Wintering Japanese marsh warblers Locustella pryeri were found using song playback at four reedbeds around Lake Izunuma-Uchinuma on the evening of 8 December 2012 and the early morning of 9 December 2012. We located six warblers on the northern shore of Lake Izunuma and two on the southern shore of Lake Uchinuma. This result suggests that Lake Izunuma-Uchinuma is a wintering site for Japanese marsh warblers in Miyagi Prefecture.

We collected Chironomidae midges in Lake Izunuma and Lake Uchinuma, in September 25 of 2011, October 3 of 2015 and September 16 of 2016. A total 496 adult males were collected and we identified them belonging to 25 species of 15 genus. Twenty three spices are new records for the area around Lake Izunuma and Lake Uchinuma. In this study Polypedilum (Pentapedilum) tigrinum, (Hashimoto), a species which feeds on macrophytes, is the dominant species. These observations provide information about the aquatic plants growing in the environment of Lake Izunuma and Lake Uchinuma.

On May 2, 2016, from 18:13–19:30, we confirmed the tracking behavior of the Tokai fluvial eight-barbel loach (Lefua sp.2) at the headwater stream in Toyokawa-shi, Aichi Prefecture. During this time, loaches entered gaps between cobbles and were seen contacting anal fins with other loaches. At this time eggs were observed on tree branches and stones. We report this behavior because it seems to be an egg laying behavior of this species.

One pied avocet Recurvirostra avosetta was observed in lotus Nelumbo nucifera fields around Lake Izunuma-Uchinuma, Miyagi Prefecture, from 20 April to 2 May 2017. This is the first record of the occurrence of this species at Lake Izunuma- Uchinuma.

Abstract The native piscivorous fish Opsariichthys uncirostris uncirostris, a representative vulnerable species, were investigated at the northwest shoreline of Lake Biwa, central Japan. Fourteen females and 51 males were captured; their sex ratio was biased to males. Remarkably, all of the females had empty guts. The overall empty gut ratio (0.83 overall) was higher than that in Lake Biwa in 1963 (<0.5 throughout the year). The length–weight relationship analysis found a negative allometric growth in females, though the sample size for this analysis was small. Future studies must examine the relationship between the recent reduction in catch, biased sex ratio, and negative allometric growth in females.

Recent studies have revealed that lacustrine consumers such as zooplankton assimilated methane-derived carbon by feeding on planktonic methane-oxidizing bacteria. In this study, we estimated the use of methane-derived carbon by zooplankton (copepods and cladocerans) using carbon stable isotope analysis. Carbon stable isotope ratios (δ¹³C) of zooplankton fluctuated from -38.4‰ to -26.5‰ during June 2006 to September 2008. Zooplankton often showed more depleted δ¹³C values than particulate organic matter (POM) collected at the same time, whereas δ¹³C values of phytoplankton, which were estimated from δ¹³C values and C/Chl ratios of POM, were often more depleted than those of zooplankton. These results indicated that zooplankton selectively fed on phytoplankton contained in POM. On the other hand, zooplankton showed more depleted δ¹³C values than phytoplankton in August and September 2007, and August 2008, indicating that zooplankton assimilated 13C-depleted methane-derived carbon by feeding on methane-oxidizing bacteria. We estimated dietary contributions of methane-oxidizing bacteria to zooplankton using a two-source mixing model. The dietary contributions were 6.5 to 9.6% in August 2007, 2.3 to 3.5% in September 2007, and 7.3 to 10.9% in August 2008, whereas the contributions were not detected in other months. During August and September, biogenic methane produced in the sediment could reach the water column without being oxidized due to a depletion of dissolved oxygen concentrations above the lake bottom. Consequently, the methane-derived carbon was able to be transferred to zooplankton via methane-oxidizing bacteria.

Corbicula leana, classified as a vulnerable species in Japan, is a freshwater bivalve. While the species is declining in number across Japan, research into the current population size and cause of decline is lacking, and an investigation into effective conservation methods is overdue. This study focuses on the waterways connecting to Lake Biwa and aims to define approaches to manage clam numbers in the wild through the following: (1) measuring seasonal changes in the number of clams in drainage ditches, (2) examining conditions of the sedimentary environments preferred by the species, and (3) evaluating the influence of predation of the red swamp crayfish Procambarus clarkii on the clam. Over the research period, the number of freshwater clams in the drainage ditches fluctuated and reproductive individuals increased in summer and autumn. We also found that large numbers of the species could be found in environments containing sedimentary materials such as sand. It was also clear from our laboratory experiments that the red swamp crayfish preys on small freshwater clams but we also found that predation pressure varied depending on whether sediment was present. Thus, to manage clam habitats, encouraging silt deposition and developing a means of measuring sediment thickness may be effective, in addition to regularly removing red swamp crayfish from drainage ditches.

An immature Golden Eagle Aquila chrysaetos was observed at Lake Izunuma-Uchinuma, Miyagi Prefecture, Japan, on December 9, 2016. This is the first record of this species from Lake Izunuma-Uchinuma. An individual reasonably presumed to be the same bird, based on plumage peculiarities, was observed around Mt. Goyo, Iwate prefecture, on March 28, 2017. These observations reveal a 72 km northeastward migration of this individual.

Seven specimens of the non-indigenous Wuchang bream Megalobrama amblycephala (Cyprinidae) were collected from the inner part of Edosaki-iri inlet in Lake Kasumigaura, Ibaraki Prefecture, central Japan, from 2009 to 2017. Four of these specimens, aged successively 1 to 2 years , were collected repeatedly in 2016 and 2017 indicating that this alien species has begun reproduction in the lake. Lake Kasumigaura, in the Kanto region of Japan, has rich fish diversity and many endangered species. The establishment of M. amblycephala will likely cause unpredictable ecological and economic problems. Attention from stakeholders and early control are necessary to prevent further range expansion of the Wuchang beam.

To mitigate the negative impacts caused by red swamp crayfish, Procambarus clarkii, crayfish eradication programs are in progress in various regions of Japan. Bait trapping is among the most popular eradication methods adopted by many crayfish control programs. In bait trapping, raw fish is generally used for the bait of a trap. One significant problem with the use of raw fish, however, is its high cost. By conducting studies about effective bait strategies effective baits besides raw fish have been discovered. These baits, however, have some problems with capture efficiency and cost- effectiveness. In this study, we aimed to reveal attractive and cost-effective baits for trapping the crayfish. We evaluated the crayfish capture efficiency and cost- effectiveness of processed dog, trout, and carp food against raw fish and dough balls “Nukadango (made of rice bran and flour)”. The results showed that the capture efficiency of dog food was higher than that of the dough balls, though the capture efficiency of processed trout food was similar to those of raw fish and dough ball. The cost-effectiveness of dog food and trout food were both higher than that of raw fish. These results suggest that dog food is the bait of highest capture efficiency as well as highest cost-effectiveness. Processed carp food exhibited similar capture efficiency to dog food and trout diet, but lower cost- effectiveness than dog food. We suggest that dog food is best for crayfish trap bait in view of capture efficiency and cost-effectiveness, but to minimize the effect on the environment, carp food is also suitable as crayfish trap bait.