Largemouth bass, Micropterus salmoides, is a piscivorous fish species native to North America. This species has been introduced into many regions outside its native range for sport fishing and food. Due to predation, introduced largemouth bass have altered native fish communities, lowering both the species richness and abundance of native fish species. The diet of largemouth bass changes as they grow. Largemouth bass either move directly from zooplanktivory to piscivory, or they may include a period of insectivory. In this review, we first examined studies discussing the timing of the switch to piscivory in native and introduced areas with the minimum size of individuals being used as an indicator of timing. Then we discuss the significance of ontogenetic shift to piscivory of largemouth bass, the dietary switch at the population level during the first year and the factors affecting the shift to piscivory. The minimum body size at the onset of the shift to piscivory is variable among regions and water systems. After the switch to piscivory, the growth rates of bass increase significantly due to the higher energy content of prey fish, resulting in large body size in autumn. Since over winter mortality is size-dependent, an early shift to piscivory increases the recruitment of 0+ largemouth bass to the future adult population. In their native range, 0+ bass often fail to shift to piscivory during their first year. Such a phenomenon could divide the 0+ population into large piscivorous and small zooplanktivorous individuals, resulting in bimodal body size distribution. In introduced areas, to our knowledge, there has been no investigation on the ontogenetic shift to piscivory at the population level except for 2 studies in Japan. One of these studies shows that all 0+ individuals can become piscivorous during their first year; another shows that some individuals can become piscivorous, but others cannot. Based mainly on investigations in their native range, the success of 0+ bass to switch to piscivory is considered to be influenced by the following factors; 1) growth rate before the shift to piscivory, 2) hatching date, and 3) the relative timing of spawning season in reference to those of prey fishes. However, few studies have examined the effects of the above 3 factors on the diet shift to piscivory in introduced areas. Further studies are required to enhance a more complete understanding of the factors affecting the shift of 0+ bass to piscivory especially in introduced areas.

Population control of the red swamp crayfish Procambarus clarkia (Girard) was conducted in a small irrigation pond (670 m²) using bait traps, hand nets and artificial burrows from May to September, 2010. The initial population size of the crayfish recruited before 2010 (large crayfish) and recruited in 2010 (small crayfish) were estimated to be 1,886 and 3,192 individuals respectively. The control project was conducted biweekly (36 times in total) during which 1,885 large and 3,176 small crayfish were captured in the pond. At the end of the project, the estimated numbers of the large and small crayfish in the pond decreased to 1 large and 16 small individuals. During this project, invading crayfish from adjacent areas were captured by using a surrounding barrier with traps. The total number of crayfish captured by these traps was 1,050 individuals. These results indicate that bait traps, hand nets and artificial burrows are effective to control or eradicate red swamp crayfish in a small pond if methods to prevent re-invasion are used.

Radioactivity monitoring was conducted around Lake Izunuma-Uchinuma and in its watershed. Lake Izunuma-Uchinuma is located 140 km north of the Fukushima Daiichi Nuclear Power Station. The average radioactivity at the Izunuma-Uchinuma Sanctuary Center, which is located on the north side of Lake Izunuma, was calculated with data gathered from the 28th of September, 2011 to the 22nd of February, 2012. The average radioactivity at 1 m above ground was measured to be 0.08 μSv / h (N = 22, range: 0.07 - 0.09) and at 10 cm above ground was 0.10 μSv / h (N = 22, range: 0.07 - 0.11).

Radioactive Cesium (Cs) concentration in sediment, mussels, fish, reeds and the ash of reeds was investigated in Lake Izunuma-Uchinuma and its watershed. The Cs concentration of sediment in the Arakawa River (850 Bq/kg) which flows into Lake Izunuma was greater than that found in the Yasawagawa River (390 Bq/kg) which flows into Lake Uchinuma. The Cs concentrations in the sediment of Lake Izunuma were 400 Bq/kg and 336.7 Bq/kg in Lake Uchinuma respectively. No Cs concentrations were detected in the fish collected before the Fukushima nuclear accident. After the accident, the Cs concentrations in freshwater mussels Cristaria plicata, Crucian Carp Carassius auratus langsdorfii and C. cuvieri, and Largemouth Bass Micropterus salmoides in the Lake Izunuma-Uchinuma watershed were 4.6 - 4.9 Bq/kg, 63.5 - 98 Bq/kg and 109.5 - 260 Bq/kg respectively. The Cs concentration in reeds Phragmites australis was 67.5 Bq/kg and 1,050 Bq/kg in that of the reed ash.

Spawning behavior of the fluvial eight-barbel loach (nagare-hotokedojo) Lefua sp. (sensu Hosoya, 1993) collected in the Yoshino River system in Tokushima Prefecture was observed in a tank with three males and eight females. Each male briskly patrolled the bottom of the tank and chased and bit at other individuals irrespective of their sex. In this study, egg-eating behavior was observed in both males and females. It was considered that the male's ongoing aggressive behavior may protect eggs from being eaten by other individuals. Patrolling males who found a female just before spawning could participate in spawning with the female. The number of individuals that participated in a given spawning event was one female to between one and three males. In the midst of this competitive spawning environment it was thought that males have a strategy of briskly patrolling to increase the encounter rate with females thereby increasing their reproductive successes.

The numbers of Greater White-fronted Geese roosting at several lakes in northern Miyagi prefecture have been monitored twice a month from October to February since the winter of 2003/04. We analyzed the monitoring data from the last five winters, 2007/08 to 2011/12. The maximum number of the geese in northern Miyagi pref. increased every year, from 116,147 in 2007/08 to 172,613 in 2011/12. The percentage of geese roosting in Lake Izunuma-Uchinuma was highest early in the wintering season (60% to 80%), whereas the percentage of geese roosting in Lake Kabukurinuma and Lake Kejonuma increased later in the wintering season. Seasonal variation in the percentage of geese roosting at various lakes in northern Miyagi pref. is related to the variation in food availability around each respective lake.

The author conducted a survey of the distribution of Lefua echigonia and Cottus spp. in three river systems in the vicinity of Lake Izunuma: the Eai, Kyu-Hasama and Hasama. In addition to the three aforementioned river systems, Lefua echigonia was also surveyed in the Naruse, Kinryu and Ichinono rivers. Based on this survey, it was confirmed that Lefua echigonia is distributed with its northern-most range limit in some tributaries of the Hasama. As for Cottus nozawae, it was confirmed to populate three tributaries of the Hasama. It is unknown whether Cottus pollux (large-egg type) still occurs in the upper Hasama after the Iwate-Miyagi Nairiku Earthquake in 2008, but Cottus nozawae is found in its original habitats even after the earthquake. The author reports that the Nagasaki river, a tributary of the Hasama, is an unusual river in Miyagi Prefecture in the sense that it is a shared environment for both Lefua echigonia and Cottus nozawae.