The freshwater fish community of Lake Biwa, Japan includes many potamodromous species, which migrate upstream seasonally to tributary rivers in order to reproduce. However, most of these rivers used by large numbers of migrating fish have weir fish traps that are set by local fisheries at the river mouths, which are thought to negatively affect the population density of potamodromous species. This study examined factors that are critical for conservation of three-lips (Opsariichthys uncirostris uncirostris), the only piscivorous cyprinid in Japan, which is vulnerable and endemic in Lake Biwa. During its reproductive season, we counted the number of individuals and determined their sex, body size, and frequency of spawning behaviours in a view of comparing them between rivers with and without weirs and between seasons when the weir is not operational. Illuminance, water temperature, turbidity, and current velocity were also measured to explore environmental factors that limit fish reproduction. The frequency of spawning behaviours, numbers of individuals, and fish body size were larger, while turbidity was lower in the river with a weir than in the river without a weir; thus, the former river is considered favourable for fish reproduction. When the weir was operational, the population density and frequency of spawning behaviours were negatively correlated and the proportion of females in the population was lowest among the three conditions examined. This suggests that excessive gathering of individuals (particularly males) during periods of an operational weir negatively affect their reproduction. For effective conservation of this species, further ingenuity is needed regarding the operation of weirs, such as minute changes in their position or season.

Tree cavities are a vital microhabitat in forested ecosystems, providing nesting and roosting sites for cavity-using species. The factors regulating tree-cavity formation and abundance vary substantially depending on the climate zone and/ or region, necessitating regional-level investigations. In this study, we investigated tree size, tree species composition, and the numbers of tree cavities in mature and secondary subtropical moist evergreen broad-leaved forests on Amami Oshima Island, Japan, with a focus on differences in cavity characteristics among tree species. Tree cavity abundance was high relative to findings from tropical or subtropical forests in other regions. Nearly all cavities were formed by decay, rather than being excavated by woodpeckers. In large trees with a diameter at breast height (DBH) . 30 cm, the numbers of tree stems, stems bearing a cavity, and cavities were higher in mature forests than in secondary forests. Castanopsis sieboldii was the dominant species in both forest types (48 and 66% of trees . 15 cm DBH in the mature and secondary forests, respectively). Other dominant tree species included Schima wallichii (10.8%) and Distylium racemosum (10.3%) in mature forests and S. wallichii (9.9%) and Pinus luchuensis (7.6%) in secondary forests. We used a generalised linear mixed model to examine the factors affecting the number of decay-formed cavities per stem. The results showed that stem DBH was significantly associated with the number of cavities, and D. racemosum had the greatest number, followed by C. sieboldii and S. wallichii. Almost all cavities (90%) found were in D. racemosum and C. sieboldii, and cavity entrances were significantly higher in D. racemosum. Observations using a charge-coupled device camera showed that cavities were occupied by multiple taxa, including Otus elegans, Garrulus lidthi, and Diplothrix legata. These results demonstrate the value of conserving the limited remaining mature subtropical forest on Amami Oshima Island, as these forests contain large D. racemosum and are vital habitats for cavity-using birds and mammals.

To organise state-of-the-art evidence on the ecological uses of macrophytes as food resources, spawning sites, and habitat for fish and crustaceans, we systematically reviewed research on this topic. In October 2017, we searched refereed papers available in the Web of Science Core Collection and J-STAGE. A total of 512 papers were selected via a review process. Most of the selected studies were conducted in North America, Latin America, Europe, and Oceania, while fewer were conducted in Asia and Africa. Lakes and rivers were the most commonly studied water bodies, with fewer marine studies. Submerged plants were the most commonly studied macrophytes, followed by emerged plants, free floating plants, and floating-leaved plants. Fish accounted for half of the studied organisms. The use of macrophytes as habitat was the focus of more than 80 percent of the studies, with fewer focusing on macrophytes used as spawning sites. An insufficient number of studies focused on macrophyte use in spawning, and more studies are needed from Asia and Africa. As a novel trial, we classified ten ecological research methods into three evidence levels to identify whether causal inference was possible. As a result, we successfully extracted papers which presented strong evidence that aquatic plants are ecologically useful for fish and crustaceans.

The Yatsugatake Forest of Tsukuba University contains a large regional population of Primula sieboldii E. Morren, a semi-endangered heterostylous clonal herb. Although P. sieboldii individuals have been observed intermittently in several local populations since 1990, no survey of the entire area has been conducted. Therefore, to clarify the population dynamics of P. sieboldii, we conducted surveys in 2006 and 2018, and compared the results with the 1990 survey records. The total number of P. sieboldii ramets did not change significantly during the 28-year period from 1990 to 2018; however, the number of flowering ramets decreased significantly in recent years, from 2,833 in 2006 to 1,518 in 2018. An even more pronounced decrease was seen in the number of flowering genets, with 939 genets observed in 2006 compared to only 434 in 2018. These decreases resulted in prominent deviations in the morph ratios of local populations, suggesting a likelihood of low seed production and low genetic diversity in future generations.

Although many urban coastal ecosystems around the world are in close proximity to large urban centres, they are often underutilized by tourists and citizens. In the Tokyo metropolitan area, urban coasts are often restricted areas and many attract few visitors. Here, we determined the density of visitors to different urban coast types, including concrete and masonry seawalls and sandy and rocky coasts, and the activities they engaged in, to understand the demand for coastal ecosystems by urban citizens. Typical activities included fishing, gathering organisms such as crabs, playing with sand and sea water, photography, and walking. We then used a gravity model to assess the number of potential users within 30 km of the study sites. More than half of the visitors reported engaging in organism-related activities; coastal ecosystems were an important resource for citizens. Activity types were related to the age and gender of users, as well as to coast types. Our results show that the density, activity, and personal attributes of coast users can be readily predicted, which may be valuable for urban coastal ecosystem planning.

Seepage marshes, which are mainly distributed in the hilly areas of western Japan, are important habitats for endangered species. However, little is known of the functions of seepage marshes as habitats for wild mammals and birds or of the effects of animal behavior on the seepage marsh ecosystem. This paper provides basic data on the species composition, frequency of appearance, and behavior of wild mammals and birds in and around seepage marshes. From a total of 4,602 days of camera trap survey data collected from Tokai district, Japan, more than 13 species of mammals and 19 species of bird were recorded from seven investigated marshes. The species composition of mammals recorded in seepage marshes was almost the same as that in the surrounding forests, however, their frequency of appearance was generally lower in herbaceous marsh than in forested marsh. Wild boars, Sus scrofa, were the most abundant among mammals. Wild mammals and birds actively used seepage marshes for drinking, feeding, mud bathing, and water bathing. In particular, rooting by wild boars was frequently observed in almost all seepage marshes. Some mammals and birds discharged their excrement into the marshes. Although more detailed investigation is needed, these behaviors indicate that seepage marshes are important biotopes for wild mammals and birds, and that the ecosystem might be affected through vegetation disturbance and seed dispersal.

We investigated the population dynamics of Japanese sika deer (Cervus nippon) in the absence of hunting and natural predators in a warm temperate broad-leaved forest on Yakushima Island (World Heritage Area), southern Japan, from 2001 to 2018. We established two study sites 1.3 km apart (Hanyama and Kawahara) and counted the number of deer encountered while walking 5-km-long census routes at each site three times each year from late July to August to obtain a deer density index (the number of deer observed/km). We also set 15 trap cameras at Hanyama in August-September 2014, 2015, 2016 and 2018 and measured the deer photo rate of each camera (the number of deer photographed/day). At both sites, the deer density index increased by 9.1% annually from the initial survey in 2001 to 2014, after which it decreased by 15.2% annually until 2018. The density indices at the sites did not differ during the increase (2001.2014) or decrease (2014-2018) phases. The deer photo rate also decreased by 10.0% annually from 2014 to 2018. During the decrease phase, we observed 19 individually identified deer (six males and 13 females) at Hanyama. The annual migration rate was, at most, 3.5% and most individuals did not move from Hanyama. These findings suggest that the sika deer population declined gradually in the absence of hunting because of some ecological factors at the study sites.

To determine whether the decline in forest understory vegetation on Yakushima Island, Japan is due only to the increase in deer or whether it is also affected by changes in the light environment, we compared changes in vegetation coverage and plant species richness between 2006 and 2016 inside and outside of four deer-proof enclosures on eastern Yakushima Island, in which canopy openness varied from 1.4% to 8.2%. The effects of environmental factors were tested using a generalized linear mixed model. Vegetation coverage was higher inside the enclosures, irrespective of the light environment. Species richness (for vegetation with coverage of at least 1%) increased inside enclosures, although this differed by species. Further research examining other sites is needed, with explicit consideration of the ecological traits of various species.

Summertime temperature reduction is an important ecosystem service of green spaces in urban ecosystems. However, many urban green spaces are formed by non-native plants, which have the potential to negatively influence local biodiversity. Unfortunately, due to the difficulties of evaluation, there have been few studies comparing differences in the temperature-reducing effects of native- and non-native species. In this study, we attempted to establish a method for comparing differences in temperature-reducing effects between native- and non-native species. Using aerial photographs taken in summer in a heavily urbanized area of Tokyo, we compared radiant temperatures between green spaces comprised of native and non-native trees, and in areas varying in the number of species and various other factors. Although we were not able to obtain sufficient data for statistical analysis in this case study, the results indicated some differences in temperature-reducing effects among different species of plants. Additional case studies performed using our method may allow us to derive other ecosystem services from green spaces formed only by native plants.

In conservation science, citizen science enables long-term and large-scale monitoring. All stakeholders in a citizen science project need to derive benefit from the project for it to continue; however, benefits to participating citizens are generally non-economic and difficult to evaluate. In this study, we used questionnaires and interviews to focus on participant motivation (i.e. expected benefit) for a bird survey project conducted in the Izu Islands, Japan. Most participants who attended came from off the island, and the project was conducted as volunteer tourism. In questionnaires, a high percentage of participants cited "fascinating ecosystem in the islands", suggesting their motivation was based on tourism, and "sympathized with the objective of the project" suggesting a motivation to perform voluntary work. The next most popular responses were "learning survey methods and studying bird ecology", "fun to survey" and "contribution to science" as citizen scientists. Usual human relationships such as "to make friends" and "recommendation from friends" were not important motivators.

Wild boars (Sus scrofa) cause agricultural damage and are a reservoir of livestock diseases, such as classical swine fever. Monitoring their density is a basic management task, although appropriate methods have not been established. We surveyed the distribution of wild boar rooting in a 90 × 92 km area subdivided into 18 × 23 km areas. Approximately 10-km survey lines, passing through a mosaic of vegetation and topography, were placed in each area to record wild boar rooting, and the rooting density (rooting/km) was obtained. Camera traps were used to check the reliability of the rooting survey. The effect of the local environment was removed by statistical analysis to obtain density indices from the rooting and camera surveys. This showed that the rooting density was high in mountain areas where wild boars are expected to occur and low in fragmented forests surrounded by urban areas. The rooting density correlated with the camera measurements; however, density indices were not significant after removing local environmental effects, probably due to the small number of cameras used in this study.

The food habits of sika deer (Cervus nippon) in Hayakawa, Yamanashi Prefecture, central Japan, a depopulated area, were studied through faecal analysis. Faecal analysis showed that the diets of deer in this area were relatively poor, with plant-supporting organs like fibre and culms comprising a large part of the diet, while live leaves accounted for only a small proportion of the faecal composition. In spring, fibre and culms comprised as much as 45.0% and 17.7% of the faecal composition, respectively. These proportions were not significantly different in summer, when fibre (54.6%) and culms (14.2%) remained predominant, although the proportion of dicot leaves increased to 13.5%. In autumn, the proportion of live leaves increased to 36.0%, probably because deer fed on newly fallen leaves on the forest floor. The diets were poorest in winter, when fibre accounted for 82.7% of faecal composition and the proportion of live leaves was extremely small (2.5%). Comparison with three other areas showed that deer in Hayakawa had the poorest diet. We discuss the importance of food analysis for deer management with reference to depopulated areas.

Ex situ conservation of endangered species involves breeding and cultivation of wild populations to reduce the risk of their extinction. Acilius kishii (Dytiscidae) is only known to inhabit Lake Yashaga-Ike, Honshu Island, Japan; therefore, this species was classified as a “national endangered species of wild fauna and flora” according to the Law for the Conservation of Endangered Species of Wild Fauna and Flora, Japan. In 2016, ex situ conservation of A. kishii was conducted at three facilities: the Ishikawa Insect Museum, Echizen Matsushima Aquarium, and Fukui Nature Conservation Center. In this study, we examined the effects of ex situ conservation on the genetic diversity of wild populations of A. kishii, including specimens collected in 2016 and before 1995, using 14 microsatellite markers. We also examined wild populations of the related species A. japonicus. Genetic diversity was lower in the wild A. kishii population than in A. japonicus; however, no decline in genetic diversity is thought to have occurred before 1995 or in 2016. At all three facilities, the numbers of alleles in the ex situ conservation populations of A. kishii were lower than that of the wild population. However, pooling the alleles of all three ex situ conservation groups resulted in almost the same alleles as the wild A. kishii population, with a reduction in only one allele. These results suggest that independent ex situ conservation at multiple sites and regular exchange of ex situ individuals among sites is important for maintaining genetic diversity.

The importance of biodiversity conservation in paddy field ecosystems is widely recognised, as is the importance of maintaining a water body in the paddy field throughout the year. This study reports on the fish community in a fish-retreat ditch constructed in a paddy field near the sea in Kunitomi District, Obama, Fukui Prefecture, Japan. The fish-retreat ditch contained purely freshwater, migratory, brackish water, and marine fish. The specimens collected in this ditch included 565 Misgurnus anguillicaudatus, 306 Cobitis sp. BIWAE type A, 132 Tribolodon hakonensis, 122 Acanthogobius flavimanus, 33 Gymnogobius urotaenia, and 34 other fish. M. anguillicaudatus and Cobitis sp. BIWAE type A (pure freshwater fish) use the fish-retreat ditch mainly as a spawning ground during the irrigation season; their numbers dropped during the non-irrigation season. T. hakonensis, G. urotaenia (migratory fish), and A. flavimanus (brackish water/marine fish) used the fish-retreat ditch mostly as a growing ground. They swim upstream to the fish-retreat ditch in spring, grow from summer to autumn, and remain until spawning. As the biodiversity conservation function of the fish-retreat ditch was confirmed, I propose increasing this function by forming a network of multiple fish-retreat ditches in the future.