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In this study, the early development of Cobitis striata fuchigamii was described using aquarium-spawned eggs and juveniles. Egg yolk diameter after water absorption was 1.0‒1.1 mm, and the spherical, demersal eggs had a light-yellow yolk, no oil droplets, and low viscosity. Newly hatched larvae [4.0–4.5 mm in total length (TL)] had 44‒45 (27‒28 + 17‒18) myomeres (26‒27 between the pectoral fins and the middle of the anus), two pairs of short tubular outer gill filaments on the cheek, and only a few melanophores on parts of the eye. Notochord flexion began at 5.1–6.8 mm TL and ended at 10.0 mm TL. The number of fin rays on each fin was finalized at approximately 25.0 mm TL. Lateral line spots of the larvae were indistinct, and juveniles formed blotches at approximately 25.0 mm TL. The barbels were formed in the following order: third, second, and then first. The formation of membranous fins occurred in the following order: pectoral, caudal, dorsal, anal, and then pelvic; full fin ray complements occurred in the caudal, dorsal, anal, pectoral, and pelvic regions. Some individuals (5.1–7.5 mm TL at the flexion stage) had free lateral neuromasts on the caudal region, each with a short cupula.

[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).

The Kanehira bitterling, Acheilognathus rhombeus, is a freshwater fish, discontinuously distributed in western Japan and the Korean Peninsula. Unusually among bitterling it is an autumn-spawning species and shows developmental diapause. Consequently, the characterization of its evolutionary history is significant not only in the context of the fish assemblage of East Asia, but also for understanding life-history evolution. This study aimed to investigate the phylogeography of A. rhombeus and its sister species Acheilognathus barbatulus, distributed in China, using a mitochondrial analysis of the ND1 gene from 311 samples collected from 50 localities in Japan and continental Asia. Phylogenetic analysis revealed that A. barbatulus is included in A. rhombeus and genetically closer to Japanese A. rhombeus than to Korean A. rhombeus. Divergence of Korean A. rhombeus and A. barbatulus from Japanese A. rhombeus was estimated to be from the late Pliocene (3.44 Mya) and the early Pleistocene (1.98 Mya), respectively. Each event closely coincided with the time of the Japan Sea opening. Japanese A. rhombeus comprised seven lineages: three in Honshu and four in Kyushu. One lineage in central Kyushu was genetically closer to the Honshu lineages than to other lineages in northern Kyushu. Divergence of Japanese lineages was estimated to be from the early to middle Pleistocene (0.55-0.93 Mya), during a period of geological and paleoclimatic change, including volcanic activity. Population expansion in the late Pleistocene (

1. For effective biodiversity conservation, verifying the correspondence of conservation sites among taxa and identifying the environmental characteristics of these sites are essential; however, only a few such studies have been performed in estuaries. The aim of the present study was to verify the surrogacy of estuarine gobies and crabs, to identify tidal rivers of high conservation priority, and to describe their environmental characteristics. / 2. Distribution data for gobies and crabs were collected from 158 tidal rivers in the Kyushu region, Japan. Three conservation scenarios were analysed based on the distribution data of gobies alone, of crabs alone, and of both taxa, in order to assess the correspondence of the conservation candidates (i.e. tidal rivers) between taxa. / 3. The degree of correspondence was poor for the candidates selected on the basis of the distribution data of gobies or crabs separately. More efficient candidates were selected based on the data for both taxa. The environmental characteristics of tidal rivers with high irreplaceability for conservation differed between the taxa. Tidal rivers forming and maintaining large tidal flats covered with fine sediment might have high irreplaceability for goby conservation, whereas rivers with saltmarshes connected to supratidal and intertidal zones might have high irreplaceability for crab conservation. / 4. Tidal rivers with a high priority for conservation were identified by overlapping the candidates for three scenarios. These tidal rivers are not necessarily large, but have steep basins with river mouths that are less exposed to ocean waves. Moreover, the percentage of artificial areas in these rivers was low, suggesting that these rivers have not been exposed to excessive anthropogenic disturbance that leads to loss of estuarine habitat. / 5. These results show that gobies and crabs are not surrogates for one another.

Rhodeus ocellatus kurumeus is a small cyprinid fish endemic to the Japanese archipelago. This fish frequently hybridizes with an exotic subspecies Rhodeus ocellatus ocellatus, and non-introgressed populations of R. o. kurumeus have greatly decreased. Previous studies based on mitochondrial and nuclear DNA identified introgressed populations and inferred phylogenetic relationships, but these approaches may lead to underestimates of introgression or ambiguous results owing to the small number of genetic markers used. The present study applied double digest restriction site-associated DNA (ddRAD) sequencing to assignment tests and phylogenetic inferences. Data matrices can vary in size and content depending on the strategies used to process ddRAD sequences; therefore, we prepared 25 data matrices with various processing strategies. The assignment tests based on the 25 data matrices resulted in similar assignment patterns and provided evidence for introgression in some populations that had been identified as non-introgressed populations in previous studies. The maximum-likelihood (ML) phylogenetic trees differed in robustness and topology among the 25 matrices; interestingly, ML trees with low statistical support reflected geographical distributions of fish better than ML trees with high statistical support. These results indicate that ddRAD sequencing can detect introgression with greater sensitivity than conventional DNA markers, that ddRAD sequencing is useful for phylogenetic inference among closely related populations within a subspecies, and that statistically robust ML trees do not necessarily reflect the true phylogeny. Application of ddRAD data to conservation genetics and evolutionary history of this subspecies are also discussed.

Estuaries are important environments for the sustainable use of natural resources; however, these coastal areas are deteriorating continuously owing to anthropogenic impact, and thus their conservation has become a global issue. This study aimed to identify the physicochemical factors that influence goby fauna and richness, which have high species diversity in temperate riverine estuaries, by conducting field surveys. We collected gobies and measured six physicochemical factors (median particle size; percentage of gravel, sand, and mud; salinity; and elevation) in the intertidal zone of two riverine estuaries flowing into the Seto Inland Sea of Japan. Twenty-six species of gobies were found at 191 sites during our surveys. To classify the survey sites by goby fauna, we stratified 132 sites, where more than two species of goby were found, into seven groups by using two-way indicator species analysis. The results of canonical correspondence analysis and classification and regression tree suggested that the goby fauna changed along these physicochemical environmental gradients. In particular, sediment characteristics might be an important factor that influences the goby fauna. However, no relationship was found between species richness of gobies, as revealed by the result of generalized linear mixed model. Therefore, our data indicate that species diversity of gobies utilising various environments cannot be maintained by conservation of a specific environment in riverine estuaries. The diversity and heterogeneity of the physicochemical environments, especially sediment conditions, need to be maintained and controlled for the conservation of the gamma diversity of estuarine goby.

The Chinese false gudgeon, Abbottina rivularis, is a common cyprinid fish that is widely distributed throughout continental East Asia, but exhibits a restricted, discontinuous distribution in western Japan, including Honshu and Kyushu islands. In this study, analyses of mitochondrial (cytochrome b) and nuclear (glyt, myh6, and RAG1) genes were conducted to investigate patterns and magnitudes of intraspecific differentiation among A. rivularis populations in Japan and adjacent continental areas. Phylogenetic analysis of the mitochondrial gene sequences resolved four major lineages—the Japan lineage (JL), a northern continental lineage (NCL), and two southern continental lineages (SCL1 and SCL2)—with uncorrected pairwise sequence distances of 9.4–15.2% (estimated divergence times, 7.9–17.1 Myr). Two lineages (JL and SCL1) occurred in both the Honshu and Kyushu districts of Japan. Compared with populations in continental areas, most Japanese populations exhibited less genetic diversity. The JL was divided into two well-differentiated sub-lineages distributed on Honshu and Kyushu islands, respectively. Kyushu Island, as well as areas on Honshu where the species is known to have been introduced, also harbored the SCL1 lineage, which constituted most of the populations on Kyushu. The applied nuclear DNA data strongly suggest that hybridization between the Japan and continental lineages has occurred on Kyushu Island. The artificial introduction hypothesis, instead of a two-origin scenario, best explains the origin of the SCL1 in Japan.

The tri-spine horseshoe crab,Tachypleus tridentatus, is a threatened species that inhabits coastal areas from South to East Asia. A Conservation management system is urgently required for managing its nursery habitats, i.e., intertidal flats, especially in Japan. Habitat suitability maps are useful in drafting conservation plans; however, they have rarely been prepared for juvenileT.tridentatus. In this study, we examined the possibility of constructing robust habitat suitability models (HSMs) for juveniles based on topographical data acquired using unmanned aerial vehicles and the Structure from Motion (UAV-SfM) technique. The distribution data of the juveniles in the Tsuyazaki and Imazu intertidal flats from 2017 to 2019 were determined. The data were divided into a training dataset for HSM construction and three test datasets for model evaluation. High accuracy digital surface models were built for each region using the UAV-SfM technique. Normalized elevation was assessed by converting the topographical models that consider the tidal range in each region, and the slope was calculated based on these models. Using the training data, HSMs of the juveniles were constructed with normalized elevation and slope as the predictor variables. The HSMs were evaluated using the test data. The results showed that HSMs exhibited acceptable discrimination performance for each region. Habitat suitability maps were built for the juveniles in each region, and the suitable areas were estimated to be approximately 6.1 ha of the total 19.5 ha in Tuyazaki, and 3.7 ha of the total 7.9 ha area in Imazu. In conclusion, our findings support the usefulness of the UAV-SfM technique in constructing HSMs for juvenileT.tridentatus. The monitoring of suitable habitat areas for the juveniles using the UAV-SfM technique is expected to reduce survey costs, as it can be conducted with fewer investigators over vast intertidal zones within a short period of time.

We evaluated the morphological, distributional, and genetic characteristics of the freshwater sculpin, Cottus pollux, in Kyushu Island, Japan. Based on pectoral fin ray number, the sculpins inhabiting 30 rivers were divided into two types [modes 13 (M13) and 15 (M15)]. We evaluated four environmental parameters: length of main river (L-MR), average gradient of main river (G-MR), distance from sampling site to river mouth (D-SM), and gradient around sampling site (G-S), and compared the two types. L-MR, D-SM, and G-S were significantly larger for the rivers that contained M13 fish than for those containing M15 fish. M13 individuals were distributed in the upstream areas of large river systems, suggesting a fluvial life history, whereas M15 individuals were distributed in the downstream areas of small river systems, indicating an amphidromous life history. We conducted phylogenetic analysis based on mitochondrial 12S rRNA [788 base pair (bp)] and control regions (386 bp). Mitochondrial DNA analysis showed that both M13 and M15 groups were genetically of C. pollux middle-egg type (ME). Our findings proposed the hypothesis that C. pollux ME in Kyushu Island exhibits dimorphism in both morphological and distributional traits. Additionally, haplotype distribution indicated that the fluvial M13 populations had higher genetic specificity in each river in contrast to the existence of one genetic group of amphidromous M15 individuals in Kyushu Island.

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium-and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a 'very high risk' of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate 'rapid' management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/)., Cefas Science Excellence fund; [TKP2020-NKA-16], This study is dedicated to our co-author, the late Prof. Olaf Weyl, whose sudden passing during field work in November 2020 was received by us with great sadness. This study represents a contribution to the term of reference 'd' (Advance knowledge base to further develop indicators to evaluate the status and impact of non-indigenous species in marine environments) of the ICES working group on Introductions and Transfers of Marine Organisms. The participation of GHC was supported by the Cefas Science Excellence fund. AW and AF were supported by TKP2020-NKA-16 project.

We investigated the spawning nests of Gymnogobius macrognathos on a tidal flat in the Tatara River, Fukuoka Prefecture, Japan. Digging uncovered 19 spawning nests. The number of eggs and the standard length of the guarding male were positively correlated. Nine spawning nests were examined using in situ resin casting. All casts had structures characteristic of callianassid shrimp burrows and were most likely those of Nihonotrypaea japonica. Spawning nests had significantly greater average diameters than shrimp burrow openings and may have been widened by G. macrognathos.

Freshwater mussels (Bivalvia: Unionidae), which are keystone species of freshwater ecosystems, are in global decline. In addition to ecological/genetic studies, morphological examinations are needed to help provide information for the development of additional freshwater mussel studies and eventually conservation efforts for freshwater ecosystems.The microscopic structure, which can be obtained by scanning electron microscopy (SEM) and elemental composition, which can be obtained with energy dispersive X-ray spectrometry (EDS), of mollusc shells are of interest to malacologists. However, information about freshwater mussels is still limited.Kyushu Island is the southernmost island of the four major islands of Japan. Kyushu Island is a hotspot of bitterling fishes in Japan, which simultaneously means that the island is a hotspot of freshwater mussels. The Ryukyu Islands stretch southwest from Kyushu Island to Taiwan; a freshwater mussel of unknown origin was reported from the Ryukyu Islands.Digital archiving for biology and ecology is a continuing challenge for open science. This data paper describes online published photo images, 3D/CT and mtDNA data and SEM/EDS analyses of the shell of freshwater mussels that inhabit the Kyushu and Ryukyu Islands, Japan. Our data will provide basic information regarding freshwater biology and be of public interest as open science.Photo images, 3D/CT data, mtDNA data, SEM images and EDS elemental analysis of freshwater mussels that inhabit the Kyushu and Ryukyu Islands (61 individuals, nine species/subspecies) were published online in a local database (http://ffish.asia/Unionidae3D), GBIF (http://ipt.pensoft.net/resource?r=unionidae3d) and DDBJ/EMBL/Genbank (LC431810–LC431840).

The freshwater Fish Invasiveness Screening Kit (FISK) has been applied in 35 risk assessment areas in 45 countries across the six inhabited continents (11 applications using FISK v1; 25 using FISK v2). The present study aimed: to assess the breadth of FISK applications and the confidence (certainty) levels associated with the decision-support tool’s 49 questions and its ability to distinguish between taxa of low-to-medium and high risk of becoming invasive, and thus provide climate-specific, generalised, calibrated thresholds for risk level categorisation; and to identify the most potentially invasive freshwater fish species on a global level. The 1973 risk assessments were carried out by 70 + experts on 372 taxa (47 of the 51 species listed as invasive in the Global Invasive Species Database www.iucngisd.org/gisd/ ), which in decreasing order of importance belonged to the taxonomic Orders Cypriniformes, Perciformes, Siluriformes, Characiformes, Salmoniformes, Cyprinodontiformes, with the remaining ≈ 8% of taxa distributed across an additional 13 orders. The most widely-screened species (in decreasing importance) were: grass carp Ctenopharyngodon idella, common carp Cyprinus carpio, rainbow trout Oncorhynchus mykiss, silver carp Hypophthalmichthys molitrix and topmouth gudgeon Pseudorasbora parva. Nine ‘globally’ high risk species were identified: common carp, black bullhead Ameiurus melas, round goby Neogobius melanostomus, Chinese (Amur) sleeper Perccottus glenii, brown bullhead Ameiurus nebulosus, eastern mosquitofish Gambusia holbrooki, largemouth (black) bass Micropterus salmoides, pumpkinseed Lepomis gibbosus and pikeperch Sander lucioperca. The relevance of this global review to policy, legislation, and risk assessment and management procedures is discussed.

Environmental changes due to non-native species introductions and translocations are a global concern. Whilst understanding the causes of bioinvasions is important, there is need for decision-support tools that facilitate effective communication of the potential risks of invasive non-native species to stakeholders. Decision-support tools have been developed mostly in English language only, which increases linguistic uncertainty associated with risk assessments undertaken by assessors not of English mother tongue and who need to communicate outcomes to local stakeholders. To reduce language-based uncertainty, the ‘ecology-of-language’ paradigm was applied when developing the Aquatic Species Invasiveness Screening Kit (AS-ISK), a decision-support tool that offers 32 languages in which to carry out screenings and communicate outcomes to stakeholders. Topics discussed include uncertainty related to language-specific issues encountered during the AS-ISK translation and the potential benefits of a multilingual decision-support tool for reducing linguistic uncertainty and enhancing communication between scientists, environmental managers, and policy and decision makers.

The piscivorous chub (Opsariichthys uncirostris) is a Japanese predatory cyprinid with a native distribution restricted to a few large lakes. It has now established in a large region of Japan following accidental translocation. Although large water bodies with abundant food resources were long considered essential for establishing this species, the chub has settled in small irrigation ditches in Kyushu. In this study, we explored the phenotypic responses of the chub in these small water bodies by comparing life history traits and morphology with those of chub inhabiting a native lake. Growth rate, fecundity-related traits, and trunk length shifted markedly following translocation to the new habitat. These phenotypic shifts were typical reactions to characteristic conditions of irrigation ditches, such as habitat instability, lotic conditions, and limited food. Adaptability via a rapid phenotypic shift by the chub may have facilitated establishment of populations in small irrigation ditches.

We collected two gobies, Apocryptodon punctatus and Acentrogobius sp. A, and four alpheid shrimps from an estuary in southern Japan, to identify the symbiotic shrimps with gobies and to understand their partner specificity and dependency. Analysis based on generalized linear models identified two specific partners for each goby. A. punctatus frequently coexisted with partners and showed similar habitats, suggesting that this goby might be an obligate mutualist. Acentrogobius sp. A had lower rates of coexistence and appeared in habitats different from one of its partners, suggesting that this goby might be a facultative mutualist.

Selecting candidate areas to protect the habitats of threatened freshwater fish species is a major challenge in urban areas. Therefore, we conducted a case study using a Marxan analysis based on fish fauna and land use data of five rivers flowing in the Fukuoka Plain, northern Kyushu Island, Japan, to construct priority maps to protect threatened freshwater fishes in the urbanized plain. We organized threatened fish fauna and land use data in the fourth-mesh scale, drawn as a 500-m square, resulting in 147 meshes with fauna and land use data. We assessed two cases—meshes were either analyzed as having the same cost (case 1) or having cost sizes classified into four classes based on cluster analysis of land use data (case 2). We divided the threatened species into those from either stream fish or floodplain fish and analyzed them separately. When meshes with high priority in both case 1 and case 2 were defined as primacy meshes for habitat protection, 10 and 28 meshes were identified in the stream and floodplain fish, respectively. Of the primacy meshes, 40 % for the stream fish and 54 % for the floodplain fish were distributed in urbanized areas, indicating that habitat protection was necessary in several urbanized areas on the plain. Meshes with low priority in case 1 and with high priority in case 2 were defined as the second most important meshes for habitat protection. The number of second most important meshes for the floodplain fish was smaller than that for the stream fish; therefore, the floodplain fish required habitat protection in urbanized areas to a greater extent than the stream fish.

We developed habitat suitability models for eight threatened goby species inhabiting tidal flats in the estuary of Kuma River in Kyushu Island, Japan. The best models selected several environmental factors, which were supported by area under the curve (AUC) values ranging from 0.793 to 0.976. The habitat suitability curves for each variable demonstrated various slopes, suggesting interspecific differences in habitat suitability for each environmental factor. The results suggested that the range of environmental gradients in tidal flats influences the richness of the threatened goby species.

The spawning behaviour of Pseudogobio esocinus was examined in an experimental water tank. Spawning was observed on 66 occasions in five experiments, and one female repeatedly spawned 7–18 times during one night. Four easily distinguishable behavioural phases were recognised during the spawning sequence: phase 1, male nuzzling to the female’s body or face; phase 2, male pursuing a swimming female; phase 3, pair or trio trembling while swimming; and phase 4, spawning (scattering eggs and sperm) near the water surface. The spawning behaviour mainly occurred between pairs (53 times) and occasionally among a trio (13 times). A generalised linear mixed model was used to analyse the relationships between male spawning success and four fixed variables. As a result, more aggressive and larger males tended to be successful spawners. A digital video image of P. esocinus spawning behaviour is available at http://www.momo-p.com/index.php?movieid=momo150129pe01b .

The variability of life history traits in Pseudogobio esocinus was investigated in a single river (Nakagawa River, Kyushu Island, Japan) by comparing two sub-populations inhabiting river reaches with different thermal characteristics. A total of 689 individuals in the upper reach (St. A) and 705 individuals in the lower reach (St. B) were collected from April 2004 to March 2006 at monthly intervals. Water temperatures of both stations were measured by a logger during the period of survey, and these dates clearly showed that St. A was colder than St. B. The sub-population of St. A consisted of six age groups, and the age at maturity was 2 or 3 years. Spawning occurred between April and July, and peaked in May. The sub-population of St. B consisted of four age groups, the age at maturity was 1 or 2 years and spawning occurred between March and July, peaking in April. The length–weight relationship and body condition were also different between the two sub-populations. In conclusion, the sub-population in the colder reach was characterised as longer lived, slower growing and later maturing, with larger body size and higher fecundity compared with the sub-population of the warmer reach. These results showed that the life history traits of P. esocinus were variable under the influence of water temperature, even in a single small river.

Biological invasion by non-native subspecies or populations is one of the most serious threats to ecosystems, because these species might be easily established in the introduced area and can negatively affect native populations through competition and hybridization. Pale chub Opsariichthys platypus, one of the most common fish in East Asia, exhibits clear genetic differentiation among regional populations; however, introgression and subsequent loss of genetic integrity have been occurring throughout Japan due to the artificial introduction of non-native conspecifics. In this study, we developed a simple SNP genotyping method to discriminate between native and non-native mitochondrial DNA (mtDNA) haplotypes in pale chub using real-time PCR assay. We then investigated the distribution patterns of non-native pale chub in Tokai region, located in the center of Honshu Island, Japan and developed a predictive model of the occurrence of non-natives to reveal the factors influencing their invasion. The specificity and accuracy of the genotyping method were confirmed by using samples whose haplotypes were determined previously. Extensive occurrence of non-native haplotypes in Tokai region was detected by this method. In addition, our models suggested that the presence of non-natives varied greatly depending on the river system, and was positively influenced by the impounded water areas. Our method could accurately distinguish between native and non-native haplotypes of pale chub in Japan and suggested key environmental factors associated with the presence of non-natives. This approach can greatly reduce experimental costs be a great contribution for quantitative investigation.

We describe the larval and juvenile development of Pike Gudgeon, Pseudogobio esocinus, using laboratory-reared specimens. Newly hatched larvae with a 4.2–4.6 mm body length (BL) and 22–23 + 16 = 38–39 myomeres had melanophores on their head and body. The yolk sac was completely absorbed at 5.0 mm BL. Notochord flexion was initiated at 5.0–6.0 mm BL and completed at 7.3 mm BL. The aggregate number of all fin rays was completed at 11 mm BL. Several rod-like cupulae were observed on the head and lateral side of the body at 4.2–11.0 mm BL and were completely distinguished at 11.0–14.0 mm BL. Squamation was initiated on the caudal body at approximately 11.0 mm BL and completed at 11.0–14.0 mm BL. The newly hatched larvae had well-developed eyes and large pectoral fins.

The aim of this study was to propose a method for site selection for habitat conservation or restoration of threatened freshwater fishes inhabiting ditches or canals in the main plains of northern Kyushu Island, Japan. The environmental data of 4,084 third meshes in six regions and faunal data of 337 meshes that included 462 sites were analyzed using generalized liner mixed models, and species distribution models with high accuracies were developed for nine threatened species. Habitat conservation or restoration for each species was discriminated using gaps between actual and potential distributions. The number of species under each management was determined for each site, and the management type with a large number of species was selected (Case 1), or the target species were set for each potential faunal group based on similarities of fish fauna, and the type was selected by counting only the target species (Case 2). On the basis of the conserved sites showing actual presences, Case 2 showed higher effectiveness than Case 1. The estimated practices and successes of all habitat managements in Case 2 showed an increase of 1.3–4.6 times for actual presences, with optimal habitats reaching 78–91 % of their potential presence and conserved sites attaining 64–97 % of the actual presence of each species. In the case with special attention to the most threatened species, Acheilognathus tabira nakamurae, a small decrease in effectiveness was noted for several species.

Habitat matching is an important factor for the establishment of alien fishes in recipient environments. The piscivorous chub, Opsariichthys uncirostris uncirostris, originally exclusively inhabited large water areas; however, the species has been introduced and established in small irrigation ditches on Kyushu Island. The evaluation of the habitat use of the piscivorous chub suggested that this alien fish uses the lentic-type irrigation ditches as a nursery ground and the lotic-type ditches as a spawning ground. This finding implies that the establishment of the piscivorous chub may require connectivity between lentic and lotic habitats.

The genetic population structure of the small cyprinid Hemigrammocypris rasborella, distributed widely in lowlands of western Japan, was examined using partial sequence data of mitochondrial DNA (mtDNA). Molecular phylogenetic analysis revealed that the populations of the western Kyushu region were markedly differentiated from all eastern populations, such that the groups would be comparable to different species; their divergence was inferred to have occurred in the Late Miocene–Pliocene. Also, a largely divergent mtDNA group (with divergence in the early Pleistocene) was found in the Sanyo and northeastern Shikoku regions, forming a secondary contact zone in the western Kinki with the eastern mtDNA group. To date, these aspects of the population structure of H. rasborella appear to be unique among lowland fishes in western Japan. Deeper understanding of the formation processes of freshwater faunas in western Japan will require further comparisons of the phylogeographic patterns and ecological traits of constituent species.

We formulated a species distribution model (SDM) for the amphidromous fish Sicyopterus japonicus on the basis of presence/absence data and confirmed its performance at various population densities. The best-fit SDM selected several environmental factors, including water depth and velocity, and performed validated prediction of presence/absence of various densities. The predicted probability of occurrence was positively correlated with the observed density. The density was positively related to habitat occupancy, suggesting that this species occupied a wide range of habitats under high densities, but only optimal habitat under low densities. Therefore, the threshold value for predicting presence/absence increased with decreasing densities.

Topmouth gudgeon (Pseudorasbora parva) is widely known as a highly invasive freshwater fish and has expanded from East Asia (native range) to Central Asia, Europe and Northern Africa (introduced range). Although the relationship between the occurrence of P. parva and its habitat conditions remains unclear, information on factors affecting its distribution, especially in its native range, is important for predicting its expansion. This study provides primary information on the distribution of P. parva in rivers and agricultural canals in northern Kyushu Island, Japan, where the fish is native. Fuzzy habitat preference models (FHPMs) and Random Forests (RF) were applied to link landscape features to the distribution of P. parva based on field observation data collected from two distinct ecoregions, the north-western (NW) and north-eastern (NE) parts of Kyushu Island. The results show a clear habitat preference of P. parva for areas with a lower elevation, a gentler slope and a smaller number of river-to-river connections as general landscape features across the ecoregions. Weak preferences are observed for sites with a higher number of river-to-canal connections, a higher canal network index, a larger area of paddy fields, a larger residential area, more crop fields and fewer forests and orchards. Of these site-specific features, five landscape features – elevation, slope, canal network index, area of paddy fields, and presence of forests and orchards – are identified as the most important features for predicting the distribution of P. parva. The general and specific habitat preference information, as demonstrated in this study, may be important in biogeography and invasion ecology. Further research is needed to accumulate information for a better understanding of the invasion ecology and the design of improved management and control strategies against P. parva. Copyright © 2013 John Wiley & Sons, Ltd.

Information on a population of Abbottina rivularis inhabiting an agricultural ditch was collected during field surveys and was analyzed for age, growth, and habitat use. Measurements of 1,035 individuals revealed that the population had two size classes, a maturation age of 1 year, and a lifespan of 1–2 years. On the basis of the growth pattern and life stage, we classified the life cycle of this species into four stages: the juvenile stage, the immature stage with rapid growth and with no growth, and the adult stage. Habitat use during each stage was analyzed with a generalized linear mixed model. The best fit models revealed that 3–5 environmental factors were important predictors of population size in each stage. In particular, the number of fish increased with increased variation in water depth and with smaller median particle size of the bottom substratum in all stages.

The Kuroshio Current transports various marine organisms, including tropical and subtropical fishes, from the southern regions to the northern Pacific coast of Japan (Senou et al. 2006; Matsuura 2012). The demersal fishes, including brackish water gobies, are transported during the pelagic larval phase (Senou et al. 2006; Maeda et al. 2007; Matsuura 2012). However, the path of the current shows various changes along the Japanese archipelago at various time periods, from days to decades (Kawabe 1995; Yamashiro and Kawabe 1996; Nagano and Kawabe 2004). Thus, it is possible that the path changes of the Kuroshio Current influence the presence/absence of fishes along the coastal areas of the archipelago. In this study, we examined the relationships between the path of the Kuroshio Current and the presence of several gobies by conducting a decadelong monitoring of the northeastern region of the Kyushu Island (Fig. 1a). Data on the presence/absence of fishes were collected from 1999 to 2011 in the brackish water area of the Kita River, Gokase River system, located at the northeastern region of the Kyushu Island and flowing into the Nobeoka Bay (Fig. 1b). Monitoring was conducted in an artificial backwater zone, ‘‘Wando-pool,’’ located approximately 4 km upstream of the river mouth (Nakajima et al. 2008). Since many gobioid species were shown to inhabit the artificial backwater zone in our previous study (Eguchi et al. 2008), we selected gobies as the target species for analysis. The survey was conducted 2–5 times each year, and annual surveys were conducted during July and November in 2002, 2004, and 2007–2011. Therefore, for this analysis, we used only the data collected from July to November. The surveys in 2000 and 2003 were excluded from this analysis because no data were collected in these months during both years. Most individuals collected during the surveys were estimated to be of the age class 0, because we used a small seine net with 1.5-mm mesh size, which is often used to capture juveniles and immature fishes. Because the sampling site had brackish water during all tides (Nakajima et al. 2008), we analyzed 24 gobioid species (see Table 1) whose adults and juveniles inhabited brackish water areas (Eguchi et al. 2008). Data on the Kuroshio axis were gathered from a public database (Japan Meteorological Agency 2011). Using analysis maps of the current axis on the 20th of every month, we measured the shortest distance from the Nobeoka Bay to the axis (Fig. 1a). Because we did not estimate the length of stay of the gobies since their arrival from the southern regions, we prepared two data sets with different periods: one covering each survey month up to a year ago (12 months) and the other covering each survey month up to half a year ago (6 months). In addition, location of the current axis indicated irregular changes (Fig. 1c). Therefore, we prepared average and minimum distances for each period. A receiver-operating characteristic (ROC) curve (Metz 1978) was generated to illustrate the relationship between the presence/absence of each goby species and the current path of the Kuroshio Current. The presence/absence of N. Onikura (&) S. Oikawa Fishery Research Laboratory, Kyushu University, 4-46-24 Tsuyazaki, Fukutsu, Fukuoka 811-3304, Japan e-mail: onikura@agr.kyushu-u.ac.jp

Summary In Japan, Pseudorasbora parva has not been negatively affected by artificial changes in its habitat. Ecological traits of the species may explain this easy adaptation to artificial habitats. An ecological investigation of P. parva inhabiting irrigation ditches was conducted monthly for approximately two years on northwestern Kyushu Island, Japan. Measurements of 1927 individuals revealed two size classes, maturation age (1 year), and lifespan (1–2 years). Results of this study and previous studies show that the species exhibits life history plasticity. In addition, habitat use of ditches indicates that abundances correlated positively with water temperature and negatively with current velocity in the crop-growing season, and positively with water depth and negatively with current velocity in the fallow season. Structural factors such as ditch revetment conditions and aquatic macrophyte cover were unimportant for this species. The study shows that the gudgeon adapts to artificial ditches easily and successfully because of both life history plasticity and wide-scale use of the habitat.