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Periphytic biofilms in aquaculture waters are thought to improve water quality, provide an additional food source, and improve the survival and growth of some reared animals. In the Asia- Pacific region, particularly in China, artificial reefs are commonly used in the commercial farming of sea cucumbers. However, few studies have examined the epilithic biofilms on the artificial reefs. To gain a better understanding of the succession of epilithic biofilms and their ecological processes in sea cucumber culture waters, two experiments were conducted in culture waters of the sea cucumber Apostichopus japonicus in Rongcheng, China, using artificial test panels. On the test panels of succession experiment, more than 67 species were identified in the biofilms. On the test panels of seasonal variation experiment, more than 46 species were recorded in the biofilms. In both experiments, communities of epilithic biofilms were dominated by diatoms, green algae and the annelid Spirorbis sp. In the initial colonization, the dominant diatoms were Cocconeis sp., Amphora spp. and Nitzschia closterium in June, which were succeeded by species of Navicula, Cocconeis and Nitzschia (July to September), and then by Licmophora abbreviata, Nitzschia closterium and Synedra spp. in the following months. A diatom bloom in the autumn and filamentous green algae burst in the summer were also observed. Ecological indices well annotated the succession and seasonal changes in epilithic communities. Multidimensional scaling (MDS) analysis found significant differences in diatom community composition among months and seasons. Fast growth of biofilms was observed in the summer and autumn, whereas the biomass of summer biofilms was largely made up of filamentous green algae. Present results show that the components of epilithic biofilms are mostly optimal foods of A. japonicus, suggesting that biofilms on artificial reefs may contribute important nutritional sources for sea cucumbers during their growth seasons. Future works should include quantitative determination of the contribution of epilithic biofilms to the diet of A. japonicus, potential roles of epilithic biofilms in regulating the water quality of sea cucumber ponds, and the regulation of epilithic biofilms in sea cucumber culture ponds. 相似文献
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据统计,截止1993年底,陕西省共有机井约14.37万眼,总装机容量101.3万kW,年提取地下水20.42亿m~3,其中直接为农业提供水量14.27亿m~3,发展井灌面积703.3万亩。然而,目前的机井工作中还存在不少问题,诸如投资短缺,基础工作薄弱,行业管理不善等。为此,本文似就全省“九五”机井建设管理工作,提出几点建议,以供探讨。 相似文献
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2013年4月29日至2013年11月21日全部采用人工配合饲料对松江鲈鱼仔、幼鱼进行了投喂研究,在水温18.2~22.6℃的室内循环水中,松江鲈鱼通过升索S1~S8苗种料投喂,体重由平均0.084g/尾增至23.55g/尾,体长由平均1.95cm增至12.45cm;最大个体体长14cm,体质量33.5g;最小体长8cm,体质量14.5g。研究表明:仔鱼开口摄食外源性营养时,应以投喂卤虫幼虫为主,逐步减少卤虫幼虫,增加S1人工饲料,直至养到2cm左右,全部采用人工配合饲料喂养松江鲈鱼达到成熟规格完全可行,其平均日增长量0.115g/尾,饲料系数平均为1.1,总特定生长率(SGR)为2.76%d~(-1)。期间定时测定养殖水体的温度、pH、盐度、DO、COD、氨氮、亚硝酸盐、硝酸盐等水质指标均在正常范围内。实验还表明,在盐度范围20.3~27.1的条件下松江鲈鱼可以养至成熟规格。 相似文献
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黑鲪仔、稚、幼鱼生长、发育与成活率变化的研究 总被引：1，自引：0，他引：1
在人工池养条件下,根据2批黑鲪实验鱼苗外部形态特征和生态习性的变化,将其早期发育阶段划分为A～P共16个阶段。黑鲪早期发育阶段的消化系统要发生胃的分化、肠管的折叠、肝脏的形变和幽门垂的形态和数量变化等显著变化,其中稚鱼期的J～O阶段是消化系统变化最为剧烈的时期。2批鱼苗的生长速度均表现为逐渐加快,且全长生长均可拟合为3段直线,出现2个生长转折点:第一批苗第一个生长转折点在15～17d(多数为G阶段仔鱼,全长(8.07±0.63)～(8.44±0.66)mm);第二个生长转折点在49～51d(多数为O阶段稚鱼,全长(20.27±2.15)～(2l.13±2.17)mm)。第二批苗的2个生长转折点分别发生于14～16d(多数为G阶段仔鱼,全长(8.19±0.73)～(8.80±1.01)mm)和38～40d(多数为O阶段稚鱼,全长(21.18±2.49)～(22.77±2.83)mm)。对仔、稚、幼鱼成活率变化研究表明,黑鲪早期发育阶段存在4个临界期("危险期"):A～B阶段、D～F阶段、L～M阶段和N～O阶段,以L～M阶段鱼苗死亡率最高,而且临界期和鱼苗的形态变化、器官分化密切相关。黑鲪早期发育的阶段划分、生长转折点和临界期的确立,丰富了其早期生物学的内容,对苗种培育措施的实施具指导意义。 相似文献
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Broodstock of Verasper moseri (Jordan and Gilbert) aged 3–4 years old were selected, and reinforced cultivation was conducted to promote maturation under
controlled water temperature and photoperiod conditions. Fertilized eggs were obtained by artificial fertilization, and the
development of embryos, larvae and juveniles was observed continuously. The results showed that the fertilized eggs of V. moseri were spherical, with transparent yolk and homogeneous bioplasm, and had no oil globule inside. The average diameter of the
eggs was 1.77±0.02 mm. The eggs of V. moseri were buoyant in water with salinity above 35. The cleavage type was typical discoidal. Young pigment cells appeared when
olfactory plates began to form. Hatching occurred at 187 h after fertilization at a water temperature of 8.5°C. The newly
hatched larvae, floating on the water surface, were transparent with an average total length of 4.69±0.15 mm. During the cultivation
period, when the water temperature was raised from 9 to 14.5°C, 4-day old larvae showed more melanophores on the body surface,
making the larvae gray in color. The pectoral fins began to develop, which enabled the larvae to swim horizontally and in
a lively manner. On days 7–8, the digestive duct formed. The yolk sac was small and black. The yolk sac was absorbed on day
11. Larvae took food actively, and body length and body height clearly increased. The rudiments of dorsal and anal fin pterygiophores
were discernible and caudal fin ray elements formed on day 19. On day 24, the larval notochord flexed upwards, and the rays
of unpaired fins began to differentiate. Pigment cells converged on the dorsal and anal fin rays, and the mastoid teeth on
the mandible appeared. On day 29, the left eyes of juveniles began to move upwards. Depigmentation began in some juveniles
and they became sandy brown in color on day 37. Most juveniles began to settle on the bottom of the tank. The left eyes of
juveniles migrated completely to the right side on day 50, when the average body length attained 2.5±0.18 cm, and juveniles
accomplished metamorphosis to young. The embryonic and larval characters of several flounder species are compared. 相似文献
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中国气象局S2S（Sub-seasonal to Seasonal）数据归档中心建设是中国气象局承担世界气象组织（WMO）的世界天气研究计划（WWRP）和世界气候研究计划（WCRP）任务,由国家气象信息中心负责设计和实现。该文介绍了S2S数据归档中心建设中涉及的数据交换、数据检查及处理、数据归档存储及数据服务门户全流程系统设计和实现。针对各业务中心生产的S2S数据配置差异较大造成数据交换、同步较难这一问题,采用基于FTP（file transfer protocol）的数据推送和基于ECMWF（European Center for Medium-range Weather Forecasts）WebAPI主动数据下载相结合的方式,说明数据交换、同步方法和策略。由于S2S数据量巨大难以高效管理服务,已设计统一的数据组织形式和存储规则,实现根据数据检索条件解析获取数据存储位置,提供便捷的数据检索下载服务。自2015年11月15日中国气象局S2S数据门户系统对外开放,目前数据门户系统已有超过18个国家的300个用户注册并下载数据。 相似文献
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通过设置在刺参(Apostichopus japonicus Selenka)养殖池塘中的9个2 m3保苗网箱(2 m×1 m×1 m)进行现场实验,比较研究了波形网(CU)、地笼(地笼网CN+地笼板CP)、尼龙网片(NM)等3种类型附着基(共4种附着基材料)在投苗状态下表面附着生物的发生与演替,及其在刺参苗种中间培育过程中对刺参生长、存活和产量的影响。结果表明:不同附着基表面的附着生物群落具有相似的演替过程。地笼板(CP)上附着生物的干质量、无灰分干质量显著高于其他3种附着基材料(P0.05),而CU、CN和NM之间差异不显著(P0.05);4种附着基材料表面附着生物的叶绿素a含量表现为CUCPNMCN,且相互间差异显著(P0.05);参苗培育12周时,采用波形网附着基的网箱苗种产量显著高于地笼(P0.05),波形网成活率最高,且显著高于其他2种附着基(P0.05)。参苗培育17周后,采用波形网附着基的网箱,苗种产量显著高于地笼和尼龙网片(P0.05),波形网的苗种成活率和特定增长率显著高于尼龙网片(P0.05),地笼与其他两者之间差异不显著(P0.05)。上述结果显示,附着基类型对刺参中间培育过程中苗种产量、成活率、增长率有显著影响。通过对刺参保苗效果的综合分析,推荐采用波形网作为刺参室外池塘保苗的附着基。 相似文献
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我国是一个具有五千年悠久历史的明古国。而诗词又是我国珍贵的化瑰宝。一篇篇脍炙人口的佳作，内容极其丰富。有的写景，有的写物；有的抒情，有的叙事；有的写人民的悲欢离合，有的写国家的治乱盛衰；有的情意绵绵，有的豪迈奔放。其中，不乏描写地理景观、地理规律、地理原理的诗篇，教师上课时如能将富有情趣的诗词引入到课堂教学之中，不仅利于课堂知识的理解，利于学生视野的开拓，更利于构建开放式的课堂教学氛围，形成知识的跨学科联系。激发学生学习地理的兴趣。 相似文献