共查询到10条相似文献，搜索用时 54 毫秒
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Pop‐up archival tags (PAT) provide summary and high‐resolution time series data at predefined temporal intervals. The limited battery capabilities of PATs often restrict the transmission success and thus temporal coverage of both data products. While summary data are usually less affected by this problem, as a result of its lower size, it might be less informative. We here investigate the accuracy and feasibility of using temperature at depth summary data provided by PATs to describe encountered oceanographic conditions. Interpolated temperature at depth summary data was found to provide accurate estimates of three major thermal water column structure indicators: thermocline depth, stratification and ocean heat content. Such indicators are useful for the interpretation of the tagged animal's horizontal and vertical behaviour. The accuracy of these indicators was found to be particularly sensitive to the number of data points available in the first 100 m, which in turn depends on the vertical behaviour of the tagged animal. Based on our results, we recommend the use of temperature at depth summary data as opposed to temperature time series data for PAT studies; doing so during the tag programming will help to maximize the amount of transmitted time series data for other key data types such as light levels and depth. 相似文献
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Winter‐to‐spring variability in sea surface temperature (SST) and mixed layer depth (MLD) around the Kuroshio current system and its relationship to the survival rate (ln [recruit per spawning stock biomass], LNRPS) of Japanese sardine (Sardinops melanostictus) were investigated based on a correlation analysis of data from 1980 to 1995. The data were from a high‐resolution ocean general circulation model using the ‘Kuroshio axis coordinates’, in which the meridional positions are relocated to a latitude relative to the Kuroshio axis at each longitude, rather than the geographically fixed coordinates. A significant positive (negative) correlation between LNRPS and winter MLD (winter–spring SST) was detected near the Kuroshio axis from areas south of Japan (where eggs are spawned) to the Kuroshio Extension (where larvae are transported). This result is in contrast to previous studies using geographically fixed coordinates, which showed a significant correlation predominantly in the area south of the Kuroshio Extension in winter, where at this time few larvae have been found. From the late 1980s to early 1990s, when the survival rate was remarkably low, MLD around the axis was shallow and SST was high. Although MLD and SST show a significant correlation, significant partial correlations were also observed between February MLD and LNRPS when the contribution of SST was excluded, and between March SST and LNRPS when the contribution of MLD was excluded. We presume that MLD shoaling reduced the nutrient supply from deep layers, resulting in less productivity in the spring, and SST warming could have a negative influence on larval growth. 相似文献
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ABSTRACT: The vertical distribution of jack mackerel Trachurus japonicus larvae was described based on discrete depth sampling using a MTD net system from the surface down to 100 m depth at 13 stations in the southern East China Sea between 27 February and 10 March 2002. Of the 20 782 fish larvae collected, T. japonicus larvae were most abundant, accounting for 37.0% of the total catch. The average abundance of the larvae was 419.0 individuals/10 m2 , with the average (± standard deviation [SD]) body length of 2.6 ± 0.3 mm (range 1.8–7.5 mm). The larvae were concentrated in the mixed layer, with peak densities in the 10–30 m layer. The average (±SD) weighted mean depth was 21.5 ± 7.8 m. There was no evidence of either diel or ontogenetic vertical migration for the early larvae of <5 mm. More than 90% of the T. japonicus larvae were collected in the water temperature ranging from 21 to 23°C. Vertical profiles of the larval densities and chlorophyll a coincided with each other, which might reflect the abundance of their main prey organisms, copepod nauplii and copepodites, since copepod production is known to be closely related with the chlorophyll a concentration. 相似文献
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基于长江口外海域2009年夏末调查的温盐和溶解氧(DO)资料,采用垂向梯度法对夏末长江口外海域温度垂向结构类型进行划分,计算了温跃层深度、强度和温跃层处DO垂向梯度等参数。长江口外海域夏末水温垂向结构类型及其温跃层强度的分布表现为长江冲淡水、黄海沿岸流、台湾暖流表层暖水和台湾暖流深层冷水交汇、混合的态势。相关性分析表明,温跃层深度与温跃层处DO垂向梯度之间为负相关,温跃层深度与垂向最小DO浓度之间为正相关,温跃层强度与温跃层处DO垂向梯度之间为正相关。最接近DO供给源的上温跃层强度与温跃层处DO垂向梯度具有较强的相关性(r=0.69)。温跃层越浅、强度越大,对底层水低氧现象的影响越大。温跃层、特别是上温跃层引起的水体层化阻碍DO向底层输运,起到了物理隔氧的作用,与低氧现象具有紧密的联系,是低氧现象在长江口外海域从春末到秋季发生、发展、维持和消亡过程的重要环境控制因素。 相似文献
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Haruka Nishikawa Ichiro Yasuda Sachihiko Itoh Kosei Komatsu Hideharu Sasaki Yoshikazu Sasai Yoshioki Oozeki 《Fisheries Oceanography》2013,22(6):509-522
Particle‐tracking experiments were performed to infer the distribution of larvae of the Japanese sardine (Sardinops melanostictus) and to detect effects of transport environment on sardine recruitment, using the output of a high‐resolution ocean general circulation model and observed data of sardine spawning grounds during 1978–2004. By the 60th day following spawning, approximately 50% of the larvae had been transported to the Kuroshio Extension (KE). Whereas the spawning period and grounds changed markedly in relation to the stock level, the proportion of larvae transported to the KE remained relatively constant and no significant correlations were found between sardine recruitment and the transport proportion. Instead, the recruitment was found to be correlated with physical parameters including the mixed layer depth and the sea surface temperature along several major transport trajectories of sardine larvae. The correlations were most significant for the trajectories in the region 0.5° south to 1° north of the Kuroshio axis (defined as the location of velocity maxima at each longitude) and for larvae spawned in February and March during the high stock period (1978–94), and for larvae spawned in March and April during the low stock period (1995–2004). 相似文献
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The landings of Indian oil sardine (Sardinella longiceps, Clupeidae) along the south‐eastern Arabian Sea are about 43.8% of total Indian oil sardine production. The annual landings of this species exhibit large‐scale variability with prolonged years of surplus or deficit landings without identified reason. Evaluating Indian oil sardine landings along the Kerala coast during 1961–2017 in relation to environmental variations, we have elucidated a putative link between variability in landings versus environmental parameters and climate indices. The variables examined in this study, such as salinity and temperature along with physical indices such as upwelling and mixed layer depth (MLD) of the ocean help to propose a mechanism to temporal variability in the landings of Indian oil sardine. Colder temperature and timely intense upwelling lead to nutrient enrichment in the surface water, which promotes the growth of phytoplankton (chl‐a) and thereby food availability to Indian oil sardine are found during years with surplus catch. Less saline surface waters and shoaling of MLD at these times could lead to the aggregation of fish at particular depths and thereby a good catches. The reverse mechanism, such as more surface saline water, warm temperature, downwelling or weak upwelling, and less nutrient enrichment, leads to deficit landings. Further, it was noticed that the Pacific decadal oscillation and Atlantic multidecadal oscillation have a more pronounced impact on Indian oil sardine landings over the coast of south‐eastern Arabian Sea than previously reported ENSO associated impacts. All these point towards climate change implications for the Indian oil sardine fishery. 相似文献
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Chugey A. Sepulveda Scott A. Aalbers Craig Heberer Suzy Kohin Heidi Dewar 《Fisheries Oceanography》2018,27(4):381-394
This study reports on the movements of swordfish tagged within the Pacific Leatherback Conservation Area (PLCA), an expansive region (>500,000 km2) off the U.S. West Coast that has been seasonally restricted to drift‐gillnet fishing since 2001 to reduce leatherback sea turtle (Dermochelys coricea) interactions. Thirteen swordfish were outfitted with satellite‐linked archival tags scheduled for short (2–20 days, n = 11) and longer‐term (150 days, n = 2) data collection. All tags were deployed on basking swordfish using traditional harpoon‐based methods during the fall of 2012–2013, near offshore seamounts (35.6°N/122.9°W to 37.4°N/123.5°W). Depth and temperature data from 11 swordfish (~90 to 150 kg) resulted in <251 days of movement information from the PLCA region. All tagged individuals exhibited surface‐oriented nocturnal movements, spending >99% of the night above the average thermocline depth (37.5 m), with an average night depth of 8.3 ± 1.6 m. Daytime depth distribution was greater and more variable (mean 107.1 ± 21.2 m), with fish primarily displaying three behavioral patterns: (i) basking activity, 16.7% of the day, (ii) a mixed‐layer distribution between 3 m and the thermocline (26.8% of the day), and (iii) prolonged dives below the thermocline, 56.5% of the day. For seven of the tracks, daytime basking rates increased when thermocline depth was <37 m. As fish moved offshore, there was less variability in vertical movements with a reduction in both basking activity and mixed layer occupancy, as well as an increase in average daytime depth. These data are discussed with respect to the potential development of alternative fishery options for the PLCA. 相似文献
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威海双岛湾人工鱼礁区刺参大面积死亡原因初探 总被引：4，自引：0，他引：4
2013年9月4日开始,威海双岛湾人工鱼礁区15 m以深水域,刺参出现大面积死亡.为了解致死原因,于9月6日开展了相关调查.结果表明,有害浮游生物与刺参死亡的相关性较小,缺氧水层的出现可能是刺参死亡的主要原因.在所调查的海区,缺氧水层的上界约为13 m～15.5 m,下界至海底.夏季的高温、多雨和少风导致温跃层和盐跃层出现,水体垂直循环受阻后在海底形成缺氧层.建议增殖生产中合理安排增殖放养密度,对海区增殖生物状况和底层溶解氧进行实时监测,开展预警、预报,合理安排采捕生产,以减少因底层缺氧造成的经济损失. 相似文献