达氏鳇（♀）×西伯利亚鲟（♂）杂交幼鱼生长特性初步研究

对野生达氏鳇（Huso dauricus）（♀）与人工养殖西伯利亚鲟（Acipenser baerii）（♂）的杂交幼鱼在人工养殖条件下的生长进行研究。结果显示：在水温14.7～16.8℃的条件下,平均全长37.43 cm、平均体重178.9 g的达氏鳇杂交种幼鱼经过80 d培育后,平均全长和平均体重分别达到51.74 cm和533.1 g。其全长与日龄呈线性关系,关系式为L=0.1683t＋10.942（R^2=0.9665）;体重与日龄呈指数函数关系,关系式为W=24.304e^0.0129t（R^2=0.9421）;体重与全长呈幂函数关系,关系式为W=0.0007L^3.4461（R^2=0.9984）,其中b大于3。结果表明：达氏鳇和西伯利亚鲟的杂交种幼鱼为异速生长类型,体重生长快于全长生长。     

达氏鳇(♀)×西伯利亚鲟(♂)杂交幼鱼生长特性初步研究

对野生达氏鳇(Huso dauricus)(♀)与人工养殖西伯利亚鲟(Acipenser baerii)(♂)的杂交幼鱼在人工养殖条件下的生长进行研究。结果显示:在水温14.7~16.8℃的条件下,平均全长37.43 cm、平均体重178.9 g的达氏鳇杂交种幼鱼经过80 d培育后,平均全长和平均体重分别达到51.74 cm和533.1 g。其全长与日龄呈线性关系,关系式为L=0.1683t+10.942(R2=0.9665);体重与日龄呈指数函数关系,关系式为W=24.304e0.0129t(R2=0.9421);体重与全长呈幂函数关系,关系式为W=0.0007L3.4461(R2=0.9984),其中b大于3。结果表明:达氏鳇和西伯利亚鲟的杂交种幼鱼为异速生长类型,体重生长快于全长生长。     

广东鲂仔幼鱼的生长特性

观测广东鲂仔鱼早期的生长特点及仔鱼开始摄食时的长度。经数理统计分析,确定幼鱼体长与日龄呈直线关系,体重与日龄、体长与体重均呈幕函数相关,此外还就幼鱼生长与水温及放养密度的关系作了探讨,初步提出幼鱼生长的最适水温范围和适宜放养密度。     

池养条件下革胡子鲶仔幼鱼摄食习性与生长的初步研究

本文报道了在人工饲养条件下革胡子鲶仔幼鱼的摄食习性和生长的研究结果。仔鱼孵出2或3日,尚残存卵黄囊时即行开口摄食。仔鱼适口的开食饵料是轮虫,随着鱼体的生长,摄食枝角类、桡足类和摇蚊幼虫的比例迅速增加。幼鱼昼夜摄食强度有一定的节律,夜间18:00～22:00时摄食强度最大。经测量和数理统计分析,确定革胡子鲶仔幼鱼的全长与日龄呈直线关系,体重与日龄和全长对体重的关系均为幂函数关系,并计算出它们相应的回归方程式。     

怀头鲇（♀）×兰州鲇（♂）杂交F1的生长特性初步研究

对怀头鲇(♀)与兰州鲇(♂)的杂交F1人工养殖条件的生长进行研究。结果显示:在水温22￣25℃条件下,平均体长(2.75±0.16)cm、平均体重(0.36±0.06)g的杂交F1幼鱼经过100d培育后,平均体长和平均体重分别达到(28.56±3.26)cm和(193.33±59.50)g。体长与日龄呈线性关系,L=0.3131t+1.4389,R2=0.9178;体重与日龄呈指数函数关系,W=0.0159L2.7664,R2=0.9148。体重与体长呈幂函数关系,关系式为W=0.0159L2.7664,R2=0.9963,其中b值接近于3,怀头鲇和兰州鲇的杂交F1幼鱼为等速生长类型,体重生长与全长生长速度相近。     

闽东北外海渔场银方头鱼Branchiostegus argentatus(Cuvier)渔业生物学初步研究

闽东北外海底层流刺网作业渔获的银方头鱼群体由Ⅰ-Ⅺ龄11个世代构成，以Ⅱ、Ⅲ和Ⅳ龄占优势；体长优势组为210-270mm，体重优势组为200-400克，体长与体重的关系W=2.1120×10-5×L2.9964，r=0.9970。初次性成熟年龄为Ⅱ-Ⅲ龄，最小性成熟个体体长为190mm，在4-8月均有产卵活动；按VonBantanffy方程拟合生长参数L∞=436.21mm，W∞=1715.05g，K=0.2357，t0=-0.9542，体重生长拐点年龄为3.702龄。     

达氏鳇１龄幼鱼生长特性的初步研究

为了解人工养殖条件下达氏鳇(Huso dauricus)的生长特性,2009年9月29日至12月24日对养殖在自然水温(13～18℃)下的1龄幼鱼进行试验研究,测量其全长和体重,应用统计软件Excel和SPSS对测量的数据进行处理分析。结果表明,在试验条件下,达氏鳇幼鱼体重瞬时增长率与水温变化有关,体重增长量和增长率随水温的降低而变慢,高峰出现在134日龄,水温为18℃;达氏鳇幼鱼的生长指标和生长常数在人工养殖条件下变化一致,平均全长30.48 cm、平均体重99.23 g的达氏鳇幼鱼经过近3个月培育后,分别达到44.54 cm和383.87 g。其全长(L)与日龄(t)的关系式为:L=2.8602t+28.395(R2=0.9759);体重(W)与日龄(t)的关系式为:W=83.571e0.2649t(R2=0.9797);体重(W)与全长(L)关系式为:W=0.0008L3.4177(R2=0.9931);其中,b>3,表明达氏鳇幼鱼为异速生长类型,体重生长快于全长生长。通过对达氏鳇幼鱼生长特性的研究,旨在掌握其人工条件下的生长规律,为养殖生产提供科学依据。     

池养条件下湖白鲑幼鱼的生长和食性的观察

池塘饲养的湖白鲑，其幼鱼的体长与日龄呈直线相关，体重与日龄，体长与体重均呈幂函数相关。此外，还对湖白鲑幼鱼做了食性的分析：湖白鲑幼鱼阶段是以动物性铒料为主的杂食性。     

罗氏沼虾第二步足的相对生长式型及其生态学意义

为探讨池塘养殖条件下罗氏沼虾(Macrobrachium rosenbergii)第二步足的相对生长生态学意义,采用生物学方法,于养殖周期内采集1 160尾罗氏沼虾(雌虾604尾,雄虾556尾),分别测定全长、体重和第二步足长,并对其第二步足的相对生长式型进行了分析。结果显示:从103日龄开始,罗氏沼虾第二步足长存在显著的性二型现象(♂♀)。在雌、雄罗氏沼虾第二步足长-体重的回归关系中,两方程的b值均显著小于3,说明体重呈负异速生长,即第二步足长生长快于体重生长。此外,雌、雄虾第二步足长-全长同样呈现出异速生长的特征,且第二步足长在拐点前、后均为正异速生长。雄虾第二步足生长在全长80.79 mm、75日龄出现生长拐点,雌虾在全长83.10 mm、89日龄出现生长拐点。无论雄虾还是雌虾,拐点之后的异速生长水平均比拐点前升高,且雄性第二步足异速生长水平大于雌性。     

池养线纹尖塘鳢仔、稚、幼鱼的食性与生长

对池养仔、稚、幼鱼的摄食与生长作了较深入研究.仔鱼的混合营养期短,仅2～3 d,并处在开食期内,开口摄食率低.5日龄仔鱼全长4.31 mm,开口饵料主要为100～150 μm轮虫:稚鱼饵料为350～800 μm裸腹溞、枝角类幼体和桡足类无节幼体,并逐渐转为枝角类为主:后期稚鱼可驯化摄食人工混合饲料.仔、稚、幼鱼具明显的昼夜摄食节率,属晚间摄食为主的昏晨摄食型鱼类.体长与日龄呈直线关系,体重与日龄呈指数函数关系,体长与体重呈幂函数关系,其曲线回归方程为W=0.0112L3.1827,b=3.1827,接近于3,属等速生长型.     

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.     

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).     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

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.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.