Influence of modern irrigation,drainage system and water management on spawning migration of mud loach, <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis> C.

We investigated the influence of human activities on the spawning migration of the mud loach, Misgurnus anguillicaudatus. Mud loaches migrate from rivers to paddy fields for spawning. In this study, the number of adult loaches in paddy fields showed a peak in late May and rapidly decreased in July. In early July, water is discharged from paddy fields in order to allow the fields to dry for a few weeks, and water is again supplied later. The spawning season of the loaches probably spans from mid May to August; this was concluded by observing physiological indicators such as the gonad somatic index, oocyte maturity and serum levels of testosterone, estradiol-17β and 17α, 20β-dihydroxy-4-pregnen-3-one. When the loaches mature, they migrated to paddy fields if they could swim upward through the drainage ditches. However, the drainage ditches of modern paddy fields were reconstructed to deepen the water levels. The artificial drought of the rice culture management led to a discharge of water and loaches from the paddy fields during their spawning season. These results indicate that modern rice cultivation causes obstruction of the migration route and loss of spawning grounds; consequently, loaches use limited space and period of the paddy field for their spawning.     

Conversion from natural wetlands to paddy field alters the composition of soil bacterial communities in Sanjiang Plain,Northeast China

The Sanjiang Plain is the largest freshwater wetlands in Northeast China. In order to feed the growing population, about 84 % of the wetlands in this area have been converted to farmland, especially to paddy fields, since the 1950s. However, little is known about the influence of this conversion on soil microbial community composition. In this study, soil samples were collected from two natural wetlands dominated by plant species Carex lasiocarpa and Deyeuxia angustifolia and from a neighboring paddy field that was changed from wetland more than 10 years ago. The composition and diversity of bacterial communities in the soils were estimated by clone library analysis of nearly full length of 16S rDNA sequences. The results revealed that bacterial diversity was higher in paddy fields, and that the composition of bacterial communities differed among the three samples; the difference was more notable between the paddy field and two natural wetlands than between two natural wetlands. The distribution of clones into different bacterial phyla differed among soil samples, and the conversion from natural wetlands to paddy field increased the abundance of Proteobacteria and Firmicutes but decreased the abundance of Chloroflexi. About 63 % and 71 % of clones from two natural wetlands and 49 % of clones from the paddy field had <93 % similarity with known bacteria, suggesting that the majority of bacteria in natural wetland soils in the Sanjiang Plain are phylogenetically novel. In general, this study demonstrated that long-term conversion from natural wetlands to paddy field changes soil bacterial communities in the Sanjiang Plain.     

A preliminary investigation into the use of the invasive golden apple snail,Pomacea canaliculata (Lamarck, 1822), as a water purifier and food source in the breeding ponds of the oriental weatherloach Misgurnus anguillicaudatus (Cantor, 1842)

This study investigated the feasibility of using an invasive snail, Pomacea canaliculata, as a food source and water purifier for the commercial breeding of the loach Misgurnus anguillicaudatus. The predatory potential of M. anguillicaudatus (3.5–5.5?g) against hatchling snails was evaluated in aquaria and simulated paddy fields. Some hatchling snails left the water to avoid being preyed upon by the loaches, and approximately 10 hatchlings died per day in the presence of five loaches in aquaria, whereas a weaker snail control effect was observed in the simulated paddy fields. The growth of rice seedlings (Oryza sativa) was not reduced by the presence of hatchling snails alone, but the shoot biomass of seedlings coexisting with snails was promoted after introducing the loaches. Additionally, the presence of P. canaliculata adults improved the aquatic environment in the short term for loach breeding by decreasing the turbidity of the water. Importantly, M. anguillicaudatus (12–18?g) mortality decreased and its weight increased in the presence of adult snails.     

Effect of loach consumption on the reproduction of giant water bug Kirkaldyia deyrolli: dietary selection, reproductive performance, and nutritional evaluation

Rice fields provide major habitats for lentic aquatic insects including the giant water bug Kirkaldyia (=Lethocerus) deyrolli (Heteroptera: Belostomatidae) in Japan. Previous researchers have emphasized that conserving populations of the frogs, Hyla japonicus and Rana nigromaculata, is very important for preserving K. deyrolli because these frogs were found to be a major component of the diet of K. deyrolli adults. However, these previous studies were carried out in rice fields with no loaches, Misgurnus anguillicaudatus, which were probably been inhabited by loaches in the past. A series of field surveys and laboratory experiments were conducted to determine the dietary preference of K. deyrolli adults for loaches, frogs, and aquatic insects; the reproductive effects of consuming these foods; and their protein content. In the rice fields, K. deyrolli adults ate loaches when they were available. When the three prey species (frog: R. nigromaculata, loach: M. anguillicaudatus, and dragonfly: Orthetrum albistylum speciosum) were supplied in laboratory conditions, K. deyrolli adults ate more loaches than frogs or dragonflies. In addition, K. deyrolli adults provided with loaches or frogs laid more egg masses within the limited breeding season than when provided with dragonflies. The edible parts of the loach bodies were the largest of the three prey types. It is possible that K. deyrolli adults have been forced to eat frogs due to reductions in the population density of loaches because modern rice cultivation obstructs loach migration routes and reduces their spawning grounds.     

Distribution of the oriental weatherloach, Misgurnus anguillicaudatus, in paddy fields and its implications for conservation in Sado Island, Japan

The distribution of the oriental weatherloach, Misgurnus anguillicaudatus, together with related environmental factors were surveyed at 185 paddy field locations on Sado Island in Japan. This was associated with the reintroduction of the Japanese crested ibis, Nipponia nippon, which prefers to feed on the loach. Loach were found to be present at 90 locations (49%). Analysis with GIS, GLM and AIC revealed that positive factors for the loach distribution included the presence of an earth ditch, the connections at outlets and the proportion of paddy field area within an 800 m radius. Conversely, pumping-up water irrigation and flow irrigation affected loach distribution negatively. In an interview survey that was conducted concurrently, older farmers in the area recalled that the loach had once been distributed over almost the entire island (89/96, 93%) about half a century ago. The farmers also suggested that the impact of agricultural chemicals was one of the main reasons for loach reduction or local extinction. A map of the current potential loach distribution was made using the best fit model from GIS variables. The loach was expected to be distributed in the Kuninaka region with high probability (60–100%) and in patches in the Osado and Kosado regions with low–medium probability (10–50%). As a feasible scenario for the conservation of the loach, another predictive map of the loach distributions was made using a model fit based on the GIS variables and outlet connection, in which the all of the outlets were presumed to be connected to the ditches without gaps. In this case, the loach were expected to be distributed almost throughout the paddy fields with medium–high probability (40–100%). In another scenario that presumed the complete land consolidation of all the paddy fields, the probability of loach occurrence was low (0–30%) throughout the island with the exception of the island’s center in the Kuninaka region.     

Characterization of the Major Capsid Genes (g23) of T4-Type Bacteriophages in the Wetlands of Northeast China

To obtain genetic information and to evaluate the composition of T4-type bacteriophage (phage) communities in wetlands, environmental soil and water DNAs were obtained from two natural wetlands dominated by Carex lasiocarpa and Deyeuxia angustifolia plant species, and a neighboring paddy field in Sanjiang plain of northeast China. The biomarker gene of g23, which encodes the major capsid protein of T4-type phages, was amplified with primers MZIA1bis and MZIA6, and the PCR products were cloned and sequenced. In total, 96 and 50 different g23 clones were obtained from natural wetlands and a paddy field, respectively. A larger number of clones with low levels of identity to known sequences were found in water than in soil both in the natural wetlands and the paddy field, suggesting that many of T4-type phages in wetland water and paddy floodwater in Sanjiang plain are uncharacterized. Phylogenetic analyses showed that the g23 clones in natural wetlands, irrespective of water and soil, were distinctly different from those in marine waters, lake waters, and upland black soils, but were similar to those in paddy fields. The UniFrac analysis of g23 assemblages indicated that T4-type phage community compositions were different between soils and waters, and also were different between the natural wetlands and the paddy field. In general, the global analysis of g23 clone assemblages demonstrated that T4-type phage community compositions were different among natural wetlands, marines, lakes, paddy fields, and upland black soils.     

Indirect positive effects of agricultural modernization on the abundance of Japanese tree frog tadpoles in rice fields through the release from predators

In Japan, the density of Japanese tree frogs (Hyla japonica) may not be necessary high in traditional rice fields compared to modern fields because the modernization of drainage systems from shallow earthen ditches to deep concrete-line ones reduces the abundance of predators/competitors for tadpoles, such as dojo loach (Misgurnus anguillicaudatus). This hypothesis was tested using two approaches. First, laboratory experiments revealed that the presence of the loach significantly reduced the survival of tree frog eggs and tadpoles. Second, observational studies in rice fields showed that the direct effect of modernization on tadpoles was not significant but the indirect (and thus total) effects were weakly positive due to the reduction in the density of dojo loach. Our study suggests that recent agricultural intensification in rice fields does not negatively impact all aquatic species but that some species may not be affected or can even flourish by having tolerance for the changes and release from potential predators or competitors.     

The distribution of an invasive fish species is highly affected by the presence of native fish species: evidence based on species distribution modelling

Topmouth gudgeon (Pseudorasbora parva) is one of the most invasive aquatic fish species in Europe and causes adverse effects to ecosystem structure and functioning. Knowledge and understanding of the species’ interactions with the environment and with native fish are important to stop and prevent the further spread of the species. Creating species distribution models is a useful technique to determine which factors influence the occurrence and abundance of a species. We applied three different modelling techniques: general additive models, random forests and fuzzy habitat suitability modelling (FHSM) to assess the habitat suitability of topmouth gudgeon. The former two techniques indicated that the abundance of native fish (i.e. biotic variables) was more important than environmental variables when determining the abundance of topmouth gudgeon in Flanders (Belgium). Bitterling (Rhodeus amarus), stone loach (Barbatula barbatula), three-spined stickleback (Gasterosteus aculeatus) and predator abundance were selected as the most important biotic variables and implemented in the FHSM to investigate species interactions. Depending on the preferred food source and spawning behaviour, either coexistence or interspecific competition can occur with bitterling, stone loach and three-spined stickleback. In contrast, the presence of predators clearly had a top down effect on topmouth gudgeon abundance. These findings could be applied as a biological control measure and implemented in conservation strategies in order to reduce the abundance of earlier established populations of topmouth gudgeon.     

上海市湿地景观格局时空演变与驱动机制的量化研究

基于1980-2018年上海市历史遥感数据,定量研究上海市湿地景观格局变化及其驱动机制。为此,采用Fragstats 4.2.1计算了景观格局指数,并在数据处理系统软件平台使用灰色关联系统分析了湿地景观格局与社会、经济以及自然环境之间的灰色关联度。结果表明：（1）自1980以来,上海市湿地面积持续缩减,尤其水田损失最多。截至到2018年,上海市共损失了21.06×10⁴hm²的湿地,现存湿地面积为38.22×10⁴hm²,其中人工湿地占85%,自然湿地占15%。人工湿地以水田为主,自然湿地以河流湿地为主。水田和河流斑块平均面积总体上呈波动缩小趋势。河流湿地的形状复杂性最高,其总面积在年际间缓慢缩减,平均分形维度指数年际间波动持平。水田平均分形维度指数年际间波动上升,景观形状向复杂化趋势发展。（2）1980-2010年间,湿地景观破碎化程度总体加剧,最大斑块指数呈波动下降趋势。2010年后,景观破碎化局势向好,最大斑块面积扩大。1980-2015年间,蔓延度指数呈波动下降趋势,香农多样性指数呈波动上升趋势。2015年是蔓延度指数和香农多样性指数变化的转折点。水库坑塘斑块形状较简单,年际间变化小,而且具有结构的自相似性。（3）湿地景观格局受自然、人为双重因素影响。城市扩张导致人工湿地面积减少。自然湿地的演变则主要受气温和降雨的影响。自然因素往往在较大的时空尺度上控制着湿地的景观格局变化。但随着经济的迅速发展,在较短的时间尺度上,国家政策等人为因素对景观格局的影响力逐渐增强。未来,国家对城市湿地保护政策的实施可以使湿地景观格局向好的方向演化。     

Fish mortality and physicochemistry in a managed floodplain wetland

Patterns of fish mortality and associated physicochemical factors werestudied during late spring in a managed wetland canal along the lowerMissouri River, Missouri. Mean dawn dissolved oxygen was lower and meanun-ionized ammonia and turbidity were higher during the fish kill thanbefore or after the kill, or than was observed in a nearby wetland canalwhere no fish kill occurred. Dissolved oxygen at dawn and un-ionizedammonia concentrations were at critically low and high levels respectively,so that both likely contributed to the fish mortality. Timing and magnitudeof observed carcasses suggested that Ameiurus melas Rafinesques wasthe most tolerant species for the sizes observed compared to Ictiobuscyprinellus Valenciennes, Lepomis macrochirus Rafinesque, Cyprinus carpio Linneaus, and Lepomis cyanellus Rafinesque.Decreasing mean lengths of fish carcasses during the fish kill for C.carpio, L. cyanellus, and A. melas, indicate that smaller fishes mayhave been more tolerant of harsh environmental conditions than largerindividuals of the same species. Differential mortalities among species andsizes during drawdowns in actively managed wetland pools may haveintentional and unintentional ramifications on wetland and riverine fishcommunity structure, fish-avian interactions, and implementing anecosystem management perspective to restoring more naturalized riverfloodplain wetland functions. Late summer and early autumn draining ofmanaged wetlands might be used to benefit a wider diversity of wildlife andfishes.     

Reproduction, Growth, and Migration of Fishes in a Regulated Lowland Tributary: Potential Recruitment to the River Meuse

Many European rivers are characterized by a canalized main channel, steep stony embankments, the absence of aquatic vegetation, regulated flow dynamics, reduced hydrological connectivity to the floodplains and a lack of spawning and nursery areas for many fish species. In such regulated rivers, tributaries may be particularly important for recruitment of fish populations in the main channel. This paper describes the reproduction, growth and migration of fishes in the Everlose Beek, a regulated lowland tributary stream of the river Meuse (The Netherlands), using bi-weekly sampling from January to December 2002. A total of 8615 fishes were caught, belonging to 13 different species. The fish species were classified into three groups, viz., residents, migrants and transients, based on the presence of various life-stages in the tributary. Size-frequency data suggest that each group uses the Everlose Beek differently: (i) Stone loach (Barbatula barbatula), Gudgeon (Gobio gobio) and Three-spined stickleback (Gasterosteus aculeatus) were resident species using the tributary as a spawning, nursery and adult habitat; (ii) Bream (Abramis brama), Roach (Rutilus rutilus), Rudd (R. erythrophthalmus), Tench (Tinca tinca), and Pike (Esox lucius) were migratory species, using the tributary as a spawning area, as well as a nursery habitat during their first year of growth, but migrating towards the river Meuse typically at a length of 5–15 cm; and (iii) Bleak (Alburnus alburnus), Sunbleak (Leucaspius delineatus), Carp (Cyprinus carpio), Crucian carp (Carassius carassius), and Perch (Perca _,fluviatilis) were transient species, characterized by an absence of reproduction, ^.and the occurrence in very low densities of >age-1 juveniles and adults only. Lowland tributaries, such as the Everlose Beek, can contribute to the recruitment of particularly migrant species, hence contributing to fish populations of the regulated river Meuse.     

Effects of reclamation of natural wetlands to a rice paddy on dissolved carbon dynamics in the Sanjiang Plain,Northeastern China

Natural wetlands play an important role in the global carbon cycle, and loss of dissolved carbon through water has been indicated as one of the most important carbon sources for riverine ecosystems. During the last century, a large natural wetland area was reported to be converted to other land use types such as rice paddy land around the world. In this study, we explored the dynamics of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in two natural freshwater wetlands and a rice paddy field, which was reclaimed from the natural wetlands in the Sanjiang Plain, Northeastern China, during the growing season (May–October) of 2009. The DOC and DIC concentrations in the two ecosystems were significantly different (P < 0.05). The mean DOC concentrations during the growing season in the surface water of the Deyeuxia angustifolia and Carex lasiocarpa wetlands were 49.88 ± 5.44 and 27.97 ± 1.69 mg/L, respectively, while it was only 8.63 ± 2.54 mg/L in the rice paddy field. Specific ultra-violet light absorption at 254 nm (SUVA₂₅₄) of DOC increased by an average of 19.54% in the surface water from the natural wetlands to rice paddy, suggesting that DOC mobilized in the natural wetlands was more aromatic than that in the rice paddy field. The mean DIC concentration in surface water of the rice paddy was 5.25 and 5.04 times higher than that in the natural D. angustifolia and C. lasiocarpa wetlands, respectively. The average ratio of DIC to dissolved total carbon (DTC) for the water sampled from the artificial drainage ditch in the rice paddy field was 61.82%, while it was 14.75% from the nearby channel of natural wetlands. The significant differences in dissolved carbon concentration in surface water and channels originating from different land use types suggested that reclamation of natural wetlands to rice paddy field would reduce DOC runoff and increase the DIC concentration to adjacent watersheds. Our study results for the changed pattern in dissolved carbon after the natural wetland was transformed to paddy field could have important implications for studying the impacts of the large-scale land use change to carbon cycle and management.     

A passive integrated transponder tag implanted by a new alternative surgical method: effects on the oriental weather loach (Misgurnus anguillicaudatus) and application in a small irrigation system

We validated the effects of a passive integrated transponder (PIT) tagging process on the oriental weather loach Misgurnus anguillicaudatus. Laboratory experiments were conducted to assess the effects of PIT tagging on fish survival, growth, wound healing, and tag omission. Two tagging protocols, standard syringe injection versus insertion through a small hole pierced by a fine needle-shaped awl, were compared using a 12.5 × 2.07 mm² tag. A control group was also included. In comparison with the awl technique, syringe injection heightened the mortality of the loach and delayed healing of the wound caused by tag insertion. No effects of either PIT tagging method were detected on the growth of surviving loach. We also field-tested similarly tagged populations within a river-based irrigation system of Sado Island, Japan. Two different sized tags (long, 12.5 × 2.07 mm²; short, 8.5 × 2.12 mm²) were compared by using antenna loggers which detected fish movement through gates and automatically logged tagged fish’s tag IDs and timestamps. By comparing logged data and actual fish collection surveys both below and above the gates, 77% and 30% of actual loach movements were confirmed to have been successfully logged for the long and short tags, respectively. The awl insertion technique with the longer tag is therefore recommended for use in similar studies of smaller fish species.     

Detection of hybridization between two loach species (<Emphasis Type="Italic">Paramisgurnus dabryanus</Emphasis> and <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis>) in wild populations

Artificial interspecific hybrids between large scale loach P. dabryanus and tetraploid pond loach M. anguillicaudatus (Cobitidae, Cypriniformes) are viable. To detect the occurrence of possible natural hybridization, genetic analyses by using microsatellite markers were performed for natural populations of large scale loach and pond loach, the reciprocal laboratory hybrids, and “supposed hybrids” with ambiguous morphology. The fertility of the artificial hybrids was also tested. At one diagnostic microsatellite (Mac50), one out of 20 “supposed hybrids” was identified to be F₁ hybrid between the two loach species because it had the same genotype as that of the laboratory hybrids. The triploid hybrids between the two species were confirmed to be female-sterile. The results show that rare hybridization has occurred between diploid large scale loach and tetraploid pond loach in nature although it may have little effect in genetic introgression. This study is helpful for fish conservation and encourages further investigation on natural hybridization and introgression of loaches.     

Molecular and morphological analyses revealed a cryptic species of dojo loach Misgurnus anguillicaudatus (Cypriniformes: Cobitidae) in Japan

Although it has been reported that populations of the Japanese dojo loach Misgurnus anguillicaudatus (Cypriniformes: Cobitidae) belong to two distinct mitochondrial (mt)DNA (Type I and Type II), the taxonomic status of the species remains unresolved. To address this question, nuclear DNA and morphological analyses were performed on M. anguillicaudatus population in the Nakaikemi Wetland, where Type I and Type II lineages are sympatric. Results suggest the existence of a cryptic species (Type I) within the Japanese dojo loach.     

Waterbird habitat-selection during winter and spring in reclaimed coastal wetlands in Nanhui Dongtan, Shanghai

From December 2009 to May 2010 goose and duck (Anatidae) community censuses in winter and shorebird (Charadriiforms) community censuses in spring were conducted across three types artificial wetlands (urban lake wetland, restorative wetland, abandoned wetland) along the coast of Nanhui, Shanghai. Correlation analyses were undertaken between community indices and habitat factors. The results showed there were significant differences in the density of geese and ducks among the wetlands, but no difference in the number of species. The density of geese and ducks in the restorative wetland was 3.77 times that of abandoned wetland and 6.03 times that of urban lake wetlands. The number of species and density of shorebirds in restorative wetlands was 2.88 and 5.70 times that of abandoned wetlands. We found significant differences in the number and density of shorebird species between restorative and abandoned wetlands. The number of species density of geese and ducks and the Shannon-Wiener (H') index were positively correlated with water area. The number of species and H' were negatively correlated with vegetation area. The number of species, species density and H' and evenness were negatively correlated with vegetation coverage. H' was positively correlated with mean water level. The results showed that the number and density of shorebird species were positively correlated with bare muddy areas. Aquaculture ponds and paddy fields in reclaimed area is efficient sufficient compensation mechanism to maintain more water areas for waterbirds and to control vegetation expansion and maintain shorebird habitat after coastal reclamation.     

Optimising environmental watering of floodplain wetlands for fish

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Morphological comparison and DNA barcoding of four closely related species in the genera Misgurnus and Paramisgurnus (Cypriniformes: Cobitidae)

To evaluate the feasibility of morphological and genetic identification of the closely related species in the genera Misgurnus and Paramisgurnus, the morphological characters of four species in these genera and DNA barcoding of five loaches (P. dabryanus, M. anguillicaudatus, M. bipartitus, M. mohoity, and Barbatula toni) were investigated. Twelve morphological characters were measured in 542 individuals to perform the comparative analysis. Among these characters, only the caudal peduncle length (L_CP) revealed significant difference (P < 0.05) among these four species. The clustering based on morphological characters formed two clusters (P. dabryanus and M. anguillicaudatus; M. bipartitus and M. mohoity). A total of 186 COI fragments for the five loaches investigated were sequenced and analyzed. The results showed that interspecific K2P distance was much higher than intraspecific distance within the five species. Bayesian inference of phylogeny showed that individuals of these species were divided into five specific clades. Meanwhile, the COI fragments exhibited 22 character attributes for the differentiation of the five loach species based on character-based method. Our results suggested that DNA barcoding based on COI can be used as an efficient identifier of these five loach species; the combination of distance-based method, Bayesian inference and character-based approach provides higher resolution of identification at species level.     

Non-random sampling and its role in habitat conservation: a comparison of three wetland macrophyte sampling protocols

Aquatic macrophytes provide essential spawning and nursery habitat for fish, valuable food source for waterfowl, migratory birds and mammals, and contribute greatly to overall biodiversity of coastal marshes of the Laurentian Great Lakes. Two approaches have been used to survey the plant community in coastal wetlands, and these include the grid (GR) and transect (TR) methods. These methods have been used to identify the average species richness at different sites, but their suitability for determining total species richness of a site has not been tested. In this paper, we compare the performance of these two established methods with that of the Stratified method (ST), which uses the sampler’s judgment to guide them to different habitat zones within the wetland. We used the three protocols to compare species richness of six coastal wetlands of the Great Lakes, three pristine marshes in eastern Georgian Bay (Lake Huron) and three degraded wetlands in Lake Ontario, Canada. The greatest species richness was associated with the ST method, irrespective of wetland quality. The ST method was also more efficient (fewer quadrats sampled), and revealed the most number of unique (those found with only one method) and uncommon species (those found in <5% of the quadrats). Despite these statistical differences, we found that sampling method did not significantly affect the performance of a recently developed index of wetland quality, the Wetland Macrophyte Index. These results have important implications for designing macrophyte surveys to track changes in biodiversity and wetland quality.     

Demonstration of migration of juvenile cyprinid fish using parasite biomarkers

Migration of juvenile (0+) cyprinid fish from the Kiso River to experimental streams in the Aqua Restoration Research Center was demonstrated by the presence of parasites on fish. The experimental streams were located a minimum of 0.7 km from the main reach of the Kiso River, and they were connected via a tributary (Shinsakai River). The experimental streams were used as a spawning site and a nursery for juveniles, similar to the use of a temporary water body such as a paddy field. A digenean trematode (Centrocestus spp.) and the glochidia of unionid bivalves, both of which did not infect fish in the experimental streams or in the Shinsakai River, were used as marker parasites. Their presence indicated that the fish moved in the experimental streams from the Kiso River. For both fish species (Gnathopogon elongatus and Zacco platypus) assessed in this study, juveniles greater than 20–30 mm standard length could migrate from the Kiso River. This study showed that temporary waters are important as a nursery for juvenile fish, for whether or not a species spawns there. For the conservation of fish populations, it is important that temporary waters that are used as a nursery are connected with a permanent water area by a channel, through which not only adults, but also juvenile fish can migrate.