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HIROTO MURASE TSUTOMU TAMURA HIROSHI KIWADA YOSHIHIRO FUJISE HIKARU WATANABE HIROSHI OHIZUMI SHIROH YONEZAKI HIROSHI OKAMURA SHIGEYUKI KAWAHARA 《Fisheries Oceanography》2007,16(2):186-201
A study of common minke and Bryde's whales was conducted in the western North Pacific in the 2000 and 2001 summer seasons to estimate prey selection of cetaceans as this is an important parameter in ecosystem models. Whale sighting and sampling surveys and prey surveys using quantitative echosounder and mid‐water trawl were carried out concurrently in the study. Biomasses of Japanese anchovy, walleye pollock and krill, which were major prey species of common minke and Bryde's whales, were estimated using an echosounder. The results suggested that common minke whale showed prey selection for Japanese anchovy while they seemed to avoid krill in both the offshore and coastal regions and walleye pollock in the continental shelf region. Selection for shoaling pelagic fish was similar to that in the eastern North Atlantic. Bryde's whale showed selection for Japanese anchovy in August 2000 and July 2001, while it showed prey selection for krill in May and June in 2001. 相似文献
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MOHAMMAD AMZAD HOSSAIN YUKIO ISHIMINE HITOSHI KURAMOCHI HIKARU AKAMINE 《Weed Biology and Management》2002,2(3):153-158
The present study was undertaken from May 1996 to October 1997 in the glasshouse of the University of the Ryukyus, Okinawa, Japan to investigate standing water (12 cm deep) and shoot removal plus standing water regimes on morphological changes, growth, regrowth and biomass production of torpedograss ( Panicum repens L.). The stem internode was longer in standing-water-treated plants than that in untreated plants. The root-crown was developed from the submerged stem-node. Spike-like tillers and sheath-like leaf blades were observed in water-treated plants. Higher shoot biomass and lower rhizome biomass were obtained in standing-water-treated plants than that in untreated plants. Standing-water-treated plants attained higher total biomass than untreated plants. Standing-water stress was the factor that inhibited regrowth of torpedograss when the above-ground shoot was removed. Rhizomes without shoots of 6-month-old torpedograss did not survive in standing water for more than 6 months. The results indicate that torpedograss can survive in standing water if the shoots remain above the water surface. Shoot removal is one effective way to control torpedograss regrowth in standing water. The results of this study may be dependent on season, day length, water temperature, water pH, water depth and salt concentration in water. 相似文献
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ABSTRACT: We examined the diets of three size groups of the Pacific pomfret Bramajaponica collected in April and May 2000 in the transition zoneof the central North Pacific. Amphipods, cephalopods and fish werethree of the most common prey groups of pomfret. Of the three size groups,small pomfret (11.0–19.9 cm standard length (SL))preyed mainly on amphipods and occasionally on cephalopods (mainlytransitional species Onychoteuthis borealijaponica ) and fish.(These prey amphipods and fish could not be identified to lowertaxonomic levels because they were too digested.) Medium and largepomfret (20.0–30.9 and 31.0–40.9 cm SL,respectively) preyed mainly on cephalopods (mainly O. borealijaponica ,but also on two subarctic species, namely Berryteuthis anonychus and Gonatopsisborealis ), suggesting that these cephalopod species ensure energyfor the northward migration of these two size groups in the transitionzone in the spring. The next most common prey for medium pomfretwas amphipods (mainly subtropical species Phronima sedentaria and Platyscelusovoides ), followed by fish (mainly Bathylagus sp.). However,in the case of large pomfret, fish (mainly Paralepididae sp. 'A')were the next most common prey, followed by amphipods (mainly P.sedentaria and P. ovoides ), indicating that the importanceof fish as prey increases with growth for medium and large pomfret. 相似文献
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Effect of nitrogen fertilizer application on growth, biomass production and N-uptake of torpedograss (Panicum repens L.) 总被引：1，自引：0，他引：1
MOHAMMAD AMZAD HOSSAIN YUKIO ISHIMINE HIKARU AKAMINE HITOSHI KURAMOCHI 《Weed Biology and Management》2004,4(2):86-94
A glasshouse study was conducted to evaluate the effects of different rates (0, 50, 100, 200 and 400 kg ha?1) of nitrogen (N) fertilizer application on the growth, biomass production and N‐uptake efficiency of torpedograss. The growth responses of torpedograss to the N application were significant throughout the observation periods. Torpedograss grown for 60 days obtained the highest total biomass of 23.0 g plant?1 with an application of 200 kg ha?1 N, followed by 20.4 g plant?1 with an application of 100 kg ha?1 N; when it was grown for 90 days a significantly higher biomass of 102.3–106.0 g plant?1 was obtained with the 200–400 kg ha?1 N than the biomass (68.0 g plant?1) obtained with the fertilizer applied at a lower rate. When the torpedograss was grown for 130 days the highest biomass was 230.0 g plant?1 with the 400 kg ha?1 N application, followed by a biomass of 150.0 g plant?1 with the 200 kg ha?1 N application, but the above‐ground shoot in all treatments was over mature for animal food. The ratio of the above‐ground shoot to the underground part increased with the increase in N application up to 400 kg ha?1 during the 90 days after planting (DAP), but the above‐ground shoot biomass was the same with the 200 and 400 kg ha?1 N. The agronomic efficiency of the N application decreased to 5–38 with the increase in N application to 400 kg ha?1, which was less than half the agronomic efficiency with the 200 kg ha?1 N. The agronomic efficiency of N was very low (5–22) during the 60 DAP, which indicated that the N application would not be economically viable in this period for torpedograss as a pasture, and short‐duration plants could be cultivated in torpedograss‐infested fields to minimize weed‐crop competition. The nitrogen concentration (%) in the torpedograss increased with the increase in N application, but N‐uptake efficiency was the opposite and the value was very low with the 400 kg ha?1 N. The above results lead us to conclude that the N application rate of 200 kg ha?1 is the most effective for torpedograss growth. 相似文献
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Diel vertical migration of myctophid fishes (Family Myctophidae) in the transitional waters of the western North Pacific 总被引：10，自引：0，他引：10
HIKARU WATANABE MASATOSHI MOKU KOUICHI KAWAGUCHI KIMIE ISHIMARU & AKINORI OHNO 《Fisheries Oceanography》1999,8(2):115-127
The diel vertical migration patterns of adult myctophid fishes were determined in the transitional waters of the western North Pacific off Japan, using day–night sampling from 20 to 700 m depths with a commercial otter trawl in the summer of 1995. A total of 12 species belonging to 9 genera were collected. Four patterns were recognized in the diel vertical migration of 11 of the 12 species. (1) Migrants showing clear day–night habitat separation with peak abundance above 200 m at night: Symbolophorus californiensis, Tarletonbeania taylori, Notoscopelus japonicus, Diaphus theta, Ceratoscopelus warmingi, and Diaphus gigas. (2) Semi-migrants, in which part of the population often remains in the daytime habitat at night. The distribution depths of migratory and nonmigratory individuals do not overlap: Stenobrachius leucopsarus . (3) Passive-migrants, in which there is no separation of day–night habitats, but the upper limit of daytime distribution depth shifts to a shallower layer at night, probably as the fish follow migratory prey: Lampanyctus jordani . (4) Nonmigrants: Stenobrachius nannochir, Lampanyctus regalis (> 140 mm SL), and Protomyctophum thompsoni . The day–night habitat temperature ranges are also given for the 11 species. No remarkable east–west differences were seen in the vertical migration patterns compared with previous knowledge of eight of these species in the eastern Pacific. The diel migration patterns are newly described for three other species endemic to the western Pacific. The standing stock of myctophids in the study area was conservatively estimated at 18.5 ± 4.7 g m−2 (avg. ± SD). 相似文献
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HIROTO MURASE MORIO ICHIHARA HIROKI YASUMA HIKARU WATANABE SHIROH YONEZAKI HIROSHI NAGASHIMA SHIGEYUKI KAWAHARA and KAZUSHI MIYASHITA 《Fisheries Oceanography》2009,18(6):386-401
The acoustic characteristics of biological backscattering in the western North Pacific were studied to verify expert knowledge on species composition in the echosigns. The survey was conducted in the Kuroshio-Oyashio inter-frontal zone and the subarctic waters in April 2003. The species composition of backscatterings was identified by using midwater trawl, Isaacs-Kidd midwater trawl and Bongo net. The differences of mean volume backscattering strengths between 120 and 38 kHz (ΔMVBS120−38 ) were calculated for the backscatterings. Six types of backscatterings were classified based on the results of net samples and the ΔMVBS120−38 . The ΔMVBS120−38 of each group was as follows: copepods 13.7–17.3 dB, krill 11.6–15.3 dB, Japanese anchovy −1.6 to 1.1 dB, a myctophid, Diaphus theta −0.8 dB, sand lance 6.1 dB and larvae and juveniles of pelagic and mesopelagic fish −9.6 to −4.0 dB. The results suggest that biological backscatterings in the Kuroshio-Oyashio inter-frontal zone and subarctic waters of the western North Pacific in spring can be characterized by using ΔMVBS. 相似文献
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