Spatiotemporal change in growth of two populations of Asian chum salmon in relation to intraspecific interaction

Spatiotemporal changes in growth patterns of chum salmon Oncorhynchus keta that returned to the Ishikari (Japan) and Namdae (Korea) rivers in 1984–1998 were investigated using scale analysis. Juvenile chum salmon from both populations left coastal marine areas after spring at a size of over 8 cm fork length (FL). In summer, juvenile salmon from the Namdae River entered the Okhotsk Sea at a larger FL than did Ishikari River juveniles. There were no significant differences in annual growth between populations of 1-, 2-, and 4-year-old fish. For 3-year-old fish, however, Namdae River salmon had significantly higher synchronous and sympatric growth than did Ishikari River salmon. Mean FL of adults was also larger in Namdae River salmon than in Ishikari River salmon. Analysis of covariance (ANCOVA) results showed (1) negative linear relations between FL and catch, (2) homogeneous slopes of those relations at regional and species levels, and (3) nonhomogeneous slopes at the population level, indicating that density-dependent effects on growth were most significant at this level. We concluded that growth of chum salmon was concurrently influenced by stronger effects of intrapopulation competition and weaker effects of inter- and intraspecific interactions in the Bering Sea.     

Visual acuity of Pacific Saury <Emphasis Type="Italic">Cololabis saira</Emphasis> for understanding capture process

ABSTRACT:   To understand the mechanism of the behavioral response in the capture process of how fish recognize fishing gear and then how they can avoid the gear, the visual acuity of Pacific saury Cololabis saira was investigated by histological examination of the retina of individuals in the size range of 75–365 mm fork length (FL). The contour map of cone density distribution shows that the highest cone density is located in the temporal area of the retina, which indicated the visual axis as the forward direction. The visual acuity (VA) depends both on the focal length of the lens and the number of cones in the retina. The lens diameter increased linearly from 1.40 to 4.73 mm with fish growth, while the cone density decreased gradually from 765 to 378 cells/0.01 mm². Our results show that the visual acuity increases proportionately from 0.057 to 0.140 for individuals ranging in FL from 75 to 365 mm as expressed by the equation VA  = 0.0065 ×  FL ^0.5271 ( r ² = 0.9624).     

Intensive Field Survey of Aerosol and Gas Concentrations with 6-h Interval Sampling in Winter in Japan

We intensively surveyed the concentrations of chemical species in aerosols and gases using a four-stage filter-pack method at a site in Japan facing the Sea of Japan in winter with 6-h sample intervals. A few chloride species emitted anthropogenically were detected, and the HCl (g) concentration was quite low. The number of chloride species artifacts was also low. The HNO₃ (g) concentration was significantly higher when the monitored air mass passed over the Korean Peninsula compared to when it did not pass over the Korean Peninsula. In addition, the HNO₃ (g) concentration was significantly higher when the air mass arrived at the monitoring site by passing the route at lower latitude than the latitude of the monitoring site. On the other hand, the SO₂ (g) concentration showed no change between various trajectories of the air mass. The $ {\text{NH}}^{ + }_{4} $ (p)/non-seasalt- (nss-) $ {\text{SO}}^{{2 - }}_{4} $ (p) ratio was intermediate between the compositions of (NH₄)₂SO₄ and NH₄HSO₄ when the air mass passed over the Korean Peninsula, whereas it was intermediate between NH₄HSO₄ and H₂SO₄ when the air mass did not pass over the Korean Peninsula. We detected the transboundary transport of sulfur dioxide with high time-resolution monitoring at two separate monitoring points: the current monitoring site and Oki Island.     

Instability of subtelomeric regions during meiosis in <Emphasis Type="Italic">Magnaporthe oryzae</Emphasis>

Dynamics of chromosomal ends during meiosis was examined using a tetrad F₁ population derived from a cross between Setaria and Triticum isolates of Magnaporthe oryzae. Telomeric fragments were liberated by six restriction enzymes and detected with a telomere probe. Each fragment was assigned to one of the 14 chromosomal ends using chromosome-specific markers. Size shifts and non-Mendelian segregation (4:0, 3:1, 1:3, and 0:4) were frequently observed in these telomeric fragments and were considered to be caused by deletion, insertion, point mutation, and gene conversion. Similar results were obtained in another tetrad F₁ population derived from a cross between Oryza and Triticum isolates. These results suggest that subtelomeric regions are unstable during meiosis and are prone to various rearrangements including gene conversion.     

Inducing infection of oak logs by a pathogenic fungus carried byPlatypus quercivorus (Murayama) (Coleoptera: Platypodidae)

This study examined the frequency of infection by an unidentified pathogenic fungus of oak logs bored into by males alone or by both males and females ofPlatypus quercivorus (Murayama) in the field. The fungus, which is associated with mass mortality of oak trees in Japan, was not isolated from logs bored into by males alone, which bored only short entrance galleries. However, it was isolated from logs bored into by both males and females, which together bored longer galleries and reproduced successfully. This suggests that it is difficult for the fungus to colonize logs bored into by males alone. The fungus was not isolated from a log in which the beetles failed to reproduce, and in which the galleries were significantly shorter than in logs where reproduction succeeded, but it was unclear whether the shortness of the galleries prevented colonization of the log by the fungus. The study also revealed that some gallery-initiating males survived for at least 2 months in the absence of females, and that females elongated entrance galleries that had been bored by the gallery-initiating males.     

On-site damage evaluation of cracked irrigation infrastructure by acoustic emission and related nondestructive elastic wave method

Paddy and Water Environment - In recent years, the relationship between the durability and the degradation of concrete irrigation infrastructure has been discussed as a technical problem. In this...     

Effect of global warming on the life history and population dynamics of Japanese chum salmon

We have reviewed the effects of long-term climatic/oceanic conditions on the growth, survival, production dynamics, and distribution of Hokkaido chum salmon Oncorhynchus keta in Japan during the period 1945–2005 using path analysis, back-calculation, and scale analyses, and applied a prediction method based on the SRES-A1B scenario of the intergovernmental panel on climate change. The populations of Hokkaido chum salmon were found to have had high growth rates at age 1 year since the late 1980s. Path analysis indicated that the growth at age 1 year in the Okhotsk Sea was directly affected by warm sea surface temperature associated with global warming, with the increased growth at age 1 year resulting in higher rates of survival and large population sizes. Predictions on the global warming effects on the chum salmon were (1) decreased carrying capacity and distribution area, (2) occurrence of a strong density-dependent effect, and (3) loss of migration route to the Sea of Okhotsk, especially for Hokkaido chum salmon. We have also outlined the future challenges of establishing a sustainable conservation management scheme for salmon that include adaptive management and precautionary principles, as well as conservation of natural spawning populations and recovery of natural river ecosystems in Japan despite the warming climate.     

Irrelevance between the induction of anti-Campylobacter humoral response by a bacterin and the lack of protection against homologous challenge in Japanese Jidori chickens

On-farm vaccination of chickens against Campylobacter jejuni is considered a potentially effective countermeasure to decrease campylobacteriosis via consumption of contaminated chicken meat, but is not yet available. In this study, 2 groups of Jidori chicks were immunized subcutaneously with a formalin-killed C. jejuni with 2 different adjuvants. Other chicks served as the unvaccinated control group. Both vaccines induced high levels of anti-Campylobacter IgG but did not decrease bacterial excretion in cecal droppings and bacterial load in the liver and spleen after oral challenge with 10(5) CFU of the homologous strain. Further study is needed to address the observed irrelevance and to develop a novel effective vaccine against C. jejuni.     

Study on Sampling Method of Rainfall, Throughfall, and Stemflow to Monitor the Effect of Acid Deposition on Forest Ecosystem

The use of samplers for rainfall, throughfall, and stemflow was studied in Chamaecyparis obtusa forest in Kobe to develop a suitable simplified collection method for long-term monitoring of the effect of acid deposition on the forest ecosystem. A filtrating bulk sampler, widely used in Japan due to its convenience, was modified for rainfall- and throughfall-sampling. The pH value, NH₄ ⁺- and NO₃ ^?- concns. did not change within a two-week sampling period, and the collection efficiency of the modified type relative to the wet/dry sampler was 97% (mean). The three samplers (shampoo-hat, vinyl chloride tube, and gauze type) were used for stemflow sampling. Collection efficiency of the samplers was in the order of shampoo-hat> vinyl chloride tube> gauze and that of the gauze type varied significantly with rainfall condition.