Far Eastern catfish (Silurus asotus) are a top predator in Japanese freshwater ecosystems. The author used lure fishing on the Ooigawa-river, of the Biwako-Yodogawa basin system, to investigate the conditions in which the catfish pursue their prey. Using the catch number as the response variable, the data was analyzed by GLM (generalized linear model) and model selection with AIC (Akaike’s information criterion). The explanatory variables were the time of day, weather, average temperature, maximum wind speed, precipitation of the previous day, atmospheric pressure, and the moon phase. Detention time was the offset value in order to standardize the survey time variable. Results indicated that two variables, weather and the maximum wind speed, were selected by GLM using AIC. It is suggested that the capture of S. asotus tended to increase with more severe weather conditions.

The occurrence of an exotic species Paramisgurnus dabryanus (Pisces: Cobitidae) in Aichi prefecture was reported based on field surveys in the Mikawa district between 1933 and 2011, cited literature and personal comments. P. dabryanus was recorded from nine stations in seven river systems.

Acheilognathus tabira, which was has 5 recognized subspecies, was reported in the Takasegawa and Iwakigawa river systems in Aomori. Few studies have examined the classification to the subspecies level and their respective origins in this region. We collected several adults from both river systems. Based on the color of the dorsal fin in nuptial males and the ratio of the long axis to the short axis of the egg, it was confirmed that A. t. erythropterus is occurring in the Takasegawa river system within its range northern-limit. Based on the color of the dorsal fin in nuptial males and the ratio of body depth to standard length, it was confirmed that A. t. tabira is occurring in the Iwakigawa river system. The natural range of this subspecies is the Kansai region (west part of main island of Japan). Therefore, A. t. tabira occurring in Iwakigawa river system is suggested to be an introduced population.

Ekiken Kaibara (1630-1714) is known as the first true naturalist and biologist in Japan. The Chikuzen'nokuni Zoku Fudoki was edited by him in 1688-1709. As part of this report the author conducted a survey of the records of freshwater fish in this historical manuscript. As a result, it was found that of the 24 taxa (fish and amphibian) recorded in the book, at least 21 taxa were able to be identified at the level of species or genera. These records indicate that the habitats of amphidromous fish, Plecoglossus altivelis, Oncorhynchus masou, O. keta and Tribolodon hakonensis have diminished over the past 300 years. It was confirmed that this book provides important information about historical freshwater fish fauna in Fukuoka prefecture.

Submerged plant communities in Lake Izunuma-Uchinuma have declined drastically in past 30 years and only isolated populations are observed now. In the past we investigated the submerged plant populations based on boat surveys but this method does not fit the present rarefied situation of submerged plants. In 2011 and 2012 we conducted careful exploratory investigations by foot. Because we already confirmed the presence of at least two stable communities of submerged plants in the lake, we concentrated our investigation efforts there. We found five species of submerged plants(Myriophyllum spicatum L., Cabomba caroliniana A. Gray, Utricularia australis R. Br., Najas oguraensis Miki, and Hydrilla verticillata (L.f.) Royle) and three species (M. spicatum, C. caroliniana, and U. australis) were found in the investigations of both years. From the comparisons of observed shoot numbers between the results of both years, the numbers in 2012 were greater than those in 2011. Especially in C. caroliniana, a rapid increase was recorded in both investigation points and now C. caroliniana is the most common submerged plant in Lake Izunuma.

Seedling emergence method was conducted on the sediments of Lake Izunuma-Uchinuma, Japan. As a result, Brasenia schreberi was rediscovered in the lake for the first time in 20 years. B. schreberi had been commonly distributed in Izunuma-Uchinuma until the 1960's. However, B. schreberi became extinct due to eutrophication and overexploitation. Considering the waters currently high COD concentration (8-10 mg/mL) and that most of the water surface is covered by lotus (Nelumbo nucifera), restoration of the rediscovered B. schreberi in the lake will be difficult at this time. The water quality gap between 1960's and now is a large problem for the restoration of the B. schreberi. Therefore, it may be a realistic to carry out the restoration of B. schreberi only in small and manageable areas around the lake.

Several Whiskered Terns Chlidonias hybridus and White-winged Black Terns C. leucopterus were observed around Lake Izunuma-Uchinuma in the inland part of Miyagi Prefecture from June to July in 2011 and 2012, and October 2012. A total of six terns, four Whiskered Terns and two White-winged Black Terns, were recorded from June to July in 2011, and total of seven Whiskered Terns were observed in 2012. Moreover, a maximum of 83 Whiskered Terns were counted on 6 October after typhoon 19 (Maliksi) passed northward and offshore of Miyagi Prefecture on 4 October 2012.

Lake Izunuma-Uchinuma is a famous migratory and wintering ground for swans. During the time when swans and other waterfowl are at this location people regularly come to feed them. Because leftover feed and waterfowl droppings were thought to be contributing to water pollution in Lake Izunuma, a feeding pond was constructed near the lake in 1991. The water quality of the feeding pond became worse year after year. It is thought that waterfowl feces caused an increase in water pollution in the pond, however, the details have not been clarified. The objective of this study was to understand the behavior of coliform bacteria in the feeding pond. The results are as follows. The number of coliform bacteria changed with variations in the water temperature of the pond. It is also probable that the concentration of Escherichia coli (E. coli) in the pond was affected by temperature, although this was not conclusive. Even though E. coli was hardly detected in the pond water, E. coli were detected in samples from the pond sediment. Considering that coliform bacteria and E. coli were detected in feces of waterfowl, it seems likely that waterfowl feces were a major source of water pollution.