important transition point, potentially representing the temporal limit to anaerobic exercise. The time between 1 and 3 min of air exposure was identified as being important to survival, and after 6 min of air exposure, endogenous energy stores may have become exhausted. Resulting recommendations include keeping nets loose during sorting, releasing fish prior to 15 min of being pursed, and keeping air exposure within the range of 1–2 min, or less. Additionally, females and less mature fish appear to be more susceptible to the injurious effects of capture.

Diverse Ecological Pathways of Salmon Nutrients Through an Intact Marine-terrestrial Interface

Based on five years of field studies (1992, 1993, 1994, 1998, 2000), I quantified bi-directional movement of salmon nutrients through an estuary, stream, and old growth forest in a large protected reserve on Haida Gwaii, British Columbia. In 1993, when most data were collected, about 6000 Chum Salmon (Oncorhynchus keta) entered the river of which 22% of the total biomass of senescent carcasses were swept downstream into the estuary and were scavenged by gulls (n = 350) and subtidal invertebrates. Of the 3700 salmon (10 000 kg) transferred by American Black Bear (Ursus americanus) to the riparian zone and partially consumed along the 800 m of stream channel, 5070 kg of salmon tissues abandoned by the bears were scavenged by Northwestern Crows (Corvus caurinus; n = 200) but mostly (4100 kg) by calliphorid blowfly larvae resulting in larval densities averaging 240/m2 throughout the riparian zone. Total nitrogen input to the soils from the combined effects of bear and scavenger activity as well as carcass input was 18 g/m2 within 10 m of the stream channel. δ15N of foliar tissues of Lanky Moss (Rhytidiadelphus loreus), Red Huckleberry (Vaccinium parvifolium), Salal (Gaultheria shallon), and Western Hemlock (Tsuga heterophylla) ranged about 15‰ to 20‰ among adjacent microsites in each species, with higher values occurring in salmon carcass zones. Total nitrogen in foliar tissues ranged from 1% to 2.4% among microsites and was best predicted by positive correlations with foliar 15N values and secondarily by presence/absence of salmon carcasses. This is the first study to integrate estuarine to riparian ecological processes in the cycling of salmonid nutrients and identifies a range of ecological baselines that can inform the multiple restoration programs underway in degraded watersheds in the North Pacific.

Eelgrass as Valuable Nearshore Foraging Habitat for Juvenile Pacific Salmon in the Early Marine Period

AbstractThe early marine period is a critical life history stage for growth and survival of anadromous juvenile Pacific salmon. The integrity of nearshore ecosystems where juvenile salmon reside and the capacity of these habitats to provide prey can thus influence overall salmon returns. Eelgrass Zostera marina beds in particular are considered critical nearshore habitat. By examining how juvenile salmon use this habitat during their early marine life, we gain insight into the trophic dynamics in these ecosystems and help gauge the effects of accelerating eelgrass loss and nearshore habitat development on juvenile salmon. This project investigated the role of eelgrass as juvenile salmon foraging habitat. We compared juvenile Chum Salmon Oncorhynchus keta and juvenile Chinook Salmon O. tshawytscha diets to prey availability in zooplankton tows and in epifaunal eelgrass samples across a gradient of eelgrass density in the Comox Estuary, British Columbia. Harpacticoid copepods dominated the diets of both juvenile Chum Salmon and Chinook Salmon and were found in abundance in eelgrass blades. We complemented diet analysis with carbon (δ13C) and nitrogen (δ15N) stable isotope analysis to examine the relative contribution of zooplankton, eelgrass epifaunal invertebrates, and terrestrial invertebrates to the diet of juvenile Chum Salmon. Juvenile Chum Salmon isotope ratios closely reflected those of eelgrass invertebrates, suggesting that eelgrass invertebrates made up approximately 80% of the diets of juvenile Chum Salmon. Our results highlight the value of eelgrass in providing nearshore foraging opportunities for juvenile salmon and suggest that eelgrass habitat protection and restoration may provide critical support for growth, thereby easing the transition of juvenile salmon from freshwater to the marine environment.

Energy allocation and feeding ecology of juvenile chum salmon (Oncorhynchus keta) during transition from freshwater to saltwater

Pacific salmon (Oncorhynchus spp.) populations near their northern range extent in the Arctic-Yukon-Kuskokwim region of Alaska have undergone major changes in population trajectory and illuminated the lack of basic information on juvenile ecology. This study fills information gaps on the early life history of chum salmon at northern latitudes. Energy allocation was examined in the context of distribution, feeding intensity, and diet during a critical life history period for a single cohort of juvenile chum salmon (O. keta) as they transition from freshwater to saltwater in Kuskokwim Bay from mid-May to early June. Juvenile chum salmon were primarily captured in the river mouth and plume. Energy density (kJ g−1 dry mass) was related to fork length, timing (day-of-year), and capture location in a general additive model. The smallest fish had slightly higher energy densities, but the change in energy density with fish size was minimal and consistent with allocating energy toward somatic growth rather than lipid storage. Fish captured earlier had higher energy density, likely reflecting the presence of residual yolk lipids during early migration. Fish captured in the river mouth and plume had higher energy densities. Feeding intensity was highest among small fish captured later within the river plume. Diet was dominated by surface prey (insects and calanoid copepods) rather than epibenthic harpacticoid copepods as commonly observed. These results provide the first data on energy allocation of juvenile chum salmon during a critical life history phase and suggest that somatic growth is prioritized over storing lipid at saltwater entry.

Current status of natural spawning of chum salmon Oncorhynchus keta in rivers with or without hatchery stocking on the Japan Sea side of northern Honshu, Japan

Information on the status of natural spawning is needed on the Japan Sea side of northern Honshu, Japan for ecosystem-based sustainable management of chum salmon resources. We conducted on-site visual surveys in October–December of 2015 and 2016 that targeted spawning chum salmon redds in all rivers > 5 km long (total 94 rivers) in Akita, Yamagata, Niigata (including Sado Island), and Toyama prefectures. The ratio of rivers found to host natural reproduction to the total number of surveyed rivers was 93.6% (44/47) in stocked rivers and 74.5% (35/47) in non-stocked rivers. These results show that there is a wide occurrence of natural reproduction of chum salmon in these rivers, regardless of the history of hatchery stocking. The density of spawning redds (number of redds/1000 m2) as an indicator of chum salmon escapements did not differ (P = 0.54) between stocked rivers (mean 3.5, N = 49) and non-stocked rivers (mean 2.4, N = 36),when rivers where no redds were observed were excluded from the analysis. These results suggest that chum salmon escapements into non-stocked rivers may not be negligible. Conservation measures for wild fish are needed in stocked and non-stocked rivers to promote enhancement programs based on natural reproduction.

Returns of Chum Salmon Released from Net‐Pens and Rivers in Eastern Hokkaido, Japan

AbstractThe effectiveness of net‐pen release of Chum Salmon Oncorhynchus keta in improving commercial coastal and river catches was examined by releasing marked fish from seawater net‐pens in Nemuro Bay or into the Nishibetsu River, eastern Hokkaido, northern Japan. Between 100,000 and 130,000 Chum Salmon fry were reared in the hatchery and marked by clipping either the left or right pelvic fin in 2006 and 2007; the fin clip was used to distinguish between net‐pen and river releases. Returning marked fish were surveyed in 17 set nets along the coast of Nemuro Bay, a small set net at the Betsukai Fishing Port, and a salmon weir in the Nishibetsu River 2–5 years after release. No differences were observed in the coastal catch period between the net‐pen‐released and river‐released fishes. Estimated coastal return rates of the net‐pen‐released fish (0.929% and 0.845%) were twice those of the river‐released fish (0.488% and 0.406%). However, six to seven times more river‐released fish (river catch rate = 9.591% and 7.513%) migrated upstream than net‐pen‐released fish (1.292% and 1.192%). Our results suggest that the use of marine net‐pens for Chum Salmon will not sustainably improve adult salmon catches in rivers, although it might increase coastal catches.

Detection and identification of furan fatty acids from fish lipids by high-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry

Using high-performance liquid chromatography coupled to high-resolution electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC/ESI-Q-TOF-MS), we have developed a new method for detection and identification of furan fatty acids (F-acids), which are widely distributed in living organisms and foods as minor lipid components and are known to have antioxidant and anti-inflammatory effects. For this purpose, total fatty acids prepared from the testis lipids of Japanese chum salmon (Oncorhynchus keta) were examined without any concentration or isolation of F-acids. In negative ESI mode, F-acids gave a prominent [M−H]− ion, by which individual F-acids could be detected and identified. High-resolution extracted ion chromatograms clearly showed the occurrence of five major F-acid homologs as already reported by GC/MS. The method was successfully applied to several fish samples and revealed the occurrence of F-acids for the first time in the two New Zealand fish, hoki (Macruronus novaezelandiae) and school shark (Galeorhinus galeus).

Quality Changes in Chum Salmon (Oncorhynchus keta) Caviar (ikura) Affected by Thermal Pasteurization, Storage Time, and Packaging Material

ABSTRACTChanges in quality parameters including pH, water activity, texture, and lipid oxidation were studied in pasteurized chum salmon (Oncorhynchus keta) ikura samples packaged using two films with different oxygen transmission rates (OTR) (40 and 62 cm3·m−2·day−1; F-40 and F-62), during 60 days storage at 4°C. No significant differences in pH and water activity (aw) were observed between ikura packaged using two different films with different OTR (P > 0.05). However, compared to the first day of study, water activity decreased significantly in ikura (P < 0.05). Ikura thiobarbituric reactive substance (TBARS) in the pouches significantly increased during the storage at 4°C (P < 0.05). Both pouches showed similar trends in TBARS until day 29, while after day 29, ikura packaged in F-62 (OTR = 62 cm3·m−2·day−1) showed a significant increase in TBARS compared to F-40 with less OTR (P < 0.05). The texture of ikura became softer compared to the first day; however, no significant difference was observed between the ikura samples in two pouches (P < 0.05). The quality changes of ikura measured during storage indicate that packaging ikura in a lower OTR film would provide greater quality retention than one with higher OTR.