Age and Growth of <Emphasis Type="Italic">Sillago aeolus</Emphasis> in Okinawa Island,Japan     

Md.?Habibur?RahmanEmail author  Katsunori?Tachihara 《Journal of Oceanography》2005,61(3):569-573

In a study of the age and growth of Sillago aeolus, a total of 414 fish were collected from December 2000 to March 2002, around Okinawa Island. Ages of 403 specimens were determined by otoliths. Monthly changes in the percentage of otoliths with an opaque zone in the outer margin indicated that an opaque ring formed once a year, occurring between February and May. The rings can therefore be defined as annual rings. Ages of females were estimated to be 0+ to 4+, while those of males were 0+ to 2+. The von Bertalanffy growth curves were well fitted to age-standard length data of males and females, as follows: Male: L_t = 209.6 [1 − exp{−0.70 (t + 0.58)}]. Female: L_t = 297.7 [1 − exp{−0.42 (t + 0.61)}].  相似文献   

Geostrophic balance of the Kuroshio as inferred from surface current and sea level observations     

Kunio Rikiishi  Katsunori Sasaki 《Journal of Oceanography》1988,44(6):305-314

Historical observations of the surface current and daily mean sea level during the period 1965–1985 are analyzed in order to examine the geostrophic balance of the Kuroshio current in the Tokara Strait and near the Izu Islands. The variation in the sea level difference across the Kuroshio is associated with a variation in surface current velocity as predicted by the theory of geostrophic balance. However, the slope of the linear relation between the current velocity and sea level difference is smaller than the theoretically predicted value by about 30%. This disagreement may be ascribed to the effects of the centrifugal force and the occasional rise in sea level due to storm surges.Absolute mean sea level differences between the tidal stations are estimated by making use of the empirical relationship between the surface current and sea level difference. Estimated differences are: 87.4±22.1 cm between Naze and Nishinoomote, 24.3±9.2 cm between Miyake and Minamiizu, 41.3±17.7 cm between Miyake and Mera and 45.1±8.8 cm between Hachijyo and Miyake. The absolute value of sea level difference between Miyake and Minamiizu and that between Miyake and Mera may be about 30 cm, since geodetic levelling tells us that the mean sea level at Minamiizu is nearly equal to that at Mera.  相似文献   

Multi‐year tracking of sediment sources in a small agricultural watershed using rare earth elements     

A. Kimoto  M. A. Nearing  M. J. Shipitalo  V. O. Polyakov 《地球表面变化过程与地形》2006,31(14):1763-1774

Rare earth elements (REEs) have been successfully used as a sediment tracer, but the REE technique has never been used for studying sediment sources for a multi‐year period. A nearly four‐year field experiment was conducted on a small agricultural watershed near Coshocton, OH, USA, to assess the applicability of the REE technique for a multi‐year period and to evaluate the relative contributions of sediment sources in the watershed. Tracer depletion and tracer enrichment ratio (ratio of the tracer concentrations in sediment to the concentrations in the soil in the areas of application) were evaluated to examine the applicability and accuracy of the technique. A minimum of 91 per cent of the mass of the applied elements was still available on any individual morphological element at the end of the experimental period. The tracer enrichment ratio varied from 0·4 to 2·3, and it was not significantly related to time. The relative contributions of six morphological elements within the watershed were evaluated as proportions to total sediment yield. The relative contribution of the lower channel was significantly increased as a function of the amount of sediment yield, while that of the lower backslope was significantly decreased. The relative contribution of the lower channel significantly decreased as a function of cumulative sediment yield, while the contributions of the shoulder and the upper backslope significantly increased. Our results showed that the REE technique can be used to track sediment sources for a relatively long period with two limitations or potential sources of error associated with a selective depletion of tracers and a contamination of downslope areas with tagged sediments from upslope areas. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Validation of age and growth of the Picasso triggerfish (Balistidae: Rhinecanthus aculeatus) from Okinawa Island, Japan, using sectioned vertebrae and dorsal spines     

Fabienne Künzli  Katsunori Tachihara 《Journal of Oceanography》2012,68(6):817-829

To understand age and growth of the Picasso triggerfish, Rhinecanthus aculeatus, monthly sampling was conducted from February 2010 to October 2011 on the subtropical Okinawa Island, Japan, using trammel net and speargun. Fish were measured by weight (W) and standard length (SL) and age was determined by examining thin-sections of the first dorsal spine and the second abdominal vertebra. A total of 352 fish were caught ranging from 20.9?mm to 209.5?mm (SL). Marginal increment analysis indicated that translucent rings were deposited annually during the colder season from October to January. The relationship of observed SL and age was described by the original form of the von Bertalanffy growth equation. Male and female growth models were significantly different. Overall growth was rapid during the first 2.5?years for both sexes, thereafter growth curves diverged. Males consequently reached larger sizes and greater ages. Maximum age for males and females was 13.5 and 9.5?years, respectively. Regression models of somatic growth (SL) as a function of vertebral and spine radii were significantly correlated (r?=?0.98 and r?=?0.96, respectively). According to the weight?Clength relationship, growth in R. aculeatus was negative allometric. Small recruits (SL?<?40?mm) appeared in high numbers in shallow coastal areas starting from August. This is the first record of age and growth for R. aculeatus. Our data suggest that the Picasso triggerfish is a moderately long-lived balistid and that the observed sex-specific growth pattern is driven by the fish??s polygynous mating system and different reproduction strategies of males and females.  相似文献   

Comparison of carbon cycle between the western Pacific subarctic and subtropical time-series stations: highlights of the K2S1 project     

Makio C. Honda  Masahide Wakita  Kazuhiko Matsumoto  Tetsuichi Fujiki  Eko Siswanto  Kosei Sasaoka  Hajime Kawakami  Yoshihisa Mino  Chiho Sukigara  Minoru Kitamura  Yoshikazu Sasai  Sherwood L. Smith  Taketo Hashioka  Chisato Yoshikawa  Katsunori Kimoto  Shuichi Watanabe  Toru Kobari  Toshi Nagata  Koji Hamasaki  Ryo Kaneko  Mario Uchimiya  Hideki Fukuda  Osamu Abe  Toshiro Saino 《Journal of Oceanography》2017,73(5):647-667

A comparative study of ecosystems and biogeochemistry at time-series stations in the subarctic gyre (K2) and subtropical region (S1) of the western North Pacific Ocean (K2S1 project) was conducted between 2010 and 2013 to collect essential data about the ecosystem and biological pump in each area and to provide a baseline of information for predicting changes in biologically mediated material cycles in the future. From seasonal chemical and biological observations, general oceanographic settings were verified and annual carbon budgets at both stations were determined. Annual mean of phytoplankton biomass and primary productivity at the oligotrophic station S1 were comparable to that at the eutrophic station K2. Based on chemical/physical observations and numerical simulations, the likely “missing nutrient source” was suggested to include regeneration, meso-scale eddy driven upwelling, meteorological events, and eolian inputs in addition to winter vertical mixing. Time-series observation of carbonate chemistry revealed that ocean acidification (OA) was ongoing at both stations, and that the rate of OA was faster at S1 than at K2 although OA at K2 is more critical for calcifying organisms.  相似文献   

New polar ring galaxies in rich clusters of galaxies     

Taniguchi  Yoshiaki  Shibata  Katsunori  Wakamatsu  Ken-Ichi 《Astrophysics and Space Science》1986,118(1-2):529-530

Four polar ring galaxies discovered in rich clusters of galaxies are presented. Brief comments on their structural properties are given.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Quartz dissolution experiments at various pH, temperature and stress conditions: CLSM and ICP-AES investigations     

Jung Hae Choi  Kazushi Kimoto  Yasuaki Ichikawa 《Environmental Earth Sciences》2012,66(8):2431-2440

To understand the effects of temperature, pH and mechanical stress on the pressure dissolution of quartz, two experiments using monocrystalline quartz samples were conducted. The first was a closed-fluid experiment to investigate the effect of pH, and the second was a flow-through experiment to investigate stress and temperature effects. To initiate the pressure dissolution, a pair of samples was immersed in a solution with a prescribed pH. The samples were stressed mechanically by pressing one sample against the other. In the closed-fluid experiments, the pH of the solution was fixed to 7, 9, 11 and 13, the applied stress was approximately 200 MPa and temperature 25°C. The flow-through experiments were conducted at three different temperatures (35, 50 and 75°C) at the same pH 11.7. The value of the applied stress was 7.32, 13.72, 21.42 or 25.27 MPa. During each of these dissolution tests, the solution was regularly sampled and analyzed by an Inductively Coupled Plasma-Atomic Emission Spectrometry technique to measure Si-concentration. With the measured Si-concentration, a dissolution rate constant was computed the different pH, stress and temperature conditions. The rate constant is proportional to pH, stress and temperature, as indicated in the literature. It should be noted that the rate constant for the highest stress (200 MPa) was considerably greater than for the other cases. In addition, island-channel patterns characterized by micro-cracks a few nanometers in length were seen on the dissolved parts of the samples. The findings and the measured data in this paper may be useful for the future development of theoretical models for pressure dissolution and its validation.  相似文献   

Upper ocean warming pattern in the past 50 years     

Sayaka Yasunaka  Masahide Kimoto 《Journal of Oceanography》2013,69(1):87-95

A long-term warming pattern of global subsurface ocean was detected separately from other natural variations. Three dominant modes were extracted: a long-term warming mode, a mode related to the El Niño/Southern Oscillation, and a mode related to the Atlantic Multidecadal Oscillation. The long-term warming mode explained 78 % of the global mean temperature variance from the surface to a depth of 300 m, and the other two modes could explain most of the residual variance. Subsurface warming associated with the long-term warming mode was strong in the subtropics. In contrast, there was a local minimum of warming in the northern hemisphere subarctic ocean, and warming was suppressed in subsurface waters south of the equator. Atmospheric changes associated with the long-term warming mode showed negative (positive) sea level pressure anomalies at high (middle) latitudes in both hemispheres, and an intensification and/or a poleward expansion of mid-latitude westerlies. Wind stress curl changes were negative in the subtropics and positive in the subarctic of the northern hemisphere; changes that were consistent with the strong warming in the subtropics and the local minimum of warming in the subarctic. Warming of Southern Ocean subsurface waters coincided with southward migration and intensification of westerly winds, whereas surface warming to the south of 50°S was suppressed, probably by strengthened northward Ekman transport. Positive wind stress curl off the equator with weakening of the tropical easterly winds in the Pacific and Indian Oceans was consistent with the subsurface negative temperature anomaly there.  相似文献   

春季欧亚大陆地表气温变化特征的气候意义   总被引：11，自引：3，他引：8       下载免费PDF全文

沈学顺  木本昌秀 《大气科学》2007,31(1):19-27

研究了春季欧亚大陆地表气温的年际变化及其相联系的环流场特征,发现春季欧亚大陆地表气温年际变化呈现为大陆尺度的南北跷跷板式的空间分布特征, 即当中高纬度地表气温为正距平时,副热带地区则为负距平,反之亦然。这种空间分布型代表了欧亚大陆中高纬度地表气温年际变化的主要特征。进一步的研究表明,这种变化与前期冬季北大西洋涛动（NAO）有着显著的正相关,而与同期的NAO无关。同时,欧亚大陆地表气温异常存在着明显的从冬到夏的持续性。与东亚初夏气候变化关系的研究表明,春季欧亚大陆地表气温的变化通过影响鄂霍次克高压的变化进一步影响初夏梅雨的变化。当春季欧亚大陆中高纬度地表气温为正距平时,鄂霍次克高压偏强,初夏梅雨较活跃,反之亦然。  相似文献