Dams in the Amazon: The importance of maintaining free-flowing tributaries for fish reproduction

1. Free-flowing tributaries are important for the maintenance of fish diversity in dammed systems. In relation to the reproduction of fish species, the role of a free-flowing tributary was evaluated and compared with that of a dammed tributary downstream of large dams in the Madeira River, one of the main tributaries of the Amazon River.
2. Two hypotheses were tested: (i) the densities of the ichthyoplankton differ between the dammed and the free-flowing tributaries; and (ii) the free-flowing tributary contributes a greater diversity of fish larvae species to the assemblage structure of the main stem than the dammed tributary.
3. Fish eggs and larvae were sampled at five sites: one in each tributary (Jamari – dammed – and Machado – free-flowing) and three in the main stem (Madeira River), upstream and downstream from the mouth of each tributary.
4. Fitted Bayesian models showed that the densities both of eggs and larvae were more than twice as high in the free-flowing tributary than in the dammed tributary. The results also indicated that the free-flowing tributary makes a major contribution to the fish assemblage structure of the Madeira River, whereas the dammed tributary does not have a significant influence on the main stem assemblage structure.
5. The results demonstrate the importance of conservation and maintenance not only of the Machado River but also of other free-flowing tributaries in dammed basins, especially those basins with high biodiversity, such as the Amazon. Moreover, this study helps inform the decision-making process regarding the location of new dams, which is critical in fish diversity conservation.

     

几种近海底层鱼类和中上层鱼类隐蔽伪装色的比较

为了探明近海不同生态类型鱼类隐蔽伪装色的差异,研究了6种中上层鱼类和5种底层鱼类的隐蔽伪装色,结果表明:无论近海中上层鱼类(包括大甲鲹Megalaspis cordyla、斑■Hemiramphus far、五条■Seriola quinqueradiata、竹■鱼Trachurus japonicus、蓝圆鲹Decapterus maruadsi、蓝点马鲛Scomberomorus niphonius)还是近海底层鱼类(海鳗Muraenesox cinereus、斑尾复虾虎鱼Synechogobius ommaturus、带鱼Trichiurus japonicus、单角革鲀Aluterus monoceros、龙头鱼Harpadon nehereus),黑色素细胞和黄色素细胞均为背部多腹部少,差异显著;相比近海底层鱼类,近海中上层鱼类背腹部体色差异更加明显,中上层鱼类黑色素细胞和黄色素细胞差异更大;虹彩细胞在背腹部皮肤中都存在,而近海底层鱼类的腹部主要为虹彩细胞;红色素细胞在近海底层鱼类中很少存在,但在中上层鱼类中较多。上述结果显示,鱼类背部体色的深浅主要与皮肤中黑色素细胞和黄色素细胞的数量有关,腹部体色的形成主要与虹彩细胞的多少有关。     

黄河水系鱼类分布的模糊聚类分析

应用模糊聚类法对黄河水系鱼类分布进行研究,结果表明,当λ＝０．５２时,黄河水系鱼类分布可分为８类：黄河上游干流、星宿海、黑河、鄂陵湖为一类;黄河中游干流、渭河为一类;乌梁素海、哈素海、陕北高原河流为一类;冯家山水库、陆浑水库为一类;黄河下游干流、东平湖为一类;洮河、伊洛河、河口干流各为一类。     

三峡库区鱼类环境和污染状况

三峡库区的自然环境适合于多种鱼类的生长,库区水质表现一定的季节变化,水体中大肠杆菌和铜等超标;鱼体内主要污染物为Ｃｄ,Ｃｒ,Ａｓ等,但未超标,食用品质较好;鱼样外周血红细胞微 ０．８２‰－４．２８‰,表明水质对鱼体细胞具诱变作用。     

Hydrological connectivity in coastal inland systems: lessons from a Neotropical fish metacommunity

de Macedo-Soares PHM, Petry AC, Farjalla VF, Caramaschi EP. Hydrological connectivity in coastal inland systems: lessons from a Neotropical fish metacommunity.
Ecology of Freshwater Fish 2010: 19: 7–18. © 2009 John Wiley & Sons A/S
Abstract –  We assessed the influence of hydrological connectivity in structuring fish communities through seasonal samplings of environmental variables and fishes in a coastal lagoon and associated pools in the Restinga de Jurubatiba National Park, Brazil. Community structure attributes such as species richness, numerical density and biomass, Shannon–Wiener diversity index and evenness were compared between periods of the lowest and highest hydrological connectivity, while the environmental gradient and fish zonation were explored through ordination techniques. The greater hydrological connectivity established in the rainy season promoted the homogenisation of most environmental variables and fish species, which differed markedly from the arrangement observed in the dry season. Despite variation in fish species composition, community attributes showed non-significant differences between the dry and rainy seasons. The patterns of composition and numerical density in pools were strongly influenced by local factors, especially salinity, dissolved oxygen, total phosphorous concentration and water colour in the dry season, in addition to total nitrogen concentration and depth in the rainy season. Comparable to the role played by flood pulses in river-floodplain systems, the hydrological connectivity in these tropical coastal waterbodies seems to strongly influence fish community structure, and, therefore to determine regional biodiversity.     

太湖主要鱼类食物组成

根据2004年9-12月和2005年4月的调查,研究了太湖8种鱼的食物组成.结果表明:优势种鲚主要摄食枝角类、占食物个数比例89.77%±13.69%;太湖新银鱼主要摄食桡足类、占个数比例70.11%±10.57%;鲢、鳙主要摄食微囊藻、占食物体积比例90%以上;鲤食物中水生植物约占体积比例70%;鲫主要摄食微囊藻、占体积比例93.99%±3.34%;翘嘴红鲌、蒙古红鲌主要摄食鲚和小型鱼类.分析认为,随着太湖富营养化程度不断加重,以蓝藻为主的浮游植物食性鱼产力在快速增加,但实际渔获量以浮游动物食性鱼类为主.如2003年浮游植物食性鱼产力为10234t、占总鱼产力37.0%.而2004年实际渔获量中浮游动物食性鱼类占80%-90%,浮游植物食性鱼类渔获量仅3637.7t、占10.9%.因此,太湖现有鱼类群落组成和实际饵料构成是不吻合的.不仅如此,浮游动物食性鱼类数量的快速增加对浮游动物形成了巨大牧食压力,这更利于藻类繁殖.太湖鲫几乎完全以微囊藻为食物,可能对蓝藻暴发有抑制作用,应重新评价其对环境的影响.     

海水鱼类保鲜技术的研究进展

随着对海洋鱼类的研究开发,人们意识到海水鱼类具有更高的营养价值,例如含有高度不饱和脂肪酸等,于是越来越倾向于食用海水鱼类。海水鱼类的保鲜技术主要有低温保鲜、化学和生物保鲜、高压保鲜、气调保鲜、辐照保鲜、臭氧保鲜等,通过逐一对其进行介绍,最后提出了今后的研究方向,以便为海水鱼类贮藏保鲜技术的发展提供依据。     

贵州省主要经济鱼类种类及开发应用前景

对贵州省主要经济鱼类种类和资源量进行调查,基本掌握了贵州省主要经济鱼类有34种.其中,鲤科鱼类22种,占64.7%;鲿科鱼类5种,占14.7%;鲶科、鮨旨科及鳢科鱼类各2种,各占5.9%;长臀鮠科鱼类1种,占2.9% .主要分布于乌江、赤水河、沅江、北盘江、红水河、柳江等水系.主要土著名特优经济鱼类资源年产量1 977t.目前,国内对翘嘴鲌、鲤、鲫、大口鲇、鲇、黄颡鱼、瓦氏黄颡鱼、长吻鮠、斑鳜、乌鳢和月鳢11种鱼类的研究已较成熟;对中华倒刺鲃、白甲鱼、瓣结鱼、华鲮、唇鲮、昆明裂腹鱼、四川裂腹鱼、岩原鲤、鲤、鲫、斑鳠、长臀鮠和大鳍鳠13种鱼类开展了养殖和繁殖研究,并取得了一些突破;适宜进行开发的鱼类有中华倒刺鲃、白甲鱼、华鲮、昆明裂腹鱼、四川裂腹鱼、岩原鲤、斑鳠、长臀鮠和长吻鮠等.     

秦岭生态保护区野生鱼类的物种多样性及其保护对策

秦岭生态保护区地表径流众多,南北气候差异明显,因而孕育了种类丰富的野生鱼类。实地鱼类资源考察、检视鱼类标本以及参考鱼类分类、分布的文献表明,区内现有野生鱼类共7目16科75属141种（亚种）。通过物种多样性G-F指数的比较分析表明：区内鱼类的物种多样性在邻近省份中是最高的,而且该地区的鱼类区系地跨古北界和东洋界,具有显著的过渡区特点;区内不同水系间鱼类组成差异显著。目前,秦岭生态保护区野生鱼类的物种多样性正面临来自不合理捕捞、水工程建设、环境污染以及生态破坏等多方面的压力。为恢复和保护这一地区的野生鱼类的物种多样性,本文提出了有针对性的建议。     

我国喀斯特洞穴鱼类研究进展

我国喀斯特洞穴鱼类物种多样性极为丰富,到目前为止,我国已发现喀斯特典型洞穴鱼类48种。喀斯特洞穴鱼类研究是喀斯特洞穴生物学研究的重要组成部分。阐述了我国喀斯特洞穴鱼类的生态类型,其中以赵亚辉、张春光为代表的生态类型划分较为成熟,将喀斯特洞穴鱼类分为典型洞穴鱼类、非典型洞穴鱼类和偶入洞穴鱼类3种类型。总结了我国喀斯特洞穴鱼类具有种类多、类群集中、分布区域狭窄和种群数量少等特点;分析了我国喀斯特洞穴鱼类适应特殊的洞穴环境而演变形成的适应性特征,这些特征主要表现在视觉器官、侧线器官、头部结构、体表鳞片、鳍和体色等方面。最后,对我国喀斯特洞穴鱼类进行了科学价值和社会价值两方面的评价,并提出了合理开发利用和保护的建议。