氟苯尼考对鲁氏耶尔森氏菌体外药效研究

本文研究了氟苯尼考对鲁氏耶尔森氏菌(Yersinia ruckeri)体外药效学,测定了最小抑菌浓度(MIC)、最小杀菌浓度(MBC)、生长动力学曲线和杀菌动力学曲线和抗菌后效应(PAE)及四种培养因子对氟苯尼考体外抑制鲁氏菌活性的影响。结果表明:MIC、MBC和MBC/MIC分别为0.5μg.mL-1、1μg.mL-1和2;鲁氏菌在液体培养基中1h后进入对数生长,大约持续7h;在用药4～6 h达到最大药效。由杀菌曲线可知,氟苯尼考的杀菌功效具有浓度依赖性;在2 MIC、4 MIC和8 MIC时,PAE分别为3.71±0.11、4.54±0.27和5.52±0.23;氟苯尼考对鲁氏菌作用最适pH值为6～8,且二价阳离子(Mg2+)、血清含量及细菌数量小于108时对药效无显著影响。因此,保证药物浓度和作用时间,并配合最适培养条件,是氟苯尼考发挥最高药效的前提条件。     

恩诺沙星控制嗜水气单胞菌性鲫败血症的防耐药用药方案

为了合理地使用抗生素,制定防止耐药菌产生的用药方案,本研究利用近年来提出的防耐药突变浓度(MPC)和耐药选择窗(MSW)这两个药效学(PD)参数,并结合药代动力学(PK)参数,制定恩诺沙星防耐药突变用药方案,控制由嗜水气单胞菌引起的鲫细菌性败血症.研究结果显示,恩诺沙星对该致病性嗜水气单胞菌的体外药效学参数为:最小抑菌浓度(MIC)为0.125μg/mL;2MIC、4MIC、8MIC的抗菌后效应(PAE)分别为(1.67±0.42) h、(2.03±0.17) h、(2.38±0.06) h; MPC为1.125μg/mL; MSW为0.125~1.125μg/mL.根据鲫(Carassius auratus)口灌恩诺沙星后的药代动力学曲线,得出血浆药物浓度>MPC的时间分别为5 h、9.5 h、23 h.PK/PD综合参数:24 h内血药浓度-时间曲线下面积与MIC的比值(AUC24/MIC)分别为137.22、285.15、426.25;峰浓度与MIC的比值(Cmax/MIC)分别为15.05、41.43、52.32.综合血浆药物浓度>MPC的时间超过(24-PAE)h、AUC24/MIC≥100或Cmax/MIC>8的指标,建议恩诺沙星在控制由嗜水气单胞菌引起的鲫细菌性败血症时的给药方案为:给药剂量20 mg/kg体质量,1次/d.根据肌肉内恩诺沙星的药动学方程,药残达到国家限量标准所需时间约为25 d,所以建议休药期不低于25 d.本研究方案也可广泛用于其他水产养殖抗菌药物的防耐药突变用药方案的制定.     

体外药动模型中强力霉素对嗜水气单胞菌的药效研究

为保证强力霉素(doxycyline)在防治水产动物疾病上的合理应用,通过建立强力霉素体外药动-药效同步(PK-PD)模型的方法,研究了强力霉素的药物动力学和抑制嗜水气单胞菌(Aeromonas hydrophila)的药效学之间的关系.结果显示,强力霉索对嗜水气单胞菌的最小抑菌浓度( MIC)和最小杀菌浓度(MBC)...     

冬凌草甲素对嗜水气单胞菌体外抑菌效果及作用机制

通过测定冬凌草甲素对嗜水气单胞菌的最低抑菌浓度(minimum inhibitory concentration, MIC)、最低杀菌浓度(minimum bactericidal concentration, MBC)和对细菌生长的影响,及其对菌体形态、电导率、乳酸脱氢酶(lactate dehydrogenase, LDH)活性、蛋白质和DNA的影响,探究冬凌草甲素对耐药性嗜水气单胞菌的体外抑菌作用及其机制。结果显示,冬凌草甲素对嗜水气单胞菌具有明显抑制作用,MIC为256μg/mL,MBC为512μg/mL。当2MIC浓度的冬凌草甲素作用于嗜水气单胞菌CW株8、16 h后,菌体变形,细胞壁和细胞膜分离,细胞质空化。与对照组相比,药物组菌悬液的电导率显著升高,并且在冬凌草甲素作用6 h后达到5.66%。冬凌草甲素作用8 h后嗜水气单胞菌的LDH活性降低了20.8%,可溶性蛋白含量显著降低。DAPI染色结果显示,药物组荧光密度和强度均较对照组弱。DNA外渗量结果显示,较对照组上升了(29.32±1.02) mg/L。研究表明,冬凌草甲素对嗜水气单胞菌具有较强的抗菌作用,主要通过增加细胞膜的通透性,干扰蛋白质代谢进而抑制细菌的生长繁殖。     

恩诺沙星控制草鱼维氏气单胞菌的用药方案

从四川成都一养殖场大规模发病死亡的草鱼(Ctenopharyngodon idella)病灶处分离一株病原菌CiAV01,结合形态学和16S rDNA序列分析,鉴定该菌为维氏气单胞菌(Aeromonas veronii)。回归感染实验结果表明,分离菌株感染草鱼致死率为100%,出现了局部出血、腹腔积水等症状。采用琼脂平板扩散法研究了16种抗生素对分离菌株CiAV01的体外抑菌作用,在供试的抗生素中,恩诺沙星对该分离菌株CiAV01最为敏感。选择恩诺沙星对分离菌株进行体外药效学研究表明,恩诺沙星对分离菌株CiAV01的最小抑菌浓度(MIC)为0.25μg/mL,最小杀菌浓度(MBC)为0.50μg/mL,MBC/MIC为2。结合其药物动力学参数和MIC、MBC、防突变浓度(MPC)、突变选择窗(MSW)和抗菌后效应(PAE)制定防突变给药方案为:剂量20 mg/kg、每日一次给药、连续给药3～5 d。     

秦皮素的抑菌作用及其对嗜水气单胞菌毒力的影响

为探讨中草药单体秦皮素对嗜水气单胞菌(Aeromonas hydrophila)生长和毒力的影响,实验测定了秦皮素对嗜水气单胞菌最低抑菌浓度(MIC)、生长曲线、生物膜以及脂肪酶活性、运动性、蛋白酶活性和溶血性等毒力相关因子的影响。结果表明,秦皮素对嗜水气单胞菌具有明显的抑制效果, MIC为128μg/mL;秦皮素浓度大于16μg/mL时,对嗜水气单胞菌的生物膜形成有显著促进作用(P0.05);秦皮素浓度大于8μg/mL时,对嗜水气单胞菌的脂肪酶活性有显著降低作用(P0.05);秦皮素浓度为2～8μg/mL时,对嗜水气单胞菌的运动性和溶血性无显著影响(P 0.05),但能降低嗜水气单胞菌蛋白酶活性(P0.05)。秦皮素对嗜水气单胞菌有一定的抑菌作用,但期望通过低浓度秦皮素实现对嗜水气单胞菌的防治仍有待进一步研究。     

氟苯尼考对六种海洋致病弧菌的体外抗菌活性研究

测定了氟苯尼考等4种抗菌药对6种常见海洋致病弧菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC)。测试结果显示,氟苯尼考对6株弧菌的MIC值范围为2～4μg／mL,氯霉素为1～32μg／mL,土霉素为4～128μg／mL,恩诺沙星为0．125～1μg／mL;对多数弧菌氟苯尼考与氯霉素的抗菌活性相似。氟苯尼考对6株弧菌的MBC／MIC值范围为2-4,而氯霉素为2～16,表明氟苯尼考的杀菌效果优于氯霉素。对照药物恩诺沙星、土霉素的MBC／MIC值分别为1-2和2-8,恩诺沙星显示出优良的抗菌和杀菌活性。随着接种菌量增加,所测3种抗菌药的MIC随之升高;当接种量达到10^7ufu／mL时．药物对多数弧菌显示出微弱的作用。     

黄河鲤嗜水气单胞菌的分离、毒力及用药分析

自发病黄河鲤4种组织中分离致病菌,结合形态学和16SrDNA序列分析,发现分离到的细菌属气单胞菌属。回归感染试验发现,患病鱼体出现鳃盖等多处组织出血且伴随肠炎等症状,表明引起黄河鲤发病的致病菌为嗜水气单胞菌,命名为HNAh01。半致死密度测定发现,嗜水气单胞菌HNAh01的半致死密度为1.38×10~7 cfu/mL。药敏结果表明,该致病性嗜水气单胞菌是典型的多重耐药嗜水气单胞菌,但对恩诺沙星极为敏感。因此,选择恩诺沙星对分离菌株进行体外药效学和用药分析试验。药效学试验表明,恩诺沙星对嗜水气单胞菌HNAh01的最小抑菌质量浓度为1.56ng/mL,最小杀菌质量浓度为3.12ng/mL,防耐药突变质量浓度为12.5ng/mL,耐药选择窗的范围为1.56~12.5ng/mL。用药分析结果显示,黄河鲤口服剂量为10mg/kg时对嗜水气单胞菌HNAh01的相对保护率达83%。本文研究为嗜水气单胞菌的防治提供了理论基础与实践依据。     

替米考星对水产致病菌体内外抗菌和对异育银鲫毒性作用

研究替米考星对3种水产致病菌体外抗菌作用,替米考星对嗜水气单胞菌(Aeromonas hydrophilia)感染异育银鲫的防治效果和替米考星对异育银鲫的急性毒性作用。应用二倍稀释法研究质量浓度为0.125、0.25、0.5、1、2、4、8、16、32、64、128 mg/L的替米考星对嗜水气单胞菌(Aeromonas hyolrophila)、温和气单胞菌(Aeromonas sobria)和鳗弧菌(Vibrio anguillarum)的最小抑菌浓度(MIC)和最小杀菌浓度(MBC),并计算MBC/MIC比值。腹腔注射0.3 m L浓度为9×10~8CFU/m L的嗜水气单胞菌菌液感染体质量为(217.65±25.26)g的异育银鲫,分别在感染后1、24和48 h以0、50、100、150 mg/kg鱼体重的剂量分别口灌替米考星,计算替米考星对嗜水气单胞菌感染异育银鲫的保护率。应用剂量为0、260、300、340、387、440 mg/kg的替米考星口灌异育银鲫,记录异育银鲫的死亡率,计算替米考星对异育银鲫的半数致死量LD_(50)。结果表明,替米考星对嗜水气单胞菌、温和气单胞菌和鳗弧菌的MIC分别为4.00、0.50和1.00mg/L,MBC分别为64、32和32 mg/L,MBC/MIC比值分别为16、64和32;100和150 mg/kg鱼体重剂量的替米考星对嗜水气单胞菌人工感染异育银鲫的保护率可达100%;替米考星对异育银鲫口灌的24、48、72和96 h的半数致死剂量LD_(50)分别为344.0、306.3、298.5和298.5 mg/kg。替米考星对3种水产致病菌具有一定的体外抗菌效果;替米考星对嗜水气单胞菌感染的异育银鲫具有一定的保护作用;但同时替米考星对异育银鲫也具有中等毒性。本研究可为替米考星在水产养殖中的合理使用提供参考。     

氟苯尼考在鲫和草鱼体内的药代/药效动力学联合参数及其临床给药方案的研究

为研究氟苯尼考在鲫和草鱼体内的药代学、药效动力学联合参数,并制定氟苯尼考对鲫、草鱼的精确用药方案,本实验结合氟苯尼考对致病性嗜水气单胞菌CAAh01的体外药效学研究和口灌不同剂量的氟苯尼考在鲫、草鱼体内药代动力学研究,确定了氟苯尼考防治该致病菌引起的鲫和草鱼细菌性败血症的给药方案。研究结果显示,氟苯尼考对CAAh01菌株的最小抑菌浓度(MIC)为0.5μg/mL,最小杀菌浓度(MBC)为1.0μg/mL,防细菌耐药突变浓度(MPC)为6.0μg/mL,防耐药突变选择窗(MSW)为0.5~6.0μg/mL。按10、20、30 mg/kg体质量剂量对鲫、草鱼口灌氟苯尼考后,在鲫体内,血药浓度大于MPC的维持时间分别为5、8、24 h;AUC24/MIC分别为177.06、265.90、426.50;Cmax/MIC分别为15.59、21.32、31.24。在草鱼体内,血药浓度大于MPC的维持时间分别为0、0、3 h;AUC24/MIC分别为38.60、75.08、121.94;Cmax/MIC分别为4.75、10.08、19.99。研究表明,综合血药浓度维持MPC以上的时间、AUC24/MIC或Cmax/MIC指标,氟苯尼考适用于鲫细菌性疾病的防治,其防突变用药方案为剂量30 mg/kg,每日1次给药,休药期不低于20 d。对于草鱼细菌性疾病的防治,氟苯尼考不宜连续使用。     

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.