厚壳贻贝人工繁殖技术的研究

厚壳贻贝(Mytilus coruscus)是我国贻贝的主要养殖品种,其苗种主要依靠天然苗种和半人工采苗获得。2006年浙江海洋学院于嵊泗县石柱育苗厂,首次突破了厚壳贻贝规模化全人工繁殖和稚贝海区中间培育技术。研究结果表明,厚壳贻贝亲贝通过室内强化培养,经人工催产可获得成熟受精卵,受精率可达95%。在水温16℃时,受精卵在受精后25min出现第一极体,受精后39h50min发育至直线绞合幼虫期,胚胎孵化率达92%,在水温15.8～21℃的条件下,经39d室内人工培育,获平均壳长0.694mm的附着稚贝1304.7×104ind;附着稚贝经102d海区中间培育,获平均壳长13.95mm的稚贝404.46×104ind,海区保苗成活率达31%。该研究结果为今后厚壳贻贝大规模苗种生产奠定了重要理论和技术基础。     

葡萄牙牡蛎工厂化人工育苗技术

葡萄牙牡蛎工厂化人工育苗技术包括亲贝促熟、饵料培养、幼虫和稚贝培育等过程。葡萄牙牡蛎受精卵卵径约60μm,在水温25.3℃、盐度26.5及p H8.2条件下受精卵经过16h左右发育为D形幼虫;幼虫经14~21 d培育进入变态附着期,幼虫培育过程投喂饵料为金藻、小球藻、角毛藻和骨条藻,稚贝加投扁藻;采用聚丙烯塑料片作为幼虫变态附着的附苗器。同时筛选出葡萄牙牡蛎受精卵孵化及幼虫生长的适宜环境条件,并进行了不同饵料投喂效果及不同附苗器的附苗效果试验。     

长肋日月贝个体发生观察及人工育苗初步试验

首次报道了长肋日月贝( Amusium pleuronectes )的诱导产卵及幼虫、稚贝培育.用阴干-流水刺激法,成功诱导亲贝产卵、排精.对胚胎和幼虫发生进行了观察.水温23.0～25.0℃,经诱导产卵的受精卵20 h可发育至D形幼虫.水温22.0～24.0℃时,D形幼虫经11 d培育到眼点幼虫期.投放附着基后,眼点幼虫在10 d内附着完毕.水温18.0～24.0℃时,稚贝经30 d培育平均壳长达(2.0±0.18)mm.此试验共培育壳长(2.93±1.15)mm稚贝49.6万粒.     

墨西哥湾扇贝选育系早期发育与生长

在水温28~29℃、盐度24~25条件下,研究墨西哥湾扇贝(Argopecten irradians concentricus)选育系的早期发育及幼虫和稚贝的生长。受精卵经50 min发育至卵裂,经22~24 h发育至D形幼虫,经11 d发育至眼点幼虫并出现足,进入附着变态阶段。选育系的胚胎发育时间和浮游幼虫前期壳长、壳高与对照系比较差异不显著(P0.05);浮游幼虫后期及至附着变态阶段,选育系与对照系的壳长和壳高差异显著(P0.05)。选育系的附着变态率和存活率与对照系比较均差异显著(P0.05),且优势明显。本研究表明,墨西哥湾扇贝浮游幼虫发育前期缓慢,幼虫后期、稚贝期生长迅速;壳长和壳高的生长速度不同步,幼虫前期壳长生长快于壳高,后期壳高生长快于壳长,并于第28~30天时壳高超过壳长。墨西哥湾扇贝选育系在幼虫和稚贝阶段生长速度明显快于对照系,具有明显的生长优势及生长潜力。     

脉红螺附着变态与食性转换的研究

为实现脉红螺苗种的规模化生产,本实验通过对脉红螺幼虫培育、采苗、稚螺培育等方面的系统研究,探索了脉红螺苗种繁育过程中幼虫附着变态率低和饵料转换难的问题。结果显示:脉红螺浮游幼虫前期(0~12 d)生长较快,壳高平均日增长21.8μm;中期(13~18 d)生长较慢,壳高平均日增长3μm;后期(19~30 d)生长加快,壳高平均日增长46.8μm。用取自沉淀池中的新鲜海水对脉红螺浮游幼虫进行附着变态诱导,诱导第1天脉红螺浮游幼虫开始出现附着变态,第4天时,附着变态活动基本结束,附着变态率为40%。为变态后的稚螺投喂刚附着的长牡蛎和魁蚶稚贝,第1~8天,稚螺壳高平均日增长65.6μm;第9天开始,稚螺生长速度加快;第9~12天,稚螺壳高平均日增长136.4μm;第13~16天,稚螺壳高平均日增长307.3μm;第17~20天,稚螺壳高平均日增长445.8μm。研究表明,用取自沉淀池中的新鲜海水诱导脉红螺浮游幼虫的附着变态效果好,刚附着的长牡蛎稚贝和魁蚶稚贝可以作为脉红螺稚螺培育阶段的适宜饵料。     

底物大小对牡蛎幼虫附着的诱导效应

为探讨底物大小对牡蛎幼虫附着的诱导效应,设计底物大小和实验环境(室内和野外)的双因子随机区组实验,检验3种规格实验底物(A:5 cm长×5 cm宽×3 cm厚、B:10 cm长×10 cm宽×3 cm厚、C:15 cm长×15 cm宽×3 cm厚,以下简称A、B、C)、实验环境以及他们之间的互作对牡蛎幼虫(室内实验:长牡蛎Crassostrea gigas;野外实验:熊本牡蛎C.sikamea)附着效果(密度和壳高)的影响。附着实验结果显示,室内实验A组附着稚贝的平均密度和平均壳高分别为1.06个·cm~(-2)和14.10 mm,B组为5.60个·cm~(-2)和8.69 mm,C组为12.01个·cm~(-2)和4.44 mm;野外实验A组附着稚贝的平均密度和壳高分别为2.41个·cm~(-2)和17.83 mm,B组为4.65个·cm~(-2)和11.61 mm,C组为6.90个·cm~(-2)和7.43 mm。单因子方差分析结果表明,室内和野外实验中底物大小均显著影响附着稚贝的密度(P<0.001),即底物越大,稚贝附着密度越高,但壳高则相反,稚贝壳高和密度之间呈显著负相关;室内和野外的实验环境对附着稚贝密度影响不显著(P>0.05),对壳高影响显著(P<0.05)。双因子方差分析结果表明,实验环境和底物大小的交互作用对附着稚贝密度影响显著(P<0.05),对壳高影响不显著(P>0.05)。研究结果表明,在牡蛎礁生态修复中,选择适合的底物大小能显著提高牡蛎附着效果。     

宽壳全海笋人工繁育技术

2003-2005年,进行了宽壳全海笋繁殖的初步观察和人工育苗技术研究.通过观察,揭示了宽壳全海笋繁殖和胚胎发育的整个过程.利用实验生态学的方法,筛选出了受精卵孵化、幼虫生长和采苗的适宜环境条件.在浙南沿海,宽壳全海笋的自然繁殖时间是每年的4-6月份,水温为18～22 ℃.壳长6 cm以上的雌性成熟个体1次产卵可超过2 000万颗,成熟卵的卵径约50 μm.受精卵发育最适宜的温度是22～26 ℃,盐度21～26,在适宜条件下经过18 h左右发育至D形幼虫.幼虫生长发育的最适宜的温度范围是22～26 ℃,而盐度范围为16～26;幼虫前期培育的最适宜饵料为球等鞭金藻;经26～50 d培育幼虫进入变态附着期.幼虫变态附着最适宜的基质为泥底质.2005年度,在面积120 m2水池中,培育出宽壳全海笋稚贝数量6 100万颗,单位面积出苗量5.08×105 grain/m2,平均壳长1.43 mm.     

波纹巴非蛤人工育苗技术初探

2008年～2009年,对波纹巴非蛤人工繁殖、胚胎发育、幼体开口饵料、幼虫变态附着和稚贝培育技术等进行研究,人工育苗获得成功。结果表明,在自然水温29.6℃～23℃,盐度28～34,pH值7.8～8.4,溶解氧4～7mg/L的生境下,受精卵约17h发育成"D"形幼虫,第6～7d,幼虫个体大小180μm×165μm(壳长×壳高),开始变态附着。经约80d人工培育,共获得壳长3.4mm～15mm的波纹巴非蛤稚贝21.6万粒。     

大竹蛏生产性人工繁育试验

2007年对大竹蛏进行了生产性人工繁育试验。对亲本不同批次催产效果、不同规格亲本产卵差异、孵化密度进行了比较,研究了D形幼虫发育与温度的关系以及幼虫发育各阶段生长规律等,结果显示,大竹蛏属分批成熟、分批产卵的潜居性贝类,不同批次个体平均产卵量(36~118)×104cell,个体总产卵量294×104cell。壳长8~10 cm的亲贝产卵量大,催产效果好。受精卵适宜的孵化密度为5~10 cell/mL。在水温21~24.5℃条件下,D形幼虫经8~5 d生长,发育变态为附着稚贝。D形幼虫壳长日生长33.33±4.22μm,1 mm前的稚贝壳长日生长108.33±22.57μm,1~10 mm的稚贝平均旬生长量2.12 mm,10.4~30.6 mm的苗种平均旬生长量为2.02 mm。当水温下降到15℃后,大竹蛏苗种生长滞缓。2007年培育出壳长11.52±0.27 mm的稚贝2 165×104cfu,平均成活率12.1%。     

中国蛤蜊生产性人工育苗试验

2016～2017年,对中国蛤蜊(Mactra chinensis)生产性人工育苗技术进行了试验研究,2016年培育出平均壳长3.5mm幼贝0.46亿粒;2017年培育出平均壳长3.8mm幼贝0.14亿粒。试验发现,中国蛤蜊在丹东近海自然海区繁殖盛期在5月中旬～6月中旬,雌雄性比约1∶1;壳长5cm左右的亲贝产卵量50万～75万粒/个,受精卵为沉性卵,卵径55μm;在水温23～24℃,盐度26‰、pH值8.0的条件下,受精卵经18h发育为D型幼虫,壳长75μm;幼虫经13～14d培育,壳长280～300μm时开始附着变态为稚贝,日生长量15.9～16.5μm;稚贝经30d培育,平均壳长可达35～38mm,平均日生长107～117μm。     

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.     

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).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

Vitamin D3 and the renal handling of phosphate in American eels

Cholecalciferol (Vitamin D₃) increased plasma inorganic phosphate concentration in American eels,Anguilla rostrata, in a dose-dependent fashion. This response was more marked in phosphate loaded fish. In control as well as phosphate loaded eels the hyperphosphatemic response to D₃ was associated with a sharp reduction in renal phosphate clearance relative to¹⁴C-polyethelene glycol (PEG) clearance. Glomerular filtration and urine flow rates were not affected by D₃. As renal phosphate clearance, even in phosphate loaded eels, never significantly exceeded that of PEG, it is suggested that D₃ reduced the relative clearance rate of phosphate by increasing renal phosphate reabsorption rather than by reducing the tubular secretion of phosphate.