彭泽鲫“一年两茬”高产高效养殖模式研究

为建立彭泽鲫“一年两茬”养殖模式，在15×667 m²标准化池塘中进行养殖试验。结果显示：第一茬放养规格为130 g/尾的彭泽鲫冬片，收获成鱼规格为310 g/尾，667 m²产1395 kg;第二茬放养规格25 g/尾的彭泽鲫鱼苗，收获冬片规格130 g/尾，667 m²产617.5 kg。全年“一年两茬”养殖模式达到了667 m²产2012.5 kg,每667m²利润10192元的养殖效益，对彭泽鲫“一年两茬”养殖模式的推广和优化具有一定的参考价值。     

鲟鱼工厂化盐度驯化高效养殖试验

为进一步拓展河北省冷水鱼产业链,有效提升冷水鱼肉质品质及养殖效益,引进平均规格200 g/尾优质大规格史氏鲟鱼种,进行鲟鱼工厂化盐度驯化高效养殖试验,咸化后鲟鱼平均规格1.165 kg/尾,成活率92.3%,平均产量10.75 kg/m²;比常规养殖鲟鱼平均产量增加2.35 kg/m²,单位产值提高200元/m²,按目前市场价格估算,效益增加75元/m²,效益提高70%以上,投入产出比为1∶2.05。     

墨瑞鳕大棚水泥池养殖技术试验

为调整上海郊区的水产养殖结构,开发水产新品种,提升养殖效益,2021年在上海市郊某合作社开展了墨瑞鳕(Maccullochella peelii)大棚水泥池养殖试验。试验采用2口大棚水泥池,投放经标粗培育的平均体质量为150 g/尾的墨瑞鳕大规格鱼种,放养密度为25尾/m²,全程投喂粗蛋白质质量分数43%的海水鱼膨化饲料。经过13个月养殖,共收获墨瑞鳕商品鱼9 576 kg(单位产量13.3 kg/m³,平均规格696.2 g/尾),饲料系数为1.58,单位产值为1 030元/m³。墨瑞鳕大棚水泥池养殖试验成功,对水产养殖结构调优具有一定的借鉴作用。     

山区小水库工程化循环水养殖技术试验

利用山区小水库水位深、水质优良的特点,结合工程化循环水养殖系统生态、环保、高效的优势,开展工程化循环水养殖罗非鱼试验,在水槽中放养平均规格100 g/尾的罗非鱼1.7万尾,放养密度170尾/m²,养殖4个月,平均规格达0.85 kg/尾,平均单产138.72 kg/m²,水库的年纯收入为7.32万元,投入产出比1∶1.23。     

七彩神仙鱼工厂化养殖技术初探

为探究七彩神仙鱼工厂化养殖技术,在水温28～30℃的室内水泥池中开展了七彩神仙鱼养殖试验,放养的幼鱼全长1.5～2.0 cm,放养密度为200尾/m³。经过约120 d养殖,试验鱼全长达9.0～10.0 cm,达到商品规格。结果表明,七彩神仙鱼每年可养殖3茬,平均成活率达87.8%,平均单位水体产出达175.6尾/m³。工厂化养殖系统可全年生产运转,水质相对稳定,单位水体养殖密度较高。     

南美白对虾工厂化错季双茬高效养殖技术试验

为提高工厂化养殖综合效益,探索南美白对虾(Penaeus vannamei)错季双茬高效养殖模式,2021年在试验点开展了南美白对虾工厂化错季双茬试验示范,实施了苗种放养、饵料投喂、水质调控和病害防控等关键技术,与传统单一工厂化南美白对虾相比,错季双茬养殖模式平均产量提高11.93 kg/m²,平均售价每公斤提高34.5元,平均效益提高1 053.05元/m²,取得了良好的经济效益、社会效益和生态效益。     

大宗淡水鱼坑塘设置网箱养殖大口黑鲈试验

在河北地区采用在大宗淡水鱼坑塘中设置网箱养殖大口黑鲈(Micropterus salmoides)的模式,4月份网箱放养大口黑鲈鱼种75尾/m²,规格126～158 g/尾;10月份网箱产量41.44 kg/m²,平均规格595 g/尾,成活率92%,饲料系数1.33,利润294.48元/m²,投入与产出比1∶1.32。网箱外坑塘大宗淡水鱼鱼种平均产量11 115 kg/hm²,饲料系数为1.08。该模式当年投放大规格大口黑鲈鱼种,可当年养成,当年销售见效益。     

黄河三角洲地区拟穴青蟹盐碱水池塘养殖技术研究

为解决拟穴青蟹(Scylla paramamosain)供不应求的难题,在黄河三角洲地区开展了盐碱水池塘养殖拟穴青蟹的试验。试验准备了3个2 000 m²的盐碱水池塘,共放养4 500只幼蟹,经122 d养殖,收获青蟹488.25 kg,平均产量2 441 kg/hm²,养成后青蟹的平均体重为311 g,最大体重为396 g。     

台湾鳗鳅一年两茬养殖试验

为有效提高淡水养殖池塘利用率,结合台湾鳗鳅生长速度快的优势和市场需求,2021年4月19日-10月23日,开展台湾鳗鳅一年两茬养殖试验,试验组平均产量41 985 kg/hm²,平均产值68.33万元/hm²,平均收益36.67万元/hm²;对照组平均产量41 657 kg/hm²,平均产值63.57万元/hm²,平均收益29.44万元/hm²,试验结果表明：河北省气候条件能够满足台湾鳗鳅一年两茬养殖周期需求,对照传统养殖,一年两茬养殖平均收入增加7.24万元/hm²,具有良好的推广前景。     

淡水池塘循环水养殖系统设计比选试验——“陆基分区”模式养殖实践(二)

通过将小型池塘(1.2×667m²)改造成养鱼区和水质处理区的方式设计了一套新型“洁水循环”系统—“陆基分区”养殖系统。并验证了该系统的养殖效果，光唇鱼经过330d的养殖成活率为84.8%,饵料系数为1.59,单位产量为10.6kg/m³;加州鲈经过180d的养殖成活率为85.33%,饵料系数为1.37,单位产量为12.19kg/m³。结果表明该系统能够实现水体循环养殖，达到低占地面积、低排污的养殖效果，但还需要进一步探讨其养殖技术，提高养殖单位产量。     

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).     

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.     

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.