Rivers In Hokkaido Research Articles

Literatur review : protozoa parasit di air sungai

River water is potentially unsafe and polluted, which can cause serious infections. Waterborne infections are a major cause of global mortality and morbidity. In cases of diarrhea, this research aims to identify the types of parasitic protozoa and their distribution in waterways in Japan and Indonesia. This research reviews literature by collecting data from various sources, such as books, national and international scientific journals. The articles analyzed are original articles relating to protozoa in river water from both countries. In Japan, protozoa such as Henneguya were found in the Omoi River and Cryptosporidium parvum in several rivers in Hokkaido. In Indonesia, species such as Codonellopsis sp., Favella sp., Tintinnopsis sp., and Codonella sp. are found. in Sorong Regency, as well as various other types in West Bandung, Central Sulawesi and South Kalimantan. The diversity and distribution of protozoa is influenced by water quality, physical conditions, water chemistry, and human activities. This research can provide information regarding protozoa which can act as bioindicators of water quality. The presence and diversity of protozoa can provide an indication of the health condition of aquatic ecosystems. As a result, conservation efforts and management of aquatic ecosystems can be improved.

Linkage between spatiotemporal distribution of environmental DNA and phenological activity in an amphidromous fish, ayu Plecoglossus altivelis altivelis, in a river located in its northernmost distributional area.

Environmental DNA (eDNA) is a promising tool for the continuous monitoring of fish ecology and diversity. However, its potential for describing the phenological activity of fish has rarely been examined. This study aimed to elucidate a linkage between the spatiotemporal distribution of eDNA and the phenology of an amphidromous fish, ayu Plecoglossus altivelis altivelis, in a river in Hokkaido, Japan, which is its northernmost distributional area. A significant positive correlation between eDNA concentration and catch per unit effort of P. a. altivelis in the river confirmed the use of eDNA as a surrogate for the abundance of P. a. altivelis. eDNA of P. a. altivelis was first detected in late April on a sandy beach adjacent to the river mouth. Subsequent to its first detection at the lowest site in the river in early May, eDNA spread throughout the river, indicating the upstream migration of P. a. altivelis. Spawning activity was also represented by a rapid increase in eDNA concentration and its surge at night in the lowest reaches of the river during September and October. These results suggest that upstream migration and spawning primarily commenced when the water temperature reached 10°C and decreased below 20°C, respectively. This observation is consistent with the behavioral responses observed in P. a. altivelis populations from other regions of Japan. Consequently, this study demonstrated that eDNA distribution was closely linked to the phenological activity of P. a. altivelis and that eDNA is a powerful tool for studying the phenology of migratory fishes.

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.

Non-native fish species expand tacitly but rapidly toward upstream oxbow lakes along the longitudinal gradient

The introduction of non-native fish species poses a threat to native assemblages in floodplain systems. Establishing oxbow lake-based conservation areas has been proposed as a practical approach to mitigate this threat. Previous studies have extensively discussed the effects of lateral connectivity between oxbow lakes and main channels on fish communities but overlooked the spatial longitudinal gradients of oxbow lakes on a broader spatial scale. Over the course of about ten years, the temporal changes in fish community diversity were estimated in 28 oxbow lakes along the Ishikari River in Hokkaido, Japan. The associations between these temporal variations and the locations of the lakes were then explored along a longitudinal spatial gradient. The results showed that upstream oxbow lakes underwent mild alterations to their species composition and maintained a high level of native uniqueness. In contrast, downstream oxbow lakes experienced intense species turnover and increased non-native fish diversity. Additionally, the dominance of non-native fish in downstream areas rapidly expanded upstream to a location 110 km from the source of the Ishikari River over the decade. It is emphasized that the lakes in the upper reaches were the only remaining refuges for native fish and should be prioritized in conservation efforts. Our study proposes the application of location and species contributions to regional community heterogeneity as indicators for highlighting native fish conservation areas.

Lateral and longitudinal flight dispersals of a stonefly, Alloperla ishikariana (Plecoptera, Chloroperlidae), from the hyporheic zone in a gravel-bed river in Japan

The life-history traits of amphibitic insects are not well understood. These insects inhabit saturated interstitial areas below the riverbed (hyporheic zone) at the larval stage, mate in terrestrial habitats, and return to rivers for oviposition, but there is no knowledge concerning their dispersal characteristics. We sought to address this by examining how far amphibitic insects disperse away from the channel (laterally) and along upstream or downstream (longitudinally) in a gravel-bed river. Alloperla ishikariana was selected as the focal species because it numerically dominates other amphibites in an 18-km study segment of a 4th-order gravel-bed river in Hokkaido, Northern Japan. Malaise traps were set at various distances from the channel towards the riparian forest to estimate lateral dispersal distances. An elevated stable nitrogen isotope ratio in downstream larvae, caused by the influence of effluent from a wastewater treatment plant, was used to assess longitudinal dispersal by identifying and tracking adult movements. Laterally, 50th and 90th percentile dispersal distances were 11.66 and 35.09 m for female A. ishikariana and 20.59 and 59.20 m for male, respectively; this overlapped with distances previously estimated for other aquatic benthic taxa. Longitudinally, 50th and 90th percentile dispersal distances were 0.74 and 1.43 km for female and 3.11 and 7.87 km for male, respectively. Alloperla ishikariana had one of the longest upstream traveling distances compared with other aquatic insects, and the longest among Plecoptera taxa known thus far where male exhibited a greater dispersal distance. A higher number of adults demonstrated upstream movement, suggesting an upstream bias in the longitudinal dispersal of A. ishikariana. Overall, amphibitic stoneflies did not exhibit distinct dispersal characteristics compared with the results of previous reports on presumably benthic taxa. Our findings support an improved visualization of a multi-dimensionally connected river ecosystem in terms of material flow, including vertical connectivity.

An Environmental DNA Survey on Distribution of an Endangered Salmonid Species, Parahucho perryi, in Hokkaido, Japan

For protecting endangered species, precise understanding of their distribution is crucial. However, it is often very difficult to estimate at a large scale with conventional methods (e.g., casting nets or electrofishing for aquatic species) because of their low densities in the wild. Sakhalin taimen (Parahucho perryi) is one of the largest and most critically endangered freshwater salmonid fishes in the world. In this study, we applied an environmental DNA (eDNA) detection system for this species to 120 rivers in Hokkaido, the second largest main island of Japan. We successfully detected eDNA from Sakhalin taimen in seven rivers (5.8%). Although these rivers were widely distributed across the island, more than 95% of the total amounts of eDNA were detected from region-A and -I, indicating that local populations in the other regions of Hokkaido are very small and on the brink of extinction. In addition, principal component analyses based on the eDNA-based estimation of Sakhalin taimen distribution and GIS revealed their distribution determinants including limited topographic relief of watershed as well as presence of wetlands and lagoons. Our results suggest that eDNA-based detection systems are an efficient means of monitoring the population status of endangered freshwater species at large scales.

Stable isotope ratios of emergent adult aquatic insects can be used as indicators of water pollution in the hyporheic food web

Bio-assessment protocols for the subsurface domain of river channels (i.e. hyporheic zone) are scarce despite of the known importance of its ecological function in river ecosystems. The larvae of the Alloperla ishikariana Plecoptera species inhabit the hyporheic zone. Therefore, we examined whether emergent adult A. ishikariana could serve as proxy indicators of the effects of pollution in the hyporheic food web. The study site comprised a 15-km stretch of a gravel bed river in Hokkaido, Japan, from which all invertebrates were collected from the riverbed at a depth of 30–50 cm, and emergent A. ishikariana adults were sampled in riparian zones. Water quality changed gradually along the river owing to the effects of a wastewater treatment plant and surrounding land uses. Nitrogen and carbon stable isotope ratios (SIRs) of epilithic biofilms, hyporheic particulate organic matter (POM), benthic POM, and invertebrates were used to determine the major basal carbon sources, the effects of water pollution on the hyporheic zone, and the trophic positions of dominant invertebrates. Generalized linear (mixed) models were used for statistical testing and modeling. Amphipoda and the larvae of A. ishikariana were considered as top predators and secondary consumers in the hyporheic food web, respectively. The observed similarity in water quality between the hyporheic and surface water suggested a large degree of hydrological exchange between the two zones, and resulted in positive increases in the nitrogen SIRs of hyporheic invertebrates, including A. ishikariana larvae, in proportion to nitrate levels in the surface water. The nitrogen SIRs of A. ishikariana adults were significantly correlated with the nitrogen SIRs of their larvae within the same location (adjusted R2 = 0.78), indicating that emerged adults can provide information on the longitudinal variability of the effects of synthetic nitrogen. In contrast, the carbon SIRs of adults did not predict those of their larvae, possibly reflecting the diverse feeding habitats of larvae. Overall, we demonstrated that adult aquatic insects emerging from the hyporheic zone can be used as indirect indicators of pollution-associated nutrient assimilation as well as the spatial heterogeneity of dietary carbon resources in hyporheic food web.

Coupled benthic–hyporheic responses of macroinvertebrates to surface water pollution in a gravel-bed river

Interactions between the hyporheic and benthic zones play a vital role in maintaining the integrity of river ecosystems, but simultaneous assessments of hyporheic and benthic macroinvertebrate responses to surface water pollution are limited. We examined how hyporheic (50 cm below surface) and benthic (surface) invertebrates responded to water pollution that originated from a point source (wastewater treatment plant) in a gravel-bed river in Hokkaido, Japan. Dissolved nutrient levels and algal biomass were significantly higher at sample sites down- than upstream of the point source. Furthermore, nitrate concentrations increased gradually from up- to downstream sites, which suggest the presence of diffuse pollution sources in the surrounding areas. Closely synchronized fluctuations of water temperature and similar water quality in the surface and hyporheic zones indicated that the hyporheic zone was highly hydrologically interactive with the surface water. Chloroperlidae (mostly Alloperla ishikariana) had a disproportionately high abundance in the hyporheic zone relative to the benthic zone, regardless of the surface water quality. Numerically dominant invertebrate taxa increased in abundance below the point source of pollution in both the benthic and hyporheic habitats. High N stable isotope ratios (SIR) of the invertebrates in both habitat types indicated that invertebrates assimilated anthropogenic N via the ingestion of pollution-contaminated food resources. End-member mixing analyses based on C SIR demonstrated that assimilation of anthropogenic N occurred because of the increase in available food resources originating from the biofilm. The trophic structure of invertebrates changed less markedly in the hyporheic zone than in the benthic zone, suggesting that the hyporheic assemblage was less sensitive than the benthic assemblage to the changes in surface water quality. Overall, our findings showed that the numeric responses of the invertebrate assemblage to anthropogenic changes in surface water quality were similar and coupled between the benthic and hyporheic zones.

Sulfur speciation in growth layers of shell cross section of the long-lived bivalve Margaritifera laevis using synchrotron spectromicroscopy analysis

To reliably utilize the information on growth and environment stored within the hard carbonate shells of long-lived bivalves, it is necessary to accurately count the annual growth lines from their shell cross-sections. In this study, we investigated the relationship between the distribution of minor elements and visual lines in the shell cross-sections of the long-lived mussel Margaritifera laevis collected from the Chitose River in Hokkaido, Japan. The distribution of minor elements, such as sulfur (S), phosphorus (P), strontium (Sr), magnesium (Mg), and sodium (Na), in a cross-section of the umbo was determined by X-ray fluorescence analysis using synchrotron soft X-ray radiation. The chemical properties of S and P were analyzed in-situ using soft X-ray photoabsorption spectroscopy, and the chemical form dependence of S distribution was determined by speciation mapping. In addition, the annual and disturbance lines were visualized by staining shell cross-sections. Our results showed that the distribution of reduced S (i.e., SC and SH) corresponded to the annual lines, whereas the distribution of oxidized S (i.e., SO42−) corresponded to the disturbance lines. Overall, this study revealed that speciation analysis of S in shell cross-sections can be used to determine the origin of visual lines in chronological studies.

北海道厚真（あつま）川を遡上した2011年東北沖地震津波による堆積物の形成過程および津波波形との対応

北海道厚真（あつま）川を遡上した2011年東北沖地震津波による堆積物の形成過程および津波波形との対応

Reversal of Secondary Flows in a Sharp Channel Bend

Field observations of the currents at a bending channel in the Abashiri River in Hokkaido, Japan have revealed an unexpected secondary circulation during flood tide with near-bed and near-surface currents toward the outer and inner banks of the bend, respectively. The direction of these cross-stream currents was reversed at the end of flood tide. The occurrence and shutdown of these observed unexpected secondary circulation were further investigated through the shape of the along-channel velocity profile by using a theoretical solution based on the steady-state momentum equation and the Stokes's second problem for oscillating flow. Also, an advanced numerical model was used to quantify the unexpected secondary flow. It was shown from the theoretical analysis that vertical advection plays a great role in the momentum balance affecting the direction of secondary flows. The typical secondary flow was found to occur throughout ebb tide with a pronounced near-surface maximum velocity profile. Whereas, during flood tide, the longitudinal velocity profile was characterized by a near-bed and mid-depth maximum, resulting an upwelling flow near the outer bank. These findings were reconfirmed by numerical simulations that were conducted for the entire estuary.

Profiles of circulating insulin-like growth factor-I during smoltification of masu salmon reared under different conditions

We compared profiles of serum insulin-like growth factor (IGF)-I levels during smoltification of masu salmon reared under different environments, hatcheries and growth histories. Masu salmon from the Kenichi River in Hokkaido showed a sharp increase in serum IGF-I from April to May, followed by a peak of gill Na+,K+-ATPase (NKA) activity. Fish at Kumaishi Hatchery had an IGF-I profile similar to that of the river fish, while the increase in gill NKA was lower. At Shimamaki Hatchery, interval feeding during winter appeared to suppress the spring IGF-I peak. At Kumaishi Hatchery, a difference in size during smoltification affected IGF-I levels at release, but the numbers of adults that returned to the release site were not significantly different. In the following year, three release groups differing in winter size and/or spring growth (Large-High, Large-Low and Small-High) were created. Large-High and Small-High fish showed a higher IGF-I peak than Large-Low fish in April, while smolt-to-adult return of Large-High fish was highest. These results suggest that in smolting masu salmon in freshwater, circulating IGF-I level alone is not a predictor of long-term survival in seawater. However, since growth history in freshwater affected the smolt-to-adult return, optimizing rearing conditions is a critical component of hatchery releases for masu salmon.

Estimating the size of the spawning population and evaluating environmental controls on migration for a critically endangered Asian salmonid, Sakhalin taimen

Sakhalin taimen Parahucho perryi, an east Asian fish noted to be one of the largest salmonids in the world, is threatened throughout its range in northern Japan and neighboring Russian Federation. We report here on the first effort to enumerate and characterize the spawning run of a river population. We applied sonar and video methods in a tributary of the Sarufutsu River in Hokkaido, Japan, and evaluated environmental controls on migration. Over two years we estimated the tributary population to range from 335 to 425. We found passage rate by our site to increase with temperature and decrease with river discharge, and migratory cues were reinforced by strong diel fluctuations in environmental conditions. Finally, we report evidence of males arriving early to the spawning grounds in this species. Given our results and data on the recreational fishery, we conclude that a substantial number of individuals in the population are affected by angling, underscoring the need to establish fishing regulations. Further, our study indicates passage success can vary over the migration period, and efforts at modifying or removing impediments, and devoting more research to factors controlling passage, could ultimately improve the status of this species.

Japanese chum salmon stock enhancement: current perspective and future challenges

This study reviews the present status of the Japanese chum salmon Oncorhynchus keta stock enhancement program and considers the ecological sustainability of wild populations while providing fishery production, exemplified by the hatchery-based Kitami region set net fishery. The return rate and the number of returns have been historically high in the Sea of Okhotsk, but have decreased in other regions since 2005. Natural spawning of chum salmon occurred in at least 160 rivers in Hokkaido. The genetic diversity of Japanese chum salmon was similar to or higher than that of other Pacific Rim populations. Numbers of alleles were high at microsatellite loci, but the loss of rare haplotypes was observed in all populations. The estimated Ne/N ratio for the Kitami region was >0.15 % including hatchery and wild fish under the present high fishing pressure. Four regional populations were inferred in Hokkaido, however, genetic differentiation was weak and some river-populations were nested. Substantial changes in run timing were observed, but it has recovered gradually owing to the recent practice of escapement. Our analyses highlight the importance of juvenile quality and the vital roles of escapements in enhanced and non-enhanced rivers. New research is needed to minimize the genetic risks associated with hatchery programs.

Five Trophically-transmitted Parasites from Adult Arctic Lampreys Lethenteron camtschaticum (Petromyzontiformes: Petromyzontidae): Biological Indicators of the Host's Marine Life as a Predator

Five species of helminth endoparasite (two digeneans, Brachyphallus crenatus (Rudolphi, 1802) and Lecithaster gibbosus (Rudolphi, 1802); two cestodes, plerocercoids of Nybelinia surmenicola (Okada in Dollfus, 1929) and a tetraphyllidean; and an acanthocephalan, post-cystacanths of Bolbosoma sp.) were found in adults of Arctic lampreys Lethenteron camtschaticum (Tilesius, 1811) arriving in the lower part of the middle reaches of a river in Hokkaido, Japan, for spawning after a period of growth in the sea. These parasites are all common species previously reported from various marine fishes in the North Pacific and all have complex life-cycles involving host-to-host transmission via a predator-prey relationship. To have become infected with these food-borne parasites, Arctic lampreys need to have ingested various body parts of infected prey fishes at sea. Consequently, the endoparasites recovered suggest that the Arctic lamprey has a role as a predator in marine ecosystems.

Information and communications technology for the construction of underground powerhouse cavern in the Kyogoku hydropower project

This paper presents the outline of observational construction scheme employed for underground cavern construction, and of the Information and Communications Technology (ICT) as a technological tool to facilitate the observational construction. The Hokkaido Electric Power Co., Inc. has been conducting a Hydropower Project in Kyogoku, on the Pepenai and Bihinai tributaries of the Shiribetsu River in Hokkaido, Japan. The Kyogoku Hydropower Plant is the first pumped-storage hydroelectric power plant that was built by the Power Co. It will output a maximum power of 600 MW, with an effective head of 369 m and a maximum water usage rate of 190.5 m 3 /s. The power plant is housed in a large underground cavern of which the dimension is 45.8 m high, 24.0 m wide, and 141.0 m deep. Its total excavated volume is 116,000 m 3 and the maximum cross-sectional area amounts to 1000 m 2 . The geology in the vicinity of cavern belongs to a so-called “Green Tuff” region of the Miocene period, primarily composed of tuff breccia. The geology presents considerable challenges, including a distribution of tuff blocks and two major fault zones with a low uniaxial compressive strength, presumably due to faulting and hydrothermal alteration. Therefore, observational construction method was applied to the project in conjunction with other ICT-solutions, and the actual rock response during excavation was examined in order to ensure the optimum structural support for the cavern and construction safety.

Historical and Current Hatchery Programs and Management of Chum Salmon in Hokkaido, Northern Japan

The hatchery program for chum salmon in Hokkaido, northern Japan, constitutes one of the largest salmon hatchery programs in the world. The hatchery program has been conducted for over 120 years, and returns of chum salmon rapidly increased during the last quarter of the 20th century. Since the 1990s, chum salmon returns to Hokkaido have remained at a historically high level, although different fluctuation trends have been observed among regions within Hokkaido. Although such intensive hatchery programs have been conducted for more than 25 generations, there has been no evidence indicating any decline of genetic diversity. The hatchery program for chum salmon in Hokkaido is successful in increasing commercial catches and will likely be the main management tool in future. However, information on naturally spawning chum salmon in Hokkaido remains scarce. Assessment of naturally spawning populations recently commenced, and it has been revealed that naturally spawning chum salmon populations remain in many rivers in Hokkaido. For future management, monitoring chum salmon of both hatchery and natural origin is important, and a novel strategy that accounts for the enhancement of commercial stocks and the coexistence of hatchery programs and wild populations should be established in Japan.

Olfactory Homing of Chum Salmon to Stable Compositions of Amino Acids in Natal Stream Water

Many attempts have been made to identify natal stream odors for salmon olfactory homing. It has recently been hypothesized that odors are dissolved free amino acids; however, it is unknown whether these odors change on a seasonal or annual basis. We analyzed dissolved free amino acid (DFAA) concentration and composition of water from the Teshio River in Hokkaido, Japan, where chum salmon (Oncorhynchus keta) returned for spawning, during juvenile downstream migration in spring and adult upstream migration in autumn with a 4-year difference. Among the 19 amino acids found in the Teshio River water, DFAA concentrations fluctuated largely, but 5-7 stable DFAA compositions (mole %) were found between the spring and autumn samples over a 4-year span. Two kinds of artificial stream water (ASW) were prepared using the same DFAA concentration in the Teshio River during the time of juvenile imprinting in spring (jASW) and adult homing in autumn (aASW), after a 4-year period. In behavioral experiments of upstream selective movement in a 2choice test tank, 4-year-old mature male chum salmon captured in the Teshio River showed significant preference for either jASW or aASW when compared to control water, but did not show any preference with respect to jASW or aASW. In electro-olfactogram experiments, adults were able to discriminate between jASW and aASW. Our findings demonstrate that the long-term stability of the DFAA compositions in natal streams may be crucial for olfactory homing in chum salmon.

人工ふ化放流河川におけるサケの成熟年齢・サイズの野生魚—放流魚間比較

人工ふ化放流河川におけるサケの成熟年齢・サイズの野生魚—放流魚間比較

Spatial distribution of juvenile masu salmon (Oncorhynchus masou) with incongruent genotypic and phenotypic sex in Hokkaido, Japan

To clarify the spatial distribution of masu salmon Oncorhynchus masou with incongruent genotypic and phenotypic sex, we compared the phenotypic sex determined by gonad analysis with the genotypic sex identified by a male-specific genetic marker, Growth hormone pseudogene (GHp), in 584 individuals inhabiting 23 rivers in Hokkaido, Japan. We found that the genotypic sex is different from the phenotypic sex for 39 individuals in 10 rivers. Among them, 35 individuals (89.7 %) were GHp + females phenotypically. The opposite feature was noted in the remaining four individuals (10.3 %). This study also revealed that GHp + phenotypic females are distributed mainly in the Sea of Japan, whereas GHp- phenotypic male tend to appear in the Sea of Okhotsk. In addition, there was a significant negative correlation between the distance from the Bishabetsu River, where frequency of GHp + phenotypic females was the highest, and the frequency of those individuals in each river. These results suggest that the distribution of masu salmon with incongruent genotypic and phenotypic sex would be related to the movement of individuals among the populations and regions.