桑沟湾筏式养殖鼠尾藻(Sargassum thunbergii)的生长特性

2014年4–6月在桑沟湾海区进行鼠尾藻(Sargassum thunbergii)海上筏式养殖实验,分析了鼠尾藻在桑沟湾的生长特性,调查了藻体上的附着生物。结果显示,(1)鼠尾藻在桑沟湾海域生长迅速,水温为10–17℃时特定生长率最高,可达6.10%/d;根据特定生长率与水温的关系,获得了鼠尾藻的最佳生长温度为14.9℃;(2)5月10日开始有生殖托形成,水温达到20.4℃时,鼠尾藻生殖托大量成熟,并有放散;(3)养殖期间,鼠尾藻最大长度达187.05 cm,均长可达112.31 cm;干湿比由0.147(4月)上升至0.189(6月);每公顷产量可达43.95 t(湿重),相当于干重为8.25 t;(4)藻体上有大型附着生物16种,主要优势种为尖嘴扁颌针鱼鱼卵、玻璃海鞘和海绵;附着生物的生物量随着水温升高而增加。研究表明,海区的附着生物对鼠尾藻的生长影响不大,在桑沟湾大规模养殖鼠尾藻是可行的。     

鼠尾藻池塘秋冬季栽培生态观察

2010年10月～2011年3月对鼠尾藻池塘秋冬季栽培的生长情况进行了观察与分析。选择池塘水温、光强、盐度和pH,研究其对鼠尾藻1年苗、两年苗在不同水层的养殖效果。结果表明,1)40～60cm水层鼠尾藻生长最好;其次是80～100cm水层;0～20cm水层生长最慢;2)1年苗、2年苗在整个试验期间均未发现生殖托。其中部分两年苗藻体生长出1～2cm左右次生分枝,而1年苗均未发现次生分枝;1年苗于11月中旬开始生长出气囊,两年苗于试验开始时就有气囊,12月中旬鼠尾藻气囊开始腐烂脱落,至翌年1月上旬池塘水温降至0℃以下,池塘水体表层出现结冰现象,此时鼠尾藻气囊已大部分脱落,同时有腐烂脱落现象,藻体缩短、变瘦,湿重降低,体色呈黑褐色。2月下旬随着水温的逐渐回升,鼠尾藻又有生长现象,体长及湿重均有增长,至3月上旬发现气囊。3)鼠尾藻两年苗生长情况比1年苗略好,其同一时期测量的藻体平均体长和单株藻体平均湿重均比1年苗大,鼠尾藻两年苗S值(S=单株藻体平均湿重(g)/藻体平均体长(cm))大于1年苗。     

烟台芦洋湾鼠尾藻种群生物量结构的季节变化

2005年2月至2006年1月对烟台芦洋湾鼠尾藻(Sargassum thunbergii)的生长情况进行了生态学调查。实验设立固定样方观测了鼠尾藻种群结构的季节变化,采用逐步回归分析法分析了生境因子对鼠尾藻生物量的影响。结果表明,(1)鼠尾藻分布在低潮线以上50～125cm的中潮带和低潮带之间;(2)生物量消长和平均藻体长度消长的季节变化趋势一致,呈双峰曲线(7月份和12月份达到峰值,9月份达到最低值);(3)生活周期可以划分为4个时期:休止期、生长期、繁殖期和衰退期,6月中旬到7月下旬为有性生殖期;(4)营养生殖贯穿全年,并呈现一定的季节变化;(5)快速生长期内(5-7月),其大小级层次明显,近似正态分布;(6)水温为影响其生长的主要因素,其次为浪冲击度和人为干扰,干露对鼠尾藻的生长影响不显著。总之,本调查区域的鼠尾藻种群呈现明显的季节变化,并与其他海区种群差异显著,生长地区的环境因素是导致差异的根本原因。     

工厂化循环水养殖条件下大口黑鲈生长特点分析

在水温17.3～28.0℃下,将体质量(4.60±0.30) g的大口黑鲈饲养在4口60 m~3工厂化循环水养殖池中,放养密度67尾/m~3,投喂大口黑鲈专用浮性颗粒配合饲料,研究大口黑鲈在工厂化循环水养殖条件下的生长规律。试验结果显示,养殖195 d后,大口黑鲈平均体质量为(303.14±73.17) g、平均体长为(26.76±3.13) cm;体质量(m)与日龄(t)间呈指数关系:m=0.0651t~(1.6147),r~2=0.9974,平均体质量特定生长率为0.46%,平均体质量日增加量为(1.82±0.57) g;体长(L)与日龄间呈线性关系:L=0.0961t+9.1442,r~2=0.9766,平均体长特定生长率为0.15%,平均体长日增长量为(0.10±0.04) cm;体质量与体长符合幂函数:m=0.0132L~(3.0455),r~2=0.9828。在工厂化循环水养殖条件下大口黑鲈的相对增加量、特定生长率趋势基本一致,水温20℃以下明显影响其生长。     

桑沟湾海带标准化养殖模式的优势探析

针对桑沟湾养殖海区海带(Laminaria japonica)的超容量养殖现象,研究了该海区中标准化养殖模式和传统养殖模式的海带生长差异。结果显示,在标准化养殖模式下,海带长、宽、平均厚度、湿重、投影面积和特定生长率均高于传统养殖模式,单棵海带重量显著提高,且海带的碳、氮和蛋白质含量明显高于传统养殖模式,海带品质大大提升。养殖后期,标准化养殖海区养殖海带垂直投影面积之和与对应养殖海区面积之比为6.33,而传统养殖模式的比值为9.15;标准化养殖海区海带所处水层下方的光照强度显著高于传统养殖区,海带所处水层的海流流速也高于传统养殖区。研究表明,桑沟湾海带标准化养殖模式使海带养殖密度降低,海带生长速度和品质均得以提高;在标准化养殖模式下,海带重叠较小,接受的光照比传统养殖模式充足;较快的海流使标准化养殖海区营养盐更新速度更快,这两方面可能是导致2种养殖模式下海带生长和品质产生差异的原因。     

鼠尾藻人工苗种保苗及海上养殖技术研究

为了完善鼠尾藻(Sargassum thunbergii)人工苗种培育及海上养殖技术,在大连旅顺海区及刺参池塘进行了鼠尾藻人工苗种保苗及养殖试验。试验结果表明,鼠尾藻人工苗种在室内培养20 d左右,株高2 mm以上,假根15根以上时,下海保苗为宜。鼠尾藻幼苗保苗、人工养殖方式为表层平养。保苗海区选择风浪不大的海湾。在刺参池塘保苗要求选择水深2 m以上的池塘,养殖位置在进水口附近。保苗3个月后海上鼠尾藻平均株高4.26 cm,刺参池塘鼠尾藻平均株高1.98 cm。将6 cm以上的幼苗夹直径1.5 cm的聚乙烯绳上进行海上养殖试验。养殖8~9个月后,鼠尾藻长至平均株高61 cm。     

鼠尾藻(Sargassum thunbergii)对刺参生长及水环境的影响

研究了在一定养殖空间内刺参–鼠尾藻适宜的养殖容量和养殖密度。将不同密度的平均体重为(16.7±0.95)g的刺参和鼠尾藻混养在1 m3水体的塑料桶内,实验分为12组,每组设3个重复,对刺参、鼠尾藻的生长及养殖水环境因子的变化情况进行了研究与分析。结果显示,1)刺参、鼠尾藻平均日增重率(Mdwg)和特定生长率(SGR)受刺参密度和鼠尾藻密度影响显著(P<0.05)。作为对照,无鼠尾藻、刺参密度为750、500、250 g/m3时,其生长均相对较差;刺参密度为250 g/m3、鼠尾藻密度为1000、1500 g/m3时,刺参生长相对最好。刺参密度为750 g/m3、鼠尾藻密度为500 g/m3时,鼠尾藻特定生长率(SGR)最大;刺参密度为250 g/m3、鼠尾藻密度为1500 g/m3时,鼠尾藻特定生长率(SGR)最小;2)NH4+-N、NO2–-N、NO3–-N和PO4–-P含量变化受刺参和鼠尾藻养殖量的影响显著(P<0.05)。无鼠尾藻,刺参密度为750、500、250 g/m3时,实验组NH4+-N、NO2–-N、NO3–-N和PO4–-P含量相对较高,其中,刺参为750 g/m3实验组含量最高;刺参密度为250 g/m3、鼠尾藻密度为1000、1500 g/m3时,实验组NH4+-N、NO2–-N、NO3–-N和PO4–-P含量相对较低。研究结果显示,鼠尾藻密度的大小对促进刺参的生长有非常显著的影响,同时对养殖水体中的营养因子具有较强的吸收能力。本研究条件下,刺参密度为250 g/m3、鼠尾藻密度为1000、1500 g/m3模式参藻搭配比例较合适,其生态互利效果最好。     

光、温对鼠尾藻卵子排放和幼孢子体生长的影响

以成熟的鼠尾藻生殖托为材料,研究了不同温度(13～23℃)、光照度(3000～12000lx)和光照周期(15L∶9D,12L∶12D,9L∶16D)对鼠尾藻排卵及幼孢子体生长的影响。结果显示,温度在20～23℃范围,有利于鼠尾藻卵子的排放;在3000～12000lx范围内,光照度越高,越有利于鼠尾藻卵子的排放;光周期不是影响卵子排放的主要因素,光照度是鼠尾藻幼孢子体生长的重要因子;温度是制约鼠尾藻幼孢子体生长的关键因子,水温低于16℃时不利于幼孢子体的快速生长。     

鼠尾藻(Sargassum thunbergii)对刺参生长及水环境的影响

研究了在一定养殖空间内刺参–鼠尾藻适宜的养殖容量和养殖密度。将不同密度的平均体重为(16.7±0.95)g的刺参和鼠尾藻混养在1 m3水体的塑料桶内,实验分为12组,每组设3个重复,对刺参、鼠尾藻的生长及养殖水环境因子的变化情况进行了研究与分析。结果显示,1)刺参、鼠尾藻平均日增重率(Mdwg)和特定生长率(SGR)受刺参密度和鼠尾藻密度影响显著(P0.05)。作为对照,无鼠尾藻、刺参密度为750、500、250 g/m3时,其生长均相对较差;刺参密度为250 g/m3、鼠尾藻密度为1000、1500 g/m3时,刺参生长相对最好。刺参密度为750 g/m3、鼠尾藻密度为500 g/m3时,鼠尾藻特定生长率(SGR)最大;刺参密度为250 g/m3、鼠尾藻密度为1500 g/m3时,鼠尾藻特定生长率(SGR)最小;2)NH4+-N、NO2–-N、NO3–-N和PO4–-P含量变化受刺参和鼠尾藻养殖量的影响显著(P0.05)。无鼠尾藻,刺参密度为750、500、250 g/m3时,实验组NH4+-N、NO2–-N、NO3–-N和PO4–-P含量相对较高,其中,刺参为750 g/m3实验组含量最高;刺参密度为250 g/m3、鼠尾藻密度为1000、1500 g/m3时,实验组NH4+-N、NO2–-N、NO3–-N和PO4–-P含量相对较低。研究结果显示,鼠尾藻密度的大小对促进刺参的生长有非常显著的影响,同时对养殖水体中的营养因子具有较强的吸收能力。本研究条件下,刺参密度为250 g/m3、鼠尾藻密度为1000、1500 g/m3模式参藻搭配比例较合适,其生态互利效果最好。     

长牡蛎夏季死亡与养殖环境及自身体质关系的初步研究

选取桑沟湾和爱连湾两个典型牡蛎养殖区为研究对象,调查了两个海区高温季节牡蛎的死亡情况,监测了不同养殖区的水温、盐度、pH和DO等环境指标,并测定了牡蛎体内超氧化物歧化酶(SOD)活性和生长指标的差异,初步探讨了桑沟湾养殖长牡蛎夏季高温死亡的原因。结果表明,实验期间(5～10月)桑沟湾崖头养殖海区(E122.498,N37.151)长牡蛎夏季累积死亡率为37%,最高死亡率出现在8月17日,高达51%,而爱连湾养殖海区(E122.582,N37.179)的累积死亡率仅为2.5%,最高死亡率出现在9月28日,为4.5%。单因子方差分析(ANOVA)表明死亡率与水温具有很强的正相关(R=0.804,P0.01),与溶氧呈明显负相关(R=-0.377,P0.01);死亡率与体重、软体湿重、性腺湿重等生长状况指标呈明显的负相关(R分别为-0.690、-0.498、-0.358),与SOD活性呈正相关(R=0.21,P0.05)。     

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.     

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).     

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.     

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.