An assessment of “fishing down marine food webs” in coastal states during 1950–2010     

丁琪  陈新军  余为  陈勇 《海洋学报(英文版)》2017,36(2):43-50

渔获物平均营养级（Mean trophic level of fishery landings,MTL）是目前评估人类捕捞活动影响的研究中使用最广泛的生物多样性指标之一。根据联合国粮农组织FAO提供的渔获生产统计数据,结合Fishbase提供的相关鱼种营养级数据,本文评估了1950-2010年太平洋、大西洋和印度洋各沿海国海洋渔业开发状态。研究发现,在全球三大洋75个主要捕捞国中,43个国家MTL呈显著下降趋势,发生了Pauly于1998年提出的“捕捞降低海洋食物网”现象;但是,仅16个国家MTL的下降是由于高营养级种类的衰退,而27个国家属于“捕捞沿着海洋食物网”的下降机制。此外,20个国家MTL呈恢复上升趋势,但是,该恢复上升趋势通常伴随着传统低营养级种类产量的大幅下降;在上述20个国家中,11个国家的低营养级鱼类产量呈显著下降趋势。需谨慎分析“捕捞降低海洋食物网”现象,掌握MTL的潜在变化机制。  相似文献   

湖泊和水库营养分类的研究     

王东 《广东海洋大学学报》1992,(2)

根据我国实际情况,并参考国外对湖泊营养分类的标准,建立了湖泊和水库FTE营养分类方法。应用Fuzzy综合评判的理论和方法,对参加分类评判的各项指标参数通过映射的方法,使每一个指标参数转换成在区间[0,1]的特性指数(d_1),同时引入一个能反映每项指标参数在评判中重要程度的权值(a_1),求得一个能统一反映湖库营养程度的综合性评价指数的计算公式:e=∑a_1d_1。以何志辉教授对我国87个湖库营养分类结果为基准,计算并确定出贫、中、富三种营养类型互不相交的FTE指数范围,作为湖库FTE营养分类标准。对任一湖库,根据九项指标参数计算获得的FTE指数e,不仅能客观地反映其营养程度,同时又以它作为唯一的数值来确定该湖库的营养类型的归属。用FTE营养分类方法对我国87个湖库营养分类结果与何氏的分类结果吻合率达97.7％。  相似文献   

Response of a stream diatom community to top predator manipulations     

Peter Koetsier 《Aquatic Sciences - Research Across Boundaries》2005,67(4):517-527

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Trophic ecology of sharks in the mid-east Pacific ocean inferred from stable isotopes   总被引：1，自引：0，他引：1  

Yunkai Li  Yi Gong  Xinjun Chen  Xiaojie Dai  Jiangfeng Zhu 《中国海洋大学学报(英文版)》2014,13(2):278-282

As apex predators, sharks are of ecological and conservation importance in marine ecosystems. In this study, trophic positions of sharks were estimated using stable isotope ratios of carbon and nitrogen for five representative species caught by the Chinese longline fleet in the mid-east Pacific, i.e., the blue shark(Prionace glauca), the bigeye thresher shark(Alopias superciliosus), the silky shark(Carcharhinus falciformis), the scalloped hammerhead(Sphyrna lewini), and the oceanic whitetip shark(Carcharhinus longimanus). Of these species, oceanic whitetip shark has the lowest trophic level and mean δ15N value(3.9 and 14.93‰± 0.84‰), whereas bigeye thresher shark has the highest level/values(4.5 and 17.02‰± 1.21‰, respectively). The bigeye thresher shark has significantly higher δ15N value than other shark species, indicating its higher trophic position. The blue shark and oceanic whitetip shark has significantly higher δ13C values than bigeye thresher shark, silky shark and scalloped hammerhead, possibly due to different diets and/or living habitats. The stable isotope data and stomach content data are highly consistent, suggesting that stable isotope analysis supplements traditional feeding ecology study of sharks, and thus contributes to understanding their trophic linkage.  相似文献   

南沙群岛西南部陆架区底层鱼类营养结构研究   总被引：3，自引：0，他引：3  

宁加佳  杜飞雁  王雪辉  王亮根  谷阳光  李亚芳 《海洋与湖沼》2016,47(2):468-475

为了解南沙群岛西南部陆架区底层鱼类食物网的营养结构特征,于2013年9月利用稳定同位素方法分析了24种底层鱼类的碳和氮稳定同位素比值(δ~(13)C和δ~(15)N值),并计算了基于δ~(13)C—δ~(15)N量化的6个营养结构的群落范围指标。结果显示:南沙群岛西南部陆架区底层鱼类的δ~(13)C值在–20.4‰—–17.0‰之间,均值为(–19.1±0.8)‰;δ~(15)N值的范围为7.9‰—12.2‰,均值为(9.7±1.0)‰。鱼类的营养位置在3.06—4.33之间,平均值为3.58±0.29,表明均以肉食性为主。根据群落范围指标结果分析,鱼类群落的δ~(13)C和δ~(15)N值范围(CR和NR)分别为3.4和4.3,表明南沙群岛西南陆架区底层鱼类的初始食源较为单一,营养层次较少;总面积(TA)和到重心的平均距离(CD)分别为5.8和1.0,意味着鱼类食物网营养级多样性的总程度和平均程度均较低;平均最近相邻距离(NND)及最近相邻距离的标准偏差(SDNND)分别为0.37和0.43,说明研究海域底层鱼类食物网的营养冗余程度较高,不同种类之间的营养生态位幅宽较小,重叠程度较高。此外,浅海长尾鲨(Alopias pelagicus)和狐形长尾鲨(Alopias vulpinus)在南沙群岛西南部陆架区底层鱼类群落的营养结构中起着重要作用。因此在对该海域渔业资源进行开发利用时,应禁止捕捞这些种类,而对一些冗余种类,如多齿蛇鲻(Saurida tumbil)、条尾鲱鲤(Upeneus bensasi)和带鱼(Trichiurus haumela)等,可以适度捕捞,以维持底层鱼类群落营养结构的完整性,在渔业资源合理开发、持续利用的同时,有效地保护海洋生态系统的安全发展。  相似文献   

Association of the scallop Patinopecten yessoensis and epibiotic barnacle Balanus rostratus: inter‐specific interactions and trophic relationships determined by fatty acid analysis          下载免费PDF全文

Alla V. Silina  Natalia V. Zhukova 《Marine Ecology》2016,37(2):257-268

Marine mollusks provide shelter to epibiotic organisms which settle on the outer surface of their hard shells. Epibionts can exert beneficial or detrimental effects on the host mollusk. In this study, the ecology of the association of the commercially valuable marine mobile scallop Patinopecten (=Mizuhopecten) yessoensis with its epibiotic barnacle Balanus rostratus was investigated. Fatty acid analysis was performed to determine the trophic relationships between these species. The distribution of fatty acid markers in this scallop species suggests an important contribution of diatoms, flagellates and animal material in its diet. The fatty acid analysis indicated a predominance of diatoms in the diet of the adult barnacles and some detrital input into the diets of young individuals. It was found that adult barnacles may compete with the scallops for food sources such as diatoms and zooplankton. It was revealed that with a negligible biomass of epibionts, the interactions between the barnacle and scallop may be regarded as commensalisms. An increase in the weight of epibiotic barnacles resulted in decreases in the weights and shell heights of the scallops, testifying to the adverse influence of a high biomass of epibionts on their host.  相似文献   

红海湾远海梭子蟹Portunus pelagicus的食物组成及营养位置分析     

宁加佳  杜飞雁  李亚芳  谷阳光  王亮根 《海洋学报》2016,38(10):62-69

利用稳定同位素技术;分析了2015年5月在红海湾海域采集的远海梭子蟹Portunus pelagicus及其潜在食物的碳（δ13C）和氮（δ15N）稳定同位素比值;通过稳定同位素混合模型（SIAR）;估算不同食物对远海梭子蟹食性的相对贡献。结果表明:远海梭子蟹的δ13C值在-18.1‰~-14.1‰之间;δ15N值的范围为9.8‰~13.8‰;平均值分别为-16.9‰±1.3‰和12.1‰±2.3‰。δ13C和δ15N值的变化范围均较大;表明远海梭子蟹食物来源广泛、多样。远海梭子蟹的食物主要由双壳贝类、螺类、鱼类、头足类、虾类、蟹类和藻类组成。SIAR模型计算结果显示:藻类为远海梭子蟹的主要食物;其平均贡献为32.5%;双壳贝类的相对食性贡献为21.9%;虾类、螺类、鱼类和蟹类的平均贡献差异较小;分别为9.7%、9.7%、9.6%和9.3%;头足类的贡献最低;仅为7.3%。此外;根据δ15N值及营养位置的计算公式得出:远海梭子蟹在红海湾海域位于2.91±0.68营养级。远海梭子蟹的7类潜在食物中;藻类的营养位置最低;为1.21±0.58;其次为双壳贝类;为2.00±0.25;蟹类、螺类、虾类和鱼类的营养位置分别为2.85±0.33、2.87±0.26、3.01±0.16和3.08±0.18;头足类的最高;为3.41±0.17。  相似文献   

沱江浮游植物群落特征及水质评价   总被引：1，自引：0，他引：1  

陶敏  谢碧文  齐泽民  杨品红  李斌 《海洋与湖沼》2016,47(4):854-861

为合理评价沱江水质现状,于2013年丰水期(8月)和枯水期(11月)对沱江浮游植物及主要水质指标进行采样调查。结果显示:(1)丰水期综合营养状态指数TLI(∑)较高,尤其是上游江段,变化范围为47.4—64.6,平均56.3;枯水期TLI(∑)变化范围为43.4—48.1,平均44.6。(2)检出浮游植物88种(属),主要为绿藻、硅藻和蓝藻。丰、枯水期浮游植物群落主要组分分别为绿藻+硅藻+蓝藻和硅藻+绿藻+隐藻。优势度分析显示,丰水期优势种主要为梅尼小环藻(Cyclotella meneghiniana)、微小平裂藻(Merismopedia tenuissima)、拉氏拟柱孢藻(Cylindrospermopsis raciborskii)等,枯水期主要为脆杆藻(Fragilaria sp.)、尖尾蓝隐藻(Chroomonas acuta)、线形舟形藻(Navicula graciloides)等。(3)丰水期浮游植物的多样性指数H?、丰富度指数d、均匀度指数J均值分别为3.66、6.21和0.69,枯水期分别为3.67、4.12和0.88。(4)聚类分析与单因素方差分析结果表明沿江水坝建设与空间分布格局对NH4+与浮游植物群落结构已有影响,表现出水坝上游湖泊型藻类数量增加、上游江段浮游植物密度高于下游江段的趋势。(5)分类回归树模型显示,营养水平与物种丰富度较高但均匀度偏低的水体中,浮游植物密度易出现高值。综合以上情况,沱江水质已处于中到富营养状态,尤其是丰水期与较上游的江段,富营养化程度更高。为预防水华的发生,出现丰富浮游植物种类的地段更应加强监控,尤其是丰水期上游的大坝坝上江段。  相似文献   

Characterisation of the dietary relationships of two sympatric hake species,Merluccius capensis and M. paradoxus,in the northern Benguela region using fatty acid profiles     

JA Iitembu  NB Richoux 《African Journal of Marine Science》2016,38(1):39-48

The two sympatric species of Cape hake, Merluccius capensis and M. paradoxus, have been the main targets of bottom-trawl fisheries off Namibia for several decades. The feeding ecology of these hakes has been studied mainly using stomach content analyses and thus there remain some gaps in our knowledge about food assimilated over the longer term. In this study, we used fatty acid (FA) profiles to characterise the dietary relationships of M. capensis and M. paradoxus. Muscle samples from hake (n=110) and their known prey (n=68) were collected during trawl surveys off Namibia during 2011. Significant differences between the neutral FA profiles of the hake populations were detected in December 2011 but not in January 2011, an indication of temporal variations in diet and resource partitioning. Comparisons of the neutral FAs in hake and the total FAs of potential prey showed no clear trophic connections, with the exception of flying squid Todarodes sagittatus, which had FA profiles very similar to those of M. paradoxus in December 2011. Our results highlight the complex and temporally shifting relationships that exist between hake and the large pool of prey available to them, and between the two hake species that overlap in their feeding habits and distribution within the highly productive Benguela Current region.  相似文献   

Responses of two trophic levels to patch enrichment along a New Zealand stream continuum     

Barry J. F. Biggs  Rex L. Lowe 《新西兰海洋与淡水研究杂志》2013,47(2):119-134

We carried out a benthic survey and two experiments in runs at eight sites down the Kakanui River (South Island, New Zealand) during summer low flows, to investigate the interaction between nutrients, periphyton, and macro‐grazers. Benthic periphytic biomass was generally low (< 20 mg m^‐2 chlorophyll a) at most sites, but high densities of macro‐grazers (mainly snails) were observed at six of the eight sites. Chlorophyll a and cellular P concentrations were generally higher on artificial substrates in the first‐ to third‐order tributaries, compared with downstream. Macro‐grazer densities (mainly snails) were also highest in the second‐ and third‐order tributaries. Enrichment of patches with N and P did not translate into significant increases in chlorophyll a concentrations. Instead there was a general increase in macro‐grazers, and an increase in the relative abundance of Cocconeis placentula. In a second experiment, the chlorophyll a level was five‐fold higher on the substrates where macro‐grazers were excluded and there was no significant response of chlorophyll a to nutrient addition on these substrates. On the grazed substrates, densities of snails and caddis‐larvae were two‐fold higher with N+P enrichment. These experiments provided evidence for a tight coupling between first and second trophic levels, and strong grazer control of periphyton, in this river.  相似文献