罗非鱼对浮游植物群落的影响

杂食性鱼类可以通过牧食和营养盐排泄影响浮游植物群落,罗非鱼是我国南方水体常见的外来杂食性鱼类,为了解其对浮游植物的影响,于2007年6～11月在广东珠海市大镜山水库进行了原位围隔实验,通过设置有鱼实验组与无鱼对照组,对比研究了尼罗罗非鱼(Oreochromis niloticus)对浮游植物群落结构的影响。结果表明,实验结束时,有鱼实验组中浮游植物的密度和生物量分别为1.2×108个/L和8.16mg/L,是无鱼对照组(0.9×108个/L、1.22mg/L)的11.0倍和8.4倍。有鱼组中甲藻的生长明显受到限制,而蓝藻的密度和生物量增加;实验结束时,从生物量上看,无鱼组中甲藻占优势,有鱼组则是蓝藻占优势。本研究说明罗非鱼对浮游植物的生长和群落结构有重要的影响,其营养盐排泄产生的上行效应大于由于摄食产生的下行效应,从而促进了浮游植物的生长。     

盐碱地池塘浮游生物调查报告

１９９７～１９９８年,调查了盐碱地池塘２４只,镜检浮洲植物录属于８阂,共７８属１０６种,平均数量７９６０．２万个／Ｌ,生物量５８．１２ｍｇ／Ｌ;浮游动物平均数量１２９９个／Ｌ,生物量９．６８ｍｇ／Ｌ,盐碱地池塘浮植物种群数量以绿藻、蓝藻占优势,生物量以硅藻、藻占优势。养殖池塘生物量较高,有价值的铒料生物能形成优势种群,可发展滤食性鱼类养殖。     

主养青鱼高产池塘的浮游植物和有机碎屑

本文报道了主养青鱼净产１１．２５、１５吨／公顷·年两个产量级池塘的浮游植物和有机碎屑组成、现存量的研究结果：浮游植物丰度为２０－６０ｍｇ／Ｌ，有机碎屑丰度为３０－７０ｍｇ／Ｌ；浮游植物群落由７种优势种群交替组成，它们分别是隐藻（Ｃｒｙｐｔｏｍｏｎａｓ．ｓｐｐ）、蓝裸甲藻（Ｇｙｍｎｏｄｉｎｕｍｃｙａｎｅｕｍ）、裸藻（Ｅｕｇｌｅｎａｓｐｐ）、针杆藻（Ｓｙｎｅｄｒａｓｐ．）和菱形藻（Ｎｉｔｚｓｃｈｉａｓｐ．）、尖头藻（ＲａｐｈｉｄｉｏｐｓｉｓｓＰＰ）、裂面藻（Ｍｅｒｉｓｍｏｐｅｄｉａｓｐｐ．）、绿球藻类（Ｃｈｌｏｒｅｌｌａｃｅａｅｓｐｐ．），隐藻为主的鞭毛藻类占优势。文中还探讨了浮游植物与鱼池水质净化、浮游植物有机碎屑丰度与鱼产量的关系。     

池塘循环流水养殖模式中浮游植物群落结构的空间变化研究

基于集约化生产的池塘循环流水养殖系统(In-pond raceway system, IPRS)是一种新兴的养殖模式,为进一步了解该系统水体循环过程中的生态结构动态,揭示系统内净水区水质的变化特点,文章研究了养殖草鱼(Ctenopharyngodon idella)的池塘循环流水系统中生长季浮游植物群落结构的空间变化特征,并通过冗余分析研究了浮游植物群落结构变化与环境因子的关系。该系统在生长季共鉴定出浮游植物7门99种,主要由蓝藻门、绿藻门、硅藻门、裸藻门、隐藻门、甲藻门和金藻门组成。其中绿藻门种类数最多(54种),其次为蓝藻门(18种)。系统中不同区域的浮游植物群落结构不同,净化区中段浮游植物的密度及生物量最高,净化区蓝藻门的密度及生物量较养殖区有所增加。池塘不同区域的蓝藻门相对密度均远高于绿藻门及硅藻门。从净化区前端至后端,蓝藻门的相对密度逐渐增加,绿藻及硅藻的相对密度逐渐下降。冗余分析结果显示,影响循环系统中浮游植物群落结构变化的主要环境因子是温度和氮、磷营养盐。     

应用浮游植物群落结构及富营养化指数评价南太湖底泥疏浚效果

应用浮游植物群落结构变化及富营养化指数来评价南太湖底泥疏浚工程对减轻太湖营养盐内负荷、控制湖泊富营养化的效果。研究结果表明：疏浚后水体中的浮游植物种类有所增加,浮游植物密度、生物量及蓝藻所占比例均有不同程度的降低,浮游植物群落结构发生变化;疏浚后水体的生物多样性指数发生变化,Shannon-Weaver指数升高,卡尔森营养状态指数降低,表明南太湖富营养化现状有所改善,从而揭示底泥疏浚工程对于减轻南太湖营养盐内负荷、控制湖泊富营养化具有积极作用。     

红水河龙滩水库浮游植物的群落结构特征

２００９年７月９－２３日（丰水期）和１１月１１－２５日（枯水期）在龙滩水库进行浮游植物采样调查,研究其浮游植物种类组成、数量变化特征、空间分布及群落多样性,评价了龙滩水库的水质现状,探讨水电开发对河流浮游植物的影响。结果表明,龙滩水库共检出浮游植物６门、３５属、５９种;其中,硅藻门２８种,绿藻门１７种,蓝藻门８种,甲藻门、红藻门、金藻门各２种。优势种为４门、１３种,包括颗粒直链藻（Melosira granulata）、钝脆杆藻（Fragi lariacapucina）、双头针杆藻（Synedra amphicephal）和双射盘星藻（Pediastrum biradiatum）等。龙滩水库浮游植物密度和生物量均值分别为３３．４×１０４个／Ｌ和２．５８０ｍｇ／Ｌ。多样性指数和均匀度指数分别为２．５８和０．９４。依据藻类生物学指标评价标准,龙滩水库水质为贫－中营养型。     

洪门水库渔业资源调查报告

洪门水库为江西第二大水库，可养鱼面积７．６５万亩，消落区面积２－３万亩，浮游植物生物量４．４０６ｍｇ／Ｌ，浮游动物生物量２．４５ｍｇ／Ｌ。初步估算，水库鱼产力在３１．３６ｋｇ／亩，而目前单产水平保持在１６．６ｋｇ／亩上下。渔获量以镛鱼为方，鲢鱼次之。全库鱼类９６种，经济鱼类占８５％，如适度开发，水库鱼产力将明显提高。     

引水对尚湖．浮游植物群落结构和营养盐浓度的影响

研究了引污补水作用下小型通江湖泊-尚湖的浮游植物群落和营养盐时空变化。结果表明,尚湖共检出浮游植物8门、39属,从望虞河引水后,尚湖浮游植物群落组成中,蓝藻门富营养化习见种的种类显著增加;引水后尚湖的西湖区营养盐浓度上升2-3倍,东湖区基本维持不变;经过较长时间的沉降和水体自净之后,浮游植物群落中蓝藻门富营养化习见种的种类减少,营养状态降至引水前水平。从望虞河引水补给尚湖,对其浮游植物群落和营养水平有显著影响。     

应用浮游植物群落结构及富营养化指数评价南太湖底泥疏浚效果

应用浮游植物群落结构变化及富营养化指数评价南太湖底泥疏浚工程对减轻太湖营养盐内负荷、控制湖泊富营养化的效果。研究结果表明,疏浚后水体中的浮游植物种类有所增加,其密度、生物量及蓝藻所占比例均有不同程度的降低,浮游植物群落结构发生变化;疏浚后水体的生物多样性指数发生变化,Shannon-Weaver指数升高,卡尔森营养状态指数(TSIM)降低,表明南太湖富营养化现状有所改善,从而揭示底泥疏浚工程对于减轻南太湖营养盐内负荷、控制湖泊富营养化具有积极作用。     

引水对尚湖浮游植物群落结构和营养盐浓度的影

摘 要：通过对引污补水作用下小型通江湖泊（以尚湖为例）中浮游植物群落和营养盐时空变化的研究发现：①研究期间,尚湖共检出浮游植物8门39属,从望虞河引水后,尚湖浮游植物群落组成中蓝藻门富营养化习见种的种类显著增加;②引水后尚湖的西湖区营养盐浓度上升2-3倍,东湖区基本维持不变;③经过较长时间的沉降和水体自净之后,浮游植物群落中蓝藻门富营养化习见种的种类减少,营养状态降至引水前水平。从望虞河引水补给尚湖,对其浮游植物群落和营养水平有显著影响。     

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).     

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.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

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.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.