Relative contributions from exposed inshore and estuarine nursery grounds to the recruitment of stone flounder, Platichthys bicoloratus, estimated using otolith Sr:Ca ratios

In Sendai Bay, stone flounder larvae settle and spend their juvenile period in either shallow exposed inshore nursery grounds or estuarine nursery grounds. The purpose of this study is to examine the relative contributions of these two kinds of nursery grounds to the flounder population using otolith strontium:calcium ratios. Stone flounder juveniles were collected from both nursery grounds, and one- and two-year-old flounder were caught deeper in Sendai Bay. Sr and Ca content in the otoliths were measured by electron probe micro analysis. The Sr:Ca ratios in the otolith section corresponding to the early postsettlement period ranged from 3.06 to 3.85 for the exposed inshore areas with stable low temperature and high salinity conditions, and from 3.81 to 5.32 in brackish estuaries with high temperature and low salinity conditions but with large diel and tidal cyclical fluctuations. Values from an estuarine site with stable salinity ranged from 3.58 to 4.15 overlapping with both the above ranges. Rearing experiments supported our inference that the high otolith Sr:Ca ratios of juveniles inhabiting estuarine nursery grounds are attributable to higher temperature and physiological stress caused by the large diel temperature and salinity fluctuations within the estuaries. Estimation of the Sr:Ca ratio of recruited fish using the otolith section formed while in the nursery area showed that at least 20 out of 42 individuals examined originated from estuarine nursery grounds. The present study indicates that estuaries play an important role as nursery grounds for stone flounder, producing about half of the stock in spite of the small and restricted area compared with the wide expanse of the exposed inshore area.     

Alternating dominance of postlarval sardine and anchovy caught by coastal fishery in relation to the Kuroshio meander in the Enshu-nada Sea

In the mid 1970s, the fishery catch of postlarval Japanese anchovy (Engraulis japonica) in a shelf region of the Enshu‐nada Sea, off the central Pacific coast of Japan, started to decline corresponding to a rapid increase of postlarval sardine (Sardinops melanostictus). In late 1980s, sardine started to decline, and it was replaced by anchovy in the 1990s. This alternating dominance of postlarval sardine and anchovy corresponded to the alternation in egg abundance of these two species in the spawning habitat of this sea. It was also noteworthy that during the period of sardine decline, sardine spawning occurred in April–May, a delay of two months compared with spawning in the late 1970s. The implication of oceanographic changes in the spawning habitat for the alternating dominance of sardine and anchovy eggs was explored using time‐series data obtained in 1975–1998, focusing on the effect of the Kuroshio meander. Large meanders of the Kuroshio may have enhanced the onshore intrusion of the warm water into the shelf region and contributed to an increase in temperature in the spawning habitat. This might favour sardine, because its egg abundance in the shelf region was more dependent on the temperature in early spring than was that of anchovy. In addition, enhanced onshore intrusion could contribute to transport of sardine larvae from upstream spawning grounds of the Kuroshio region. On the other hand, anchovy egg abundance was more closely related to lower transparency at the shelf edge, which may indicate the prevalence and prolonged residence of the coastal water, and therefore higher food availability, frequently accompanying non‐meandering Kuroshio. The expansion/shrinkage of the spawning habitat of sardine and anchovy in the shelf region, apparently responding to the change in the Kuroshio, possibly makes the alternation in dominance of postlarval sardine and anchovy most prominent in the Enshu‐nada Sea, in combination with changes in the abundance of spawning adults, which occurred almost simultaneously in the overall Kuroshio region. The implication of this rather regional feature for the alternating dominance of sardine and anchovy populations on a larger spatial scale is also discussed.     

Software development for estimating the concentration of radioactive cesium in the skeletal muscles of cattle from blood samples

The 2011 earthquake severely damaged the Fukushima Daiichi Nuclear Power Plant (FNPP), resulting in the release of large quantities of radioactive material into the environment. The deposition of these radionuclides in rice straw as livestock feed led to the circulation of contaminated beef in the market. Based on the safety concern of the consumers, a reliable method for estimating concentrations of radioactive cesium in muscle tissue is needed. In this study, we analyzed the concentrations of radioactive cesium in the blood and skeletal muscle of 88 cattle, and detected a linear correlation between them. We then developed software that can be used to estimate radioactive cesium concentrations in muscle tissue from blood samples. Distribution of this software to the livestock production field would allow us to easily identify high‐risk cattle, which would be beyond the safety regulation, before shipping out to the market. This software is planned to be released as freeware. This software would contribute to food safety, and aid the recovery of the livestock industry from the damage creacted by the 2011 Tohoku earthquake and tsunami.     

Practical Application of Miyazaki Jitokko Chickens Selected for a Superior Allele at a Single Nucleotide Polymorphism Site in the Cholecystokinin Type A Receptor Gene

This study aimed to examine 1) whether selection for a superior allele at a single nucleotide polymorphism site (SNP; {"type":"entrez-nucleotide","attrs":{"text":"AB604331","term_id":"315258605","term_text":"AB604331"}}AB604331, g.420 C>A) of the chicken cholecystokinin type A receptor (CCKAR) gene in Miyazaki Jitokko chickens is detectable in commercial poultry farms, and 2) whether the reproductive traits of the Kyushu Rhode hens, as a maternal stock line of the Miyazaki Jitokko chickens, are affected by SNP selection. Conventional and A-allele fixed (improved) Miyazaki Jitokko chicks were hatched on the same day and raised in a battery cage until 7 days of age. The chicks were then deposited at two commercial poultry farms and reared until slaughter at 126 and 163 days for cockerels and pullets, respectively. Body weight on the day of hatching (day 0), at 5 days of age, and at slaughter were measured. The differences in the body weights of the farm and test groups at slaughter were analyzed using the generalized linear model. A-allele fixation increased the body weight at slaughter by approximately +123.5 g and +131.9 g in cockerels and pullets, respectively. No significant differences between the conventional and improved hens were detected in terms of egg-laying rate, fertilization rate, and hatchability in the Kyushu Rhode hens. The data suggest that fattening chicks can be supplied as usual, even if Kyushu Rhode hens are switched from the conventional to improved type. In conclusion, genetic improvements using the CCKAR SNP site as a marker were effectively established in terms of the growth of the Miyazaki Jitokko chickens in commercial farms and the reproductive traits of the Kyushu Rhode hens.     

Fire resistance of thick wood-based boards

Thick wood-based boards are used as construction materials for walls and floors in Japan. In this study, fire resistance tests (ISO 834-1) and cone calorimeter tests (ISO 5660-1) were conducted for thick plywood, particleboard, and medium density fiberboard with sample thicknesses of about 28–30mm, and their suitabilities for quasi-fireproof or fire-preventive structures were evaluated. In the ISO 834-1 fire resistance test, the heat-shielding performance (insulation criterion) for walls was evaluated and the results showed that the larger the apparent density of a woodbased board, the higher its insulation performance. The insulation performance of thick wood-based boards in the fire resistance test could be forecast from the results of the cone calorimeter test, especially when the second peak of heat release rate appeared. In the cone calorimeter tests, the surface layer density of the plywood, particleboard, and medium density fiberboard was the dominant parameter for the time to ignition and initial heat release rate. These results indicate that thick wood-based board is a suitable fire-preventive construction material. Part of this study was presented at the Annual Meeting of the Architectural Institute of Japan, Hokkaido, Japan, August 2004     

Stand structure and composition of a 60-year-old larch (Larix kaempferi) plantation with retained hardwoods

Tree retention is understood as a key practice in creating complexity, leading to heterogeneity in resources and habitats in managed stands. In this article, we clarify the long-term effects of tree retention on stand structure and tree-species composition in a 60-year-old Larix kaempferi plantation in central Japan. In our study plot (1.5 ha) there were 18 stems/ha of retained trees (determined by tree-ring analysis), mostly Quercus crispula. We conducted spatial analyses and tested the hypothesis that tree abundance, size structure, and species composition and diversity change with distance from the retained trees. Near the retained trees, L. kaempferi showed a reduction of 40%–60% in basal area, due presumably to the shading effect. In contrast, the nearby area showed greater species diversity in the canopy layer. The retained trees created patches of different species composition in the understory. The spatial gradient of shade and colonization opportunity provided by retained trees greatly affect the distribution of the colonized species, according to their shade tolerance and seed-dispersal ability, which resulted in the stand structure with a heterogeneous shrub-layer vegetation. Retention proved particularly important for the enhancement and long-term maintenance of structural and compositional complexity in L. kaempferi plantations.     

Dormancy release in male flowers of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>

To clarify key characteristics of the process whereby dormancy is released in male flowers of Cryptomeria japonica, twigs with male flowers were collected every three days between December 1992 and February 1993. Half of the twigs collected on each date were chilled at 0°C for three days and the cumulative temperatures required by the chilled and non-chilled flowers for florescence were compared. There was no difference in the cumulative temperature required for florescence between chilled and non-chilled male flowers collected before 19 December. However, for samples collected between 21 December and 21 January, the cumulative temperature needed for the florescence of chilled male flowers was 8–68°C lower than that required for non-chilled male flowers. However, there was little difference again in the cumulative temperature required to induce the florescence of chilled and non-chilled male flowers for collection dates later than 24 January. These results suggest that the dormancy of male C. japonica flowers was gradually released by exposure to low temperature and the process was completed by 24 January. The cumulative temperature required for florescence and the sum of the mean daily temperatures between the date of collection and the date of natural pollen dispersal were almost equal after the dormancy of the male flowers was released. The exact day on which pollen will be released can be predicted using the dormancy characteristics of male flowers.     

Improvement of fiberboard made from acetylated fibers by ozonation I: effect of ozonation on mechanical properties

Acetylated fibers with a 24.8% weight gain by acetylation were ozonated with 0%–2.0% ozone on fibers. Fiberboards were then made from these treated fibers. The internal bond and bending strength of the acetylated fiberboards increased drastically with increasing ozone charge up to 0.5%–1.0%, whereas the thickness swelling of the fiberboards decreased. Ozone selectively cleaves the aromatic rings of hydrophobic lignin and introduces a hydrophilic carboxyl group into lignin. Thus, the wettability and thermoplasticity of acetylated fibers increased, and this structural modification improved the interfiber contact. Internal bond and bending strength increased as a result. In addition, steep density profiles were formed by the ozonation, resulting in high bending strength. The high compaction ratio accelerated the effect of ozonation. The optimum ozone charges for improving mechanical properties were 0.5%–1.0%.Part of this report was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999