Itsuro Koizumi

Learn More
Salmonid fishes exhibit high levels of population differentiation. In particular, the brown trout (Salmo trutta L.) demonstrates complex within river drainage genetic structure. Increasingly, these patterns can be related to the underlying evolutionary models, of which three scenarios (member-vagrant hypothesis, metapopulation model and panmixia) facilitate(More)
Stream networks and watershed systems are among the most vulnerable ecosystems to human impacts such as habitat fragmentation, water pollution, logging and flow regime alterations. Loss of ecosystem functions and extinction of freshwater and riparian species have become serious issues. To understand biological processes in watershed ecosystems we need to(More)
[1] Water column stratification increased at climatic transitions from cold to warm periods during the late Quaternary and led to anoxic conditions and sapropel formation in the deep eastern Mediterranean basins. High-resolution data sets on sea-surface temperatures (SST) (estimated from U 37 k 0 indices) and d 18 O of planktonic foraminifer calcite (d 18 O(More)
Fishermen often anecdotally report an unexpected increase of fish caught in small tributary streams during floods, presumably due to refuge-seeking behavior from the main stem. From a population perspective, this implies the significance of refuge habitats and connectivity for population viability against natural disturbances. Despite the plausibility,(More)
Intra-specific genetic diversity is important not only because it influences population persistence and evolutionary potential, but also because it contains past geological, climatic and environmental information. In this paper, we show unusually clear genetic structure of the endangered Japanese crayfish that, as a sedentary species, provides many insights(More)
Invasion status and impacts of nonnative brook trout (Salvelinus fontinalis) in a Hokkaido stream were investigated with field surveys and genetic analyses. Nonnative brook trout was detected in nine (41 %) of the 22 sampled reaches in three tributaries of the Sorachi River, Hokkaido, Japan. Based on the external pigmentation, twelve putative hybrids(More)
Identifying the patterns and processes driving dispersal is critical for understanding population structure and dynamics. In many organisms, sex-biased dispersal is related to the type of mating system. Considerably, less is known about the influence of life-history variability on dispersal. Here we investigated patterns of dispersal in masu salmon(More)
A hybrid specimen between endemic Miyabe charr Salvelinus malma miyabei and introduced masu salmon Oncorhynchus masou masou was collected in an inlet stream (Yamada Creek) of the Lake Shikaribetsu. This specimen showed intermediate external characteristics between two species and was also confirmed as a hybrid by DNA markers. The mtDNA of the specimen was(More)
Plasma lecithin:cholesterol acyltransferase (LCAT) plays an important role in early steps of reverse cholesterol transport, i.e., cholesterol efflux from peripheral tissues and cholesterol esterification in HDL. However, structural and functional relationships of LCAT have not been fully elucidated. We described a missense mutation of Gly 30-to-Ser in a(More)
Because of their high economic and recreational value, salmonids have been extensively introduced worldwide and are responsible for significant impacts on native ecosystems. However, effective methods for controlling or eradicating introduced populations of salmonids are still limited, particularly in large river systems. Here, we demonstrated that invasive(More)