红螯螯虾的繁殖与养殖技术

红螫螯虾（Ｃｈｅｒａｘｑｕａｄｒｉｃａｒｉｎａｔｕｓｖｅｎｍａｒｔｅｎｓ）属拟螯虾科，光壳虾属，俗称淡水龙虾。原生长于澳大利亚北部，为热带淡水虾类。我国自９０年代初开始引进，其有别于其它螫虾的最大特征是头胸甲前部有４条隆脊，２条位于额剑突侧沿，２条位于左右眼眶后缘。１繁殖技术１．１繁殖习性红螯螯虾个体在３０ｇ左右即达性成熟，水温在２０℃以上就开始交配产卵，在繁殖季节内可多次抱卵孵化。体重５０ｇ亲虾抱卵量约３００粒。卵粒形似粟，位于腹肢基部，共８束，每束约４０粒。随着卵粒的胚胎发育，其颜色从奶黄色…     

红螯螯虾池塘养殖与越冬试验

红螯螯虾属拟螯虾科,光壳虾属,俗称淡水龙虾。原产澳大利亚北部,个体大,生长快、食性杂。为热带淡水虾类。我国自九十年代初开始引进,其有别于其它螯虾之最大特征是头胸甲前部有４条隆脊,２条位于额剑侧沿,２条位于左右眼眶后缘。１９９７～１９９８年我们在浙江鄞县合众养殖场、石矸养鱼场进行了池塘养殖与水泥池保温越冬试验,初获成功。１条件与方法１．１养殖池：土池总面积１０．１亩,其中单养５．８亩,４口塘,混养４．３亩,３口塘。池深１～１．５ｍ,四周围栏。１．２放养前准备：清塘、培水、投放栖息物、移养水葫芦等水…     

红螯螯虾池塘生态主养试验

利用0.53 hm^2池塘试养红螯螯虾,放养体长1.5 cm红螯螯虾虾苗2万尾,收获红螯螯虾975 kg,另外收获河蟹175 kg、青虾36 kg、鲫鱼190 kg,总利润68420元。饲料系数为0.72,红螯螯虾成活率为65%。结果认为:红螯螯虾可单养,亦可与河蟹、青虾等混养;水草覆盖率80%是适宜的。     

红螯螯虾人工繁殖技术研究：II.红螯螯虾人工繁殖技术的探讨

红螯螯虾在厦门地区可以生长繁殖，其繁殖期为５－１０月份，盛期出现在６－８月份。每年自然水温上升至２６．３－２９．３℃时，受精卵孵化至稚虾需４２－４７天。用塑料编织网作为幼苗隐蔽栖息材料，投喂对虾苗在用１－２号配合饲料育效果理想。平均水温为２８℃时，由离开母体的稚虾（体长８ｍｍ）培育至体长为２－２．５ｃｍ的规格种苗，约需２５天。在正常情况下，每平方米育苗池，可生产出种苗１２３４－１９１０尾。     

红螯螯虾的室内产卵和卵发育

１９９１～１９９２年对澳大利亚北方的热带大型虾红螯螯虾ｃｈｅｒａｘｑｕａｄｒｉｎａｒｉｎａｔｕｓ在室内进行了孵化实验。６个玻璃钢水槽放养４０～１９０ｇ的性成熟红螯螯虾１０只／ｍ２，雄雌比率１：２，水温保持在２８±１℃。１９９１年采用自然光照，１９９２年控制光照。采用自然光照，每日光照不是１２小时．月产卵率为１５％；每日光照有１２小时以上，月产卵率在３５％以上。由于产卵高峰期在５～７月，故春季放养为时过晚。翌年，将光照由１２月的１０小时光照１４小时黑暗调节至２月的１４小时光照１０小时黑暗，且一直持续至７月。红螯螯虾产卵率随光照期的延长而提高，且产卵高峰期提前在３～５月，月产卵率高达５０％。５月份以后，即使水温和光照期一直不变，产卵率将直线下降。所产卵数与雌虾个体规格呈正相关。４０～１９０ｇ的雌虾平均产仔虾７．３只／克体重，卵色用于预测卵的发育期。     

红螯螯虾越冬试验

１９９７年从澳大利亚引进红螯螯虾原料,当年养成并进行井水越冬试验,采取锅炉和土暖气为越冬池增温,空压机２４ｈ充气为池水增氧,动物性饵料与植物性饵料搭配投喂,每两周大换水排污１次,池内设置隐蔽物,防治虾病等技术措施,螯虾越冬成活率８７．６０％,平均体长和体重比越冬前分别增加４．１ｃｍ和２９．６ｇ。     

崇明清水蟹与澳洲红螯螯虾高效生态混养技术

为抵御单一养殖崇明清水蟹带来的风险,开展了崇明清水蟹与澳洲红螯螯虾高效生态混养试验.以2020年上海崇东水产养殖专业合作社的混养试验为例,养殖池塘面积1 hm2,蟹种放养量12000只,产量1125 kg,澳洲红螯螯虾放养量15000尾,产量450 kg,总产值31.5万元,利润20.1万元.结果表明,采用崇明清水蟹与...     

红螯螯虾（chrtax quadricarinatus）人工繁殖试验

红螯螯虾属拟螯虾科,光壳虾属,俗称淡水龙虾,原产澳大利亚北部,个体大,生长快,食性杂,为热带淡水虾类。我国自９０年代初开始引进。１９９８年我们进行了水泥池人工繁殖试验,初获成功,现总结如下。１条件与方法１．１亲虾培育选留上年养成的成虾作繁殖之用。选择...     

澳洲红螯螯虾池塘养殖试验

红螯螯虾又名澳洲淡水龙虾，原产于大洋洲，其外形似海水中的龙虾，雄性成虾2螯足的前端有一鲜红的膜质斑块，故称红螯螯虾。该虾生存水温为5～42℃．水温20℃以下基本不生长，常见个体50～150g。为摸索红螯螯虾的生长规律，我们于2003年在吴兴区东林镇东明村进行了池塘主养澳洲红螯螯虾试验。现将试验情况总结如下。     

红螯螯虾室内产卵及其卵的发育

红螯螯虾原产于澳大利亚地区，最佳生长温度为２２～３０℃，年可产卵３～５次，６个月即可长至５０～８０ｇ，达到上市规格。生长快、易驯养是其特点。由于红螯螯虾原产于热带区域，冬季在室外不能存活，因此，成虾和稚虾必须在室内越冬。产卵主要受水温和日照时间的影响...     

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.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

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).     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

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.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.