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题名: 河流系统鲸豚类种群数量调查方法探索及其应用研究
作者: 赵修江
答辩日期: 2009-06-04
导师: 王丁
授予单位: 中国科学院水生生物研究所
授予地点: 水生生物研究所
学位: 博士
关键词: 江豚 ; 河流生态系统 ; 截线抽样法 ; 种群数量 ; 种群分布 ; 种群变动趋势 ; 栖息地选择
其他题名: Investigation of survey methodology on the abundance of cetaceans in riverine systems and its applications
摘要: 截线抽样法(Line transect sampling method)广泛应用于海洋鲸豚类种群生态学考察中,然而在淡水豚类考察中,尤其是带状的河流生态系统中鲜有应用。带状河流生态系统的特殊环境条件与截线抽样法的一些重要假设相违背,从而限制了该方法的应用范围。这些限制存在于考察的设计、实施与分析的全过程。 本研究以长江江豚(Neophocaena phocaenoide asiaeorientalis)为研究对象,依据经典截线抽样法理论,对所受限制一一提出解决对策,从而提出了适用于带状河流生态系统中的鲸豚类种群数量调查方法。本文通过三个案例研究对该方法在不同环境类型中与不同观测平台下的应用情况进行了验证,取得了可靠的结果。另外,本研究利用这些研究结果,评估了长江江豚的种群现状与IUCN濒危等级。同时,为更科学地进行截线抽样法考察设计,本文分析了长江江豚在长江干流中横向、纵向和左右岸选择性三个方面的分布特征。主要结果和结论如下: 我们以经典截线抽样法理论为基础,通过分析河流生态系统中的特点,分别从考察设计、考察方法和分析方法三个层面详细论述了适用于河流生态系统中的方法步骤。 我们利用两艘大型考察船,使用改进的截线抽样法,考察了长江干流中长江江豚的所有分布区。我们使用了三种模型进行了分析,包括两种截线抽样法模型和一种样带法模型。几种模型给出了非常相似的种群数量估计值(1111,1225和1000头)。结合鄱阳湖与洞庭湖的初步考察结果,初步估计该亚种总数量约为1800头。此次考察结果显示,长江江豚的种群数量在持续下滑且栖息地破碎化严重。分析结果显示长江干流中种群数量在~1991至2006年间下降了至少一半(>5%/年)。同时,我们在岳阳与石首之间的江段发现了明显的空白分布区,而该江段在十几年前曾是长江江豚分布的重点江段。 我们利用小型渔船,使用改进的截线抽样法,对长江八里江江段(~40 km)进行了考察。我们通过校正系数对江心区密度进行了校正。结果显示八里江江段长江江豚数量约为90头,但这个数字在各个月份之间有所变动(range:44~121)。这提示长江江豚在该江段与其他水域间可能存在一定规模的季节间迁移行为。另外,结果还显示,长江江豚对下游水域(湖口~三号洲)有偏好选择性。受考察精度影响,三年的调查中未能监测到动物明显的变动趋势。本章结果显示小型渔船考察设计能够较好的满足种群数量分析的要求。 我们利用小型渔船,对鄱阳湖分不同季节进行了截线抽样法考察。5次考察的长江江豚种群数量点估计分别为489头(95%CI:256~932),341头(95%CI:215~539),484头(95%CI:248~657),657头(95%CI:396~1091)和316头(95%CI:226~441)。这提示鄱阳湖中长江江豚数量占整个亚种种群数量的四分之一,甚至三分之一。据推测,湖区中长江江豚种群数量在过去二十年间可能一直比较稳定。不同季节之间种群数量的巨大差异提示动物可能存在季节性迁移行为。除与长江干流的迁移行为外,我们推测与五条支流间的迁移性规模可能更大。因为枯水期时种群数量比丰水期时低,我们推测其移动方向在丰水期时入湖,而枯水期时出湖。 利用上述三部分考察结果,并收集其他历史数据资料,对长江江豚的种群数量进行了种群变动趋势分析。我们的分析显示1990至2007年间上段(宜昌~鄂州)的种群下降速率最高(7.7%/年);而在中段(鄂州~华阳)和下段(华阳~上海)的下降速率均为6.2%/年。对于从宜昌到上海的整个江段,平均下降速率为6.4%/年,换言之,长江江豚种群数量在长江干流中每十年下降约一半。我们使用模型反推了1990年时长江干流中动物数量为3623头(95%CI:2734~4446),这比之前的报道要高出约1100头。按照目前的下降速率,我们推测长江江豚种群数量将在2035年前后下降至低于200头。评估显示长江江豚已经符合IUCN的“极度濒危(CR)”的相关标准。 利用长江干流的考察数据,我们计算了从宜昌到上海任意江段的目击率。纵向分布图显示,武汉以下江段比武汉以上江段动物密度高得多。几个典型的高密度水域分别为武穴至三号洲江段和南京至镇江江段。分布图同时显示了自石首至岳阳的空白分布区(~150 km)。横向分布图显示约80%的动物生活在离岸距离为351 m内的水域中。左右岸选择性分布图显示动物对某些江段的某个岸边具有特别的选择性,但尚需要收集大量生态数据对这种选择性作出深层次解释。 总之,研究结果证明我们的考察设计和分析方法能够良好地适用于带状河流生态系统中,且在不同的环境类型和不同的考察平台下取得了可靠、有效的结果。本文所做的长江江豚分布特征分析将有助于提高截线抽样考察精度。另外,本文所揭示的长江江豚的种群现状、未来变动趋势预测和IUCN地位评估对长江江豚的保护意义重大。
英文摘要: Line transect sampling method is widely employed in the study of marine mammals, but rarely used in the study of freshwater cetaceans living in the relatively narrow rivers. Some special environmental conditions of riverine systems violate some key assumptions of Line transect sampling method, which highly limit the application of this method in rivers. Limitations exist in survey design, field survey and data analysis stages. By exemplifying the survey on Yangtze finless porpoise (Neophocaena phocaenoide asiaeorientalis) in the Yangtze River, we explored a promising systematic abundance survey methodology suitable for aquatic mammals in narrow river system by coping with the pointed limitations occurring in all stages of the survey and based on the conventional line transect sampling methodology. Thereafter, we tested the application of this survey method in different platforms with different environmental conditions and got reliable results. Based on the results derived from the case studies, we revaluated the status of the freshwater porpoise subspecies, predicted its population trends, and made assessment on its IUCN status according to the updated criteria of IUCN. In addition, we figured out three types of distribution patterns of the Yangtze finless porpoises (longitudinal, cross river and bank side preferences), which we think may greatly facilitate the survey design and conservation practice in the future. Main results we obtained and conclusions we drawn based on these results are as follows: We proposed and made a detailed description of the survey methodology suitable for riverine systems including survey design, field method and analytical method based on the understanding on both conventional line transect method and the features of the riverine systems. In 2006, we surveyed the entire current range of the porpoise population by using two boats and improved line transect sampling method, except for the two lakes (Poyang and Dongting). Sighting results were similar for both boats, so we pooled all data and analyzed them using two line transect models and a strip transect model. All models produced similar estimates of abundance (1111, 1225 and 1000). We then added independent estimates of the number of porpoises from the two lakes for a total estimate of approximately 1800 porpoises. Our findings indicate that the population continues to decline and that its distribution is becoming more fragmented. Our current estimate in the main river is slightly less than half the estimate from surveys between 1984 and 1991 (which was probably an underestimate). We also found an apparent gap in the distribution of porpoises between Yueyang and Shishou (~150km), where sightings had previously been common. Between 2005 and 2008, we employed small fishing boat and line transect methods to survey the Balijiang section (~40 km) of the Yangtze River. We made correction on the density of middle river area using correction factor. The mean estimate of abundance of total 10 separate surveys is ~90 porpoises ranging from 44 to 121 among various surveys. The abundance variation indicates that specific seasonal migration may exist between this section and other water areas. Opposed to the upper area (i.e. Hukou - Jiujiang), animals showed obvious habitat preference in the lower sections (i.e. Hukou - Island #3). Small boat line transect survey was proved to be a good alternative method to monitor the abundance and even trends of porpoises when large boat survey is economically unavailable. Between 2005 and 2007, we used small fishing boat and line transect methods to survey the Poyang Lake in different seasons. The abundance estimates of 5 independent surveys conducted in different seasons were 489 (95%CI: 256~932), 341 (95%CI: 215~539), 484 (95%CI: 248~657), 657 (95%CI: 396~1091) and 316 (95%CI: 226~441), respectively. This implies that the population size in Poyang Lake accounts for one quarter, or even one third of the total abundance of this subspecies. We speculated this population was presumably stable in the last two decades. The dramatic variation between seasonal abundance estimates may suggest the seasonal migration between the lake and other water areas. Apart from the possible migration between the lake and the main stem of Yangtze River, larger scale migration could happen between the lake and its 5 tributaries. Since the abundance in flood seasons is higher than in dry seasons, we speculated that the porpoises may swim into the lake during flood seasons, and leave the lake in dry seasons. By analyzing the data achieved in present study and the data collected from previous surveys over the past three decades, we examined the abundance trends of the Yangtze finless porpoises. Our analysis indicates that the population in upper section (Yichang - Ezhou) showed the greatest rate of decrease (-7.7% yr-1), while those populations in middle and lower sections (Ezhou - Huayang and Huayang - Shanghai) shared lower decrease rates (-6.2% yr-1) between 1990 and 2007. The average rate of decline for the whole river was 6.4% yr-1, which means that the population will lose approximately half of the population in each decade. We hindcasted the abundance in the river in 1990 to be 3623 (95%CI: 2734~4446) which was much higher than earlier estimate of 2550. At the current rate of decline, we project that the population will decline to a total population size of 200 by 2035. We conclude that this subspecies is “Critically Endangered” in accordance with the criteria of IUCN. We calculated the encounter rate in all small sections between Yichang and Shanghai. The longitudinal distribution map shows that the encounter rate varied between Yichang and Shanghai, including two high density areas (Wuxue – Island #3, and Nanjing - Zhenjiang) and one distribution gap area (Shishou – Yueyang, ~150 km). The cumulative density function of porpoises from bank line to middle river shows that 80% of the animals occurred within a narrow strip (~351 m wide) along the bank line. Moreover, the porpoises showed significant preferences on specific side of the river bank in some areas, although more ecological data need to be collected to clarify this phenomenon. In summary, we are confident that the survey design, field method and analytical method developed in this study could provide reliable abundance estimate of the freshwater subspecies of the finless porpoises, and have great potential to apply in other riverine systems. In addition, the analysis on distribution patterns may help to improve the future survey design. Moreover, the current study contributed much to conservation of this animal by facilitating estimation of the abundance, prediction of its trends and evaluation of its endangered status.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ihb.ac.cn/handle/342005/12402
Appears in Collections:中科院水生所知识产出(2009年前)_学位论文

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Recommended Citation:
河流系统鲸豚类种群数量调查方法探索及其应用研究.赵修江[d].中国科学院水生生物研究所,2009.20-25
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