Threats to at-risk salmonids of the Canadian Rocky Mountain region

Trout and charr, members of the salmonid family, have high conservation value but are also susceptible to anthropogenic threats in part due to the specificity of their habitat requirements. Understanding historical and future threats facing these species is necessary to promote their recovery. Of freshwater trout and charr in the Canadian Rocky Mountain region, westslope cutthroat trout (Oncorhynchus clarkii lewisi), bull trout (Salvelinus confluentus; a charr species) and Athabasca rainbow trout (Oncorhynchus mykiss) are of conservation concern. And indeed, range contractions and declining populations are evident throughout much of their ranges. Range contraction was most evident in the southern Alberta designatable unit (DU) of westslope cutthroat trout. Diminished populations were also evident in the downstream watersheds of the Alberta bull trout range, and throughout the Athabasca rainbow trout range. We assessed historical and future threats to evaluate the relative importance of individual threats to each DU and compare their impact among species. Individual threats fall into the broad categories of angling, non-native species and genes, habitat loss and alteration, and climate change. Severity of each threat varies by DU and reflects the interaction between species’ biology and the location of the DU. Severity of threats facing each DU has changed over time, reflecting extirpation of native populations, changes in management and industry best practices, expansion of non-native species and progressing climate change. The overall threat impact for each DU indicates a high probability of substantial and continuing declines and calls for immediate action.     

《四川农业科技》期刊读者群现状浅析

对《四川农业科技》2 0 0 0年～ 2 0 0 2年读者群现状分析结果表明 ,影响读者群的因素有期刊自身原因和地域性原因等 ,扩大和稳定读者群关键在合理定位、栏目设计有特色、多渠道宣传等。     

Relating Kirtland's warbler population to changing landscape composition and structure

The population of male Kirtland's warbler (Dendroica kirtlandii) in the breeding season has averaged 206 from 1971 to 1987. The Kirtland's warbler occupies dense jack pine (Pinus banksiana) barrens from 5 to 23 years old and from 1.4 to 5.0 m high, formerly of wildfire origin. In 1984, 73% of the males censused were found in habitat naturally regenerated from wildfire or prescribed burning. The rest were in plantations (11%) or in harvested, unburned jack pine stands stocked by natural regeneration (16%). Twenty-two percent (630 of 2,886) of the Kirtland's warbler males counted in the annual censuses from 1971 through 1984 were found in 26 stands that were unburned and naturally regenerated following harvest. From 1982 to 1987, suitable regenerating areas were barely sufficient to replace currently occupied maturing stands, so population growth was impeded. Ecosystems of suitable size and regeneration characteristics (wildfire and plantation) doubled in area by 1989. In response, the population of Kirtland's warblers increased from 167 to 398 males between 1987 and 1992, but they withdrew almost entirely from the unburned, unplanted barrens by 1989 when the area of more suitable regeneration types increased. Minimum (368 males) and maximum (542 males) population estimates for 1996 were calculated based on 1984 average density (1.9 males per 40 ha) and peak population in burns (2.8 males per 40 ha).     

Importance of the River Teviot to Atlantic salmon, Salmo salar, rod catches in the River Tweed, Scotland

Abstract  The body mass distributions and variations in abundance of the spring and autumn catches of Atlantic salmon, Salmo salar L., were compared between fisheries above and below the confluence of the rivers Tweed and Teviot, Scotland. Significant differences between the distributions were found over three periods, one in spring and two in autumn, when salmon catches were high. Correlations were found between abundance trends for periods when distributions were similar or dissimilar. Abundance of salmon returning to the River Teviot was proportional to the main river. However, its population structure differed when abundances were high, suggesting different survival strategies. It appears that changes in the numbers returning to the river were resultant of changes in the marine rather than freshwater environment.     

小家鼠胴体重指标划分种群年龄的研究

对2005年1~12月在贵州省息烽县鼠情监测点捕获的258只小家鼠标本,以胴体重为指标,参照繁殖状况,用胴体重频次分配方法将小家鼠划分为4个年龄组,其划分标准为,幼年组(Ⅰ):胴体重≤6.49 g;亚成年组(Ⅱ):6.50~9.99 g;成年组(Ⅲ):10.00~13.49 g;老年组(Ⅳ):≥13.50 g。不同年龄组繁殖力差异显著,胴体重随种群年龄的增长而不断增加,各年龄组胴体重与体重、体长、尾长均呈正相关性,且与体重相关性达极显著。研究认为,采用胴体重划分小家鼠年龄是可行的,方法简便,易于操作。     

RAPD技术对地方鸡种群体遗传结构的分析

利用ＲＡＰＤ技术对４个地方鸡种和１个引进鸡种的群体遗传结构进行分析，通过筛选的５个随机引物ＯＰＨ－０２、ＯＰＨ－０５、ＯＰＨ－１３、ＯＰＨ－１６、ＯＰＧ－０７对５个鸡种的池ＤＮＡ进行多态性研究，结果表明：５个引物共产生条带６１个，扩增产物片段的长度一般从１５０ｂｐ－４ｋｂ。     

丰宁“中国沙棘”资源及种群表型结构的研究

本文用样地调查和统计分析的方法研究了丰宁“中国沙棘”主要经济性状的变异,探讨了性状相关和各主要性状的组配情况,分析了主要经济性状变异的频数分布及种群特征和优种分布范围。认为丰宁的“中国沙棘”是以主干型、桔黄扁圆果、褐色种子植株为主体的多态型种群系统,是品质较好的种质资源,是沙棘树种改良的珍贵材料。     

人工培植羊体羊黄的研究

本试验以外科手术方法在北京农户所养绵羊胆囊内放人异物网核和注入致黄菌(SEBF8,50亿/ml),诱发羊黄,均获成功.其间,对术前术后血清胆红质、胆固醇、谷草转氨酶和GROS反应等项进行测定.结果表明:上述各项指标在术后8天内与术前比,均有降低,差异显著,但以后逐渐恢复正常.而体重、临床表现,以及饲养指标本出现异常.预示着,人工培植羊体羊黄可行.同时,本试验还为进一步提高人工培植羊黄的产黄量,提供了参考数据.     

系统耦合与荒漠─绿洲草地农业系统─—以祁连山一临泽剖面为例

生态系统内部自由能的积累，使系统失去平衡并趋于同其它生态系统结合，自由能驱使两个或两个以上的生态系统或亚生态系统，通过会聚，超循环和耦合而联合，从而形成具有特殊结构一功能的更高一级的新系统。系统耦合可以多途径解放生态系统中的自由能而增加农业生态系统的生产力，亦即从催化潜势，位差潜势，多稳定潜势及管理潜势中取得能输出。上述过程可作用于农业系统中的四个子系统，这四个子系统各有自己的产品：前植物生产，植物生产，动物生产，外生物生产，从而大幅度提高其生产力。在荒漠─绿洲草地农业生态系统中，本文分别计量了各个子系统的能流单位及其流程，证明它的子系统也可以成功的发生系统耦合，其中绿洲子系统应居关键地位。     

大豆叶面积变化对田间微气象条件及产量的影响

作者通过1977～1981年和1987～1989年,分别在绥化、哈尔滨和合江地区的田间试验和生产调查,发现大豆叶面积指数的大小可造成不同的田间微气象环境条件,叶面积指数6左右时,植株似倒非倒,株间采光量和CO_2分布较为合理,光合效率高,大豆单株生育良好,群体产量高;在生产上可依据当地土地条件、施肥水平、不同品种和不同种植方式用叶面积动态变化方程式计算出适宜的密度,以使大豆群体最大叶面积指数保持在6左右,创造较理想的田间微气象效应。