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31.
为了有效监控永兴岛危险性害虫发生与危害,本研究对永兴岛可调查的所有陆地区域野生盐生植物、园林绿化植物、耐盐果蔬和绿色固沙植物害虫进行系统性普查及风险评估。普查结果表明:8种野生盐生植物上害虫(螨)19种,其中5种外来入侵害虫和11种世界危险性害虫普遍严重发生与危害;57种园林绿化植物上害虫(螨)33种,其中9种外来入侵害虫和17种世界危险性害虫普遍严重发生与危害;31种耐盐果蔬害虫(螨)36种,其中7种外来入侵害虫和20种世界危险性害虫普遍严重发生与危害;22种绿色固沙植物害虫(螨)15种,其中5种外来入侵害虫和5种世界危险性害虫普遍严重发生与危害。风险评估结果表明,椰心叶甲(Brontispa longissima)、木瓜秀粉蚧(Paracoccus marginatus)、扶桑绵粉蚧(Phenacoccus solenopsis)的综合风险值(R)均为2.09,在永兴岛均属于高度危险有害生物,椰子织蛾(Opisina arenosella)、波氏白背盾蚧(Diaspis boisduvalii)、新菠萝灰粉蚧(Dysmicoccu neobrevipes)、烟粉虱(Bemisia ... 相似文献
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James R. Guest Peter A. Todd Eugene Goh Balasubramaniam S. Sivalonganathan Konda P. Reddy 《水产资源保护:海洋与淡水生态系统》2008,18(5):570-579
- 1. Giant clams have been a sustainable resource for millennia, but unregulated harvesting has led to local extinctions within the Indo‐Pacific region. Giant clam mariculture can produce large numbers of juveniles for restocking wild populations where natural recruitment is low or absent.
- 2. Singapore is surrounded by more than 60 small islands, many with fringing reefs. These reefs, however, experience increased turbidity and sedimentation resulting from massive coastal development projects and regular dredging of shipping lanes.
- 3. Seven reefs off Singapore's southern islands were surveyed (9670 m2) for giant clams. Also, an experiment was conducted to determine the growth of Tridacna squamosa reared in aquaria under three light treatments: ~50% ambient photosynthetically active radiation (PAR); ~25% ambient PAR; and ~12% ambient PAR. Finally, 144 clams (T. squamosa) were transplanted to four reefs around Singapore to study survival and growth in a heavily impacted environment.
- 4. A total of 23 adult clams from three species were found during the survey, representing a mean density of 0.24 per 100 m2. Most clams were found at Raffles Lighthouse, Singapore's ‘best’ reef. No juvenile clams were encountered. In the aquarium experiment, clam growth was significantly different among the three light treatments, with growth greatest in the ~50% ambient PAR treatment. Of the 144 transplanted clams, 116 (80.6%) were recovered after 7 months. All specimens had increased in size, with growth rates among reefs ranging from 3.3 mm month?1 (SD=1.3 mm) to 4.8 mm month?1 (SD=1.6 mm).
- 5. Results suggest that, despite high levels of sedimentation and turbidity on Singapore's reefs, giant clams can survive and grow well. Restocking efforts using maricultured clams may be effective in enhancing the dwindling local populations. It is not clear, however, whether a self‐sustaining community can be established as high sedimentation may hinder larval settlement and survival.
34.
问卷调查折射出的辽宁渔业竞争力问题研究 总被引:2,自引:0,他引:2
针对目前辽宁渔业所面临的竞争环境,借助国际竞争理论设计出含有宏观因素、水产部门产业环境及基础设施、渔业生产管理体制和渔业有关人员力量四大系统的竞争力评价模型并进行了广域问卷调查。结果表明,近年来,辽宁渔业竞争力在很多领域有了一定的提高和增强。但是,在政策制度、管理体制和支撑体系等方面还折射出不少问题,制约着整个渔业竞争力的提升。基于此,提出了建立健全渔业保险制度和渔业贷款制度、提升渔业劳动者技术水平、加强养殖业者自律性、进一步制定渔用柴油油价上涨对策等一系列政策建议。 相似文献
35.
A generalized linear mixed model (GLMM) that treats year and spatial cell as fixed effects while treating vessel as a random effect is used to examine fishing power among chartered industry-based vessels and a research trawler, the FRV Miller Freeman, for bottom trawl surveys on the upper continental slope of U.S. West coast. A Bernoulli distribution is used to model the probability of a non-zero haul and the gamma distribution to model the non-zero catch rates of four groundfish species. The use of vessel as a random effect allows the data for the various vessels to be combined and a single continuous time-series of biomass indices to be developed for stock assessment purposes. The GLMMs fit the data reasonably well. Among the different models examined, the GLMM incorporating a random vessel × year effect had the smallest ΔAIC and was thus chosen as the best model. Also, estimated random effects coefficients associated with the industry-based vessels and the FRV Miller Freeman for each year suggests that these vessels can be assumed to be from a common random effects distribution. These results suggest that combining data from the chartered industry-based vessels and from the research trawler may be appropriate to develop indices of abundance for stock assessment purposes. Finally, an evaluation of variances associated with abundance indices from the different models indicate that analyzing these data as a fixed effect GLM may underestimate the level of variability due to ignoring the grouped nature of tows within vessels. As such, use of a mixed model approach with vessel as a random effect is a reasonable approach to developing abundance indices and their variances. 相似文献
36.
A rapid immunoperoxidase-based virus neutralization assay for salmonid alphavirus used for a serological survey in Northern Ireland 总被引:1,自引:0,他引:1
A modified virus neutralization (VN) assay was developed to replace an existing assay read on the presence or absence of virus-induced cytopathic effect (CPE). The modified assay used a monoclonal antibody to salmon pancreas disease virus as the first layer of an immunoperoxidase (IPX)-based immunostaining technique to detect viral growth. The IPX-based VN assay required only 3 days to perform, and the adoption of a 96-well microtitre format facilitated a high throughput of samples requiring small volumes of serum, cells and virus. When 352 sera from farmed salmon and 302 sera from farmed trout were tested by both the modified and the original CPE-based assays, overall correlations of 97.72 and 96.03% were, respectively, obtained (96.94% combined). When the modified assay was used to test 188 sera collected from wild salmonids in freshwater river systems in Northern Ireland, no positive results were recorded. 相似文献
37.
A tale of two seas: a meta‐analysis of crustacean stocks in the NE Atlantic and the Mediterranean Sea 下载免费PDF全文
Meta‐analysis of marine biological resources can elucidate general trends and patterns to inform scientists and improve management. Crustacean stocks are indispensable for European and global fisheries; however, studies of their aggregate development have been rare and confined to smaller spatial and temporal scales compared to fish stocks. Here, we study the aggregate development of 63 NE Atlantic and Mediterranean crustacean stocks of six species (Nephrops norvegicus, Pandalus borealis, Parapenaeus longirostris, Aristeus antennatus, Aristaeomorpha foliacea and Squilla mantis) in 1990–2013 using biomass index data from official stock assessments. We implemented a dynamic factor analysis (DFA) to identify common underlying trends in biomass indices and investigate the correlation with the North Atlantic Oscillation (NAO) index. The analysis revealed increasing and decreasing trends in the northern and southern NE Atlantic, respectively, and stable or slowly increasing trends in the Mediterranean, which were not related to NAO. A separate meta‐analysis of the fishing mortality (F) and biomass (B) of 39 analytically assessed crustacean stocks was also carried out to explore their development relative to MSY. NE Atlantic crustacean stocks have been exploited on average close to FMSY and remained well above BMSY in 1995–2013, while Mediterranean stocks have been exploited 2–4 times above FMSY in 2002–2012. Aggregate trends of European crustacean stocks are somewhat opposite to trends of fish stocks, suggesting possible cascading effects. This study highlights the two‐speed fisheries management performance in the northern and southern European seas, despite most stocks being managed in the context of the European Union's Common Fisheries Policy. 相似文献
38.
菜粉蝶绒茧蜂种群空间分布型及其应用 总被引:2,自引:0,他引:2
本文应用频次分布x~2检验法,Iwao法,Taylor幂法则以及其它聚集指标等方法,分析研究了菜粉蝶绒茧蜂种群(茧块)的空间分布型。结果表明:菜粉蝶绒茧蜂茧块在甘蓝上呈聚集分布,分布的基本成分是以个体群形式存在,个体群之间是随机的,茧块的聚集是由寄主等环境因素引起的。此外,利用分布型参数确定了理论抽样数及序贯抽样。 相似文献
39.
D L Barnes N F G Rethman C C De Witt G D Kotze 《African Journal of Range and Forage Science》2013,30(3):90-95
Abstract The feasibility and potential of reinforcing veld with legumes in the south‐eastern Transvaal highveld was assessed in a number of trials during the period 1974–84. Experience was gained with regard to methods of establishment, adaptation of legumes to the local environment, responses to fertilization, especially with lime and superphosphate, and the reaction of legumes to fire and grazing. In all, 17 legumes were involved, including the genera Coronilla, Desmodium, Glycine, Lespedeza, Lotus, Macroptilium, Medicago, Neoto‐nonia, Trifolium and Vigna. Only Coronilla varia (crownvetch) showed a satisfactory degree of persistence. However, crownvetch is slow to establish, is intolerant of waterlogging and has a relatively high requirement for lime and phosphate. Considering these features, and the probability of undesirable changes in grass species composition in reinforced veld, it is recommended that intensification be achieved through development of improved pastures for use in conjunction with veld, rather than by means of veld reinforcement. 相似文献
40.