Evaluation of stock management procedures for walleye pollock in northern waters of the Sea of Japan using a simulation

To evaluate walleye pollock stock management procedures in the northern waters of the Sea of Japan, 30-year population dynamics, including uncertainties, were forecast. Errors in current stock size estimation, variability in future recruitment and changes in future fishing mortalities were incorporated. Results of virtual population analysis (VPA) from resampled catch-at-age data with bootstrap methods was used as the current stock size estimation with uncertainty. Performances of each scenario were evaluated using conservation, utilization, stability and reliability factors. Twenty-two management scenarios and continuing the current fishing mortality were evaluated. Scenarios with minor regulation changes and continuing the current fishing mortality showed poor stock conservation performances. Scenarios with minor regulation changes produced good short-term but poor long-term utilization. Stabilities were poor in continuing the current fishing mortality and fishing ban scenarios. Reliability in all scenarios after 30 years was smaller than in continuing the current fishing mortality; however, small differences among scenarios were observed. The simulation results indicated that multilateral assessment is needed to evaluate the management candidates. Uncertainty caused by recruitment variability mostly affected future population dynamics. The role of simulations in the production of effective scientific advice is discussed.     

Anti-allergic effects of the brown alga <Emphasis Type="Italic">Eisenia arborea</Emphasis> on Brown Norway rats

To investigate the anti-allergic effects of the brown alga Eisenia arborea. A strain of Brown Norway rats know to strongly respond to immunoglobulin E (IgE) were used as an allergy model animal. The rats were immunized with ovalbumin by oral administration. The levels of serum IgE and histamine were suppressed in the rats fed a diet supplemented with dried E. arborea powder. As for the cytokine pattern, the interferon-γ production in the spleens and mesenteric lymph nodes (MLN) was enhanced, and the interleukin-4 (IL-4) production in the spleens and/or IL-10 production in the spleens and MLN were suppressed. These results, together with the change in the Th1/Th2 balance, indicate that the rats fed with E. arborea became more anti-allergic, suggesting that E. arborea might possess anti-allergic effects.     

Cloning, characterization and expression of cDNA containing major histocompatibility complex class I, IIα and IIβ genes of Japanese flounder Paralichthys olivaceus

ABSTRACT:   The nucleotide sequences of Japanese flounder Paralichthys olivaceus , major histocompatibility complex (MHC) cDNA, classical MHC class Iα, non-classical MHC class Iβ, MHC class IIα and IIβ, were determined. The domain structures and antigen binding motifs of vertebrate MHC are conserved in the Japanese flounder MHC. A phylogenetic analysis supports the classification of these genes into class I and class II MHC. Classical MHC class Iα was ubiquitously expressed, whereas the non-classical MHC class Iβ was expressed mainly in lymphoid organs, gills, intestine and stomach. The MHC classes IIα and IIβ were also ubiquitously expressed.     

The response of ectomycorrhizal fungi on Pinus densiflora seedling roots to liquid culture

Japanese red pine (Pinus densiflora) seedlings taken from a nursery were grown in liquid culture with all roots entirely submerged in water. The aims of the present study were to observe the reactions of preformed ectomycorrhizae to liquid culture and to examine new infections by ectomycorrhizal fungi on newly formed root tips in liquid culture. Inoculation levels were controlled by trimming the ectomycorrhizal roots to one of three selected root lengths. The results showed that the mantles of pre-formed ectomycorrhizae were lost during the 8 weeks of the liquid culture and that these preformed root tips became blackish and wrinkled, but Hartig nets remained in these blackish root tips. On the newly formed lateral root tips, no ectomycorrhizal mantles were formed, although Hartig nets were found. In addition, the level of inoculum did not affect the frequency of Hartig nets in newly formed root tips, suggesting that the density of inoculum was more important than the amount of inoculum for new infection. In conclusion, ectomycorrhizal fungi endured and infected new roots while submerged; however, only Hartig nets were formed and not mantles.     

Long-term growth analyses of Japanese cedar trees in a plantation: neighborhood competition and persistence of initial growth deviations

The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37–0.46) of the variation in dbh growth during a 5–11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09–0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50–0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.