Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Daytime habitat use by Japanese eel (Anguilla japonica) at the yellow eel stage (total length ≥ 15 cm) and the newly recruited glass/elver stage in spring (total length 5–7 cm) was examined in three sites of different types of streams in southwestern Japan. Although habitat use by yellow eels was examined in summer and winter, no distinct difference was found between the two seasons. Yellow eels preferred lower current velocity in all the three sites in both seasons. Cover use by yellow eels differed among the three sites having different cover-type availability. In a coarse-substrate mountain stream, the majority of yellow eels used cobble/boulders as cover, whereas in the other two fine-substrate streams, where coarse substrates were rare, large parts of yellow eels burrowed into fine sediments. In addition, undercut bank and bank vegetation were substantially used and preferred by yellow eels depending on the study site, suggesting the importance of natural bank habitat. The majority of glass/elver eels used sand substrates with current velocity < 10 cm·s−1 in all the three sites, suggesting their clear preference for such habitat. However, the preference for sand shown in this study contrasts with a general trend established by previous experimental studies that glass/elver eels prefer stony substrates over sand. Our results contrary to the general trend could be attributed to glass/elver eels displaying a stronger preference for slow currents over stony substrates, implying that current velocity has a dominant effect in habitat use by glass/elver eels under natural conditions.

DOI： 10.1007/s10641-023-01493-z

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Aim Natural disaster risk reduction (DRR) is becoming a more important function of protected area (PAs) for current and future global warming. However, biodiversity conservation and DRR have been handled separately and their interrelationship has not been explicitly addressed. This is mainly because, due of prevailing strategies and criteria for PA placement, a large proportion of PAs are currently located far from human-occupied areas, and habitats in human-occupied areas have been largely ignored as potential sites for conservation despite their high biodiversity. If intensely developed lowland areas with high flooding risk overlap with important sites for biodiversity conservation, it would be reasonable to try to harmonize biodiversity conservation and human development in human-inhabited lowland areas. Here, we examined whether extant PAs can conserve macroinvertebrate and freshwater fish biodiversity and whether human-inhabited lowland flood risk management sites might be suitable to designate as freshwater protected areas (FPAs). Location Across Japan. Methods We examined whether extant PAs can conserve macroinvertebrate and freshwater fish biodiversity and analysed the relationship between candidate sites for new FPAs and flood disaster risk and land use intensity at a national scale across Japan based on distribution data for 131 freshwater fish species and 1395 macroinvertebrate species. Results We found that extant PAs overlapped with approximately 30% of conservation-priority grid cells (1 km(2)) for both taxa. Particularly for red-listed species, only one species of freshwater fish and three species of macroinvertebrate achieved the representation target within extant PAs. Moreover, more than 40% of candidate conservation-priority grid cells were located in flood risk and human-occupied areas for both taxa. Main conclusions Floodplain conservation provides suitable habitat for many freshwater organisms and helps control floodwaters, so establishing new FPAs in areas with high flood risk could be a win-win strategy for conserving freshwater biodiversity and enhancing ecosystem-based DRR (eco-DRR).

DOI： 10.1111/ddi.13517

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10228-022-00863-4

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Other Link： https://link.springer.com/article/10.1007/s10228-022-00863-4/fulltext.html

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10228-022-00862-5

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Other Link： https://link.springer.com/article/10.1007/s10228-022-00862-5/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10201-021-00675-x

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Other Link： https://link.springer.com/article/10.1007/s10201-021-00675-x/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Vertical hydrological connectivity between the surface stream and benthic and hyporheic zones plays a key ecological role in the biodiversity of lotic ecosystems because it allows surface and benthic organisms to use the hyporheic zone as a seasonal habitat and refuge. Use of the hyporheic zone by surface/benthic organisms has been well studied in invertebrates, but little is known about the importance of this connectivity for fishes. We investigated streambed surface and hyporheic densities (5-10, 15-20 and 20-25 cm below the streambed surface) of a stream fish, Cobitis shikokuensis, over a 20-month period in the Shigenobu River, southwestern Japan, to test the hypothesis that it uses the hyporheic zone for spawning and overwintering. In total, 1,804 individuals (13-58 mm total length) were captured from 33 streambed surface samplings and 102 individuals (10-46 mm total length) were present in 1,147 samples of 57 hyporheic samplings. Population densities in both zones peaked in late summer-early autumn due to the recruitment of age 0+ fish and a female with eggs was found in the hyporheic zone during the reproductive season. Both 0+ and older fish were absent from the streambed surface during winter, and fish densities were also lower in the hyporheic zone at this time. However, the vertical distribution of the fish tended to be skewed towards the deeper hyporheic layers from autumn to spring. These findings indicate that C. shikokuensis vertically migrates between the streambed surface and the hyporheic zone for spawning, rearing and overwintering, suggesting that the integrity of vertical hydrological connectivity in lotic systems is crucial for certain fish species.

DOI： 10.1007/s10228-017-0576-5

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Language：Japanese   Publisher：Carcinological Society of Japan  

<p>On 9 November 2016, an unknown Cambaridae crayfish was collected from the outflow stream of Matsubara Izumi along the Shigenobu River in western Japan. On the basis of COI and 12S rRNA analyses, we identified the crayfish as the Marmorkrebs (<i>Procambarus fallax</i> f. <i>virginalis</i>), which serves as the first record for this species from western Japan. The Marmorkrebs is widely available across Japan through the aquarium pet trade. Because the parthenogenic Marmorkrebs has high potential to impact biodiversity, fisheries, and rice farming in Japan through rapid proliferation, transmission of diseases, and herbivory, we call for urgent management plans to restrict the import, movement, and release of this crayfish.</p>

DOI： 10.18988/cancer.26.0_5

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Language：Japanese   Publishing type：Research paper (scientific journal)  

With rapid declines in global riverine biodiversity, conservation is needed on a nationwide scale. Since 1990, the National Census on River Environments (NCRE) has collected meaningful data on riverine organisms and environments in Japan. However, there are several issues with using the NCRE database for scientific studies. In this study, we summarised issues related to the NCRE database, and used the 3rd NCRE dataset (2001-2005) to evaluate nationwide trends in species richness and the rarity of fishes (primarily freshwater and diadromous fishes) and taxon richness and the rarity of benthic animals (aquatic insects and shellfishes). First, we summarised data quality (e.g. monitoring sites and season) and data formatting issues (e.g. site name and species name). Second, we mitigated these potential issues as thoroughly as possible and tested the relationships of species (or taxon) richness and rarity with latitude using generalised linear models. We found that species and taxon richness showed different latitudinal distributions between primarily freshwater and diadromous fishes and between aquatic insects and shellfishes. In contrast, rarities showed spatial congruence with species diversity, suggesting that more species and rare species could be conserved in the same regions.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A laboratory experiment was conducted by varying the undersurface area of nesting substratum and the number of females in an experimental tank to elucidate the determinants of the mating pattern in the stream goby, Rhinogobius sp. cross-band type. Males with larger nests tended to attract two or more females to their nest in a tank. Moreover, males spawned simultaneously with multiple females and entire brood cannibalism by males was rarely observed under a female-biased sex ratio. When males spawned with a single female with low fecundity, however, entire brood cannibalism occurred at a high frequency, suggesting that a male guarding a nest with fewer eggs consumes the brood. Therefore, spawning behaviour of females that leads to a large egg mass would decrease the risk of entire brood cannibalism. In this species, simultaneous spawning by multiple females in a nest serves as a female counter-measure against entire brood cannibalism. These results suggest that a conflict of interest between the sexes through brood cannibalism is a major determinant of simultaneous spawning.

DOI： 10.1111/jfb.13060

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A negative correlation between the degree of fine sediment deposition and the abundance of stream benthic fishes has often been reported, although the causal mechanisms for this effect are not fully understood. To better understand the influence of sedimentation, it is important to clarify whether it alters the habitat required by fish, or merely preferred by them. We conducted two enclosure experiments in the field to examine (i) whether an endangered benthic fish, Cobitis shikokuensis, prefers sediment-free substrate and (ii) whether fine sediment deposition has negative effects on the physiological condition of C.shikokuensis. The first experiment, which used three types of substrates, cobble', pebble' and mixture of fine sediment and pebbles', showed that C.shikokuensis avoided the mixture. The second experiment, which compared the physiological condition of fish reared in enclosures with either a pebble or mixture substrate, showed that the condition of the fish in the latter group declined more quickly. These results suggest that, for C.shikokuensis, sediment-free substrate is a habitat requirement, not merely a preference, and that excessive input of fine sediment due to human activities can cause a decline in the population of this species.

DOI： 10.1111/eff.12171

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Habitat loss and degradation due to human activities are major threats to stream fishes. To predict and/or monitor habitat changes, quantification of suitable habitats for target fish species is indispensable. For drift-feeding salmonids, bioenergetics models that estimate energetic benefit (net energy intake: NEI) can be used for their habitat evaluation. In this study, we examined applicability of a bioenergetics model, which had been developed for Arctic grayling (Thymallus arcticus) in Alaska, North America, to habitat evaluation for red-spotted masu salmon (Oncorhynchus masou ishikawae) in southwestern Japan, by assessing whether their position choice can be predicted by the model. The results showed that the model successfully predicted their position choice in 12 of the total 16 study sections. Further, in two sections inhabited by several individuals, strong positive correlations were found between NEI potential and fish body length, being consistent with a widely reported trend in drift-feeding salmonids that larger individuals occupy more profitable positions. We concluded that the bioenergetics model we tested is useful in evaluating habitat quality for red-spotted masu salmon. Our results suggested that NEI models can be regarded as a site-independent, widely applicable tool for habitat evaluation for drift-feeding salmonids.

DOI： 10.1007/s11355-014-0247-x

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

In an intermittent reach of the Shigenobu River (Ehime Prefecture, southwestern Japan), two floodplain ponds (Matsubara Spring and Hirose-gasumi wetland) were created in 2006-2007 as a part of a habitat rehabilitation project. Fish assemblages and habitat characteristics of the two created ponds were investigated in 2008, and compared with those of ten pre-existing spring-fed ponds (reference ponds). Structural characteristics (canopy shade, cover habitat, substrate, and bank condition) of the two created ponds were similar to those of the reference ponds. The created ponds were characterized by lower values of water level fluctuation, indicating that the created ponds can function as stable, permanent habitats in the intermittent reach. The number of fish species in the reference ponds ranged from 4 to 14 species, while that in the two created ponds was 13 and 9. This indicates that most of the major fish species had colonized the newly created ponds, al-though total fish density in both created ponds was low relative to that in the reference ponds. Overall, our data suggest that the two ponds created by the habitat rehabilitation project provide suitable habitats for freshwater fishes. However, exotic largemouth bass (Micropterus salmoides), which can have strong negative effects on native biota, was found in a created pond (Hirose-gasumi). Management of the created ponds should include consideration of this invasive species.

DOI： 10.3825/ece.18.127

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

Numerous sediment-control dams are installed in most headwater catchments in Japan. These dams cause habitat fragmentation of stream-dwelling salmonids, raising the risk of local extinction of their isolated populations. We examined such an effect of habitat fragmentation due to dams on red-spotted masu salmon (Oncorhynchus masou ishikawae) in Shikoku, southwestern Japan. We hypothesized that their local extinctions would occur from uppermost reaches (uppermost margins of their distribution range), where populations are completely isolated, and then extend downstream. Our purpose was to clarify habitat size (catchment area upstream of dams) at which local extinctions becoming apparent in the present state. Classification tree analysis using presence/absence data at 69 study sites suggested that local extinctions due to dams were apparent in stream reaches at catchment area 0.49-0.89 km. In addition, regression tree analysis showed that masu salmon density increased upstream, suggesting that upper reaches have higher habitat quality. Estimations of stream length and population size based on catchment area indicated that stream reaches facing extinction threat are within 500-600 m from the headwater and have only 40-50 individuals of adult population size. Our results emphasized the priority of uppermost reaches in conservation and restoration of connectivity for populations of stream-resident salmonids. We proposed four management classes (critically endangered area: catchment area &lt
2 km
least-required area: 4 km2
required area: 10 km2
target range: 40 km2) based on previous knowledge and the present results to facilitate conservation and restoration of the headwater connectivity.

DOI： 10.3825/ece.17.17

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Language：Japanese   Publisher：The Ichthyological Society of Japan  

<p>Phylogeographic analysis of the bitterling <i>Tanakia limbata</i> in western Japan was conducted to identify the origin of the fish population in Ehime, Shikoku Island. A survey of rivers and spring-fed ponds on the Matsuyama Plain, Ehime, indicated that <i>T. limbata</i> had become distributed on the plain over a period of 19 years to the present day. Sequences of the mitochondrial cytochrome <i>b</i> gene indicated that the 42 individuals sampled included 4 haplotypes, which were shared with a <i>T. limbata</i> population in the Yabe River, Fukuoka, Kyushu Island. All 4 haplotypes belonged to the West Kyushu group of <i>T. limbata</i>. On the other hand, <i>T. limbata</i> comprising the West Seto clade inhabits western Honshu and eastern Kyushu, which regions shared the same paleoriver system with Ehime 20,000 years BP. These results suggest that individuals of <i>T. limbata</i> presently collected in Ehime originated from the Yabe River or adjacent waters, having artificially transported over the mountain chain that may act as a natural barrier separating the West Kyushu and West Seto groups. To conserve an endangered native bitterling, <i>T. lanceolata</i>, in Ehime, management of the introduced <i>T. limbata</i>, so as to prevent competition and hybridization with the former, is necessary.</p>

DOI： 10.11369/jji.61.89

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Other Link： http://agriknowledge.affrc.go.jp/RN/2010873969

Language：Japanese  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Terrestrial invertebrates falling from the riparian canopy are a major energy source for fishes in headwater streams. Because quantity and quality of such allochthonous resources can vary depending on riparian conditions, conversion of riparian forests to conifer plantations may affect stream productivity. We compared falling and drifting invertebrate abundances and the diet of masu salmon (Oncorhynchus masou) among stream reaches bordered by deciduous broadleaved forests, conifer plantations (Cryptomeria japonica), and clear-cut sites in southwestern Japan. We also examined whether among-reach variation in salmon abundance was related to the riparian vegetation types. The results indicated that, on an annual basis, falling inputs of terrestrial invertebrates at the broadleaved reaches were 2-4 times higher than those at the plantation and clear-cut reaches. In nonwinter seasons, terrestrial invertebrates made up 40-60% and 30-90% of drift and masu salmon diets, respectively, and drifting invertebrate abundance was higher in the broadleaved reaches than in the plantation reaches. Furthermore, a multivariate analysis of salmon abundance showed that variation in salmon biomass was explained primarily by riparian vegetation type, with broadleaved and clear-cut reaches having higher biomass than the plantation reaches. These results indicate that terrestrial invertebrates are an important resource for masu salmon, and suggest that streams bordered by conifer plantations receive lower terrestrial prey inputs, which results in lower salmon abundance. In regions where natural forests have been extensively converted to conifer plantations, forest management that allows and facilitates recovery of natural riparian stands is important.

DOI： 10.1111/eff.12029

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER BASEL AG  

In lotic systems, the hyporheic zone has been suggested as a potential refuge for aquatic organisms during disturbances (hyporheic refuge hypothesis). However, the supporting evidence is unclear, especially regarding the survival of hyporheic refugees and their contribution to the recovery of post-disturbance populations. Moreover, few studies have focused on the importance of the hyporheic refuge for aquatic vertebrates such as fish. In this study, we present evidence that the hyporheic zone acts as a refuge for a small benthic fish (Cobitis shikokuensis) following surface drying in an intermittent river. We examined its survival during and recolonization after dry periods by direct hyporheic sampling and mark-and-recapture surveys. When the streambed dried, hyporheic sampling was conducted 58 times across 33 locations in the intermittent reach and 31 individuals of C. shikokuensis were captured from extracted hyporheic water. Mark-and-recapture surveys revealed that recolonizers after re-wetting included C. shikokuensis individuals that had survived dry periods in the hyporheic refuge. The condition factor of C. shikokuensis significantly declined after dry periods, suggesting that most recolonizers suffered from physiological stress, probably within the hyporheic refuge. These results clearly support the long-debated, hyporheic refuge hypothesis, and provide a striking example of the critical role of the hyporheic zone in population maintenance of lotic organisms.

DOI： 10.1007/s00027-013-0289-4

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Population genetic structure of a common freshwater goby Rhinogobius fluviatilis in the Yoshino River and its tributaries was surveyed using three microsatellite loci to examine effects of dams. Allelic richness of the Akui and Sadamitsu River populations below the dams were high (15. 7, 15. 9) and that of the above the dams populations were low (10. 9 ∼13. 0). Heterozygosity was same level diversity between above and below dam populations (0. 870∼0. 890) except for Takeno river population (0. 788). Considerable genetic differences were observed between populations above and below the dams. Migratory history was also examined using otolith Sr/Ca ratio. The otolith Sr/Ca ratio analysis confirmed that the populations above the dams were landlocked by the dams. It was also suggested that some individuals below the dams do not undertake amphidromous migration.

DOI： 10.3825/ece.16.13

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

Fish assemblage structure in spring-fed irrigation ponds in the Shigenobu River watershed (Ehime Prefecture) was compared between two periods, 1998-1999 and 2008, to examine effects of revetment construction and exotic largemouth bass (Micropterus salmoides). Two of the 11 study ponds were 'altered ponds, where bank revetment was constructed during the decade, whereas another pond was 'bass pond, where largemouth bss had established a self-reproducing population. Comparisons of species richness, density of each species and assemblage structure revealed that the most distinct change occurred in the bass pond, where most species other than largemouth bass showed drastic declines in population density. On the other hand, distinct fish-assemblage changes specific to the altered ponds were not found, despite considerable habitat changes due to the revetment construction work. Our data also revealed that two species, Tanakia lanceolata and Gnatho-pogon elongatus elongatus, which had been found from six and two ponds, respectively, disappeared in 2008. These disappearances may suggest an overall degradation of irrigation-associated aquatic systems (river-pond-ditch-paddy: alternative habitats for floodplain-adapted fishes) as fish habitat.

DOI： 10.3825/ece.16.91

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

In headwater streams, conifer plantation forestry may affect stream communities through the quantity and quality of basal resources (allochthonous litter). We compared (1) the seasonal patterns of litter input from the riparian canopy, (2) those for the abundance of benthic and drifting litter in streams, and (3) the density of litter-associated invertebrates among streams bordered by deciduous broadleaved forest, a plantation of Japanese cedar (Cryptomeria japonica), and a clear-cut site, to extract the characteristics of conifer-plantation streams in terms of litter dynamics and benthic invertebrates. The results illustrate differences in litter input and in-stream processes between the broadleaved and plantation sites, although the total annual inputs from canopy were similar. In the broadleaved site, high litter storage was limited to winter, probably because pulsed inputs of litter in autumn were retained on the streambed but rapidly processed. In contrast, litter input was more constant at the plantation site, and litter was stored throughout the year. Although the litter-patch-specific density of total invertebrates was similar between the broadleaved and plantation sites, estimates of the reach-scale, habitat-weighted density considering differences in the coverage area of litter patches revealed considerable differences. Although the habitat-weighted density of total invertebrates was lower at the plantation site than at the broadleaved site in winter, it was noticeably higher at the plantation site in summer, owing to the seasonal stability of benthic litter abundance. Our results emphasized the importance of considering the spatiotemporal availability of benthic litter when assessing the effects of conifer plantations on stream ecosystems.

DOI： 10.1007/s10201-011-0369-x

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Language：Japanese   Publishing type：Research paper (scientific journal)  

We conducted a field survey in 8 tributaries of the Shigenobu River to elucidate the influence of catchment land use on fish and invertebrate assemblages and feeding habit of fish. Fish and invertebrate assemblages were dominated by high-temperature and pollution tolerant taxa in agricultural streams. Dominant omnivorous fish, &lt;i&gt;Phoxinus oxycephalus jouyi&lt;/i&gt;, selectively fed on periphyton in agricultural streams while it utilized various food items in forest streams. We concluded that changes in water temperature and nutrient concentration would generate synchronous changes in community structures of fish and invertebrates and, moreover, fish feeding, along the forest-agricultural gradient.

DOI： 10.2208/jscejhe.68.I_697

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Language：Japanese   Publishing type：Research paper (scientific journal)  

The construction of erosion control dams and the alteration of riparian forest are known to have strong influences on the density of salmonid fish that dominate in mountain streams. Our objective was to elucidate the indirect effect of the dam construction and riparian alteration on stream invertebrates through the alteration of salmonid fish (&lt;i&gt;Oncorhynchus masou ishikawae&lt;/i&gt;) density. The densities of two dominant invertebrate species, Baetis &lt;i&gt;yoshinensis&lt;/i&gt; and Baetis &lt;i&gt;thermicus&lt;/i&gt;, were low at study sites with high O. &lt;i&gt;masou&lt;/i&gt; density. In conclusion, our study suggested that human activities indirectly affect stream invertebrates via changing fish abundance in mountain streams.

DOI： 10.2208/jscejhe.68.I_691

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Influence of the dams in the Kamo and Nakayama River systems in the Ehime Prefecture on the common freshwater gobies Rhinogobius flumineus (non-diadromous species), R. sp. CB, R. fluviatilis and R. kurodai (amphidromous species) were surveyed using three microsatellite loci. Genetic variability was high in R. sp. CB (0. 900-0. 919) and low in R. flumineus (0.191-0. 278). Considerable genetic differences were observed among the species. The effects of a dam with a reservoir were examined for R. flumineus and R. sp. CB. In R. flumineus (non-diadromous species), genetic differences were not observed between populations above and below the Nakayama-gawa Dam (Nakayama R.). In R. sp. CB (amphidromous species), migratory history was also examined using otolith Sr/Ca ratio. The otolith Sr/Ca ratio analysis confirmed that the population above the Kurose Dam (Kamo R.) was landlocked by the dam. However, genetic heterogeneity was not observed between populations above and below the Kurose Dam.

DOI： 10.3825/ece.15.161

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

We examined habitat factors related to the distribution and abundance of the spinous loach Cobitis shikokuensis, an endangered benthic fish, in the Shigenobu River system, southwestern Japan. In the study river, the spinous loach was distributed widely along the main stem, from headwater to near the mouth, whereas it was rarely found in tributary streams. Classification tree analysis showed that the presence/absence of spinous loach was explained by a combination of percent pebble and length of river fragment between artificial barriers. Spinous loach incidence was high in sites with abundant pebble (&gt; 27.7%), but low in sites with short river fragment (a parts per thousand currency sign0.97 km) even if pebbles were abundant. A regression tree model for loach density retained only percent pebble as a single best predictor, with sites with higher percent pebble (&gt; 40.4%) having higher density. These results suggest that substrate condition is an important factor determining the distribution and abundance of spinous loach and also that habitat fragmentation by artificial barriers has great potential to threaten the spinous loach population in this river. Considering the highly fragmented situation of the study river and prevention of upstream migration by barriers, we conclude that maintenance of suitable habitats in upper reaches has high priority for conservation of the spinous loach.

DOI： 10.1007/s10228-011-0208-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Breakdown and macroinvertebrate colonization of conifer needles (Cryptomeria japonica) and deciduous broadleaves (Euptelea polyandra) were investigated using litter bags in two study sites in streams flowing through a conifer plantation of C. japonica in Shikoku, southwestern Japan (one site with conifer canopy and another with mixed conifer and broadleaved canopy). Breakdown rates and macroinvertebrate densities were compared between litter species (conifer needle vs broadleaf) and between the two sites (conifer vs mixed canopy) to determine (1) whether breakdown rate of broadleaves is higher than conifer needles, (2) whether macroinvertebrates prefer broadleaves to conifer needles, and (3) whether the difference in riparian canopy is reflected in macroinvertebrate abundance. The results indicated that breakdown rates of broadleaves were higher than those of conifer needles, suggesting poorer quality of the latter as food for macroinvertebrates. Differences in macroinvertebrate density between needles and broadleaves were generally consistent with those in breakdown rates: broadleaves tended to have higher densities than needles, suggesting that conifer needles were not preferred by macroinvertebrates. However, total macroinvertebrate density in the conifer site was not significantly different from that in the mixed site, although the dominant shredder taxon differed (conifer site: gammarids; mixed site: lepidostomatids). Although conifer needles are low-quality food for macroinvertebrates, this may offer some advantages. Conifer needles remain on the streambed for longer periods owing to their lower breakdown rates, being a constantly available resource. In addition, accumulations of conifer litter may effectively trap and retain particulate organic matter.

DOI： 10.1007/s10310-010-0210-0

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Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Population genetic structure and migratory history of the common freshwater goby Rhinogobius sp. LD in the Shigenobu River system were surveyed by using three microsatellite loci and otolith Sr /Ca ratio, to examine effects of two types of dams, a single dam with a reservoir (Ishite-gawa Dam) and multiple erosion-control dams without reservoir. Genetic variabilities were high in the Shigenobu River populations and the estimated hetero zygosity ranged from 0.843 to 0.889. Considerable genetic differences were observed between populations above Ishite-gawa Dam (two sites) and populations of the other nine sites (above multiple erosion-control dams), within which the genetic heterogeneity was not observed. These results suggested that the populations above Ishite-gawa Dam were landlocked and differentiated genetically by the dam, whereas the goby populations were not isolated by multiple erosion-control dams. This was supported by the otolith Sr /Ca analysis, which indicated that the goby individuals sampled from the sites above the Ishitegawa Dam had not experienced saltwater whereas those above multiple erosion-control dams had experienced. In addition, Sr /Ca analysis suggested that a population just below the Ishitegawa Dam consisted of both landlocked (drifted from the reservoir) and sea-migratory individuals.

DOI： 10.3825/ece.14.35

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

We examined habitat use by spinous loach (Cobitis shikokuensis), an endangered benthic fish in Japan, in relation to distance to the stream bank, water depth, current velocity, substrate types and bed-subsurface conditions (fine-sediment volume, vertical hydraulic gradient). In the study reach (Shigenobu River in Shikoku Island), spinous loach exhibited a patchy distribution within the channel, being limited to sloping bed of channel margins. Although high selectivities were detected for three variables (close to the stream bank, pebble-dominant substrates, and low fine-sediment volume) from univariate perspective, decision-tree analysis indicated that their distribution pattern was best explained by the two variables representing subsurface conditions. Locations occupied by spinous loach were characterized by extremely low fine-sediment volume (a parts per thousand currency sign1.5%), or by moderate fine-sediment volume (1.5-9.8%) with positive vertical hydraulic gradient (indicative of upwelling). Our results suggest that subsurface interstices are essential habitat for spinous loach and that prevention of excessive inputs and deposition of fine sediments, which cause interstitial sedimentation, is crucial for conservation of this endangered species.

DOI： 10.1007/s11284-010-0714-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

1. Species richness in a habitat patch is determined by immigration (regional) and extinction (local) processes, and understanding their relative importance is crucial for conservation of biodiversity. In this study, we applied the Island Biogeography concept to spring ponds connected to a river in southwestern Japan to examine how immigration and extinction processes interact to determine fish species richness in temporally variable environments.
2. Fish censuses were conducted 15 times in 13 study ponds at 1-4 month intervals from August 1998 through October 2000. Effects of habitat size (pond area), isolation (distance from the river) and temporal environmental variability (water level fluctuation) on (i) species richness, (ii) immigration and extinction rates and (iii) population size and persistence of each fish species were assessed.
3. The results revealed predominant effects of distance on species richness, immigration/extinction rates and population size and persistence. Species richness decreased with increasing distance but was not related to either pond area or water level fluctuation. A negative effect of distance on immigration rate was detected, while neither pond area nor water level fluctuation had significant effects on extinction rate. Further, population size and persistence of four species increased with decreasing distance, suggesting that, in ponds close to the river, immigrants from the river reduce the probability of extinction (i. e. provide a rescue effect), contributing to the maintenance of high species richness.
4. Overall results emphasise the importance of immigration processes, rather than extinction, in shaping patterns of species richness in our system. The predominant importance of immigration was probably because of (i) high temporal variability that negates habitat-size effects and (ii) continuous immigration that easily compensates for local extinctions. Our results suggest that consideration of regional factors (e. g. connectivity, locations of source populations and barriers to colonisation) is crucial for conservation and restoration of local habitats.

DOI： 10.1111/j.1365-2427.2009.02335.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS  

Factors controlling invasion success of rainbow trout (Oncorhynchus mykiss) and interactions with native masu salmon (Oncorhynchus masou) were examined by field investigations. The results suggested that flow regime has a major role in controlling rainbow trout invasion success. Although competitive relationships were found between the two species, masu salmon were not likely to prevent trout invasion. Analyses on the distributions and abundances of the two species indicated that the occurrence of rainbow trout was limited to streams with stable flows, and the density of each species was negatively related with that of the other. Habitat use and diet analyses revealed a pattern of their resource partitioning; rainbow trout occupy positions near the bottom or cover, foraging benthic prey, while masu salmon feed drifting prey at the middle layers of the water column. This resource partitioning was suggested to reflect a diet shift by rainbow trout. Our results also have a management implication that dams, which control flow regime, can be a key factor in managing rainbow trout invasion and its effects.

DOI： 10.1139/F09-088

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Flow fluctuation is an important factor determining the characteristic of the stream ecosystem. In this study, we investigated stream fish, invertebrates and their habitat characteristics before and after a spate, in order to reveal the dynamics of lotic animal community in intermittent reach. Fish and invertebrates were observed after rewetting by the spate in the intermittent reach, Fish community established within the intermittent reach were suggested to have colonized from the downstream perennial reach. However, both fish and invertebrates are finally killed by drying up with the decreasing flow in the intermittent reach. We concluded that flow fluctuation induced drastic temporal change in stream animal assemblages.

DOI： 10.2208/proer.36.445

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Language：English   Publishing type：Research paper (scientific journal)  

Exotic largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus), both of which were introduced from North America, are now widespread throughout Japan, often dominating in irrigation ponds and reservoirs. The rapid expansions of their distributions beyond watersheds are obviously due to human agency
however, their expansions within a watershed may be, more or less, attributable to natural dispersal, which has rarely been investigated. This study presents circumstantial evidence of their dispersal from artificial ponds to irrigation ditches. In the Shigenobu River watershed (Ehime Prefecture, southwestern Japan), 21 study sites were established in river pools and irrigation ditches associated with 6 ponds inhabited by the two species. In each site, population densities of both species were monitored from the spring of 2002 to the autumn of 2003. The monitoring showed that (1) both species attained high densities (maximum density, 8.0 and 12.1 individuals/m2 for largemouth bass and bluegill, respectively) in ditches just downstream of ponds in summer, (2) most of them were small in size (&lt
10 cm in fork length), (3) at every study site, their densities were temporarily variable and zero densities were often recorded (i. E., neither of the two species was found), and (4) the two exotic species comprised considerable percentages of fish assemblages in the ditches (41.9 % in the sum total of estimated number of fishes). These results, in combination with a fact that most study ditches had potential barriers to upstream migration (i. E., falls of 0.8-2 m in height), suggest that individuals of both species in the ditches were immigrants from the ponds. © 2007, Ecology and Civil Engineering Society. All rights reserved.

DOI： 10.3825/ece.10.117

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Tolerance to current velocity was compared among six stream gobies of the genus Rhinogobius (cross-band, dark, large-dark, cobalt, and orange types, and R. flumineus). Each individual of the six gobies was exposed to incremental increases in current velocity within a laboratory flume. The current velocity at which each individual was dislodged was recorded and compared by species. Results from comparisons showed that the tolerance of gobies declined in the following order: cobalt, large-dark, dark, cross-band, R. flumineus, and orange type. This interspecific difference in velocity tolerance is consistent with their habitat segregation patterns as previously reported by field observations.

DOI： 10.1007/s10228-006-0347-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING  

in streams, physical and biotic conditions change from the headwaters to the mouth, shaping longitudinal patterns in community structure. We examined how fish foraging effects on periphyton and benthic invertebrates changed along a longitudinal gradient of a warm-temperate stream in southwestern Japan. We established three study sites according to changes in the composition of fish feeding guilds (upper site characterized by drifting-invertebrate feeders, Oncorhynchus mason; middle site by benthic invertebrate feeders, Rhinogobius spp.; lower site by the presence of periphyton grazers, Sicyopterus japonicus), and performed two manipulative experiments to examine effects of different fish assemblages on periphyton and benthic invertebrate abundances. Results of an exclosure experiment suggested that fishes had no effect on the benthic assemblages at the upper and middle sites whereas fishes reduced the abundances of both periphyton and invertebrates on stone surfaces at the lower site, where both benthic invertebrate feeders and grazers inhabited. A subsequent enclosure experiment showed that the reduction of invertebrate densities at the lower site was caused by the grazers rather than benthic invertebrate feeders. These experimental results suggested that effects of fishes on benthic assemblages are intensified downstream, owing to the occurrence of the grazing fish. Furthermore, observational data based on field sampling suggested that such grazing effects were reflected in longitudinal patterns in periphyton and invertebrate abundances. Overall results emphasize an important role of the grazing fish (S. japonicus) in shaping longitudinal patterns in benthic assemblage structure.

DOI： 10.1111/j.2006.0030-1299.14388.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Competition between two congeneric gobies, Rhinogobius sp. LD (large-dark type) and CB (cross-band type), for habitat was studied in a tributary of the Shimanto River, southwestern Shikoku, Japan. Habitat use by CB, measured by water depth, current velocity, and substrate, was compared between before and after the removal of LD. After the removal of LD, CB shifted their habitat use to coarser substrates than previously, suggesting a release from effects of LD. This result supports a hypothesis from our previous study that habitat partitioning between CB and LD is a consequence of interference effects of LD on CB.

DOI： 10.1007/s10228-005-0308-0

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Language：Japanese   Publisher：日本陸水学会  

DOI： 10.14903/jslim.71.0.122.0

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Fragmentation of lotic habitat by a drought is assumed to intercept the longitudinal movement of organisms and alter the community structure of them. In this study, we compared the community structure of freshwater animals between upstream and downstream of intermittent reach caused by human activities, in order to reveal the impacts of drought on spatial distribution of stream fish and invertebrates. Obvious influence of droughts was not observed for the community structure of fish and invertebrates. In contrast, spatial distribution of some dominant invertebrate taxa was seemed to be altered by droughts. However, there remains a possibility that strong effects of physicochemical habitat condition on invertebrates were more important than influence of a drought.Fragmentation of lotic habitat by a drought is assumed to intercept the longitudinal movement of organisms and alter the community structure of them. In this study, we compared the community structure of freshwater animals between upstream and downstream of intermittent reach caused by human activities, in order to reveal the impacts of drought on spatial distribution of stream fish and invertebrates. Obvious influence of droughts was not observed for the community structure of fish and invertebrates. In contrast, spatial distribution of some dominant invertebrate taxa was seemed to be altered by droughts. However, there remains a possibility that strong effects of physicochemical habitat condition on invertebrates were more important than influence of a drought.

DOI： 10.2208/proer.34.57

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

The densities of two benthic fishes, the Siberian stone loach (Noemacheilits barbatulus) and the wrinklehead sculpin (Cottus nozawae), and the biomass of their food resources (i.e., periphyton and benthic invertebrates) were compared between forest and grassland streams in northern Hokkaido, Japan, to examine whether riparian deforestation had positive effects on the benthic fishes via enhancement of food availability. The comparisons indicated that riparian vegetation had little influence on periphyton, invertebrates, or fishes. Regression analysis indicated that spatial variations in loach and sculpin densities were explained more by substrate heterogeneity, competitor abundance, or both, rather than by food abundance. However, when the two species were combined as benthic insectivores, a strong correlation was found between total benthic fish density and invertebrate biomass. Our results suggest that, although total benthic fish abundance was food limited, riparian vegetation had no positive effects via food availability on the benthic fishes in our streams.

DOI： 10.1007/s10201-004-0136-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Habitat use and foraging behavior of two benthic insectivorous gobies, Rhinogobius sp. CO (cobalt type) and Rhinogobius sp. DA (dark type), were examined in relation to their predation effects on local prey density in a small coastal stream in southwestern Shikoku, Japan. Correlations among the foraging range, frequency of foraging attempts and current velocity indicated that individuals using fast-current habitats had small foraging ranges and infrequently made foraging attempts while those in slow currents frequently foraged over large areas. The former and the latter were recognized as ambush and wandering foragers, respectively. Interspecific comparisons of habitat use, foraging behavior and prey preference suggested that Rhinogobius sp. CO selectively forage mobile prey by ambushing in fast currents, whereas Rhinogobius sp. DA randomly forage available prey by wandering in slow-current habitats. A cage experiment was conducted to assess prey immigration rate and the degree of predation effects on local prey density in relation to current velocity. The results of the experiment support, at least in part, our initial predictions: (1) prey immigration rates increase with current velocity and (2) the effects of fish predation on local prey density are reduced as current velocity increases. Overall results illustrated a link between the foraging modes of the stream gobies and their predation effects on local prey density: fish adopt ambush foraging

DOI： 10.1007/s11284-004-0022-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

Microhabitat use and habitat-abundance relationships of four freshwater shrimps, Atyopsis moluccensis, Macrobrachium pilimanus, Macrobrachium trompii and Macrobrachium neglectum, were surveyed in tropical streams running through primary and secondary forests in Borneo, East Malaysia. Underwater observations revealed that A. moluccensis preferred relatively high water velocity and a boulder substrate. Macrobrachium pilimanus also preferred high water velocity and a cobble substrate, whereas M. trompii occupied stream margins with slow current and fine substrates (from POM (particulate organic matter) to pebbles). In contrast, M. neglectum was distributed relatively evenly through the stream channel. The abundance of A. moluccensis, M. pilimanus and M. trompii in the stream reaches was best explained by the abundance of boulders, cobbles and POM, respectively, suggesting that the amount of preferred microhabitat is an important factor affecting shrimp abundances in the tropical rain-forest streams. The primary-forest reaches were dominated by coarse substrates, such as cobbles and boulders, while a great proportion of the streambeds in the secondary-forest reaches were covered with sand. Owing probably to such habitat differences, the abundance of both A. moluccensis and M. pilimanus, which preferred coarse substrates, was less in the secondary- than in the primary-forest reaches. These suggested that loss of preferred habitat, namely decreased coarse substrate availability, by sedimentation resulting from riparian deforestation had altered the shrimp assemblage structures.

DOI： 10.1017/S0266467403003432

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ECOLOGICAL SOC AMER  

Tropical stream communities are increasingly threatened by A vast array of human perturbations. However, ecological impacts of deforestation on stream communities are poorly understood in tropical rain forests of Southeast Asia. We investigated the impacts of past riparian deforestation associated with slash-and-burn agriculture on stream habitats and communities in Borneo, East Malaysia, by comparing streams running through primary forests and those through secondary forests that had been deforested 9-20 yr previously. Distinctive differences were found in depositional character of stream habitats; secondary-forest reaches had finer substrates, more eroded banks, and larger areas of depositional habitat and cover than did primary-forest reaches. Although our findings suggest that such, altered habitats are recovering toward a predisturbance state with redevelopment of the secondary forests, effects of the habitat alteration on stream communities were still evident. The habitat alteration (i.e., sedimentation) lowered the abundance and/or diversity of every benthic assemblage (periphyton,, aquatic insects, shrimps, crabs, and benthic fishes), while nektonic fishes were less affected. Although the habitat alteration benefited a few benthic taxa, such a's caenid mayflies and two shrimps (Macrobrachium trompii and Caridina nilotica peninsularis), the overall effects were apparently detrimental, leading to a reduction in biodiversity of the stream communities. We concluded that slash-and-burn agriculture, which alters vegetation and soil conditions more intensively than logging, caused long-term degradation of stream communities (at least nine years in our study). These findings emphasize the importance of management practices that protect the stream biodiversity from poorly regulated land use in Southeast Asia.

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Language：English   Publisher：Association of Wildlife and Human Society  

Habitat use, abundance-habitat relationships and assemblage composition of tropical freshwater fishes were surveyed in streams running through primary and secondary (deforested 9-20 years prior to the survey by slash-and-burn agriculture) forests in the Rayu River watershed, Sarawak, Borneo. Five species (Puntius kuchingensis, P. binotatus, Rasbora sarawakensis, R. caudimaculata, and Hemirhamphodon kuekenthali), of which habitat use was investigated, exhibited distinct diel habitat shifts between midstream and channel margin. Their abundances were related to habitat variables with the exception of P. binotatus. Puntius kuchingensis decreased with the increase of eroded banks. The abundance of R. caudimaculata increased downstream, while R. sarawakensis was less abundant in streams without riffle habitats. Hemirhamphodon kuekenthali was absent from high-gradient streams. Both habitat characteristics and fish assemblage composition differed distinctly between the primary-and secondary-forest streams. The secondary-forest streams were characterized by sandy substrates and eroded banks, suggesting a long persistence of sedimentation caused by the past deforestation. Macrognathus maculatus, Betta akarensis and P. kuchingensis appeared to be susceptible to sedimentation effects. Our data provide circumstantial evidence of the impact of past deforestation on fish assemblages in the Rayu River watershed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING LTD  

1. Stream reaches contain assortments of various habitat types that can be defined at different spatial scales, such as channel unit (e.g. pools, riffles) and subunit (patches within channel units). We described longitudinal (upstream-downstream) patterns of stream habitat structure by considering subunits as structural elements, and examined their effects on the abundance of masu salmon (Oncorhynchus masou ) and rosyface dace (Leuciscus ezoe ) in a third-order tributary of the Teshio River in northern Hokkaido, Japan.
2. Nine subunit types were determined on the basis of water depth, current velocity and substrate, using 0.5 x 0.5 m grids. Although both masu salmon and rosyface dace used pools as a major habitat, the former preferred a subunit type occurring at pool heads (PH subunit) while the latter preferred a slow-current edge type (SE-2 subunit).
3. Along the course of the stream, slow-edge subunits (SE-1, 2 and 3) increased in frequency downstream while fast-edge subunits (FE-1 and 2) decreased, suggesting a downstream development of slow-current edges. Regression analyses indicated that longitudinal variation in masu salmon abundance was explained by the area of PH, rather than pools. Masu salmon density increased with the area of PH. Rosyface dace abundance was explained by a combination of water depth and the area of SE-2, both effects being positive.
4. Longitudinal variations in the abundance of both species were related to the abundance of their preferred habitat at the subunit scale, rather than channel-unit scale. The results emphasise the importance of fine-scale patchiness when examining stream fish habitats.

DOI： 10.1046/j.1365-2427.2002.00898.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING LTD  

1. The effects of channelisation on macroinvertebrates were examined in relation to a spate and flow refugia. Habitat components that can function as flow refugia were identified in a small, low-gradient stream in northern Hokkaido, Japan.
2. Macroinvertebrates and their habitat characteristics (depth, current velocity and substratum) were sampled and measured in natural and channelised sections on three occasions: before, during and immediately after a spate. For macroinvertebrate sampling and habitat measurements, five (riffle, glide, pool, backwater and inundated habitats) and three (channelised-mid, channelised-edge and inundated habitats) habitat types were classified in the natural and channelised section, respectively.
3. The rate of velocity increase with discharge was compared among habitat types to determine which habitat types were less affected by increased discharge. The rate was the highest in riffles followed by glides and channelised-mids. Backwaters maintained low current velocity even at high flow. In addition, current velocity in both natural and channelised inundated habitats was low relative to other habitat types during the spate.
4. Through the spate, total density of macroinvertebrates in channelised-mids and taxon richness in both channelised-mids and edges decreased. In the natural section, however, such a significant decrease was not found except for taxon richness in pools. This indicated that the spate had a greater impact on assemblages in the channelised section. Riffle assemblages exhibited a rapid recovery immediately after the spate, suggesting the existence of flow refugia in the natural section. Among the habitat types we examined, backwaters and inundated habitats appeared to have acted as flow refugia, because these habitats accumulated macroinvertebrates during the spate.
5. The lower persistence of the macroinvertebrate assemblage in the channelised section was attributable to the lower availability of flow refugia such as backwaters and inundated habitats. Our results emphasised the importance of considering flow fluctuations and refugia in assessing the effects of channelisation. In addition, the lateral heterogeneity of stream channels should be considered in stream restoration and management.

DOI： 10.1046/j.1365-2427.2002.00877.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL UNIV SINGAPORE, SCHOOL BIOLOGICAL SCIENCES  

We surveyed fish fauna in 21 locations over the Rayu River system running through the Kubah National Park, Sarawak. In this study, we recognized 27 species in 18 genera belonging to 13 families. Ambassis miops Gunther, 1872 and Stenogobius ingeri Watson, 1991 were newly recorded. Pseudomystus rugosus (Regan, 1913) was rediscovered from Sarawak.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

The relationships between habitat variables and population densities of masu salmon (Oncorhynchus masou), rosyface dace (Leuciscus ezoe), Siberian stone leach (Noemacheilus barbatulus) and wrinklehead sculpin (Cottus nozawae) were examined by data collected at 55 reaches in forest and grassland streams in northern Hokkaido, Japan. Regression analysis suggested that salmon and dace densities were affected by water temperature (negative for salmon, positive for dace) and structural habitat factors (woody debris for salmon, pools for dace). Salmon density was higher in forest reaches than in grassland reaches, whereas dace density was higher in grassland reaches, suggesting that the removal of riparian forest had raised water temperature and allowed upstream invasions by dace. In contrast to salmon and dace, neither the density of leach nor sculpin differed between the forest and grassland reaches. For their densities, a negative effect of each on the other was most important, suggesting a strong effect of interspecific competition between leach and sculpin on their distributions. However, regression models also suggested that substrate heterogeneity mediated the outcome of their interspecific competition. On the basis of the results, a scenario is predicted for a fish-assemblage change with a typical land-development process in Hokkaido, and the importance of leaving or restoring riparian buffer for conservation and restoration of stream habitat is emphasized.

DOI： 10.1046/j.1440-1703.2001.00389.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

The importance of interspecific competition to habitat use by two congeneric stream gobies, Rhinogobius sp. LD (large-dark type) and CB (cross-band type), was studied by: (i) examining differences in habitat use by each species along the course of the stream; and (ii) comparing microhabitat use and the diet of each species between in allopatry and in sympatry in tributaries of the Shimanto River, south-western Shikoku, Japan. Rhinogobius sp. LD mainly used riffles through the course of the stream. Although CB also mainly used riffles in the lower reaches where CB was numerically dominant, the greater use of riffles by CB was not observed in upper reaches where LD was dominant. Microhabitat analysis revealed that both LD and CB preferred lower bottom velocity in faster current in both allopatry and sympatry. Tn sympatry, however, LD used coarser substrate and faster current than CB, and both LD and CB used narrower ranges of microhabitat conditions than in allopatry. Dietary analysis indicated that both allopatric and sympatric LD preferred baetids, which are apt to drift, suggesting they adopted ambush foraging. Allopatric CB preferred leptophlebiids and chironomids, which are also apt to drift, whereas sympatric CB did not prefer such invertebrates. Overall results of this study suggest that LD and CB compete for better feeding habitats, CB shift their habitat use and foraging mode under the influence of LD, and current velocity and substrate coarseness are key factors in their habitat segregation.

DOI： 10.1046/j.1440-1703.2001.00387.x

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Language：Japanese   Publisher：一般社団法人 日本生態学会  

DOI： 10.18960/seitai.51.2_144_2

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Language：English   Publishing type：Research paper (scientific journal)  

Japanese freshwater fish habitats can be generally categorized into 1) rivers and streams, 2) ponds and lakes, and 3) rice fields and small irrigation channels connecting them. Of these, reviewing studies on stream fish habitat is the primary objective of this paper. Streams in Japan have widely received severe habitat alterations through construction of artificial instream structures as well as modification of riparian vegetations. As a result, streamdwelling fishes that require natural flow regimes, substrates, and riparian vegetation have declined their populations in great deal in many parts of the country. Recent studies have found riparian forests control water temperature and provide woody debris creating cover structures for the stream fishes resulting in enhancing their carrying capacity. Differences in riparian vegetation types (forest versus grass) played an important role in determining the local distribution of salmonids. Also, experiments removing concrete-lined channel and installing log-drop structures demonstrated that such the treatment greatly improved fish habitat. As the general public became aware of the serious degradation of aquatic habitats, river management policy has gradually shifted to include conservation and improvement of river environment as habitat for wildlife during the last two decades. For fish migration, installation of fishway on dams has been prevailing, and research efforts have been made to design more effective fishway and passable weirs. In many cases, however, such restoration work lacks ecological data for assessment of their effectiveness. When such knowledge on fish habitat are accumulated, a vital issue will be how it is accounted into actual management. Future studies on fish habitat should shift toward treating habitat network at larger spatial scales to seek better designs for distributing appropriate habitats over a whole catchment. Such studies should also include clarifying the habitat requirements of endangered species and effects of non-native on native species. © 2001, Taylor &amp
Francis Group, LLC. All rights reserved.

DOI： 10.1080/146349801317276035

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL SCIENCE LTD  

1. Habitat structure and habitat use by juvenile masu salmon, Oncorhynchus masou Brevoort, in small streams in northern Hokkaido, Japan, were examined by considering 'subunits' (patches within channel units) as structural elements of stream reaches.
2. Whole wetted channel surfaces of three study reaches were divided into 0.5 x 0.5 m quadrats, which were grouped into eight subunit types according to water depth and velocity, and substratum conditions by a cluster analysis. The subunit distribution showed a regular mosaic pattern corresponding to the channel-unit sequence in each of the three reaches.
3. Juvenile masu salmon exhibited a strong preference for a subunit type characterized by greater depth and moderate current velocity (deep-moderate subunit; mean depth = 0.29 m; mean velocity = 0.19 m s(--1)). This subunit type usually occurred downstream of stretches with fast current. The preference of masu salmon for the deep-moderate subunit could be because of its usual spatial position in relation to other subunit types as well as to the characteristics of the subunit itself.
4. The results suggest that the value of a habitat is determined not only by the characteristics of the habitat itself, but also by those of adjacent habitats. Therefore, habitat use by stream fish should be studied in the context of the whole 'in-stream landscapes'.

DOI： 10.1046/j.1365-2427.1999.00481.x

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Language：Japanese  

DOI： 10.3739/rikusui.60.385

CiNii Books

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Publishing type：Research paper (scientific journal)  

Inputs, outputs, and retention of leaf litter from deciduous riparian forest were examined in a headwater section of Horonai Stream, a low-gradient, gravel-bed stream in southwestern Hokkaido, Japan. During the leaf-fall season (late September-early November), total inputs exceeded total outputs, and 56% of the former was stored in the stream section. In contrast, during the post-leaf-fall season (mid November-early March), total outputs amounted to 609% of total inputs, suggesting that leaf litter stored during the leaf-fall season was decreased by fluvial transport after all of the leaves had fallen from the riparian trees. Correspondingly, leaf litter retention was highest in late autumn (November), followed by early spring (March), and the lowest in early summer (June). Irrespective of season, pools were more retentive than riffles. Further more, leaf litter retention in riffles and pools increased with woody debris abundance in autumn and early summer, respectively. Pools and woody debris were suggested to be important retention structures in the low-gradient, gravel-bed stream.

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DOI： 10.18960/seitai.49.1_11

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL SCIENCE LTD  

1. The effects of woody debris on stream habitat of juvenile masu salmon (Oncorhynchus masou) were examined at two spatial scales, stream reach and channel unit, for first- to third-order tributaries of the Teshio River in northern Hokkaido, Japan. The forty-eight study reaches were classified into three distinct types: coarse-substrate step-pool (CSP), coarse-substrate pool-riffle (CPR) and fine-substrate pool-riffle (FPR) reaches. Each reach type included reaches with different riparian settings, broadly classified as forest (relatively undisturbed forest and secondary forest after fires) or grassland (bamboo bushland and pasture).
2. The reach-scale analyses showed that neither total pool volume nor pool-to-pool spacing was correlated with woody debris abundance in any of the three reach types. Masu salmon density was positively correlated with both woody-debris cover area and total cover area, but not with total pool volume in the reaches.
3. Channel-unit-scale analyses revealed that woody debris reduced non-pool velocity, increased pool depth and retained fine sediment in pools in FPR reaches, where the size of woody debris was very large relative to the substrate material size. However, woody debris did not influence any of the hydraulic variables (depth, velocity, substrate) in either non-pools or pools of CSP and CPR reaches. Habitat use by masu salmon in non-pools or pools was affected by woody-debris cover area or total cover area rather than by hydraulic variables in any of the reach types.
4. The effects of woody debris on habitat at the reach- and channel-unit scales in the study area were less than those indicated by previous work in the Pacific Northwest, North America, owing to the relatively small size of the riparian trees. However, the overall results suggested that woody debris in the study area contributed to masu salmon habitat by providing cover at the smaller, microhabitat scale.

DOI： 10.1046/j.1365-2427.1998.00346.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL RESEARCH COUNCIL CANADA  

Relationships between abundance of juvenile masu salmon (Oncorhynchus masou) and stream habitat were analyzed on two spatial scales, stream reach and channel unit, in northern Hokkaido, Japan. Reach-scale analyses revealed that high water temperatures limited the salmon population level and that the salmon abundance increased with cover availability. These two limiting factors were strongly associated with the presence of riparian forest, emphasizing its importance for the salmon population. Channel-unit scale analyses showed greater use of pools by the salmon, with greater depth and abundant cover underlying the patterns of habitat use. However, the relative importance of depth and cover varied among the reach types having different cover availability. In reaches that had abundant cover, cover itself was less important in determining patterns of habitat use within the reaches. In contrast, in reaches with poor cover, patterns of habitat use were strongly affected by cover. The results indicated that habitat characteristics at the reach scale affect not only the salmon abundance of the stream reaches, but also the determinants of local abundance patterns of the salmon within the reaches. It was suggested that larger-scale influences in a hierarchy of habitat scales should be considered for better understanding of fish-habitat relationships.

DOI： 10.1139/cjfas-54-6-1331

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DOI： 10.18960/seitai.46.1_9

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DOI： 10.18960/seitai.44.2_151

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC SCI FISHERIES TOKYO UNIV FISHERIES  

Diet, foraging behavior, growth, sexual maturity, and spawning site selection were studied in a wild population of exotic rainbow trout Oncorhynchus mykiss in the spring-fed Horonai stream in Hokkaido, Japan. During spring and summer, the rainbow trout ale primarily aquatic and terrestrial invertebrates, but eggs and larvae of river sculpin Coitus nozawae constituted 10% of the diet by number in spring. Rainbow trout typically held focal points in the stream Bow and intercepted food items in the drift. Sexually mature individuals caught in late January were ages 1-5(+). Males ranged 11.0-36.5 cm and females 16.8-33.1cm in fork length. Females constructed spawning redds in calm riffles with fine gravel substrate. Our results suggest that introductions of rainbow trout may have detrimental effects on Japanese stream fishes and other aquatic biota through interspecific competition for food and space and/or predation.

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Language：English   Publishing type：Research paper (scientific journal)  

Diet, foraging behavior, growth, sexual maturity, and spawning site selection were studied in a wild population of exotic rainbow trout Oncorhynchus mykiss in the spring-fed Horonai stream in Hokkaido, Japan. During spring and summer, the rainbow trout ate primarily aquatic and terrestrial invertebrates, but eggs and larvae of river sculpin Cottus nozawae con-stituted 10% of the diet by number in spring. Rainbow trout typically held focal points in the stream flow and intercepted food items in the drift. Sexually mature individuals caught in late January were ages l-5+. Males ranged 11.0-36.5 cm and females 16.8-33.1 cm in fork length. Females constructed spawning redds in calm riffles with fine gravel substrate. Our results suggest that introductions of rainbow trout may have detrimental effects on Japanese stream fishes and other aquatic biota through interspecific competition for food and space and/or predation. © 1993, The Japanese Society of Fisheries Science. All rights reserved.

DOI： 10.2331/suisan.59.1837

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Language：Japanese  

CiNii Books

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Language：Japanese  

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Language：Japanese  

CiNii Books

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Publisher：北海道大学図書刊行会  

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CiNii Books

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Language：Japanese   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Presentation type：Poster presentation  

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Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Presentation type：Poster presentation  

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