Effects of water-current speed on hematological,biochemical and immune parameters in juvenile tinfoil barb,Barbonymus schwanenfeldii(Bleeker,1854)

This study examines the effect of water-current speed on hematological,biochemical and immune parameters in juvenile tinfoil barb(B arbonymus schwanenfeldii). Blood samples were taken on days 1,23 and 45 from control fish and from two training groups maintained at current speeds of 0.06 bl/s(body length per second),0.66 bl/s,and 1.92 bl/s,respectively. Significantly increased red-blood-cell counts and hematocrit were observed in the post-training groups on days 23 and 45. Significantly increased hemoglobin concentrations were also observed in the 1.92 bl/s group on days 23 and 45. In contrast,values of mean corpuscular volume were significantly lower in the 1.92 bl/s group than in the other groups on day 45. Nitroblue-tetrazolium-positive cells and lysozyme and superoxidase dismutase activities in the plasma increased significantly with increasing training intensity on days 23 and 45. Antibacterial activities were significantly increased in the trained groups compared with the control group on day 23; significantly elevated alkaline phosphatase activity was observed in the 1.92 bl/s groups on day 45. Therefore,training intensities of 0.66 and 1.92 bl/s enhanced the blood oxygen-carrying capability and plasma immune parameters of juvenile tinfoil barbs.     

饲喂频率对奥尼罗非鱼仔稚鱼生长、体成分和消化酶活力的影响

研究在(28.0±1)℃条件下,5种不同饲喂频率对奥尼罗非鱼(Oreochromis niloticus×O.aureus)仔稚鱼的生长、体成分及几种消化酶活力的影响。结果显示:随着饲喂频率的增加,奥尼罗非鱼仔稚鱼的摄食率和特定生长率逐步提高,1次/d组的摄食率和特定生长率显著低于其他组(P<0.05);2、3、4、5次/d组的相对增重率之间差异不显著(P>0.05),但显著高于1次/d组;各组的饲料转化率随饲喂频率的增加而降低;胃蛋白酶、脂肪酶和淀粉酶活力随饲喂频率的增加而显著降低(P<0.05);各组胰蛋白酶变化差异不明显(P>0.05);随饲喂频率的增加,奥尼罗非鱼仔稚鱼的灰分和蛋白质含量无显著变化(P>0.05);脂肪含量显著上升,水分含量则明显下降(P<0.05)。分析表明,奥尼罗非鱼仔稚鱼最适饲喂频率为3次/d。     

Effect of substrate component on the growth and survival of juvenile sunray surf clam (<Emphasis Type="Italic">Mactra chinensis</Emphasis> Philippi)

Substrate is a critical environmental factor affecting the activity of bivalves. To examine the effect of the substrate component on the growth and survival of juvenile sunray surf clam(Mactra chinensis Philippi), a series of short-term experiments were conducted using a variety of substrates with different ratios of sand to mud. The experimental group cultured without substrate showed poor survival, with all juveniles died after day 20. The juveniles cultured in mud without sand showed a lower survival rate(25.54% ± 0.40% on day 45) than those in other groups. The juveniles cultured in sand without mud, or the mixtures of sand and mud with a ratio of 1:1 and 2:1, respectively, exhibited modest survival at day 45. Maximal weight gain rate(WGR), shell length growth rate(LGR), and specific growth rate(SGR) were observed when the sand concentration was 61.97%, 77.69%, and 64.64%, respectively. As the fast growth and high survival were observed when the sand to mud ratio was 1:1(50% sand) and 2:1(67% sand), a sand concentration of more than 50% is optimal. The optimal concentration of sand in the substrate for rearing juvenile sunray surf clams was 67% which resulted in the fastest growth and highest survival. These results can be used to developing a nursery/farming technique of improving the yield of sunray surf clams.     

Non-specific immune response of bullfrog <Emphasis Type="Italic">Rana catesbeiana</Emphasis> to intraperitoneal injection of bacterium <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Non-specific immune response of bullfrog Rana catesbeiana to pathogenic Aeromonas hydrophila was studied to 60 individuals in two groups. Each bullfrog in bacterium-injected group was injected intraperitoneally （i.p.） with 0.2 ml bacterial suspension at a density of 5.2 × 10^6 CFU/ml, while each one in control group injected i.p. with 0.2 ml sterile saline solution （0.85%, w/v）. Three bullfrogs in both groups were sampled at 0, 1, 3, 7, 11, 15 and 20 days post-injection （dpi） for the evaluation of non-specific immune parameters. It was observed that intraperitoneal injection of A. hydrophila significantly increased the number of leucocytes and that of NBT-positive cells in peripheral blood. Significant increases in serum bactericidal activity and serum acid phosphatase activity were also observed in the bacterium-injected frogs when compared with those in the control group. However, a significant reduction was detected in vitro in phagocytosis activity of peripheral blood phagocytes. No significant difference in changes in the number of peripheral erythrocytes, serum superoxide dismutase （SOD） activity, and lysozyme activity was detected between the two groups. It is suggested that bullfrogs may produce a series of non-specific immune reactions in response to the A. hydrophila infection.     

不同糖源对方斑东风螺生长、饲料利用和消化酶活性的影响

以鱼粉、酪蛋白和明胶为蛋白源,分别以20%添加水平的葡萄糖、糊精、蔗糖、玉米淀粉、小麦淀粉和马铃薯淀粉为糖源,配制成6种不同糖源的等氮等能饲料,研究不同糖源对方斑东风螺幼螺生长性能、饲料利用、消化酶活性、糖原含量、蛋白质含量及肉壳比的影响。结果表明:方斑东风螺幼螺的增重率、特定生长率、饲料系数、蛋白质效率,消化酶活性、糖原含量、蛋白质含量及肉壳比均受到糖源种类的显著影响(P<0.05)。增重率、特定生长率从高至低依次为小麦淀粉组、玉米淀粉组、马铃薯淀粉组、糊精组、葡萄糖组、蔗糖组;饲料系数及蛋白质效率均以小麦淀粉组表现最好,与马铃薯淀粉组和玉米淀粉组无显著性差异,显著优于糊精组、葡萄糖组及蔗糖组。消化酶活性的分析结果表明,淀粉酶活性最高的是蔗糖组和小麦淀粉组,糊精组次之,葡萄糖组和马铃薯淀粉组的淀粉酶活性最低;各处理组脂肪酶活性存在显著差异,从高至低分依次为马铃薯淀粉组>小麦淀粉组>糊精组>玉米淀粉组>蔗糖组、葡萄糖组;蛋白酶活性以小麦淀粉组最高,其次为蔗糖组,其他糖源组并无显著差异;而内脏团糖原和肌糖原含量,除了葡萄糖组外,其他各组差异不显著(P>0.05);蛋白质含量以葡萄糖组最高,小麦淀粉组最低,而肉壳比则刚好相反,以小麦淀粉组和玉米淀粉组最高,葡萄糖组最低。以生长、饲料利用率和消化酶活性为评价指标,方斑东风螺饲料中采用小麦淀粉作为糖源效果最优。     

斜带石斑鱼幼鱼对羟基蛋氨酸铜的需求

在斜带石斑鱼(Epinephelus coioides)幼鱼基础饲料(铜质量分数2.03 mg/kg)中分别添加6个水平的羟基蛋氨酸螯合铜(hydroxy methionine copper,HMC),制成铜质量分数分别为2.03、4.04、6.20、10.67、13.96 mg/kg的实验饲料,饲喂6周后,探讨HMC对幼鱼生长、非特异性免疫酶活性和组织铜沉积的影响,确定幼鱼饲料中铜的最适需要量。结果表明,饲料中添加HMC,对石斑鱼的增重率、特定生长率(SGR)和饲料系数等生长性能的影响有统计学意义(P0.05),以铜质量分数6.20 mg/kg组增重率和特定生长率最高,饲料系数最低,高于或低于2.03和13.96 mg/kg组,差异有统计学意义(P0.05),与4.04和10.67 mg/kg组差异无统计学意义(P0.05);但对成活率、肝体比影响差异无统计学意义(P0.05)。饲料中添加HMC对全鱼水分和粗蛋白含量影响无统计学意义(P0.05),对全鱼粗灰分和粗脂肪含量影响有统计学意义(P0.05)。石斑鱼血浆铜蓝蛋白(CP)的含量、血清和肝脏总超氧化物歧化酶(T-SOD)及铜锌超氧化物歧化酶(Cu-Zn-SOD)活性均以6.20 mg/kg组最高;饲料中铜的添加对血清谷胱甘肽过氧化物酶(GSH-Px)活性和肝脏硫代巴比妥酸反应物(TBARS)含量影响无统计学意义(P0.05)。与对照组相比,饲料中添加HMC均提高鱼体、肌肉和肝脏中铜含量,差异有统计学意义(P0.05),且以13.96 mg/kg组最高。饲料中添加适量的HMC可提高石斑鱼幼鱼的生长性能,提高抗氧化能力。在本实验条件下,以SGR为判据,通过二次回归方程拟合可得,以HMC为铜源,斜带石斑鱼幼鱼铜需要量为7.09 mg/kg。     

Effects of irradiated Ergosan on the growth performance and mucus biological components of rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>

Effects of irradiated and non-irradiated Ergosan extract (alginic acid) on rainbow trout growth performance and skin mucosal immunity were compared. Ergosan was irradiated at 30 kGy in a cobalt-60 irradiator. A total of 252 fish (128.03±9.4 g) were randomly divided into four equal groups, given the basal diet either unsupplemented with Ergosan (control group) or supplemented with crude Ergosan (5 g/kg), ethanol-extracted Ergosan (0.33 g/kg) or irradiated Ergosan (0.33 g/kg) according to this protocol: basal diet for 15 days, treatment diet for 15 days, basal diet for 10 days and treatment diet for 15 days. Highest growth performance was observed in fish fed irradiated Ergosan (P <0.05). Dietary administration of different Ergosan types did not cause any changes in mucus protein level, but improved alkaline phosphatase level and hemagglutination titer compared with the control (basal diet without Ergosan) on day 55 of feeding trial (P <0.05). Furthermore, the highest value of lysozyme activity was observed in gamma-irradiated Ergosan on day 55. In conclusion, gamma-irradiated Ergosan at 0.33 g/kg was found to improve growth performance and mucus biological components significantly in comparison with the control group (basal diet without Ergosan).     

饲粮添加人参对贵妃鸡肌肉氨基酸水平和血液生理生化指标的影响

选用90日龄的贵妃公鸡随机分成4组,在基础日粮中按质量分数0.00%﹑0.02%﹑0.04%和0.08%添加人参,实验期45 d,探讨人参对贵妃鸡肌肉氨基酸含量和血液生理生化指标影响。结果表明:0.04%的人参添加量使得腿肌总氨基酸量和鲜味氨基酸含量比对照组分别提高19.19%和14.81%;0.04%的人参添加量使得胸肌总氨基酸含量和必需氨基酸含量比对照组分别提高18.84%和16.54%,鲜味氨基酸含量比对照组提高了14.82%。日粮中添加0.04%的人参能显著提高贵妃鸡胸肌和腿肌的苏氨酸﹑蛋氨酸和缬氨酸的含量。各实验组血清谷草转氨酶和谷丙转氨酶的活性均低于对照组,差异具有统计学意义(P0.05)。饲粮中添加0.04%人参添加实验剂效果最佳。     

Colonization and Probiotic Effect of Metschnikowia sp. C14 in the Intestine of Juvenile Sea Cucumber,Apostichopus japonicus

Viable cell count was used to determine whether Metschnikowia sp.C14 can colonize the intestine of juvenile sea cucumber Apostichopus japonicus.Sea cucumber individuals were divided into two groups,which were fed the control diet for 38 days or the C14-supplemented diet at 105 cells g−1 diet for 28 days,then the control diet from day 29 to day 38.The number of C14 cells in the intestine of sea cucumber fed the C14-supplemented diet significantly increased from day 7 to day 28,and decreased from day 29 to day 38.Sea cucumber fed with the diet containing C14 showed a significant increase in trypsin activity and lipase activity from day 21 to day 33 compared with the control.Feeding C14 significantly improved the phagocytic activity and respiratory burst in coelomocytes from day 21 to day 35 and from day 14 to day 38,respectively.In addition,there was an obvious enhancement in lysozyme activity(from day 21 to day 38 or day 33),phenoloxidase activity(from day 21 to day 28)and total nitric oxide synthase activity(from day 14 to day 38)in coelomic fluid supernatant and/or coelomocyte cell lysate supernatant compared with the control.There were significant positive correlations between the number of C14 cells colonizing the intestine and trypsin activity of the intestine,lysozyme activity of the coelomic fluid supernatant and coelomocyte lysate supernatant from sea cucumber.These data suggested that the number of C14 cells should be maintained at 105 cfu(colony-forming units)g−1 intestine material for the maximum benefit.     

Non-specific immune response of bullfrog Rana catesbeiana to intraperitoneal injection of bacterium Aeromonas hydrophila

Non-specific immune response of bullfrog Rana catesbeiana to pathogenic Aeromonas hydrophila was studied to 60 individuals in two groups.Each bullfrog in bacterium-injected group was injected intraperitoneally(i.p.) with 0.2 ml bacterial suspension at a density of 5.2 × 106 CFU/ml,while each one in control group injected i.p.with 0.2 ml sterile saline solution(0.85%,w/v).Three bullfrogs in both groups were sampled at 0,1,3,7,11,15 and 20 days post-injection(dpi) for the evaluation of non-specific immune parameters.It was observed that intraperitoneal injection of A.hydrophila significantly increased the number of leucocytes and that of NBT-positive cells in peripheral blood.Significant increases in serum bactericidal activity and serum acid phosphatase activity were also observed in the bacterium-injected frogs when compared with those in the control group.However,a significant reduction was detected in vitro in phagocytosis activity of peripheral blood phagocytes.No significant difference in changes in the number of peripheral erythrocytes,serum superoxide dismutase(SOD) activity,and lysozyme activity was detected between the two groups.It is suggested that bullfrogs may produce a series of non-specific immune reactions in response to the A.hydrophila infection.     

Effect of water temperature on digestive enzyme activity and gut mass in sea cucumber Apostichopus japonicus （Selenka）, with special reference to aestivation

The effect of water temperature on gut mass and digestive enzyme activity in sea cucumber Apostichopus japonicus, including relative gut mass (RGM), amylase, lipase, pepsin and trypsin activities were studied at temperatures of 7, 14, 21, and 28°C over a period of 40 days. Results show that RGM significantly decreased after 40 days at 21°C and markedly decreased over the whole experiment period at 28°C; however, no significant effect of duration was observed at 7 or 14°C. At 14°C, trypsin activity significantly decreased over 10 and 20 days, then increased; amylase and trypsin activity significantly decreased after 40 days at 28°C. However, no significant effect of duration was found on amylase, pepsin or trypsin activities in the other temperature treatment groups. At 28°C, lipase activity peaked in 20 days and then markedly decreased to a minimum at the end of the experiment. On the other hand, pepsin activity at 28°C continuously increased over the whole experimental period. Principle component analysis showed that sea cucumbers on day 40 in the 21°C group and in the previous 20 days in the 28°C group were in the prophase of aestivation. At 28°C, sea cucumbers aestivated at 30–40 days after the start of the experiment. It is concluded that the effect of temperature on the digestion of A. japonicus is comparatively weak within a specific range of water temperatures and aestivation behavior is accompanied by significant changes in RGM and digestive enzyme activities.     

Immune response of <Emphasis Type="Italic">Pseudosciaena crocea</Emphasis> to the injection of <Emphasis Type="Italic">Vibrio alginolyticus</Emphasis>

For the investigation of anti-infection immune response of Pseudosciaena crocea, 160 healthy fish samples were categorized into infected and control groups. Each individual fish in the infected group was injected intraperitoneally (i.p.) with 0.2 ml bacterial suspension of Vibrio alginolyticus in density of 2×10⁷ CFU/ml, while each individual in the control group was injected i.p. with 0.2 ml sterile saline solution (0.85%). It was observed that the artificial injection of V. alginolyticus significantly increased the number of erythrocytes, leucocytes, lymphocytes in peripheral blood as well as peripheral serum antibacterial activity and antibody titer of large yellow croaker, and significantly reduced the number of peripheral blood granulocytes as compared with those in the control group. No significant difference in acid phosphytase and superoxide dismutase activity of serum was detected between the two groups. It is suggested that non-specific immune factors including leucocytes and anti-bacteria substance in peripheral blood played important role at the initial stage of infection, and specific immune factors such as antibody then played important role in response to anti-infection at the latter stage. Supported by the National High Technology Research and Development Program of China (863 program, No. 2007AA09Z115) and Technology Program of Xiamen (No. 3502Z73019)     

Effects of Pseudoalteromonas sp. BC228 on digestive enzyme activity and immune response of juvenile sea cucumber (Apostichopus japonicus)

A marine bacterium, Pseudoalteromonas sp. BC228 was supplemented to feed in a feeding experiment aiming to determine its ability of enhancing the digestive enzyme activity and immune response of juvenile Apostichopus japonicus. Sea cucumber individuals were fed with the diets containing 0(control), 105, 107 and 109 CFU g-1 diet of BC228 for 45 days. Results showed that intestinal trypsin and lipase activities were significantly enhanced by 107 and 109 CFU g-1 diet of BC228 in comparison with control(P 0.01). The phagocytic activity in the coelomocytes of sea cucumber fed the diet supplemented with 107 CFU g-1 diet of BC228 was significantly higher than that of those fed control diet(P 0.05). In addition, 105 and 107 CFU g-1 diet of BC228 significantly enhanced lysozyme and phenoloxidase activities in the coelomic fluid of sea cucumber, respectively, in comparison with other diets(P 0.01). Sea cucumbers, 10 each diet, were challenged with Vibrio splendidus NB13 after 45 days of feeding. It was found that the cumulative incidence and mortality of sea cucumber fed with BC228 containing diets were lower than those of animals fed control diet. Our findings evidenced that BC228 supplemented in diets improved the digestive enzyme activity of juvenile sea cucumber, stimulated its immune response and enhanced its resistance to the infection of V. splendidus.     

壳寡糖对吉富罗非鱼幼鱼生长性能、非特异性免疫及血液学指标的影响

用添加质量分数0.00(对照组)、0.10%、0.30%、0.50%和0.70%壳寡糖的饲料饲喂初始体重(3.81±0.23)g的吉富罗非鱼幼鱼(Oreochromis niloticus)10周,研究不同浓度壳寡糖的添加对吉富罗非鱼幼鱼的生长、非特异性免疫功能以及血脂指标的影响。结果表明:与对照组相比,在4个不同浓度添加组中,添加质量分数0.50%壳寡糖能显著提高幼鱼的增重率(P<0.05)、特定生长率(P<0.05),并降低饲料系数(P<0.05);添加质量分数0.3%和0.5%壳寡糖能显著提高幼鱼抗嗜水气单胞菌感染的能力(P<0.01);添加质量分数0.10%、0.30%、0.50%壳寡糖能显著提高幼鱼血清中碱性磷酸酶活性(P<0.05)。同时,各浓度的壳寡糖均能明显提高幼鱼血清中溶菌酶和超氧化物歧化酶活性以及抗嗜水气单胞菌感染的能力(P<0.05),并降低幼鱼血清中总胆固醇和低密度脂蛋白胆固醇水平(P<0.05)。在本实验条件下,添加壳寡糖可提高吉富罗非鱼幼鱼生长性能、饲料利用率、非特异性免疫功能和调节血脂水平,添加量以质量分数0.30%~0.50%为宜。     

大黄对凡纳滨对虾生长和非特异性免疫指标的影响

在凡纳滨对虾饲料中分别添加大黄0、0.5、1.0、5.0、10.0和20.0g/kg,研究大黄对凡纳滨对虾(初始体重为0.34±0.004g)生长及非特异性免疫指标的影响。结果表明,大黄对凡纳滨对虾成活率、增重率、特定生长率、饲料系数、蛋白质效率和蛋白质累积率的影响不显著(P>0.05),对全虾和尾肌肉的灰分、脂肪和粗蛋白含量影响显著,全虾的粗蛋白和粗脂肪含量以1.0g/kg组最高(P<0.05),对凡纳滨对虾血清碱性磷酸酶、酸性磷酸酶、酚氧化酶、超氧化物歧化酶、溶菌酶以及血清总蛋白量等的影响显著,溶菌酶活性以1.0g/kg组最高(P<0.05);细菌感染实验中以1.0g/kg组存活率最高(P<0.05)。以非特异性免疫反应指标及感染实验存活率为指标,凡纳滨对虾饲料中大黄的适宜添加量为1.0g/kg。     

Effect of stocking density on water quality and (Growth,Body Composition and Plasma Cortisol Content) performance of pen-reared rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

The goal of the study was to examine the effect of stocking density on the water quality of culture area, as well as the growth, body composition and cortisol content of rainbow trout（Oncorhynchus mykiss）. Pen-reared trout were stocked in densities of 40, 60, 80 fish individuals m^-3(4.6, 6.6, 8.6 kg m^-3, SD1, SD2 and SD3 groups, respectively) for 300 days. Compared to the water from SD1 and SD2, that from SD3 exhibited significantly higher NH₄⁺-N content and COD（chemical-oxygen-demand）, and a significant reduction of dissolved oxygen in day 180(40.6 kg m^-3). Stocking density was significantly associated with body weight, standard length, VSI（viscerosomatic index）, CF（condition factor） and FC（food coefficient） in group SD3, particularly in day 240 and day 300(45 or 49.3 kg m^-3). Increased crude fat and decreased crude protein were displayed in high density group when the density reached to 36 kg m^-3. As a cumulative effect of density-related stress, VSI, CF, FC, moisture, and crude protein content varied over time in each density group（SD1, SD2, and SD3）. In summary, trout exhibited a better growth performance in low density(26.3 kg m^-3) than those reared in high densities(36 and 45 kg m^-3). The results indicate that rainbow trout（114.44 g ± 6.21 g, 19.69 cm ± 0.31 cm） initially stocked in 6.6 or 8.6 kg m^-3 should be lightened to less than 36 kg m^-3 after an intensive rearing for 240 days.     

Screen and effect analysis of immunostimulants for sea cucumber, <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>

Immunostimulants may improve disease resistance of aquaculture animals by promoting the nonspecific immunity response of the organisms. Five types of saccharides, including chitosan, yeast polysaccharide, burdock oligosaccharide, seaweed polysaccharide and lentinus edodes polysaccharide, were screened for potential use as immunostimulants by using spectrophotometry. The saccharides were injected into Apostichopus japonicus, a sea cucumber, and the lysozyme and superoxide dismutase (SOD) activities of the coelomic fluid and epidermal slime were monitored in six consecutive days. The results show that the lysozyme activity of the animal’s coelomic fluid was significantly stimulated on day 2, day 4 and day 6 after the injection of the saccharides (P<0.05). The effects of chitosan and yeast polysaccharide were the most notable. The lysozyme activity of the epidermal slime was significantly increased by chitosana, yeast polysaccharide, seaweed polysaccharide, and burdock oligosaccharide on day 1 and day 2 after the injection (P<0.05). The SOD activity of the coelomic fluid was significantly promoted by the saccharides on day 2 and day 4 post-injection (P<0.05), while the SOD activity of the epidermal slime increased on day 2. These findings indicate that chitosan and yeast polysaccharide are the most effective immunostimulants and potential healthy anti-disease feedstuff for A. japonicus. Supported by the National Key Technology Research and Development Program (863 Program, No. 2006BAD09A06) and the Special Fund of Chinese Central Government for Basic Scientific Research Operations in Commonweal Research Institutes (No. 02-2007B03)     

Immunotoxicity Effect of Benzo[α]Pyrene on Scallop Chlamys farreri

The toxic effects of benzo[α]pyrene (B[α]P) at different concentrations (0.1, 0.5, 1, 2.5 and 7.5 ugL-1) on scallop (Chla-mys farreri) immune system were studied. The results showed that B[a]P had significant toxic effects on the haemocyte counts, neu-tral red uptake, phagocytosis, bacteriolytic and antibacterial activity (P<0.05), while the seawater control and acetone control had no significant differences. The haemocyte counts, neutral red uptake, phagocytosis and bacteriolvtic activity in all B[α]P treatment groups as well as antibacterial activity, in groups of 0.5, 1, 2.5 and 7.5 ugL-1 B[α]P decreased significantly (P<0.05). Some of these indices tended to be stable on the sixth day and others on the ninth day, and the indices showed clear time- and concentra-tion-response to B[α]P. Bacteriolytic activity in 0.1ugL-1 B[α]P treatment group and antibacterial activity in 0.1 ugL-1 and 0.5 ugL-1 B[α]P treatment groups increased at the beginning of exposure and reached their peaks on day 1 and day 6, respectively. Following that, both activities decreased gradually and became stable after day 9. When all the indices reached stability, they were significantly lower than those in control group (P<0.05), except for antibacterial activity in 0.1 ugL-1 B[α]P treatment group (P<0.05). Thus, B[α]P has evident toxic effects on scallop immune system, which supports the view that a relationship exists between pollution and immu-nomodulation in aquatic organisms.     

Application of hydroacoustics to investigate the distribution,diel movement,and abundance of fish on Zhubi Reef,Nansha Islands,South China Sea

A combination of traditional fish sampling methods(hand-line and gill net) and modern hydroacoustic techniques were used to study fish community structure,distribution,and diel movements of fish on Zhubi Reef to enhance understanding of the ecosystem.We collected 126 individuals from 29 species,20 genera,17 families,three orders,and two classes using traditional gear.Perciforms were the dominant group in terms of species richness and biomass.The acoustic data indicated that very small(target strength[TS],dB) -60 dB) and small(-60 dB≤TS-45 dB) fish contributed the most to abundance and species richness on the coral reef,and that the proportion of medium-sized(-45 dB≤TS-35 dB) and largesized(-35 dB≤TS) fish increased gradually as depth increased.The single-target detection method revealed two distinct size classes during the day in the 12-16 and 16-20-m layers.One group consisted of very smallsized fish(TS-60 dB) and the other consisted of medium and large-sized fish(TS-55 dB).The number of single-target detections was significantly higher during the night than during the day(P0.05).The singletarget TS frequency distribution during the day was significantly different than during the night at depths of4-8,8-12,12-16,and 16-20 m.Significant differences were observed among the 4-8,8-12,12-16,and16-20-m-depth layers during day and night.Diel vertical movement was evidenced as fish began to spread and move upward just before sunset and began to assemble and descend shortly(15 min) after sunrise.     

Effects of varying densities on serum reproductive parameters in pen-reared juvenile female rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> farms

The primary goal of this study was to assess the effect of varying densities on serum reproductive parameters of immature rainbow trout Oncorhynchus mykiss. Experimental trout were maintained in intensive, pen-reared farms for 300 days in fresh water reservoirs. Initial densities were 4.6, 6.6, and 8.6 kg/m³ (40, 60, 80 ind./m³), indicated as SD1, SD2, SD3, and final densities were 31.1, 40.6, 49.3 kg/m³, respectively. A summary of the ovarian stages were observed by histological examination. Serum E₂ (estradiol), T (testosterone) were evaluated by radioimmunoassay and FSH (follicle-stimulating-hormone), LH (luteinizing-hormone), vitellogenin, 17α,20β-P (17α,20βdihydroxy4-pregnen-3-one) were measured by enzyme-linked immunosorbent assay. Our findings demonstrated that ovarian development were retarded (from stage III to stage IV) at highest rearing density (SD3) after 180 days of intensive culture (over 40.6 kg/m³). In addition, we observed an inverse relationship between serum reproductive parameters and rearing density. Furthermore, compared to serum reproductive parameters of SD1, E₂, T, FSH, vitellogenin, 17α,20β-P, GSI and LH of two higher density groups decreased firstly and significantly at 60 (over 15.9 kg/m 3 ), 180 (over 31.7 kg/m 3 ), 180 (over 40.6 kg/m³), 240 (over 36 kg/m³), 240 (over 36 kg/m³), 240 (over 45 kg/m³) and 300 (over 49.3 kg/m³) days, respectively. Comparing serum reproductive parameters within the same ovarian development stage of rainbow trout from varying densities revealed that higher population density also led to significantly lower overall serum reproductive parameters. Overall, this study presents the reproductive, endocrinological parameters of juvenile female rainbow trout at high rearing densities and indicates the need for rainbow trout (114.44±5.21 g, 19.69±0.31 cm) that are initially stocked at 6.6 or 8.6 kg/m³ should be classified and subdivided into lower density after 180 days of farming (not over 31.7 kg/m³).