虾池暂养海湾扇贝稚贝试验报告

１９９２年莱州湾畔利用虾池暂养出池 海湾扇贝稚贝１１．１５亿粒，出商品苗２．４亿粒，保苗率为２１．５％，出苗规格３～５ｍｍ，比到外地购飞商品苗提前１５～天下海养殖。     

海湾扇贝大规模虾池保苗研究简报

１９９８￣１９９９年，在４０９０亩虾池中，入池海湾贝稚贝２５９．０６亿粒，生产商品苗８５．５４亿粒，成活率３３．０２％。试验点保苗１．９２亿粒，生产商品苗成 活率５７．７３％。试验表明，虾池保苗可缩短生产周期２０－３０天，并对影响成活率的有关原因进行了分析，提出了相应的技术措施。     

大亚湾翡翠贻贝增养殖技术及效果的研究

１９９２－１９９４年在大亚湾西北部的哑铃湾开展翡翠贻贝的延绳式及筏式吊养增养殖试验，养殖面积约９．１ｈａ，总产量４０６ｔ。种苗来源中有４０％为人工培育苗，其余为天然苗。两种吊养方式的贻贝经１至１．５年的养殖，壳长可达７０－８０ｍｍ。研究结果表明，人工苗可补充天然苗的不足，延绳式为最佳养殖方法。     

渤海湾海湾扇贝早晚苗养殖效果对比

通过调查和养殖试验证明:在渤海湾内,5月中旬开始培育的海湾扇贝晚苗可以在当年10月中旬前养成至商品规格。晚苗比早苗附着杂物少、出肉率高、养殖成本低,经济效益较高.在养殖生产中使用几个批次的不同规格苗种有利于合理安排生产,有效地利用人力物力。     

中间球海胆早繁育苗技术的研究

中间球海胆的繁殖期通常为10－11月，通过生物促熟技术使其繁殖期可提前至4－5月。亲胆在18－20℃的条件下投喂自制的促熟饵粒培育，当亲胆积温达到1850℃时，即可进行人工催产，催产诱导率达80％以上。结果表明：促熟水温以18－20℃；促熟饵粒以HD－2＋海带为最佳，海胆幼虫培育成活率为87％，早繁育苗与10月份育苗相比可减少能源消耗，育苗生产成本可降低71％，经济效益显著。     

虾夷扇贝大水体人工育苗试验

５００ｍ＾３水体育出虾夷扇贝商品苗１．２亿粒。虾夷扇贝幼虫培育最适水温１４－１５℃；以金藻和扁藻投喂效果较好。     

海湾扇贝稚贝暂养技术研究

通过１９９２，１９９３年稚贝在不同条件下暂养对比得出：１９９２年虾池暂养稚贝效果最佳。稚贝自出池至分苗仅用１７天，比海上暂养少了８天，成活率达到了２５．７％，比海上成活率１３．５％提高了１２．２％，６月中旬可达商品规格，比海上提前了一个月左右。为养殖单位提供了早苗，大苗。通过两年虾池暂养结果我们认为，稚贝出库规格应在平均８００μｍ以上，网袋网目为４０－５０目，每亩稚贝投入量在２０００万个左右，每袋     

栉孔扇贝中间育成技术的研究

我国的扇贝养殖业目前主要靠人工育苗获得苗种。在人工育苗中室内幼虫培育和稚贝附着方面技术上基本过关，每米^3出池稚贝(壳高300-400微米)高达228万粒。但是，稚贝出池下海到商品苗(壳高1厘米左右)的中间育成过程中，生产技术上存在很多问题，主要表现在育成率低(一般只有5％左右)，单位水体出苗量少，仅3-5万粒／米^3。     

泥蚶苗中间培育技术研究

利用虾池进行泥蚶苗中间培育、初始培育密度100万粒／亩，平均壳长1．93mm，经过3个月的培育，长至平均壳长5．6mm，中间培育成活率为47．3％。     

罗氏沼虾早繁苗中间培育及商品虾两茬养殖技术探讨

在上海地区进行罗氏沼虾商品虾两茬养殖，关键是抓好早繁苗的中间培育和第二茬养殖用苗的囤养。采用温室保温、锅炉增温和气泵充气等技术措施对罗氏沼虾的早繁苗进行集约化中间培育，可以提前１个月，在５月１０日左右为商品虾的第一茬养殖培育出大规格虾苗。利用室外土池囤养晚苗，为第二茬养殖培育虾苗，重点应处理好饲料投喂与水质调节之间的矛盾。     

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.