|其他题名: ||Population biology of an alien Pelteobagrus fulvidraco and invasive risk forecasting in Lake Fuxian, Yunnan|
|摘要: ||抚仙湖(102°49′-102°57′E，24°21′-24°38′N)是云南高原湖群中一个深水湖泊，2002-2005年期间渔获物统计表明该湖现有鱼类42种，隶属8目18科36属，其中土著鱼类18种，外来鱼类24种。本研究以抚仙湖外来鱼类黄颡鱼(Pelteobagrus fulvidraco)为研究对象，对黄颡鱼种群的年龄、生长、繁殖和死亡等生活史特征进行了研究；抚仙湖作为一个外来鱼类入侵的基本地理单元，其鱼类区系和群落结构具有地域代表性，通过对比外来鱼类入侵成功和失败的生活史特征，探讨了外来鱼类成功入侵的一般生活史策略。依据入侵性相关因子建立外来鱼类入侵抚仙湖的风险评估体系，以期对高原水体的外来鱼类入侵预测和防范提供依据。主要研究结果如下：
以脊椎骨作为黄颡鱼年龄鉴定材料，抚仙湖种群分别由雌性0+-5+龄6个龄组和雄性0+-7+龄8个龄组组成，渔获物中群体优势年龄组为3+-4+龄；拟合的Von Bertalanffy生长参数为雄性L∞＝294.68 mm，k＝0.2476 year-1，t0＝-0.0298 year，W∞＝209.93 g；雌性L∞＝257.13 mm，k＝0.2219 year-1，t0＝-0.3329 year，W∞＝184.45 g；生长特征参数分别为φ＝4.3324(♂)和φ＝4.1665(♀)。雄鱼体重生长的拐点年龄为3.1龄时，重60.98 g；雌鱼为3.6龄，重54.47 g。繁殖群体的性比为1:2.55，性成熟年龄为2+龄，绝对繁殖力为431－7169粒，卵母细胞分批同步发育，繁殖时间为5月初至8月末，产卵类型为一次性产卵。与黄颡鱼原分布区种群的生长和繁殖特征相比，抚仙湖种群表现出年龄结构复杂，生长缓慢，个体繁殖力偏低及初次性成熟年龄延迟的特点。
外来种种群增长是一个随机过程。黄颡鱼建群初期受Allee效应和繁殖体压力的影响，入侵过程会出现了一个较长的时滞；在长期种群动态(即续存)过程中统计随机性、环境随机性和Allee效应是可以忽略的，种群数量变动除自然死亡外，捕捞死亡是一个非常重要的因素。估算的群体死亡参数分别为雄性Z＝0.99 year-1，M＝0.40 year-1；雌性Z＝1.22 year-1，M＝0.43 year-1，资源开发率(E)为0.57和0.67。雄性群体单位补充量的相对渔获量(Y'/R)的最大值出现在Emax＝0.634，Ecur < Emax，雌性群体的Y'/R的最大值出现在Emax＝0.719，Ecur < Emax。假定起捕全长不发生改变的情况下，种群近期还将维持在一个较高的水平上。
|英文摘要: ||Lake Fuxian is an oligotrophic and deepwater lake in the Yunnan plateau lake groups. During the survey of the catches from 2002 to 2005, 42 species of fishes belonging to 18 families were collected and identified. 18 species of 24 were locally successfully established. The nonnative Pelteobagrus fulvidraco was the object of the present study. The life history characteristics were studied, such as age, growth, reproduction and mortality. Lake Fuxian was considered as a fundamental geographical units where was invaded by the nonnative fishes, and was representative in fish composition and community structure of the plateau lake. The common life-history strategies were explored on the basis of the contrast between successful and failed fishes. The risk assessment system of alien fishes was founded based on the relative factor of invasiveness in order to forecast and keep away the invasion in the highland river system. The main result summarized as:
Ages were determined based on the annuli of vertebrae. The estimated age range was between 0+-5+ years for females and 0+-7+ years for males. The age groups of 3+-4+ years old were predominant in the catches. The growth parameters used to fit the Von Bertalanffy equation were L∞＝294.68 mm, k＝0.2476 year-1, t0＝-0.0298 year, W∞＝209.93 g for male and L∞＝257.13 mm, k＝0.2219 year-1, t0＝-0.3329 year, W∞＝184.45 g for female. The growth performance indices were φ♂ = 4.3324 and φ ♀ = 4.1665. The inflexion point of age and body weight was estimated at 3.1 years and 60.98 g for males, correspondingly, 3.6 years and 54.47 g for female. There was the significant difference in the sex ratio in favor of male (1:2.55). The estimated age of the first mature was 2+ year. The Mean absolute fecundity (F) was 2374 oocytes, ranging from 431 to 7169. The evolvements of eggs were batch-synchronous. The reproductive activity extended from pre-May to end of August, with peaks in June. The type of reproduction was a batch spawner. The aforementioned life-history characteristic demonstrated P. fulvidraco is one of equilibrium strategist of the adaptive stable habitat. Comparing with the data of other source distribution populations, these results suggested there were typical characters of a complex age structure, relatively slow growth, low individual fecundity and delay in the first maturity age.
Growth of newly introduced populations is a process of the stochastic differential equation models. Allee effects and propagule pressure may restrict establishment of introduced species. Invasive process in a fluctuating environment could represent a lag time. It is negligible for the long-term persistence model to demographic and environmental stochasticity and Allee effects. Fishing is an important factor in population dynamics of species. The instantaneous coefficients of total mortality (Z) and natural mortality (M) were assessed 0.99 year-1and 0.43 year-1 for male, 1.22 year-1 and 0.40 year-1 for female, respectively. The maximum value of Y'/R occurred at Emax = 0.634 for males and Emax = 0.719 for females, Ecur < Emax. Therefore, on the supposition that capturel length was not changed, population dimension will maintain at a high level in the following years.
We compared the overlap of native and exotic fishes in habitat spaces, feeding types and reproductive season. The native fish of diverse niche was differed in responding to invasion of alien species. The endemic and spawning fish in spring and summer were more prone to become extinct, and the threatened rate of the special in habitat space and carnivores was lower. The results suggested the invasion resistance decreased by disruption and less of resident functional group richness. The niche opportunities may be key factors to explain community invisibility.
The variables of 14 biological and ecological attributes for 18 alien species were analyzed. The results suggested that the opportunistic strategists with small-bodied, early maturation, short lifespan, low fecundity per spawning event, and low egg diameter, and the equilibrium strategists with small- to medium-bodied, moderate maturation age, low fecundity per spawning event, protracted spawning season and high juvenile survivorship (greater parental care), were successful invader. The breeding migration of the periodic strategists did not be satisfied because of the obturated property of Lake Fuxian, thus establishment was failed despite of repetitive introduces. In general, it is very high for the alien fishes with wide geographical distribution, intended fishery introduction and prior invasion success to invade successfully. Our expectation was that nonnative equilibrium strategists would spread most rapidly because of niche opportunities created by extensive environmental change and minimal niche overlap with native species. In addition, we expected rapidly declining native species to be either opportunistic or periodic strategists.
We brought forward 36 universal problems in correlation to the invasive factors for the plateau water body, which included geography and domestic history, biological and ecological characteristics, genetics characteristics, human interest and community characteristics. Quantitative risk assessments protocol was constituted based on the descriptive enquiries that species was potentially invader. The proposed system would be identified risk for the recent introduction of nonnative species, and then take the corresponding management measures (accepts, declines or needs to further study).|
|Appears in Collections:||中科院水生所知识产出（2009年前）_学位论文|
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