Re‐evaluating the population size of South American fur seals and conservation implications

相似文献   

农业普查PDA应用前瞻与探讨

2016年农业普查要求对智能手持电子数据采集设备(PDA)进行广泛使用,建立普查数据联网直报系统。全国大型普查第三次全国经济普查首次使用手持电子数据采集设备(PDA)进行上门登记,PDA应用显现出诸多优势,但也暴露出不少问题,但PDA在今后大型普查中的全面应用已是势在必行。该文阐述了运用PDA调查的优势,分析了其调查方法的不足,提出了应用建议,以促进PDA的广泛使用。     

张家界市土壤硒分布规律和富硒作物研究

基于张家界市各乡镇位置对土壤中总硒含量进行普查(采样点不包括岩石露头、严重的工业污染和垃圾倾倒点),结合张家界市土壤背景值及采样点的经纬度,划分出张家界市富硒土壤分布图,发现其总硒含量平均值为0.38 mg/kg,富硒地区分布呈斑点状、零星状。其中,永定区和桑植县的大部分土壤中硒含量≥0.40 mg/kg,属于典型富硒区。不同土壤类型中硒含量差异显著,其中黑色石灰土高山草甸土石灰性黄壤肥熟旱耕人为土中性石质土钙质石质土水稻土。此外,发现富硒土壤上生长的植物基本达到富硒食品标准;土壤中总硒含量高的情况下植物中的硒含量相对较高。     

Counting elusive animals: Comparing field and genetic census of the entire mountain gorilla population of Bwindi Impenetrable National Park, Uganda

Accurate population size estimates are an essential part of every effective management plan for conserving endangered species. However, censusing rare and elusive wild animals is challenging and often relies on counting indirect signs, such as nests or feces. Despite widespread use, the accuracy of such estimates has rarely been evaluated. Here we compare an estimate of population size derived solely from field data with that obtained from a combination of field and genetic data for the critically endangered population of mountain gorillas (Gorilla beringei beringei) in Bwindi Impenetrable National Park, Uganda. After genotyping DNA from 384 fecal samples at 16 microsatellite loci, the population size estimate was reduced by 10.1% to 302 individuals, compared with 336 gorillas estimated using the traditional nest-count based method alone. We found that both groups and lone silverbacks were double-counted in the field and that individuals constructed multiple nests with an overall rate of 7.8%, resulting in the overestimation of the population size in the absence of genetic data. Since the error associated with the traditional field method exceeded the estimated population growth of 5% in the last 4 years, future genetic censusing will be needed to determine how the population size is changing. This study illustrates that newly improved molecular methods allow fast, efficient and relatively affordable genotyping of several hundred samples, suggesting that genetic censusing can be widely applied to provide accurate and reliable population size estimates for a wide variety of species.     

Assessment of rocky reef fish assemblages close to seaweed farming

The seaweed Kappaphycus alvarezii (Doty) Doty ex P. C. Silva, a red algal species, is the main global source of Kappa carrageenan. The introduction of such exotic species in regions outside their original locale can change the community structure of the areas into which they are introduced. The possible influence of seaweed farming on the rocky reef fish assemblage was assessed in Paraty, Brazil. The reef fish assemblage in the seaweed farming area was compared before and after the commencement of farming with two undisturbed control areas. Among the ten species ranked as the most frequently occurring in each area, eight were the same. The fish community structure close to the seaweed farming area did not change from that of the control areas, over the months of the study. Neither the fish diversity and richness indices, nor the total average abundance among areas was significantly altered. The average abundance of the different trophic groups varied over time in both the farm and control areas, revealing similar patterns. These results suggest that K. alvarezii can be cultivated up to at least 50 m from a rocky coast without altering the fish community structure of the surrounding waters.     

湖南省鱼类寄生虫及其病原区系调查研究

1989～1992年,对湖南省的鱼类寄生虫及其病原区系进行了调查研究.在84种鱼类中(分属7目15科),发现鞭毛虫3科4属6种;孢子虫1科1属5种;粘孢子虫6科8属56种;纤毛虫7科8属24种;单殖吸虫5科13属86种;复殖吸虫14科20属32种;绦虫5科7属9种;线虫10科15属18种;棘头虫5科8属9种;蛭类1科1属1种;瓣鳃类1科1属1种;甲壳类3科8属21种.在268种寄生虫中,有18种待进一步鉴定的新种,并发现10个虫种的新寄主;有184种为湖南省的新纪录.全部寄生虫都绘有插图和种的简要记述.对鱼类危害比较严重,能引起鱼病的寄生虫,在相应部分作了有关的说明.     

THE GROUND CENSUSES ON RED-CROWNED CRANE IN KHANKA LAKES DISTRICT OF CHINA

Coordination of the aenal servey,the author carried ground census on the popula-tion size of Red-erowned crane(Grus japonensis)in Khanka Lakes District from 1984 to 1986.Ac-cording to the census in spring of 1984,the total number of Red-crowncd crane is 72 individualsand 20 nests.So that this pound census has recorded 59 indivlduals more than the aerial survey of13 individuals,and the percentage of nesting individuals in his flock is 55.6％,which is obviouslyhigher than 36.9％ of the average ration in China.After this,in fall of 1984 and in spring of 1985 and1986,we repeated the same censuses three times in the same districts,the results indicated that theflock of the crane in Khanka Lakes District is stable basiuclly,but some individuals interchangewith opposite flock of USSR because of gegraphical adjoin So,We blieve this flock in China andthat lock in USSR belong to the same population and suggest two countries should act in concertto studing on this population in future. Meanwhile,the aerial servey     

Estimating effective population size of large marine populations,is it feasible?

Sustainable exploitation of marine populations is a challenging task relying on information about their current and past abundance. Fisheries‐related data can be scarce and unreliable making them unsuitable for quantitative modelling. One fishery independent method that has attracted attention in this context consists in estimating the effective population size (N_e), a concept founded in population genetics. We reviewed recent empirical studies on N_e and carried out a simulation study to evaluate the feasibility of estimating N_e in large fish populations with the currently available methods. The detailed review of 26 studies found that published empirical N_e values were very similar despite differences in species and total population sizes (N). Genetic simulations for an age‐structured fish population were carried out for a range of population and samples sizes, and N_e was estimated using the Linkage Disequilibrium method. The results showed that already for medium‐sized populations (1 million individuals) and common sample sizes (50 individuals), negative estimates were likely to occur which for real applications is commonly interpreted as indicating very large (infinite) N_e. Moreover, on average, N_e estimates were negatively biased. The simulations further indicated that around 1% of the total number of individuals might have to be sampled to ensure sufficiently precise estimates of N_e. For large marine populations, this implies rather large samples (several thousands to millions of individuals). If however such large samples were to be collected, many more population parameters than only N_e could be estimated.     

Marine fish diversity on the Scotian Shelf,Canada

• 1. Marine life in offshore regions has not been fully censused, yet related conservation policy relies on our ability to identify areas of high biodiversity.
• 2. We assessed the census of marine finfish on the Scotian Shelf, Northwest Atlantic using data collected during annual research vessel surveys between 1970 and 2000. The species accumulation curve did not reach an asymptote reflecting that new species continued to be discovered throughout the survey period. Only 0.12% of the area of the Scotian Shelf has been sampled since 1970.
• 3. Since 1974, when over 50% of the species had been discovered, the community composition has been relatively constant. However, the dominance structure has changed dramatically as reflected in the geographic contraction of the formerly abundant, large‐bodied piscivores concomitant with the geographic expansion of their prey species.
• 4. The region is under‐sampled, and species' distribution and abundance are changing. A precise estimate of diversity is elusive. As an alternative, we searched for physical correlates of finfish diversity to identify its possible surrogates. Surrogates have potential both as a method for understanding process and as a tool for conservation management. We examined the effect of area and depth range on species richness. High species richness was associated with larger areas and greater depth range at large spatial scales.
• 5. Highly diverse areas include the Bay of Fundy, the Eastern Gully, the slopes, Western Bank and the northeastern shelf. Until now, the northeastern shelf has been under‐appreciated as a highly diverse area. Such information will be important for environmental impact assessments as well as selection of ‘sensitive’ or protected areas.

Copyright © 2003 John Wiley & Sons, Ltd.     

Coastal breeding aggregations of threatened stingrays and guitarfish in the Levant

1. Stingrays and guitarfish are globally threatened by overexploitation, particularly so in the Mediterranean Sea. Nevertheless, very little information is known about their ecology, behaviour, and taxonomy in the Mediterranean, and especially in the Levant, where water temperature, salinity, and the impact of invasive species are relatively high.
2. Although it has been suggested that some species may aggregate in the Levant, this has not been formally documented and the scale of this phenomenon, the taxonomic composition, and the temporal dynamics are unknown.
3. Visual surveys were conducted, which allowed the documentation of stingrays and guitarfish behaviour, and which was not available from data based on fishery catches. The census took place within a marine protected area over a period of 3 years.
4. Altogether, we documented 675 batoid observations. One of the observed species is Endangered (Glaucostegus cemiculus) and one is Vulnerable (Dasyatis pastinaca), whereas the others are classed as Least Concern (Torpedo torpedo and Torpedo marmorata), Data Deficient (Taeniurops grabatus), non‐assessed within the Mediterranean (Dasyatis chrysonota), and Not Evaluated (Himantura uarnak). Results show clear seasonal patterns, with dense aggregations recorded during spring and early summer, when densities reached 85 observations per kilometre. In addition, there were clear indications of breeding behaviour in D. pastinaca and D. chrysonota, including the first recorded documentation of D. pastinaca courtship in the Mediterranean.
5. Large seasonal stingrays and guitarfish aggregations in shallow waters have not, to our knowledge, been documented in the Mediterranean Sea previously. This highlights the importance of conserving shallow habitats as potential breeding grounds. As these sites are easily reached while both snorkelling and diving, the aggregation of these charismatic species can serve as potential ecotourism sites. Finally, this study shows the benefits of using simple visual census, as opposed to catch‐based methods, to record both the diversity and the behaviour of batoids.