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排序方式: 共有3277条查询结果,搜索用时 15 毫秒
41.
Claudia A. Bustos Mauricio F. Landaeta Enrique Bay-Schmith Rodrigo Lewis Ximena Moraga 《Aquaculture (Amsterdam, Netherlands)》2007,270(1-4):535-540
Effects of exogenous (water temperature) and endogenous (lipid droplet adherence) factors were experimentally tested on early survival of southern hake Merluccius australis reared under controlled conditions. Experiments to determine the effect of temperature (10, 12 and 14 °C) on larval growth rates and yolk-sac absorption rates of unfed southern hake were carried out under laboratory conditions. There was no significant differences in growth rates at the temperature range tested (ANCOVA, F = 0.164, p > 0.25), but yolk-sac absorption rates and mortality increased with temperature (ANCOVA, F = 53.84, p < 0.001). A high percentage (between 31 and 81%) of hake eggs showed a lipid droplet not adhered (i.e., freely moving in the yolk, and not located in the posteriormost portion of the yolk-sac). In a second experiment, fed southern hake larvae with the lipid droplet not adhered during embryonic development did not survive after yolk-sac absorption. This study provides the first data on the influence of the lipid droplet absorption on larval survival of cultured hake, and can be used as an early indication of the quality of the batch. 相似文献
42.
关键种及其与群落中其他物种的联系,对维持整个生态系统的稳定性发挥了重要作用。基于2016-2018年山东半岛南部海域渔业资源调查与渔业种类食性文献数据,构建了山东半岛南部海域食物网拓扑结构并计算了拓扑重要性指数,筛选了群落关键种并分析了其年际变化。2016-2018年山东半岛南部海域食物网包含物种20~22个,摄食关系数量59~65个,年际差异不明显;食物网拓扑结构密度范围为0.3048~0.3684,种间关联度为0.1451~0.1634;群落关键种均为鳀(Engraulis japonicus)和黄鮟鱇(Lophius litulon)。鳀作为关键被捕食者,黄鮟鱇作为关键捕食者,两者对群落结构的能量流动和信息传递起关键作用;鳀和黄鮟鱇在2016-2018年均为优势种,但鳀优势度逐年下降,细纹狮子鱼(Liparis tanakae)从2017年开始也成为优势种。 相似文献
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探讨了新疆阿克苏地区膜下滴灌棉田施肥及病虫害防治技术,分别从施肥技术和病虫害防治技术两方面提出技术指导。 相似文献
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为给改进实验室馒头制作和评价方法提供参考依据,以3种弱筋面粉(市售美玫牌面粉;磨自弱筋小麦品种宁麦9号和生选6号的面粉)为基础粉,采用响应面法中心组合试验设计,研究了酵母、糖、起酥油和泡打粉含量对南方馒头加工品质的影响,并建立了南方馒头感官得分与因素变量的二次回归模型方程,该模型回归显著。响应面分析结果表明,南方馒头加工中的最佳辅料配比条件为:酵母含量1.0%、糖含量15.0%、起酥油含量1.8%、泡打粉含量1.0%。在此配比条件下,3种弱筋粉制作南方馒头的感官得分预测值分别为86.5、88.3和84.5分,验证值分别为86.1、87.8和83.7分,与预测值的相对误差分别只有0.46%、0.57%和0.95%。 相似文献
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From small-scale habitat loopholes to decadal cycles: a habitat-based hypothesis explaining fluctuation in pelagic fish populations off Peru 总被引:22,自引:0,他引:22
Arnaud Bertrand Marceliano Segura Mariano Gutiérrez & Luis Vásquez 《Fish and Fisheries》2004,5(4):296-316
The Peru‐Humboldt Current system (HCS) supports the world's largest pelagic fisheries. Among the world's eastern boundary current systems, it is the most exposed to high climatic stress and is directly affected by El Niño and La Niña events. In this volatile ecosystem, fish have been led to develop adaptive strategies in space and time. In this paper, we attempt to understand the mechanisms underlying such strategies, focusing on the El Niño 1997–98 in Peru from which an extensive set of hydrographic, capture and acoustic survey data are available. An integrated analysis of the data is crucial, as each has substantial shortcomings individually; for example, both catch data and acoustic surveys may easily lead to wrong conclusions. Existing hypotheses on anchovy and sardine alternations lead us to a ‘habitat‐based’ synthetic hypothesis. Using our data, an integrated approach evaluated how fish responded to habitat variation, and determined the consequences in terms of fish‐population variability. Various factors occurring at a range of different spatio‐temporal scales were considered: interdecadal regime (warm ‘El Viejo’/cool ‘La Vieja’ decadal scale); strength and the duration of the El Niño Southern Oscillation event (interannual scale); population condition before the event (interannual scale); fishing pressure and other predation (annual scale); changes in reproductive behaviour (intra‐annual scale); presence of local upwelling (local scale). During El Niño 1997–98, anchovy was able to exploit a small‐scale temporal and spatial ‘loophole’ inside the general unfavourable conditions. Moreover, sardine did not do better than anchovy during this El Niño and was not able to take advantage of the ‘loophole’ opened by this short‐term event. Our results question the traditional view that El Niño is bad for anchovy and good for sardine. 相似文献
50.
基于新疆102个气象台站1961−2019年逐日平均气温、最低气温资料,采用统计学方法以及ArcGIS的空间插值技术,在对影响新疆紫花苜蓿种植的主要气候因子 ≥ 5 ℃积温、冬季最低气温时空变化特征分析的基础上,以80%保证率 ≥ 5 ℃积温和90%保证率冬季最低气温作为指标因子,研究了气候变暖背景下,新疆不同秋眠级紫... 相似文献