【作者】 金斌松；

【导师】 傅萃长；

【作者基本信息】 复旦大学 ， 生态学， 2010， 博士

【摘要】 河口与滨海盐沼的重要生态功能之一是维持河口、近海鱼类多样性及其渔业种群。盐沼高生产力、生境高度异质化的特征为鱼类提供了充足的饵料生物与逃避捕食者的避难场所。因此,盐沼生境中的鱼类密度、生长率和存活率通常显著高于河口与滨海其它生境类型。盐沼鱼类的优势种通常是河口、近海重要渔业捕捞对象,已有研究揭示盐沼面积与近海渔业产量之间存在显著的正相关关系。此外,盐沼还是净生产力的输出者,其部分初级生产力通过鱼类随潮汐的迁徙输送到河口与近海生态系统,可能是这些生态系统食物网中次级生产力的主要能量来源。然而,盐沼一般位于人口密集、经济发达的区域,全球盐沼面积已迅速减少。在人类活动不可避免的情况下,认识盐沼对于鱼类的保育价值,鉴定河口与近海鱼类必需的盐沼生境,对河口与近海鱼类多样性的保护、近海渔业的可持续发展十分关键。当前,海洋科学领域的科学家提出充分认识盐沼鱼类多样性时空分布格局是评估盐沼鱼类保育价值、是科学地保护、恢复与管理盐沼生态系统的前提条件。我国在长江河口、杭州湾、黄海沿岸、渤海湾等区域有大量盐沼分布。过去的60年,这些地区由于围垦已导致盐沼面积迅速减少,现存盐沼也正面临着多重威胁。开展盐沼鱼类多样性研究,充分认识盐沼对于我国近海鱼类多样性的保育价值十分迫切。然而,我国盐沼鱼类多样性时空分布格局的基础研究相当缺乏,亟待开展全面系统的研究。本研究选择长江口上海市崇明东滩与九段沙湿地为研究地点,以盐沼潮沟生境为切入点,认识鱼类利用河口盐沼的潮汐、昼夜、月相与季节变化特征,量化沿盐度梯度与沿潮沟级别梯度盐沼鱼类多样性的空间分布格局,并探讨潮沟地貌特征对盐沼鱼类多样性空间分布的影响,旨在系统揭示长江口盐沼潮沟鱼类多样性的时空分布格局。2004年7月至2008年12月,在长江口崇明东滩、九段沙湿地使用插网、拖网、拦网进行了系统的盐沼潮沟鱼类野外实地调查,主要研究结果如下：(一)鱼类多样性的群落组成2004年7月与11月、2005年2月与5月、2007年3至7月与9至12月、2008年1至3月、5至7月与12月在崇明东滩、九段沙湿地盐沼潮沟的野外调查共捕获鱼类136,425尾、157.417kg(湿重),记录到鱼类13目25科63属70种(详见附录Ⅰ)。物种数最多的目为鲈形目Perciformes(10科30属34种)与鲤形目Cypriniformes(2科17属17种),分别占鱼类总物种数的48.6%与24.3%。物种数最多的科为虾虎鱼科Gobiidae (8属22种)与鲤科Cyprinidae (14属14种),分别占总物种数的31.4%与20.0%。数量优势的科依次为虾虎鱼科(39.0%)、鲤科(24.4%)、鲻科Mugilidae (20.2%)、鳀科Engraulidae (12.1%)、花鲈科Lateolabracidae (2.7%)。占鱼类总捕获个体数百分比大于或等于1%的鱼类物种依次为飘鱼Pseudolaubuca sinensis (19.5%)、斑尾复虾虎鱼Synechogobius ommaturus (15.0%)、前鳞鮻Liza affinis(14.5%)、阿部鲻虾虎鱼Mugilogobius abei(9.5%)、纹缟虾虎鱼Tridentiger trigonocephalus (7.1%)、凤鲚Coilia mystus(6.3%)、刀鲚Coilia nasus(5.8%)、鮻Chelon haematocheilus (5.7%)、贝氏口Hemiculter bleekeri (4.5%)、花鲈Lateolabrax maculatus (2.7%)、大鳍弹涂鱼Periophthalmus magnuspinnatus(2.3%)、棕刺虾虎鱼Acanthogobius luridus(2.2%)、弹涂鱼Periophthalmus modestus (1.0%)。这十三种鱼类占总捕获个体数的96%。其中,斑尾复虾虎鱼、前鳞鮻、凤鲚、刀鲚、鮻与花鲈是长江口重要的渔业对象。可见,长江口盐沼对于长江口渔业可持续发展十分重要。依据Elliott et al. (2007)定义的生态类群划分(详见第二章),盐沼潮沟中记录到的鱼类包括8个生态类群,即海洋洄游鱼类(21种)、淡水偶见鱼类(16种)、河口鱼类(15种)、淡水洄游鱼类(8种)、海洋偶见鱼类(6种)、溯河洄游鱼类(2种)、降河洄游鱼类(1种)、半溯河洄游鱼类(1种)。这些生态类群按占鱼类总个体数百分比从大到小依次排列为：海洋洄游鱼类(33.8%)、河口鱼类(29.4%)、淡水洄游鱼类(19.9%)、半溯河洄游鱼类(6.3%)、溯河洄游鱼类(5.8%)、淡水偶见鱼类(4.8%)、降河洄游鱼类(0.04%)和海洋偶见鱼类(0.04%)。可见,长江口盐沼是多个鱼类生态类群的重要栖息生境,具有强大的维持鱼类多样性的生态系统服务功能。依据鱼类生活史阶段划分,幼鱼占总捕获鱼类个体数的85%。淡水洄游、淡水偶见、降河洄游、溯河洄游、半溯河洄游鱼类的幼鱼占各自类群数量的百分比均在90%以上；河口鱼类和海洋洄游鱼类幼鱼百分比分别是80.4%和75.2%；海洋偶见鱼类幼鱼比例为50.8%。由此可见,长江口盐沼可能是鱼类重要的育幼场。(二)鱼类多样性时间分布格局1)季节变化特征为了认识长江口盐沼鱼类多样性的季节变化特征,2004年7月(夏季)与11月(秋季)、2005年2月(冬季)与5月(春季)大潮期间使用插网在九段沙湿地盐沼潮沟开展了鱼类调查。研究期间共捕获鱼类25010尾、29.5 kg,隶属于17科31属34种。优势鱼类(相对重要性指数IRI>100)包括斑尾复虾虎鱼、前鳞鮻、鮻、尖吻蛇鳗Ophichthus apicalis、花鲈、拉氏狼牙虾虎鱼Odontamblyopus lacepedii。四个季节鱼类群落主要由幼鱼构成,优势生态类群是河口定居鱼类。春季、夏季、秋季和冬季分别记录到鱼类19、20、13、9种。春季鱼类数量最多,夏季鱼类生物量最高。双因子方差分析揭示鱼类物种数、总个体数、总生物量及优势种个体数与生物量季节间差异显著。无度量多维排序结果显示鱼类群落在四个季节明显分离。单因子相似性分析揭示季节间鱼类群落结构差异显著。导致鱼类多样性季节变化的主要原因可能是与水文特征(温度与盐度)相适应的鱼类繁殖期的选择。2)大小潮变化特征为了认识长江口盐沼鱼类多样性的大小潮变化特征,2007年3月至2008年2月(2007年8月因天气原因未采样)大潮和小潮期间使用插网在崇明东滩湿地盐沼潮沟开展了鱼类周年调查。研究期间捕获鱼类74062尾、47kg,隶属于18科45属50种。优势鱼类(IRI>100)包括斑尾复虾虎鱼、前鳞鮻、鮻、飘鱼、棕刺虾虎鱼、刀鲚、纹缟虾虎鱼、拉氏狼牙虾虎鱼和贝氏口。鱼类群落主要由幼鱼构成,占鱼类总个体数的97%。方差分析显示鱼类物种数、生物量在大小潮间差异显著,但总个体数在大小潮间没有显著差异。春、秋、冬三季鱼类物种数大潮阶段显著多于小潮阶段,夏季鱼类物种数大小潮间没有差异。刀鲚、拉氏狼牙虾虎鱼个体数大小潮间差异显著,其它优势鱼类大小潮间个体数没有显著差异。刀鲚仅出现在夏季,其个体数小潮阶段显著地多于大潮阶段。拉氏狼牙虾虎鱼主要出现在夏、秋两季,其大潮阶段的个体数明显多于小潮阶段。导致鱼类多样性大小潮变化的主要原因可能与水深有关。3)月相变化特征为了认识长江口盐沼鱼类多样性的月相变化特征,2008年5至6月在九段沙湿地使用插网进行了8个月相阶段的鱼类调查。研究期间捕获鱼类17935尾,隶属于9科21属23种。方差分析揭示不同月相阶段间鱼类物种数、总个体数和总生物量存在显著差异。满月、下弦凹月、新月与上弦凹月鱼类的物种数、总个体数和总生物量均高于另外四个月相阶段,鱼类总个体数和生物量的峰值出现在新月阶段。数量优势的鱼类显示了不同月相变化格局,阿部鲻虾虎鱼、棘头梅童鱼Collichthys lucidus的个体数峰值出现在新月或上弦凸月,而前鳞鮻、大弹涂鱼、花鲈的个体数在满月或下弦凸月成峰。双因子相似性分析揭示不同月相阶段间鱼类群落差异显著(Global test R=0.542, P=0.001)。冗余分析表明水深与水温是导致鱼类多样性月相变化的主要环境因子。可见,盐沼潮沟水文特征可能是决定鱼类多样性月相变化的主要原因。4)日夜变化特征以上三个时间动态研究均涉及鱼类多样性的日夜比较。结果表明在不同的季节、大小潮以及月相阶段鱼类物种数、总个体数和总生物量以及优势鱼类物种的个体数与生物量一般没有显著的日夜差异。仅仅在特定的季节、大小潮或月相阶段显示鱼类个体数或生物量存在日夜间的差异。(三)鱼类多样性空间分布格局1)沿潮沟级别梯度鱼类空间分布特征为了认识沿潮沟级别梯度盐沼鱼类空间分布特征,2008年5至7月大潮期间在九段沙湿地选择具有1至4级发育良好的潮沟系统使用拖网开展了鱼类调查。研究期间捕获鱼类1169尾、1.5 kg,隶属8科14属16种。优势种依次为大鳍弹涂鱼、前鳞鮻、阿部鲻虾虎鱼、花鲈、弹涂鱼、鮻和斑尾复虾虎鱼。1级、2级和4级潮沟各捕获鱼类11种,3级潮沟中捕获鱼类13种。各级潮沟间鱼类物种数差异不显著。鱼类总捕获个体数在潮沟级别间差异显著,从1至4级趋向于增加。数量排序图显示低级别(1至2级)潮沟鱼类群落的均匀度高于高级别潮沟(3至4级)。沿潮沟级别梯度,优势鱼类的个体数和体长分布频率显示不同的变化趋势。聚类分析揭示鱼类群落能划分为1至3级与4级两个亚群落。典范对应分析揭示距潮沟入口的距离和潮沟截面面积这两个地貌因子是导致鱼类亚群落间显著差异的原因。可见,不同级别盐沼潮沟对于各生态类型的鱼类和不同生活史阶段都有着重要作用。2)盐度对鱼类空间分布的影响为了认识盐度对盐沼鱼类空间分布的影响,2008年5月与12月大潮期间在崇明东滩湿地低盐区3条盐沼潮沟(盐度值为0.3-4.5,平均值2.0)与中盐区(5.8-13,平均值8.8)6条潮沟进行了鱼类调查。研究期间捕获鱼类7818尾、18.6kg,隶属于12科31属33种。优势种依次为阿部鲻虾虎鱼、前鳞簸、花鲈、大鳍弹涂鱼、鮻、大弹涂鱼、斑尾复虾虎鱼、拉氏狼牙虾虎鱼和纹缟虾虎鱼。这些优势种对于水体盐度值的响应不同。阿部鲻虾虎、大鳍弹涂鱼、大弹涂鱼与拉氏狼牙虾虎鱼主要分布在中盐区的潮沟；花鲈、前鳞鮻主要分布在低盐区潮沟；纹缟虾虎鱼中盐、低盐区均有分布；鮻5月主要分布于低盐区潮沟,而12月主要分布于高盐区潮沟；斑尾复虾虎鱼5月主要分布于中盐区潮沟,而12月主要分布于低盐区潮沟。中盐区主要以河口定居鱼类为主,而低盐区主要以海洋暂居鱼类为主。冗余分析揭示崇明东滩湿地盐沼潮沟群落能清楚地划分为低盐区与中盐区两个亚群落。可见,河口不同盐度区域的盐沼对于维持不同生态类群的鱼类和生活史阶段有着重要作用,盐度在长江口盐沼鱼类多样性空间分布格局中扮演重要角色。3)潮沟地貌特征对鱼类空间分布的影响为了认识潮沟地貌特征对鱼类空间分布的影响,2007年3至7月、9月、11月和2008年2月在大小潮之间使用拦网对崇明东滩湿地一条较大潮沟的主干两侧7条小潮沟进行了地貌变量测量和鱼类调查。研究期间捕获鱼类10432尾、46kg,隶属于8科23属25种。优势种包括前鳞鮻、鮻、鲫Carassius auratus auratus、斑尾复虾虎鱼、棕刺虾虎鱼和花鲈。典型相关分析揭示鱼类的物种数、密度、生物量与潮沟地貌变量显著相关。具有较小深度和倾斜度的小潮沟能够容纳更多的鱼类个体。具有较大水深、截面面积、容积以及倾斜度的潮沟中有更多的鱼类物种数。前鳞鮻和鮻的密度在高程较高的小潮沟中较多,而花鲈偏好具有较大水深、截面面积和坡度的潮沟。可见,潮沟地貌在鱼类选择盐沼微生境中扮演重要角色。综上所述,长江口盐沼具有强大的维持鱼类多样性的生态系统服务功能,是多个鱼类生态类群的重要栖息生境,是长江口重要渔业物种的育幼场所,对于长江口渔业可持续发展十分重要。长江口盐沼潮沟鱼类群落的主要时空分布格局特征可概括为：a)少数鱼类物种占优势；b)幼鱼是鱼类群落的主体；c)海洋洄游鱼类、河口鱼类是优势生态类群；d)鱼类群落呈现明显的季节与月相变化动态,相对较弱的大小潮与日夜变化动态；e)沿海岸线垂直方向,低级别潮沟与高级别潮沟鱼类群落结构差异显著；f)沿海岸线平行方向,低盐区与中盐区鱼类群落结构差异显著。水文特征、潮沟地貌特征与鱼类生活史特征是长江口盐沼潮沟鱼类多样性时空分布格局形成的主要成因。本研究结果对于长江口盐沼湿地的保护、恢复与管理的指导意义为：a)盐沼湿地是长江口渔业可持续发展不可或缺的生境；b)春、夏季是鱼类利用盐沼生境的关键时期；c)恢复盐沼湿地时应考虑恢复具有不同地貌特征的潮沟；d)在围垦盐沼湿地不可避免时,应考虑保留不同盐度区域潮沟系统发育良好的盐沼生境。更多还原

【Abstract】 One salt marsh function in estuarine and coastal ecosystems is to be an important nursery habitat for fishes and thus support estuarine and coastal fisheries. Due to high productivity and habitat heterogeneity, salt marshes provide abundant food sources and shelters for fish to escape predators. Therefore, fish densities, growth rates and survival in salt marshes are generally higher than in other estuarine and coastal habitats. Most dominant fishes in salt marshes constitute important fishery populations. Findings from previous studies have revealed that estuarine or near shore fishery yields were positively correlated with the areas of salt marsh. In addition, salt marshes export net productivity and are considered to be a significant source of secondary production in food webs of estuarine and coastal ecosystems. Part of the primary productivity is delivered to estuarine and coastal ecosystems by fishes. However, salt marshes are commonly located in regions with high human population density and developed economies. Salt marsh areas have rapidly decreased in the world in recent decades. Under unavoidable human activities, it is important to understand the conservation value of salt marshes for fishes, and to identify essential fish habitats in salt marshes. Therefore, fish knowledge is greatly needed for the conservation, restoration and management of salt marsh ecosystems.In China, salt marshes are widely distributed in the Yangtze River estuary, Hangzhou Bay, Yellow Sea and Gulf of Bohai. In the past 60 years, the area of salt marshes has greatly diminished owing to reclamation. The extant salt marshes have also multiple additional threats such as alien species invasions. It is necessary to study fish diversity patterns in Chinese salt marshes to understanding the salt marsh’s conservation value for offshore fish diversity and to improve the knowledge of salt marsh ecosystem functions. However, baseline research on salt marsh fishes is very limited in China.In this study, intertidal salt marsh creeks in the Chongming Island and Jiuduansha Islands of the Yangtze River estuary are selected as study sites. The aim of this study is to reveal the temporal and spatial distribution patterns of fish diversity in these intertidal salt marsh creeks. Dial, lunar and seasonal changes of salt marsh fishes are delimited. Along a creek-order gradient, the spatial distribution patterns of salt marsh fishes are also described. Effects of salinity and geomorphological features on fish spatial distributions of intertidal salt marsh creeks are explored.From July 2004 to December 2008, fyke nets, seine nets and channel nets were used to sample fishes in intertidal salt marsh creeks of Chongming Island and Jiuduansha Islands. The major results are listed as follows:I. Composition of fish communities in intertidal salt mash creeksA total of 136,425 individuals weighing 157.417 kg were caught from intertidal salt marsh creeks in Chongming Island and Jiuduansha Islands in July and November 2004, February to May 2005, March to July and September to December 2007, January to March, May to July and December 2008. Fishes belonged to 13 orders,25 families,63 genera and 70 species (for details see Appendix I).The most species-rich orders were Perciformes (10 families,30 genera and 34 species) and Cypriniformes (2 families,17 genera and 17 species), which comprised 48.6%and 24.3% of the total species. The most species-rich families were Gobiidae (8 genera and 22 species) and Cyprinidae (14 genera and 14 species), together comprising 31.4% and 20.0% of the total species. The most numerically abundant families were Gobiidae (39.0%), Cyprinidae (24.4%), Mugilidae (20.2%), Engraulidae (12.1%) and Lateolabracidae (2.7%).The dominant species (percentage contribution of individuals equal to or greater than 1%) were:Pseudolaubuca sinensis (19.5%), Synechogobius ommaturus (15.0%), Liza affinis (14.5%), Mugilogobius abei (9.5%), Tridentiger trigonocephalus (7.1%), Coilia mystus (6.3%), Coilia nasus (5.8%), Chelon haematocheilus (5.7%), Hemiculter bleekeri (4.5%), Lateolabrax maculates (2.7%), Periophthalmus magnuspinnatus (2.3%), Acanthogobius luridus (2.2%), Periophthalmus modestus (1.0%). These 13 fish species comprised 96% of the total catch. Among these, S. ommaturus, L. affinis, C. mystus, C. nasus, C. haematocheilus and L.maculatus were important fishery species in the Yangtze River Estuary. These findings indicate that salt marshes are important for sustaining fisheries in the Yangtze River Estuary.According to the division of fish ecological guilds defined by Elliott et al. (2007), eight such guilds using intertidal salt marsh creeks were recognized:marine migrants (21 species), freshwater stragglers (16 species), estuarine species (15 species), freshwater migrants (8 species), marine stragglers (6 species), anadromous (2 species), catadromous (1 species) and semi-anadromous (1 species). The fish ecological guilds ranking by the individuals percentage were:marine migrants (33.8%), estuarine species (29.4%), freshwater migrants (19.9%), semi-anadromous (6.3%), anadromous (5.8%), freshwater stragglers (4.8%), catadromous (0.04%) and marine stragglers (0.04%). These findings indicate that the salt marshes of the Yangtze River Estuary are important habitats for different fish ecological guilds with different ecological functions.Fish communities were dominated by juvenile fishes, which comprised 85% of the total catches. Juvenile individuals in each of freshwater migrants, freshwater stragglers, anadromous, catadromous and semi-anadromous fishes, respectively comprised more than 90%of the total catch of each ecological guild. Juveniles of estuarine species and marine migrants comprised 80.4% and 75.2%. Juveniles of marine stragglers comprised 50.8% of its total catch. Thus, the salt marshes in the Yangtze River Estuary are likely to be important nursery habitats for juvenile fishes.II. Temporal distribution patterns of fishes in intertidal salt marsh creeks1) Seasonal changesSeasonal changes of fish diversity in intertidal salt marsh creeks were investigated in July and November,2004, and February and May,2005 in Jiuduansha. Fishes were collected by consecutive day and night samplings using fyke nets during the ebbing spring tides. A total of 25,010 individuals were caught during the study.17 families, 31 genera and 34 species were documented. The dominant species (Index of Relative Importance, IRI> 100) were:S. ommaturus, L. affinis, C. haematocheilus, Ophichthus apicalis, L. maculatus and Odontamblyopus lacepedii. There were significantly seasonal changes in fish use of salt marshes. No significant effects of diel periodicity on the fish community were found except for fishes sampled in summer. There were 19,20,13 and 9 fish species respectively recorded in Spring, Summer, Autumn and Winter. The highest abundance of fishes was documented in Spring, and the highest biomass of fishes in Summer. Non-metric multidimensional scaling analysis showed a clear separation of fish communities for different seasons. The seasonal pattern in fish species was probably due to fish spawning seasons adapted to hydrological characteristics (temperature and salinity).2) Tidal patternsThe changes in fish diversity between spring-neap tides were investigated from March 2007 to February 2008 in Dongtan, except for August 2007 owing to poor weather. Fishes were collected using fyke nets. A total of 74,062 individuals, belonging to 18 families,45 genera and 50 species, were captured. The dominant species (IRI> 100) were S. ommaturus, L. affinis, C. haematocheilus, P. sinensis, A. luridus, C. nasus, T. trigonocephalus, O. lacepedii and H. bleekeri. The fish community was dominated by juvenile individuals, comprised 97% of the total catches. ANOVA analysis revealed that fish species richness and total biomass were significantly affected by spring-neap tides, but the total abundance was not significantly different between spring and neap tides. In Spring, Autumn and Winter, there was higher richness of species during spring tides than during neap tides. In Summer, no significant difference in species richness between spring and neap tides was observed. Among dominant species, only C. nasus and O. lacepedii showed significant differences in abundance between spring and neap tides. C. nasus only appeared in Summer. More individuals of C. nasus were captured during neap tides than spring tides. O. lacepedii showed a reversed trend. The spring-neap changes of fish diversity in salt marsh creeks may be associated with water depth.3) Lunar patternsThe lunar changes of fish diversity were investigated in eight lunar phases in May through June 2008 in intertidal salt marsh creeks of the Jiuduansha wetland. A total of 17,935 individuals, belonging to 9 families,21 genera and 23 species, were captured. ANOVA analysis revealed that fish species richness, abundance, and biomass were significantly affected by lunar phases. There were higher species richness, abundance and biomass in the full moon, waning crescent moon, new moon and waxing crescent moon than in other lunar phases. Fish abundance and species richness peaked in the new moon and full moon. Abundance of M. abei and C. lucidus reached maxima during the new moon and waxing gibbous moon. There was higher abundance of L. affinis, B. pectinirostris and L. maculatus in the full moon or waning gibbous moon than in other lunar phases. Two-way ANOSIM analyses revealed significant lunar changes in fish communities (Global test R=0.542, P=0.001). Redundancy analysis revealed that water depth and temperature are the main environmental variables in shaping lunar changes in fish communities. Thus, hydrological characteristics of salt marsh creeks may determine lunar changes in fish diversity. 4) Diel patternsEffects of diel periodicity on fish communities were all involved in above-mentioned three studies. Generally, there were inconspicuous differences between day and night for species richness, total abundance, total biomass and abundance of dominant species. Significant differences in fish abundance and biomass between day and night were only observed in special season, month, spring-neap tides or lunar phases.Ⅲ. Spatial distribution patterns of fishes in intertidal salt marsh creeks1) Spatial distribution along a creek order gradientFish spatial distribution patterns along a creek order gradient (1-4 orders) were investigated in a low salinity intertidal salt marsh creek network. Fish were sampled using seine nets during daytime high slack water of spring tides for two or three days each in May through July 2008. A total of 1169 individuals, belonging to 8 families, 14 genera and 16 species, were captured. The dominant species were P. magnuspinnatus, L. affinis, M. abei, L. maculatus, P. modestus, C. haematocheilus and S. ommaturus. Rank abundance curves indicated a higher evenness of nekton assemblages in lower-order creeks compared to higher-order creeks. Fish abundance tended to increase with increasing creek order. Dominant fish species displayed different variation trends in abundance or in size-frequency distribution along the creek order gradient. The spatial separation of fish assemblages between the first-third orders and the fourth order could be attributed to geomorphological factors (distance to mouth and cross-section area). These findings indicate that both lower-and higher-order creek edges play important yet different roles for nekton species and life history stages in salt marshes.2) Effects of salinity on spatial distributions of fishesEffects of salinity on spatial distributions of fishes were investigated in three oligohaline creeks (salinity 0.3～4.5, mean 2.0) and six mesohaline creeks (salinity 5.8～13, mean 8.8) in the Chongming Dongtan wetland. Fishes were sampled with fyke nets during spring tides between May and December 2008. A total of 7818 individuals, belonging to 12 families,31 genera and 33 species, were captured. The dominant species were M. abei, L. affinis, L. maculatus, P. magnuspinnatus, C. haematocheilus, B. pectinirostris, S. ommaturus, O. lacepedii and T. trigonocephalus. These dominant species responded to salinity differently. M. abei, P. magnuspinnatus, B. pectinirostris and O. lacepedii were mainly distributed in the mesohaline creeks; L. maculates and L. affinis were mainly distributed in the oligohaline creeks; T. trigonocephalus was distributed in both mesohaline and oligohaline creeks. A higher abundance of L. affinis was found in oligohaline creeks during May and in mesohaline creeks in December. S. ommaturus showed the reversed trend. Estuary residents dominated the fish assemblage in mesohaline creeks, and juveniles of marine transients dominated fish assemblage in oligohaline creeks. Redundancy analysis revealed a clear spatial separation of fish assemblages between oligohaline and mesohaline marsh creeks, which could be attributed to salinity.3) Effects of geomorphological features on spatial distributions of fishesEffects of geomorphological features on spatial distributions of fishes were investigated in seven small creeks within one large creek at the Chongming Dongtan wetland. Fishes were collected using channel nets in March through July, September, November 2007 and February 2008. A total of 10432 individuals, belonging to 8 family,23 genera and 25 species, were captured. The dominant species were L. affinis, C. haematocheilus, C. auratus, S. ommaturus, A. luridus and L. maculatus. Canonical correlation analyses showed that species richness, total abundance and biomass were strongly related to the creek geomorphological variables. Intertidal creeks with shallow water depth, gentle slope and steepness supported higher fish abundance. Species richness was positively correlated with depth, cross sectional area, volume and steepness. L. affinis and C. haematocheilus favored small size creeks with high elevations, and L. maculatus preferred deep creeks with large cross section, slope, and steepness. Geomorphological features of creeks play important roles for fishes in selecting habitats.In sum, salt marshes in the Yangtze River estuary show strong ecosystem functions for supporting fish diversity, and provide important habitats for multiple fish ecological guilds and as nursery grounds of economically important fishery species. The temporal and spatial distribution patterns of the fish community in the intertidal salt marsh creeks can be summarized as follows:a) The fish community was dominated by a few species; b) Juveniles comprised the major part of the fish community; c) Marine migrants and estuarine species were the dominant fish ecological guilds; d) The fish communities showed strong patterns of seasonal changes or lunar changes, and related weak patterns of spring-neap tide changes or diel changes; e) Along a vertical direction to the coastline, fish community structures showed significant differences between lower-order creeks and higher-order creeks; f) Parallel to the coastline, fish community structures showed significant differences between oligohaline and mesohaline creeks; g) Hydrological characteristics, geomorphological features and fish life history are the major forces shaping temporal and spatial distribution patterns offish diversity in these habitats.These findings have important implications for the conservation, restoration and management of the Yangtze River Estuary salt marshes:a) Salt marshes are important for sustainable utilization of fisheries in the Yangtze River estuary; b) Spring and Summer were the critical periods for fish use of salt marshes; c) Creek geomorphological features should be taken into account for salt marsh restorations; d) Well-developed intertidal creek systems in salt marsh zones with different salinity should be protected and reserved.更多还原