长江口及邻近水域渔业环境质量的现状及变化趋势研究

本文根据2000～2002年6个航次的调查资料,对长江口及邻近水域的渔业环境质量进行全面研究及变动趋势分析。研究结果表明,长江口及邻近水域营养盐含量十分丰富,约90％无机氮是以硝酸盐形态存在。该水域主要受营养盐、重金属及有机物的污染。其中杭州湾水域受污染程度最为严重。长江口及邻近水域浮游植物初级生产主要受磷营养盐的限制。总的来说,长江口及邻近水域渔业环境质量正呈逐步下降趋势。     

2003年度冬季东海暖流状态分析

由黑潮派生的各种暖流在冬季对东海而言是重要的热能来源,它们的态势会极大地影响东海的温度分布,从而影响到生态系统的变化和发展。通过对2003年度冬东海暖流主干温度、暖舌前锋位置进行空间分析,并与历史状况比较显示今冬的黑潮、台湾暖流和对马暖流都接近历史最强水平,而黄海暖流也比多年平均略强一些。同时期沿岸水体的表面温度与历史的比较结果显示出与多年平均差不多的状况,且在整个冬季表现出明显地随沿岸气候变化的波动状态。所以,2003年度冬暖流的强势对暖流附近海域有一定的影响但并未波及沿岸海域。而对黑潮与其他暖流、沿岸水体以及中西太平洋热带表面水温的相关分析表明,黑潮对对马暖流、台湾暖流有很强的影响作用,但对黄海暖流、沿岸水体的影响不明显,此外,黑潮的水温变化则与中西太平洋热带海域水温的变化有关。     

A cross-sectional survey of Australian chicken farms to identify risk factors associated with seropositivity to Newcastle-disease virus

Several outbreaks of virulent Newcastle-disease occurred in Australia in 1998–2000. We conducted a cross-sectional survey of 753 Australian chicken farms to identify risk factors associated with the seroprevalence of chicken flocks with Newcastle-disease virus (NDV). We had a 99.7% response rate to the survey and the overall prevalence of NDV seropositive farms was 39.8%. Associations were analysed for the layer, chicken-meat and breeder production sectors in sector-specific logistic-regression models using 187, 198 and 146 farms, respectively. In the layer sector, increased risk of seroprevalence was associated with increasing age of the chickens, and decreased risk when the nearest-neighbour poultry farm was >10 km distant (odds ratio (OR) = 0.30). In the chicken-meat sector, increased risk of seroprevalence was associated with location in the Sydney basin (OR = 13.67), eastern Victoria (OR = 26.10) or western Victoria (OR = 5.43), and decreased risk when the nearest-neighbour poultry farm was greater than 0.5 km distant (OR = 0.34). In the breeder sector, increased risk of seroprevalence was associated with increasing age of the chickens, the presence of wild birds on the farm (OR = 5.28) and location in eastern Victoria (OR = 16.19). A conditional logistic-regression for 112 pairs of farms matched for age, survey region and production sector identified a distance of >1.0 km to the nearest-neighbour poultry farm (OR = 0.24) and ownership by owner 2 (OR = 0.02), owner 5 (OR = 0.11) or owner 9 (OR = 0.25) as significant in reducing the risk of NDV seroprevalence. Our survey found that high levels of biosecurity and hygiene practices had been adopted by most farms.     

Severe Streptococcus infection in spotted hyenas in the Ngorongoro Crater, Tanzania

In a population of spotted hyenas (Crocuta crocuta) monitored between 1996 and 2005 in the Ngorongoro Crater, Tanzania, 16 individuals from five of eight social groups displayed clinical signs of an infection, including severe unilateral swelling of the head followed by abscess formation at the mandibular angle, respiratory distress, mild ataxia, and lethargy. Two (12.5%) of these 16 individuals died within days of developing signs. Clinical signs in hyenas were first noted in 2001, and most cases occurred between September 2002 and February 2003, suggesting an outbreak of infection during this period. Histopathological examination of internal organs from one hyena that died with signs revealed morphological changes consistent with severe bacterial infection. Phenotypic examination and phylogenetic analysis of the 16S rRNA gene of the causative agent of infection revealed a Lancefield group C Streptococcus with a high level of homology to S. equi subsp. ruminatorum, a subspecies of S. equi recently described in domestic sheep (Ovis aries) and goats (Capra hircus) with mastitis in Spain. Strains similar to this bacterium were also isolated from two hyenas without obvious clinical signs, suggesting that hyenas may be 'carriers' of this bacterium, and from a sympatric Burchell's zebra (Equus burchelli), a herbivore species often consumed by hyenas. To our knowledge this is the first report of a Streptococcus infection in these two wildlife species. The high genetic similarity between the hyena and zebra isolates indicates that inter-specific transmission may occur, possibly when hyenas consume infected zebra carcasses.