赤点石斑鱼人工繁殖试验

赤点石斑鱼（Epincphelusakaara）是名贵的海水经济鱼类之一，因其肉质爽滑、味道鲜美，深受消费者的欢迎。近年来，由于受到近岸海水污染，滥捕的影响，赤点石斑鱼已很少捕获，在我省沿海已接近绝种的边缘。开展对赤点石斑鱼人工繁殖，拯救该鱼类，已是水产业界的当务之急。近十多年来，各国水产工作者也十分重视，对赤点石斑鱼进行过人工繁殖，并获得成功，     

赤点石斑鱼人工繁殖和仔鱼培育试验

赤点石斑鱼(Epinephelus akaara)是名贵海洋经济鱼类，活石斑鱼畅销于港澳市场。近年来福建、广东和浙江沿海渔民大力发展石斑鱼钓渔业，以活鱼外销，为国家创汇。随着我国海水增养殖业日益发展及香港企业化网箱养殖石斑鱼，对赤点石斑鱼需求量与日俱增，出现苗种供不应求局面。目前，天然种苗已不能满足生产的需求，因此开展石斑鱼人工繁殖势在必行。     

赤点石斑鱼的病害及其防治的初步研究

赤点石斑鱼(Epinephelus akaara)是经济价值很高的名贵海产鱼类。近几年来,广东、福建、浙江等省除暂养出口外,尚大力发展网箱养殖,开展人工繁殖研究。在生产与试验中,鱼病成了一个突出的问题。有关石斑鱼的病害,Yamaguti(1934,1935,1941,1965,1970),汪溥钦(1984,1986)等曾做过研究,但多偏重于病原体的分类方面,对鱼病则研究得很少,尤其是防治方面。黄琪琰等(1981)报导了石斑鱼的白斑病及其防治,欧瑞木等(1987)记载了石斑鱼的病害及防治。除外,新加坡、香港也有过一些报道。 1984年以来,作者就赤点石斑鱼的病害进行调查,并开展防治试验,先后发现有烂尾病、隐核虫病、鳞盘虫病及鱼虱病等10余种病害,可引起石斑鱼严重死亡或影响鱼的生长。现将初步结果报告于下。     

17α-甲基睾酮对赤点石斑鱼性逆转的影响

采用腹部埋植方式,用17α-甲基睾酮(17-αMT)以10mg.kg-1剂量处理2龄雌性赤点石斑鱼(每4周埋植1次,共埋植2次),检查埋植前后性腺结构、血清中性类固醇激素水平以及脑和性腺芳香化酶活性的变化。结果显示:一次埋植17-αMT即可诱导赤点石斑鱼发生不同程度的性逆转,性腺成熟系数(GSI)明显下降,性腺中卵细胞退化,精原细胞增殖,出现大量精母细胞和精子细胞,性逆转雄鱼精巢的组织结构与正常雄鱼精巢相似,部分鱼转变为功能性雄鱼,经轻微的腹部挤压可排精,精子活力与正常雄鱼相似。赤点石斑鱼埋植17-αMT后前脑、中脑的芳香化酶活性明显提高而后脑的芳香化酶活性降低,但性腺芳香化酶活性无显著变化。埋植17α-MT后第4周血清中11-酮基睾酮(11-ketotestosterone,11-KT)浓度显著升高,而睾酮(testosterone,T)和雌二醇(estradiol-17,βE2)浓度变化不显著。这些结果表明,脑部芳香化酶活性的显著升高与性逆转密切相关,17-αMT主要通过提高血清中11-KT水平诱导赤点石斑鱼发生性逆转。     

赤点石斑鱼人工育苗的初步研究

<正> 赤点石斑鱼Epinephelus akaara(Temminck et SchIegel)广东俗称红斑,分布于我国南海和东海南部,是我国南方沿海地区主要网箱养殖鱼类之一。由于还未掌握人工育苗方法,在以往的网箱养殖生产中,全靠天然鱼苗。研究解决赤点石斑鱼人工繁殖与育苗问题,已列为重要攻关课题之一。各有关水产单他相继开展对此课题的研究。许波涛等1983     

赤点石斑鱼雄性性腺及性转变的研究

赤点石斑鱼Epinephelus akaara(Temminck et Schlegel)是名贵的海产经济鱼类，近年来因钓捕过度，资源日趋衰退。为了开展赤点石斑鱼人工增养殖，我们进行了繁殖生物学的研究。S．M．Tan和K．S．Tan(1974)报道了巨石斑鱼(Epinephelus tauvina)雌雄同体现象，曾文阳(1982)对赤点石斑鱼性转变年龄作过描述，     

赤点石斑鱼低盐养殖技术

<正>赤点石斑鱼俗称红斑、鲙鱼,近年来已成为我国海水网箱养殖的一种重要鱼类。尽管网箱养殖石斑鱼优点很多,但是仍然存在着养殖过密、海区污染严重,以及病害严重,特别是赤点石斑鱼被鱼虱寄生而发病致死,造成养殖户经济损失惨重。同时,随着温室效应的不断加剧,扩大了江河入口的湖泊沼泽等低盐水环境,因此,海水养殖石斑鱼并不是唯一理想的养殖方式。但鱼虱等多种海水寄生虫在低盐环境中不易存活,进行低盐养殖石斑鱼的试验研究具有生产上的实际意义。目前已有学者在赤点石斑鱼成鱼对盐度范围11~41适应性方面与盐度对受精卵发育的影响做     

赤点石斑鱼胚胎及仔鱼发育的初步观察

赤点石斑鱼(Epinephelus akaara)是我省近年来发展起来网箱养殖的主要海洋经挤鱼类。为了解决苗种问题，我所从1985年开始进行人工繁殖的研究，但偏重于解决人工繁殖技术上的问题。     

赤点石斑鱼低盐养殖技术研究

<正>赤点石斑鱼俗称红斑。目前,国内外的许多学者已经对多种海水鱼类,例如大黄鱼、美国红鱼、红笛鲷、黑鲷苗种等慢慢地引进低盐水域养殖,并且取得了较好的经济效益。但就赤点石斑鱼而言,早期福建省进行过盐度对赤点石斑鱼受精卵发育的影响及仔鱼活力的判断的研究,并未对低盐驯养苗种养殖情况进行分析。本次总结了     

石斑鱼娇贵难养 廿多年未能突破

全国首届＂石斑鱼类繁育与养殖产业化论坛＂分量足,三院士齐亮相。我国从20世纪80年代开始进行青石斑鱼和赤点石斑鱼的人工繁殖试验,但到目前为止,成活率一般很难突破10%,未能实现苗种的规模化生产,成鱼人工养殖成活率也只有40%。12月19—21日,首届＂石斑鱼类繁育与养殖产业化论坛”在中山大学召开，     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

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 performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

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.     

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).