Diet of landlocked sockeye salmon (Oncorhynchus nerka) and trout in the Waitaki lakes,New Zealand     

E. Graynoth  L. C. Bennett  J. C. Pollard 《新西兰海洋与淡水研究杂志》2013,47(4):537-549

Landlocked sockeye salmon (Oncorhynchus nerka), ranging in fork length (FL) from 105 to 313 mm, were captured in fine‐mesh gill nets set in the limnetic zone of the Waitaki hydro lakes (44° 30′ S, 170° 10’ E) in the South Island, New Zealand. A total of 443 stomachs was examined and the frequency of occurrence, volume and weight of prey items calculated. In the Ahuriri Arm of Lake Benmore the principal food (54% by weight) was zooplankton (Boeckella dilatata) whereas in the Haldon Arm of Lake Benmore it was larval and juvenile common bullies (Gobiomorphus cotidi‐anus) (73% by volume). In Lake Waitaki in winter, salmon had eaten insects (43% by volume) with smaller amounts of snails (Potamopyrgus antipo‐darum, 23%) and bullies (24%). In Lake Ohau adult insects may be an important food. There were also variations in diet with season and fish size. The stomachs of 147 brown trout (Salmo trutta) and 181 rainbow trout (S. gairdnerii) caught in the same gill nets were also examined. In contrast to sockeye salmon stomachs they contained negligible amounts of zooplankton (< 1% by weight) and large amounts of aquatic insects (50–58% by weight in the Ahuriri Arm of Lake Benmore). Comparisons with juvenile sockeye salmon and kokanee in North American lakes are made. The impact of introductions of sockeye salmon into other New Zealand lakes is discussed.  相似文献   

Food and energy in the diet of brown and rainbow trout from Lake Benmore,New Zealand     

N. H. McCarter 《新西兰海洋与淡水研究杂志》2013,47(4):551-559

The diet of brown trout (Salmo trutta) and rainbow trout (S. gairdnerii) was studied in specimens from Lake Benmore, a deep, oligo‐trophic lake in South Island, New Zealand. Between November and July, both species fed mainly on small molluscs (Potamopyrgus antipodarum, Physa sp., and Gyraulus corinna) gleaned from the littoral weed beds. Energy values for the three species of mollusc were determined: P. antipodarum, 6000 J g^‐1; G. corinna, 5500 J g^‐1; Physa sp., 9800 J g^‐1. Potamopyrgus antipodarum yielded little energy to the fish, unless its shell broke during passage through the gut. Physa sp. was the most profitable mollusc, irrespective of shell breakage and Potamopyrgus antipodanim the least profitable. The mean energy value per snail for G. corinna and Physa sp. eaten by rainbow trout was 25–30% less than for snails eaten by brown trout, possibly because rainbow trout ingested empty shells from the sediment surface. Rainbow trout extracted about 20% more energy than brown trout from unbroken shells. In July, 84% of the brown trout switched to predation of common bullies, Gobio‐morphus cotidianus, probably as a result of bully reproductive behaviour. Rainbow trout did not show the same change, apparently because they were feeding in deeper water where few bullies were available. The low‐energy diet and its possible connection with growth rate are discussed.  相似文献   

Tackling illegal, unregulated, and unreported trade towards Humphead wrasse (Cheilinus undulatus) recovery in Sabah, Malaysia     

Tun-Min Poh  Lucia M. Fanning 《Marine Policy》2012,36(3):696-702

The live reef food fish trade (LRFFT) has caused severe depletion of the Humphead wrasse (Cheilinus undulatus) populations globally, a species considered endangered by the International Union for the Conservation of Nature. In 2010, signatories to the Convention on International Trade in Endangered Species of Wild Fauna and Flora recognized that illegal, unregulated, and unreported (IUU) activities in the LRFFT were undermining the efforts to protect this species. Management recommendations have yet to be effectively implemented at national and local levels where the fish is harvested. This paper analyzes the threats to, and socio-economic impacts of, Humphead wrasse recovery in Sabah, Malaysia, and offers both short- and longer-term recommendations for the local recovery of the species. Key issues addressed centre around understanding the threats to recovery, specifically the role of IUU and the context-specific considerations, including the socio-economic aspects of the IUU trade in Sabah. The analysis confirms that deliberate management planning and action at multiple levels are required to prevent local-scale extinction. Lessons for other species and countries involved in the LRFFT suggest that to be effective, broad management frameworks must be tailored to local situations and must focus on gaining support and participation of fish harvesters if the recovery and long-term sustainability of both the Humphead wrasse and the LRFFT are to be achieved.  相似文献   

Food web structure within kelp holdfasts (Laminaria): a stable isotope study     

Gauthier Schaal  Pascal Riera  Cédric Leroux 《Marine Ecology》2012,33(3):370-376

Kelp holdfasts are highly reticulated structures which host a large diversity of small fauna. These microhabitats have been reported to play a crucial role in the biodiversity associated to kelp forest ecosystems. This study aimed at identifying trophic links and the main food sources sustaining food webs within communities associated with kelp holdfasts, through a stable isotope (δ¹³C and δ¹⁵N) approach. Sampling of the main invertebrates inhabiting Laminaria digitata holdfasts, and of their potential food sources, took place in February and May 2007. Stable isotope results reveal that most of the primary consumers, including filter-feeders and deposit-feeders, rely on the particulate organic matter sedimented within kelp holdfasts. Only three grazers departed from this general pattern. The correspondence between the stable isotope ratios of predators and sediment consumers indicated that this source is at the base of the main pathway through which energy and matter transit in the food web. δ¹⁵N ranges found for consumers revealed that the food web associated with kelp holdfasts is composed of 3.5 levels. In spite of the low diversity of food sources at the base of the food web, these microhabitats can therefore be considered micro-scale ecosystems, from a functional perspective.  相似文献   

1999-2007 年中国粮食安全的关键影响因素   总被引：24，自引：2，他引：22  

宋小青  欧阳竹 《地理学报》2012,67(6):793-803

选取耕地保护“新政”时期的1999-2007 年为研究时段,以耕地面积与粮食产量变化的分歧原因—耕地生产力变化为切入点,通过比较分析、空间与计量分析探寻粮食安全的关键影响因素。结果表明:农民种粮积极性变化决定着耕地集约利用是影响粮食安全的关键;2003-2007 年农民种粮积极性的持续提高主要来自市场粮价的上涨;粮食直补仅在开始实施的年份激发了农民对种粮收益的预期。此外,本文从提高农民种粮积极性、优化粮食生产投入及改进耕地保护模式3方面,提出了耕地保护发展的政策建议。  相似文献   

温度和盐度对龙虎斑存活与摄食的影响     

梁华芳  黄东科  吴耀华  王成桂  钟卫军 《广东海洋大学学报》2013,(4)

龙虎斑是由棕点石斑鱼(Epinephelusfuscoguttatus♀)和鞍带石斑鱼(Epinepheluslanceolatus♂)的杂交种。研究水温及盐度在骤变和渐变情况下龙虎斑的存活和摄食情况,结果表明:龙虎斑在温度为14³5℃的海水中均能存活和摄食,最适宜温度环境为2535℃的海水中均能存活和摄食,最适宜温度环境为25³5℃;温度从30℃骤变至20、25、35℃时,龙虎斑100%存活;从30℃骤变至10℃和15℃时,龙虎斑全部死亡;水温从30℃开始渐变,下降幅度为1℃/d,当下降至24℃时摄食减少,13℃时停止摄食,下降至11℃时出现死亡。龙虎斑在盐度为135℃;温度从30℃骤变至20、25、35℃时,龙虎斑100%存活;从30℃骤变至10℃和15℃时,龙虎斑全部死亡;水温从30℃开始渐变,下降幅度为1℃/d,当下降至24℃时摄食减少,13℃时停止摄食,下降至11℃时出现死亡。龙虎斑在盐度为1⁵5的海水中均能存活和摄食,摄食适宜海水盐度为455的海水中均能存活和摄食,摄食适宜海水盐度为4⁴5;盐度从30骤变至5、10、15、20、25、35、40、45、50、55等盐度时,龙虎斑100%存活,骤变至0时,4 h内存活率100%,16 h存活率55.5%;盐度从30渐变,每天降低2,降至6后,每天降低1,盐度降到1时,龙虎斑的活动和摄食明显减少,渐变至0时,36 h出现死亡,48 h内全部死亡。  相似文献   

我国食物安全研究进展及展望   总被引：5，自引：1，他引：4  

孟繁盈  许月卿 《地理科学进展》2008,27(2):89-95

保障我国食物安全是我国一切建设发展的前提和基础。在我国农业基础资源日益紧缺以及加入WTO 的 国情下, 食物安全面临着新的机遇与挑战。本文回顾了食物安全概念的演变过程, 综述了我国在自然基础资源与食 物安全、食物安全现状及其评价、国际贸易和经济全球化对食物安全的影响以及食物安全预警和管理等方面的研 究进展, 并对未来我国食物安全研究进行了展望。研究表明: 今后我国食物安全研究应在以下方面需要加强: 在研 究内容上, 不仅重视食物数量保障, 更应注重食物质量安全、食物资源可持续利用和综合食物安全风险评价与预警 等方面; 在研究视角上, 不仅重视宏观食物安全研究, 更应重视微观食物安全; 在研究方法和手段上, 应当充分运用 现代科学技术, 如网络技术、空间模拟技术以及3S 技术等, 进一步加强综合食物安全的定量和动态研究。  相似文献   

土地利用变化对土地生产力的影响研究进展   总被引：6，自引：0，他引：6  

潘佩佩  杨桂山  苏伟忠 《地理科学进展》2012,31(5):539-550

土地利用变化对土地生产力的影响是土地利用/覆被变化(LUCC)效应研究的重要内容之一。本文基于对土地利用变化和土地生产力概念的辨析, 着重从土地利用变化对土地生产潜力、粮食生产能力和土壤质量3 个方面的影响, 总结梳理了当前的主要研究内容和方法, 探讨了研究的影响尺度特征。最后指出今后的研究应加强土地利用结构、方式和强度变化对小尺度范围内耕地生产力的影响, 强化不同尺度的综合以及空间分析和动态评估方法的应用。  相似文献   

Problematising justice definitions in public food security debates: Towards global and participative food justices     

《Geoforum》2017

In the current environment of austerity, social justice concerns are increasingly permeating the food security agenda. However, there is a need to clarify what it means to create socially just food systems conceptually and practically. To address this gap, this paper proposes an analytical framework to embed a more complex conceptualisation of justice in food security debates that also serves as a bridging device across competing narratives. This framework is mobilised to analyse the framing process of the UK media, which plays a key role in developing narratives that provide audiences with schemas for interpreting events. Results show the emergence of eleven frames which highlight different solutions to deliver food security. The application of the justice analytical framework evidences the contingent relationship between food security and justice claims and discusses how these food security frames address differently what counts as a matter of justice (including economic, socio-cultural and political dimensions) and who counts as a subject of justice, tackling issues around delimitation of scales and sites of justice. The analysis reveals polarised positions between whether the sites subject to justice should be individuals or structures and uncovers how political and global elements of justice are largely by-passed in food security debates. These conceptualisations of justice and associated policy recommendations neglect the potential for people to participate fully in the conditions and decisions that give rise to particular distributions of goods and bads in the first place; limiting the construction of shared responsibilities to deliver global and participative food justices.  相似文献   

基于空间模型的全球粮食安全评价   总被引：7，自引：1，他引：6  

吴文斌  唐华俊  杨鹏  周清波  陈仲新 《地理学报》2010,65(8)

在综合考虑自然、社会和经济等因子对粮食安全影响的基础上,选择了人均粮食占有量和人均GDP两个指标空间显性评价全球粮食安全状况。为此,本研究构建了3个模型,即空间EPIC模型、作物选择模型和IFPSIM模型,分别模拟作物单产、作物播种面积和作物价格。利用构建的评价框架和模型,以网格大小为6分弧度的地理单元为评价对象,选择水稻、玉米、小麦和大豆等4类全球主要作物类型,以2000年为初始年份,对未来2020年的全球粮食安全状况进行了评价。结果表明,到2020年,多数南亚国家和非洲国家,由于其人均粮食占有量和人均GDP两个指标值都显著降低,粮食供应不足和贫困一起将可能导致该区域存在粮食危机和饥饿风险。对于其他区域,日益增长的粮食需求可以通过本区域的粮食生产自给予以满足,或通过外部购买或粮食进口得到满足,总体上不存在粮食安全问题。为保障未来粮食安全,一方面要保护耕地数量和质量、防止土壤退化、增加资本投入、进行技术创新和升级,提高粮食综合生产能力,保障粮食的有效供给;另一方面加大农业补贴,切实提高农民收入,保障农民利益,增强农业购买力。同时,大力改善粮食流通和农产品贸易体制,通过外部市场来调节粮食供给;积极应对气候变化,提高农业生产对气候变化的适应能力,保证粮食生产的稳定。  相似文献