Two specimens of Rhinogoboius nagoyae (23.1–30.6 mm in standard length), were collected from the lower reach of the Tama-gawa River, which flows into the Tokyo Bay, central Japan. The domestic distribution range of this species is from Ryukyu Islands to the northernmost Honshu Island. Although the locality of specimens is at the middle for its range, voucher-based records have not been reported from the Tokyo Bay tributary basin. Thus, the present specimens, which are described in this article, represents the first voucher-based records of R. nagoyae from the bay basin.

Significance Larger ecosystems support more species; this ubiquitous pattern is the foundation of current conservation schemes. However, many ecosystems possess a complex spatial structure that cannot be represented by area, and the role of such complexity in regulating biodiversity patterns is largely unknown. Here, we use theory and extensive fish community data to show that ecosystem size and complexity dictate riverine biodiversity. We found that larger and more branched “complex” river networks harbored greater species richness due to increased space and environmental heterogeneity. The complexity effect was comparable to the size effect, and this pattern has emerged regardless of ecological contexts. Our discovery illustrates a fundamental ecological law in complex ecosystems, laying the groundwork for future research exploring macroecological patterns.

To determine directions for future developments in citizen science, we examined differences between the Japaneselanguage concepts of 科学, 研究, and 市民 and the English-language concepts of science, research, and citizen. We found that the English word “research” is important in denoting new findings, whereas the corresponding Japanese word “研究” does not communicate novelty. East Asians, particularly those from Japan, tend to apply the word “citizen” to adults, whereas Europeans and North Americans apply the word to members of all generations, including babies and children. We also examined the applicability of the new concept of “市民科学” (citizen science), as defined by Sasaki et al. (2016), in studies of fish. Based on our findings, the use of “市民科学” (citizen science) is suitable for describing the process of becoming a scientist as well as indirect contributions to science. We also discussed the value of pursuing Japanese originality in science.

Five specimens of a threatened goby, Apocryptodon punctatus (21.2-40.1 mm in standard length), were collected at a mudflat site of Kushima City, Miyazaki Prefecture, Kyushu, southern Japan over two seasons, autumn (September 2015) and spring (April 2016). A review of distributional records of A. punctatus revealed that this population represents the southernmost record of the species in Japanese waters, and is isolated ca. 200 km south-southwest from the nearest point of the main range of the species along the Pacific coast of Japan. Publicising this population will help conserve it and its vulnerable habitat.

In river systems, considerable debate exists as to why small-scale conservation with a primary focus on habitat quality brings little improvement to biological communities. To reveal potential causes of the enigmatic consequences, further explorations should focus on how species' response to local environments is determined within a watershed. Here, we examined how immigration potential influences habitat associations of four diadromous fishes in the Shubuto River system in Hokkaido, Japan: sculpins (Cottus sp. ME and C. hangiongensis), gobies (Gymnogobius opperiens) and sea lamprey larvae (Lethenteron japonicum). We used closeness to the sea (i.e., distance from the sea) as a proxy for immigration potential, since the source of immigrants of the diadromous fishes is the river mouth. A multilevel modeling approach revealed that immigration potential had a "bottom-up effect" on local habitat-abundance relationships (current velocity and substrate coarseness), but habitat preferences did not vary along the gradient of immigration potential. This likely reflects the limited dispersal capabilities of the study species, whereby shorter travel distances may greatly enhance colonization success. Our study raises the possibility that the effectiveness of small-scale riverine conservation can be improved by selecting areas where successful colonization would be expected. Explicitly incorporating this consideration into conservation decision-making would help achieve greater success in environmental restoration and preservation actions.

Many biodiversity databases have been launched in recent years. Various species of certain developed taxa, such as fish, quadrupeds, and butterflies, are currently able to be photographically identified, in particular for ecological and biogeographic studies. However, there are problems that result from registration of images from countries with different primary languages. In this study, we provide an example of the challenges associated with registering fish images, specifically one case that has functioned as a voucher for the range extension of Labrisomus jenkinsi (Heller and Snodgrass, 1903) (Perciformes: Labrisomidae) from the Galapagos Islands to the Pacific coast of Costa Rica. The fish image database in question belongs to a Japanese public museum [the Kanagawa Prefectural Museum of Natural History; the online version (FishPix) is provided by the museum and the National Museum of Nature and Science]. We propose that there are problems associated with image registration caused by using different languages. Furthermore, these challenges should be a common subject for discussion among museums as they attempt to accumulate biodiversity data from citizens in the future.

The longitudinal and cross-sectional differences in habitat use between Gymnogobius oppeiens and Gymnogobius urotaenia (sister species) were investigated from June to July 2011 in the Shubuto River System, southwestern Hokkaido, Japan. Generalized linear model revealed that watercourse distance from the sea had a significant influence on the abundances of both G. opperiens and G. urotaenia but in different ways. That is, G. opperiens had a distributional peak at the middle reaches, but the abundance of G. urotaenia gradually decreased with increasing distance from the sea. In addition, the lateral distribution patterns of G. opperiens and G. urotaenia, and all the local environmental variables were significantly different between the fringe and the mid-channel habitats. Both G. opperiens and G. urotaenia were most abundant along the margins of the river. However, the former species was frequently collected from the mid-channel, whereas the latter species was never collected in the habitat. These results coincide with previous observations asserting habitat segregation of the two goby species. The differential habitat use between the two species may be related to the differences in their population sizes and morphologies.

A major goal of stream ecology is to identify environmental gradients that shape riverine communities. We examined the relative importance of three ecological factors that have been hypothesized to influence a longitudinal pattern of fish diversity: habitat capacity, heterogeneity and immigration of diadromous fishes. Field surveys were carried out in the entire network of the Shubuto River system, Hokkaido, Japan. A hierarchical partitioning approach revealed that distance from the sea, a proxy for immigration potential of diadromous fishes, had the greatest explanatory capacity, by which 24.9 % of variation in fish species richness was explained. Habitat capacity (approximated by catchment area) was also identified as a significant predictor of fish diversity, whereas habitat heterogeneity brought little improvement to the model performance. These results reflect the fish fauna of the Shubuto River system, in which diadromous fishes are dominant in both abundance and species richness.

An apparent illegal introduction of Lepomis macrochirus macrochirus from Yokohama City, Kanagawa Prefecture, Japan, is reported based on a juvenile specimen and a photograph of two adults collected on 14 June 2015 and deposited in the Kangawa Prefectural Museum of Natural History. The specimens and photographs were initially reported on the internet-based social networking site, Twitter. Two specimens of Carassius auratus, including an aquarium form, were also reported at the same locality and date, suggesting that the illegal introductions originated from an aquarium release. Our report demonstrates an example of web data mining in the discipline of Citizen Science.

We investigated the fluvial fish communities at 16 sites that cover the entire Shubuto River in northern Japan in July and September 2010. A total of 5,552.9 g of biomass and 980 individuals were identified as produced by and belonging to 11 species, and 7,079.7 g of biomass and 2,587 individuals were pinpointed as produced by and belonging to 17 species. The data on the 11 and 17 species were recorded in July and September 2010, respectively. The July and September data exhibited significant differences in individual and biomass compositions (G-test; both P < 0.001). The number of recorded amphidromous Gymnogobius opperiens and Rhinogobius sp. (a species complex of Rhinogobius brunneus) individuals was significantly affected by the interaction term between watercourse distance from the sea and sampling season (July or September). By contrast, no such significant influence was found for the biomass produced by the aforementioned species. Fisher's exact tests revealed that the G. opperiens and Rhinogobius sp. compositions during the growth stage (larva-juvenile vs. post-juvenile) significantly differed between July and September 2010. These results are probably attributed to part of the seasonal trend exhibited by the fish communities in the Shubuto River; that is, the spatial pattern of the fluvial fish communities from July to September is probably caused by an increase in the species occurrence and larval and juvenile recruitment of G. opperiens and Rhinogobius sp. migrating from the sea to the river.

Long-distance dispersal of freshwater mussels (order Unionoida) has been assumed to occur mainly during a parasitic larval stage (glochidia) via movements of host fishes, but its empirical evidence is largely lacking. Here, we applied a "parasite-tag" approach to the riverine mussel Margaritifera laevis and its obligate host fish Oncorhynchus masou masou. This method examines the relationship between the prevalence of glochidia and distance from the nearest mussel population (i.e., the putative source of glochidia), a proxy that should quantify distance moved by host fish. We hypothesized that infected fish would be found in wider habitats at the end of the parasitic period (August) than at the beginning (July) if they were functioning as effective dispersal agents. In July, the prevalence of glochidia was highest in the vicinity of mussel beds but decreased rapidly with distance from the nearest mussel bed. In August, however, infected fish were distributed diffusively across the riverine network and dispersed over 4.8 km, demonstrating substantial dispersal of glochidia by the host fish. The results of our study build upon current knowledge of mussel's dispersal ecology by providing highly needed evidence: host fish can be effective in mediating long-distance dispersal of a riverine mussel species.

We report a photograph of the rare triggerfish hybrid, Rhinecanthus aculeatus x R. rectangulus (order Tetraodontiformes; family Balistidae), from Miyako-jima Island, Ryukyu Islands, southern Japan, that was provided by a sport fisherman via WEB sakana-zukan (an online photographic database of fish in Japan). The image was registered in the Fish Image Database of the Kanagawa Prefectural Museum of Natural History to make it available for scientific scrutiny. Here we emphasize the importance of communication between citizens, such as fishermen, scuba divers, and others, and experts via the Internet, to make possible the processing of biodiversity information provided by citizens into museum collections. This communication contributes Global Biodiversity Information Facility data for various biological studies, such as those on taxonomy, morphology, fauna/flora, community ecology, and biogeography.

Current theories predict that Allee effects should be widespread in nature, but there is little consistency in empirical findings. We hypothesized that this gap can arise from ignoring spatial contexts (i.e. spatial scale and heterogeneity) that potentially mask an existing fitness-density relationship: a 'cryptic' Allee effect. To test this hypothesis, we analysed how spatial contexts interacted with conspecific density to influence the fertilization rate of the freshwater mussel Margaritifera laevis. This sessile organism has a simple fertilization process whereby females filter sperm from the water column; this system enabled us to readily assess the interaction between conspecific density and spatial heterogeneity (e.g. flow conditions) at multiple spatial levels. Our findings were twofold. First, positive density-dependence in fertilization was undetectable at a population scale (approx. less than 50.5 m(2)), probably reflecting the exponential decay of sperm density with distance from the sperm source. Second, the Allee effect was confirmed at a local level (0.25 m(2)), but only when certain flow conditions were met (slow current velocity and shallow water depth). These results suggest that spatial contexts can mask existing Allee effects.

Two specimens of Chromis notata (Pomacentridae) and one specimen of Sagamia geneionema (Gobiidae) were captured in Suttsu Bay, the Sea of Japan. These constitute the first records of the species from Hokkaido Island, northern Japan.

A checklist of the fishes of the Tusubres River basin, Pacific coast of Costa Rica, compiled from field and museum surveys is herein presented. A total of 54 species, representing 47 genera and 27 families, were recorded. Peripheral species were dominant (64.8%), followed by secondary freshwater fishes (20.4%) primary freshwater fishes accounted only for 14.8% of the total fish diversity. Eleotridae (6 spp.), Gobiidae (6 spp.), Poeciliidae (5 spp.) and Characidae (4 spp.) were the most diverse. Two species (Caranx sexfasciatus, Carangidae and Opisthonema libertate, Clupeidae) were new records for Costa Rican freshwaters, and two species (Gymnotus maculosus, Gymnotidae and Lebiasina boruca, Lebiasinidae) was found to have expanded ranges. An identification key and a complete photographic album of all fish species recorded in the basin are presented. The results of this investigation provide a framework for future studies on biogeography, ecology and conservation on fishes from this area.

Natural history museums provide permanent storage for specimen collections, including non-native species. We extracted the records for specimens and photographs of exotic non-native fishes collected in Japan by experts and citizens at the Kanagawa Prefectural Museum of Natural History, Japan. The museum began operation in 1994. The records of alien species known to be established in Japan (FSAK) consisted of 1756 specimens (789 lots) belonging to 29 species and 611 photographs (494 lots) of 25 species. Additionally, there were records of alien species that were introduced to Japan but not known to be established (FSUK) consisting of 23 specimens (23 lots) belonging to 11 species and of 46 photographs (31 lots) of 17 species. The FSAK could be classified as 22 primary freshwater, six diadromous, and one marine species, whereas the FSUK were classified as 12 primary freshwater, one diadromous, and six marine species. We identified a significant difference in the life-cycle types of FSAK and FSUK suggesting that fluvial species are established more easily than marine species, which reflects the biogeography of Japan. In addition, the records of FSUK were probably caused by an increase of aquarium fish introductions due to dereliction of pet fish, ejectment for pleasure, or crime by traders. The museum collections were mostly provided by experts, followed by citizens and other institutions. We also discussed the functions of a public museum of natural history for accumulating information and for citizen participation.

Unidirectional water flow results in the downstream-biased, asymmetric dispersal of many riverine organisms. However, little is known of how asymmetric dispersal influences riverine population structure and dynamics, limiting our ability to properly manage riverine organisms. A metapopulation of the freshwater pearl mussel Margaritifera laevis may be sensitive to river currents because mussels are repeatedly exposed to downstream drift during floods-a parasitic life stage is the only, limited period (similar to 40 days) during which larvae (glochidia) can move upstream with the aid of host fish. We hypothesized that water-mediated dispersal would overwhelm upstream dispersal via host fish, and therefore, that upstream subpopulations play a critical role as immigrant sources. To test this hypothesis, we examined the effects of both up-and downstream immigrant sources on the size of target subpopulations in the Shubuto River system, Hokkaido, Japan. We found that target subpopulation size was dependent on the upstream distribution range of reproductive subpopulations and the number of upstream tributaries, which are proxies for the number of potential immigrants moving downstream. In contrast, little influence was observed of downstream immigrant sources (proximity to downstream reproductive subpopulations). These results were consistent even after accounting for local environments and stream size. Our finding suggests that upstream subpopulations can be disproportionately important as immigrant sources when dispersal is strongly asymmetric.

The Internet has changed the way biologists communicate; this includes the collection of information on fish biology. This technological change may allow the possibility for biological monitoring by general citizens via the Internet. The Japanese Internet atlas of fishes, WEB sakana-zukan, has been in operation since 2002. It provides an opportunity to communicate and accumulate information on fish biology by amateur users, who consist mainly of sports fishing fans. This website has functioned not only as an entertainment and educational tool for users with an environmental and ichthyological interest. To date, more than 35,000 photographs of fishes have been registered on the website by more than 1,000 unique users, and more than 37,500 photographs of fishes have been posted in its bulletin board system (linking approximately 28,000 photographs to the website) by more than 2,000 unique users. As these photographs almost always include time and locality data, it is possible to provide distribution data by publishing the information as scientific papers or registering them as collections at the Kanagawa Prefectural Museum of Natural History (the Image Database of Fishes (KPM-NR) contributing to the Global Biodiversity Information Facility). If the communication method is developed and improved, various scientists will be able to collect much more biodiversity data from general citizens via the Internet.

Local aggregations of unionoids (mussel beds) represent subpopulations constituting a riverine meta-population and are presumed to be linked by dispersal of parasitic mussel larvae (glochidia) on host fishes. We examined movement patterns of Masu Salmon (Oncorhynchus masou masou), the obligate host fish for the freshwater pearl mussel Margaritifera laevis, during the mussel's parasitic period to determine the dispersal potential of glochidia via host fish in the Shubuto River system, Hokkaido, Japan. We conducted a mark-recapture study in a 650-m river section to describe the distance and directionality of host fish movement, and we used fyke net sampling to quantify the number of host fish moving from mainstem rivers to tributaries. Most individuals of Masu Salmon captured in the study were infected with glochidia of M. laevis. The displacement distance of infected fishes ranged from 37.5 m downstream to 512.5 m upstream (mean = 36.5 m upstream from marking location). The dispersal kernel based on a diffusion-advection model represented a leptokurtic distribution with a fat-tailed upstream bias, but most recaptured fish remained near the initial capture location. Movement of fish from mainstem rivers to tributaries was strongly affected by differences in water temperature among tributaries. Most individuals moved to cooler tributaries, but tributaries did not support populations of M. laevis. These results suggest that glochidial dispersal via host fish is important for local recruitment and upstream dispersal, but dispersal to tributaries may be a source of mortality for M. laevis.

A checklist of the marine and estuarine fishes of the inner part of the Gulf of Nicoya, Pacific coast of Costa Rica, Central America, was compiled by examining a museum fish collection, resulting in 72 families and 274 species. Of these species, 127 (46.4%) were marine species and 147 (53.6%) were estuarine-associated species. In terms of their life history and considering the habitat type classification, 188 (almost 70% of the total) were categorized as species inhabiting soft-bottom habitats, reflecting the large estuarine environment and rich fish diversity of the Gulf despite its relatively small area in the tropical Eastern Pacific region. Furthermore, the list contains 13 threatened species of IUCN Red List, which need further research to understand their abundance and their exposure to habitat loss in the Gulf. Further detailed studies on its fish fauna and habitat are needed to better understand and conserve biodiversity within the whole Gulf.

We proposed a method for evaluating the quantitative contributions of hypothesized focal pressures to biodiversity loss from freshwater ecosystems at regional or local scales. The method, called the "lost biodiversity approach" (abbreviated as "LBA") focuses on local biodiversity losses caused by focal pressures. Lost biodiversity is explicitly estimated by statistically modeling the relationships between factors or focal pressures and "differential biodiversity," defined as the difference between local biodiversity at a sampled site and regional species pool(s). We applied LBA to two cases in Japan: (1) the damselfly fauna of 56 agricultural ponds in a rural region sharing the same regional species pool and (2) freshwater fish fauna in the 13 largest river systems in Hokkaido, which includes multiple species pools. In the former, where nestedness of sampled damselfly assemblages was detected, and thus the difference between local species richness and species pool size was used as a simple indicator of differential biodiversity, biodiversity lost to invasive alien species was successfully quantified. In the latter case, where no nestedness of fish assemblages was detected, and differential biodiversity was analyzed based on an index weighting rare species, biodiversity lost to dams and eutrophication were quantified. The advantages of LBA supported by the case studies were its (1) feasibility, using species snapshot presence-absence data, (2) ability to quantify a baseline for each local community when focal pressures were removed, and (3) ability to evaluate impacts of focal pressures even if each local community belonged to a different species pool. This method will be effective in biodiversity hotspot areas. (C) 2013 Elsevier Ltd. All rights reserved.

Population status and physicochemical factors affecting local density of endangered freshwater pearl mussels, Margaritifera laevis, in Shubuto river basin were investigated through measurements of local density and individual size of M laevis, and environmental variables at 27 sites (including 324 quadrats: 0.5 × 0.5 m). Proportions of small-sized juveniles were 34 - 100 % depending on the reach, suggesting relatively high recruiting rates. Generalized linear mixed models (GLMMs) revealed that the local density is strongly affected positively by dissolved oxygen, %sand, and current velocity. Quadratic terms are also strong for two physical factors, %sand and water depth. The local density tended to be higher at quadrats with 9.30 - 10.2 mg/l dissolved oxygen, 10 - 50 % sand proportion, 0.2 - 0.6 m water depth, and 0.05 - 0.30 m/s current velocity. There were little differences in the factors affecting local density among three size classes (< 20 mm, 20 - 50 mm, > 50 mm). Therefore, the local density was significantly higher at the river fringe with a combination of more suitable physical environment factors than middle of the river. These results suggest that artificial alteration of river fringe could have adverse influences on M. laevis population.

Homologies of the branchial arch muscles in the cyprinid Zacco platypus are assessed based on their innervation. Muscles serving the first gill arch are innervated by branches of the glossopharyngeal (IX) nerve and those serving other arches by the vagal (X) nerve. Absence of the levator posterior is confirmed. Five pairs of muscles originating from the cranium and inserted onto the specialized 5th ceratobranchial, all unique to cyprinids, are innervated by the 4th branchial trunks of X, indicating that all pairs are derivatives of the sphincter oesophagi, involving reorganization from intrinsic to extrinsic elements. Homologies of some ventral branchial muscles are also discussed and the criteria for homology improved by clarifying the innervation pattern. J. Morphol. 272:503-512, 2011. (C) 2011 Wiley-Liss, Inc.

We investigated the presence/absence of common carp (Cyprinus carpio) and coverage of aquatic plants including endangered species in 74 small agricultural ponds in hilly regions of Iwate Prefecture, Japan. Our results revealed that the presence of common carp has significant negative effects on the coverage of floating-leaved plants and submerged plants, but not on emergent plants. This indicates that the introduction of common carp to small agricultural ponds can modify habitat conditions for many aquatic organisms by reducing the coverage of aquatic plants.