宁夏沙湖浮游植物群落结构及多样性研究

于2008年4月-2009年1月对宁夏沙湖浮游植物的种类组成、密度、生物量、优势种以及物种多样性进行了分析研究,并依据浮游植物种类组成和密度,对浮游植物群落结构进行了聚类分析(Cluster Analysis,CA)和多维分析(Multidimensional scaling,MDS)。结果表明,沙湖浮游植物共有8门94属117种,种类构成比例为绿藻49.6%、硅藻21.6%、蓝藻16.0%和其它12.8%。春季优势种的种类较多,蓝、硅、绿藻均有,夏、秋季蓝藻占绝对优势,冬季以绿藻为主。浮游植物种类、密度、生物量和分布依季节而异,高峰期出现在7月,低谷期出现于1月。Margalef指数2.872~4.652,Shannon指数2.058~3.057,均匀度指数0.521~0.759,综合评价沙湖水体为中富营养水平。浮游植物群落结构春、夏、冬季聚为3类,秋季聚为2类,除春季外,MDS分析结果和聚类分析结果一致,支持和证实了聚类分析的结果,很好地揭示了沙湖各季节、各样点间浮游植物群落结构的相似性与差异性。b     

三角湖浮游植物群落结构与水质评价

2011-2012年对三角湖浮游植物进行季节性调查,以了解浮游植物群落结构特征及其对水质的指示作用,为污染防治和生态修复提供依据。结果表明,在三角湖共采集浮游植物94种(变种),隶属于8门、25科、51属;其中,绿藻种类最多,约占总种数的59.6%,其次是硅藻、蓝藻和裸藻,分别占12.8%、11.7%和8.5%,其他门类种类较少。浮游植物细胞密度平均值为(102.32±59.89)×106个/L;其中,蓝藻密度最大,占浮游植物总丰度的86.69%,其次是绿藻和硅藻,分别占7.77%和4.91%,其他门类密度较低。浮游植物密度具有明显的季节变化规律,夏季的密度最大,秋季次之,冬季和春季较低。夏季和秋季蓝藻细胞密度占绝对优势,绿藻和硅藻次之,而冬季蓝藻密度下降,硅藻和绿藻占优势,春季蓝藻又重新占据优势。三角湖浮游植物Margalef丰富度指数、Shannon-Weaver多样性指数和Pielou均匀度指数平均值分别为2.75、1.78和0.46。Shannon-Weaver多样性指数和Pielou均匀度指数以冬季和春季较高,秋季最低,表明冬季和春季浮游植物群落结构相对复杂,而秋季的群落结构相对简单。综合水质生物学和水体理化指标评价结果,三角湖水体为中-富营养型。     

抚仙湖浮游植物群落结构特征及多样性研究

为了了解抚仙湖浮游植物群落结构特征,于2014年9月(秋季)、2014年12月(冬季)、2015年3月(春季)以及2015年7月(夏季)对抚仙湖进行采样,在全湖共设置12个样点,通过野外调查及实验室研究的方法,对抚仙湖浮游植物群落结构及物种多样性进行了分析。结果表明,抚仙湖共有浮游植物8门、66属、101种,种类构成比例中,绿藻占54.46%、硅藻占21.78%、蓝藻占9.90%、其他13.86%;不同季节浮游植物的种类组成差异极显著(P0.01),夏季种类最多,有79种,冬季最少,仅有61种。优势度分析显示,抚仙湖共有优势种4门、13种,其中绿藻门最多,有8种,且在全年均形成优势种,蓝藻在夏季、秋季和冬季成为优势种,硅藻和金藻在春季和夏季形成优势种。抚仙湖浮游植物细胞密度为29.9×104~193.2×104个/L,平均为61.51×104个/L;生物量为0.242~0.567 mg/L,平均为0.455 mg/L。浮游植物Margalef丰富度指数为2.31~3.18,Shannon-Weaver多样性指数为3.14~3.65,Pielou均匀度指数为0.89~0.95,综合评价抚仙湖水体为无污染至轻污染。聚类分析表明,抚仙湖浮游植物的种群结构四季变化明显,不同区域浮游植物的种类和密度差异较大。将抚仙湖浮游植物与国内外典型的贫营养湖泊进行相似性比较,Jaccard相似性指数表明,抚仙湖浮游植物群落与其他湖泊均为极不相似,说明其物种及群落结构具有一定的独特性。     

２０１１年春秋季大渡河河口浮游植物群落结构特征研

对大渡河河口春秋季的浮游植物群落结构特征进行了调查,共采集到浮游植物6门、53属、157种;其中,硅藻种类最多,共109种,占总数的69.43％,其次是绿藻和蓝藻.左侧汊河和青衣江浮游植物种类较多.优势度分析显示,大渡河河口浮游植物优势种季节演替明显.浮游植物平均密度和生物量分别为469 040个/L和0.9051mg/L,均以硅藻最高.浮游植物密度春季高于秋季,生物量则春季低于秋季,青衣江浮游植物密度和生物量较干流低.大渡河河口多样性指数春季平均为3.1728,秋季平均为3.3547;均匀度指数春季平均为0.5300,秋季平均为0.5749.秋季浮游植物多样性指数和优势度均高于春季,青衣江两指标均较干流低.     

三角帆蚌养殖池塘浮游植物群落时空动态及其多样性指数

通过对某一套养有青鱼、鲢和草鱼的2.4 hm2三角帆蚌（ Hyriopsis cumingii）养殖池塘2011-2012年的水质和浮游植物调查,分析了浮游植物群落的时空动态,同时运用细胞密度及群落多样性指数等进行了水质综合评价。调查结果显示,浮游植物群落组成中绿藻44.07％,其次是硅藻（16.95％）;浮游植物群落结构、密度及生物多样性指数都具有明显的季节和月份变化特征。绿藻种类数在秋季最多,硅藻种类数在冬季和春季最多,而蓝藻种类数在夏秋季最多,隐藻种类数在秋季最多;浮游植物细胞密度秋季＞春季＞夏季＞冬季。4月份密度最大,达21.12×106 cells/L,其次是11月份,达到13.68×106 cells/L;整个冬季和春季的3月份浮游植物密度偏低;11次采样获得的 Shannon -Wiener 指数（ H′）与 Simpson 指数（ D ）、 Pielou 指数（ J ）的相关性系数分别达0.934、0.858,说明都具有显著相关性。综合浮游植物细胞密度、多样性指数及污染程度指示种类分析结果,说明该养殖水体处于中污状态。本研究对于利用浮游植物监测三角帆蚌养殖池塘水质综合状况及进行生态评价提供了依据。     

淮河流域西淝河浮游植物群落结构特征

为探究淮河流域西淝河浮游植物群落结构特征及其与环境因子的关系,在2016年和2017年冬季(2月)、春季(4月)、夏季(8月)和秋季(11月)对淮河流域西淝河浮游植物群落结构特征进行研究。结果显示,共鉴定出浮游植物236种(含变种和变型),隶属于8门、103属。其中,绿藻门(Chlorophyta)最多,有37属、83种,占浮游植物物种总数的35.17%;其次为硅藻门(Bacillariophyta)28属、78种,占33.05%;蓝藻门(Cyanophyta)20属、40种,占16.95%。浮游植物群落结构组成及变化显示,蓝藻门物种的细胞密度占绝对优势,其次为绿藻门,分别占总细胞密度的57.04%、17.66%。硅藻门物种的相对生物量最大,其次为绿藻门,分别占总生物量的35.69%和28.81%,且浮游植物细胞密度与生物量均在夏季达到最大值。浮游植物细胞密度为(7.24±1.13)×10~7个/L,生物量年均值为(34.08±3.20) mg/L。Shannon-Wiener多样性指数、Margalef丰富度指数和Pielou均匀度指数为3.27～4.66、2.75～6.10和0.73～0.94。Pearson相关性与RDA分析表明,影响浮游植物群落结构的主要因子有溶解氧、水温、水生植被盖度、电导率、营养盐和透明度。研究结果可为揭示淮河流域浮游植物群落结构特征提供基础理论依据。     

新疆乌伦古湖春、秋季浮游植物群落结构的聚类和多维分析

2007年4月和8月对乌伦古湖浮游植物进行了调查。经鉴定,调查区域内浮游植物共计8门172种(含未定种)。其中绿藻门74种(含未定种),硅藻门50种(含未定种),蓝藻门27种(含未定种),其他种类占12.2%。4月浮游植物平均细胞密度和生物量分别为33.49×104ind/L和0.4552mg/L;8月分别为276.28×104ind/L和3.6578mg/L。依据浮游植物物种组成和细胞密度,利用Bray-Curtis相似性测定,对浮游植物群落结构进行聚类(Cluster analysis)和多维(Multidimensional scaling,MDS)分析。结果显示,春、秋季布伦托海浮游植物群落结构聚为两大类,吉力湖聚为三大类;由于各采样点的水深、水温、pH值、透明度等环境因子的差异导致浮游植物群落结构发生变化,采用聚类和多维分析,有效地揭示了乌伦古湖春、秋季各采样点间浮游植物群落结构的相似性;多维分析与聚类分析结果一致,从二维空间角度证实了聚类结论。乌伦古湖属高纬度地区水体,春、秋两季出现以硅藻为优势类群的浮游植物群落类型;结合乌伦古湖浮游植物的优势种、数量和生物量的检测结果,该湖属于贫-中营养型湖泊。本研究旨在群落结构层面探讨春、秋季乌伦古湖浮游植物的变化规律,为今后进一步合理利用该湖丰富的水生生物资源提供科学依据。     

千岛湖浮游植物群落结构时空分布及其与环境因子的关系

研究千岛湖浮游植物群落结构特征及其与主要环境因子的关联性,为了解千岛湖水环境变动规律及水环境的保护与管理提供依据。沿水流方向在水库上中下游依次设置5个采样点,2010年对千岛湖浮游植物群落开展了周年调查。共鉴定出浮游植物8门223种,其物种数、密度和生物量均主要由硅藻、蓝藻和绿藻组成。不同浮游植物门类物种数、密度和生物量组成比例站点间无显著差异;群落总密度和生物量站点间无显著差异,但有显著的季节变化,它们的垂直分布均呈现先增加后下降的趋势,在4~8 m水层具有最大值。Shannon多样性和Pielou均匀度指数在空间和季节间均无显著差异,但Margalef丰富度指数存在显著的季节和空间差异。聚类分析(CA)和多维尺度分析(MDS)表明,藻类物种组成在站点间无显著差异,但具有显著的季节变化,即分化为春季、冬季和夏秋季3种群落类型,春季群落主要特征种为颗粒直链藻及其狭窄变种和尖尾蓝隐藻,冬季为水华鱼腥藻、颗粒直链藻狭窄变种和脆杆藻,夏秋群落为网状空星藻、水华鱼腥藻和梅尼小环藻。相关性分析表明,浮游植物密度和生物量与水温、pH值、CODMn和Chl-a显著正相关,与SD和DO显著负相关;生物量与Si O2-3-Si显著正相关。典范对应分析(CCA)显示,水温、DO和NO-3-N及pH值是影响浮游植物时空分布的主要因子。     

连环湖铁哈拉泡浮游植物群落结构及其与水环境因子的关系

2021年4月(春季)、7月(夏季)、10月(秋季)和2022年1月(冬季),采用规范方法调查监测和分析受面源污染的浅水铁哈拉泡(46°30’～46°50’N,123°59’～124°15’E)浮游植物群落结构特征及其与水环境因子的关系,并对湖泡水生态保护和治理提出了建议。连环湖铁哈拉泡共鉴定出浮游植物7门66属115种及变种,绿藻门、硅藻门和蓝藻门种类优势占比较大,占总种类数的85.22%。浮游植物的总平均丰度为464.4×10⁴ind./L,总平均生物量为1.533 3 mg/L,绿藻门、硅藻门和蓝藻门丰度和生物量均高于其他门类,其中蓝藻门平均丰度(217.8×10⁴ind./L)和平均生物量(0.489 4 mg/L)均最高。铁哈拉泡浮游植物群落结构季节变化显著,春季蓝藻门、硅藻门和绿藻门为优势门类;夏季和秋季分别为蓝藻门的微囊藻(Microcystis sp.)和硅藻门中的小环藻(Cyclotella sp.)凸显出较大优势;冬季则演变为隐藻门、裸藻门、甲藻门和硅藻门共同占优势的群落结构。TSIM评价结果表明,湖泡营养状态为轻微的富营...     

沅水浮游植物群落结构特征

于2005年3、6、9、12月对沅水浮游植物群落结构进行了调查。结果表明:沅水浮游植物共计6门147种,以硅藻和绿藻为主,分别占43.53%和36.73%。浮游植物平均密度为2.21×105ind./L,蓝藻密度最大为1.33×105ind./L;浮游植物平均生物量为3.97 mg/L,蓝藻生物量最大为3.42 mg/L。浮游植物季节变化比较明显,密度秋季最大(4.64×105ind./L),夏季最小(1.6×104ind./L);生物量冬季最大(12.86 mg/L),夏季最小(0.2 mg/L)。水平分布密度和生物量均是牛鼻滩站最大,分别为6.03×105ind./L和29.6 mg/L。调查显示沅水浮游植物中巴豆叶脆杆藻、颗粒直链硅藻、钝脆杆藻、美丽星杆藻、细星杆藻、格孔单突盘星藻、泥污颤藻、铜绿微囊藻等为优势种。浮游植物Shannon-Wiener多样性指数较低,在1～2之间。指数变化由高到低分别为冬季、秋季、春季、夏季。     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven,Hemitripterus americanus

The sea raven, Hemitripterus americanus, is a sit-and-wait, low metabolic rate, marine teleost. The objective of this study was to determine i) whether cortisol implantation (50 mg. kg^-1) for 7 days altered hepatocyte metabolism, and hepatocyte responsiveness to epinephrine, glucagon and insulin, and ii) whether 8 weeks of food-deprivation modified the above response. Cortisol implantation significantly increased hepatocyte total glucose production and oxidation from alanine compared to the sham group. There was no cortisol effect on glycogen breakdown, suggesting that the activation of other pathways, including gluconeogenesis, are required to account for the increased glucose production. Epinephrine-mediated (10^-5M) glycogen breakdown and insulin-mediated (10^-8M) total glucose production were enhanced in hepatocytes of cortisol implanted sea ravens, but there were no change in any glucagon (10^-7M) effects. The enhanced glycogen breakdown in the absence of similar increases in total glucose production with epinephrine indicates mobilization of carbohydrate reserves for endogenous use by the liver. Food-deprivation for 8 weeks significantly decreased condition factor, plasma cortisol concentration and liver glycogen content in the sea raven, but had no effect on plasma glucose concentration. Hepatocyte total glucose production and flux rates from alanine increased significantly with food-deprivation. Moreover, food-deprivation increased responsiveness of total hepatocyte glucose production to the actions of glucagon and insulin, but not to epinephrine; none of these effects were modified by cortisol implantation. Our results indicate that cortisol in the sea raven exerts both a direct and an indirect or permissive effect on hepatocyte metabolism by modifying hepatocyte responsiveness to epinephrine and insulin stimulation. Cortisol implantation did not modify the effects of glucagon or food-deprivation in this species.     

Simulation and quantification of enrichment and retention processes in the southern Benguela upwelling ecosystem

Important environmental processes for the survival and recruitment of early life stages of pelagic fishes have been synthesized through Bakun's fundamental triad as enrichment, concentration and retention processes (A. Bakun, 1996, Patterns in the Ocean. Ocean Processes and Marine Population Dynamics. San Diego, CA, USA: University of California Sea Grant). This conceptual framework states that from favourable spawning habitats, eggs and larvae would be transported to and/or retained in places where food originating from enrichment areas would be concentrated. We propose a method for quantifying two of the triad processes, enrichment and retention, based on the Lagrangian tracking of particles transported within water velocity fields generated by a three‐dimensional hydrodynamic model. We apply this method to the southern Benguela upwelling ecosystem, constructing putative maps of enrichment and retention. We comment on these maps regarding main features of the circulation in the region, and investigate seasonal variability of the processes. We finally discuss the results in relation to available knowledge on the reproductive strategies of two pelagic clupeoid species abundant in the southern Benguela, anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax). Our approach is intended to be sufficiently generic so as to allow its application to other upwelling systems.     

Effects of capture,loading density and transport stress on the mortality,physiological responses,bacterial density and growth of rohu <Emphasis Type="Italic">Labeo</Emphasis><Emphasis Type="Italic"> rohita</Emphasis> fingerlings

This study evaluated the effects of three levels of loading density (200, 300 and 400 g L⁻¹) and four levels of duration (1, 3, 6 and 9 h) on the mortality, plasma cortisol and chloride levels and growth of rohu Labeo rohita fingerlings in a transport simulation. While total immediate mortality was low (4–12%), delayed mortality was high (27–49%). Initial capture and handling were found to constitute the most stressful phase as indicated by elevated plasma cortisol. The levels of cortisol continued to rise at 6 and 9 h after transport, with the highest level observed at 9 h after transport. The level of plasma chloride fell after transport across all density levels and treatment durations. Specific growth rate (SGR, %/day) and total bacterial density (cfu/g) were not different between and within treatments, and between treatments and the controls. This study demonstrates that transport has a profound effect on the stress responses of rohu fingerlings. Although the level of immediate mortality was low, the higher level of delayed mortality has serious implications in terms of production inefficiency for grow-out farmers.     

The effects of introduced tilapias on native biodiversity

• 1. The common name ‘tilapia’ refers to a group of tropical freshwater fish in the family Cichlidae (Oreochromis, Tilapia, and Sarotherodon spp.) that are indigenous to Africa and the southwestern Middle East. Since the 1930s, tilapias have been intentionally dispersed worldwide for the biological control of aquatic weeds and insects, as baitfish for certain capture fisheries, for aquaria, and as a food fish. They have most recently been promoted as an important source of protein that could provide food security for developing countries without the environmental problems associated with terrestrial agriculture. In addition, market demand for tilapia in developed countries such as the United States is growing rapidly.
• 2. Tilapias are well‐suited to aquaculture because they are highly prolific and tolerant to a range of environmental conditions. They have come to be known as the ‘aquatic chicken’ because of their potential as an affordable, high‐yield source of protein that can be easily raised in a range of environments — from subsistence or ‘backyard’ units to intensive fish hatcheries. In some countries, particularly in Asia, nearly all of the introduced tilapias produced are consumed domestically; tilapias have contributed to basic food security for such societies.
• 3. This review indicates that tilapia species are highly invasive and exist under feral conditions in every nation in which they have been cultured or introduced. Thus, the authors have concluded that, despite potential or observed benefits to human society, tilapia aquaculture and open‐water introductions cannot continue unchecked without further exacerbating damage to native fish species and biodiversity. Recommendations include restricting tilapia culture to carefully managed, contained ponds, although exclusion is preferred when it is feasible. Research into culture of indigenous species is also recommended.

Copyright © 2005 John Wiley & Sons, Ltd.