不同生态因子对日本矶海绵耗氧率的影响

静水条件下,研究了温度、盐度和pH值对日本矶海绵耗氧率的影响。试验结果表明:温度在13~22℃范围内,日本矶海绵的耗氧率随着温度的增大而增大,温度高于22℃,耗氧率则开始减小(P0.05);盐度在20‰~35‰范围内,日本矶海绵的耗氧率随着盐度的增大而增大,盐度高于35‰,耗氧率则开始减小(P0.05);pH在5~8范围内,日本矶海绵的耗氧率随着pH的增大而增大,pH高于8,耗氧率开始减小(P0.05)。     

不同生态因子对多棘麦秆虫耗氧率的影响

在静水条件下,研究了温度、盐度、pH对多棘麦秆虫Caprella acanthogaster耗氧率的影响及其昼夜变化规律。结果表明:温度为12～24℃时,多棘麦秆虫的耗氧率随温度的升高而增大,高于24℃时则出现明显的下降趋势(P<0.01);盐度为20‰～35‰时,多棘麦秆虫的耗氧率随盐度的升高而增大,盐度高于35‰时则出现明显的下降趋势(P<0.01);pH为4～8时,多棘麦秆虫的耗氧率随pH的升高而增大,pH 8～10时多棘麦秆虫的耗氧率随pH的升高而减小,pH对多棘麦秆虫的耗氧率影响极显著(p<0.01)。     

温度、盐度和pH值对疣荔枝螺耗氧率的影响

以疣荔枝螺(Thais clavigera)为材料,用碘量法测定温度、盐度及pH变化对疣荔枝螺耗氧率的影响。结果表明:温度、盐度及pH值对疣荔枝螺的耗氧率有明显影响。在13~28℃范围内,疣荔枝螺的耗氧率随温度的升高而增大,但当温度达到32℃时,耗氧率反而下降。疣荔枝螺的耗氧率在自然盐度和pH值时均最大,随着偏离自然盐度(28℃)和自然pH值(7.5)的逐渐增大,其耗氧率均逐渐下降。     

水温、盐度对不同规格鱼尾楔蚌耗氧率的影响

在不同水温、盐度条件下检测了不同规格鱼尾楔蚌的耗氧率,研究发现当水温在20-25℃范围内,耗氧率随着水温的升高而升高,超过25℃,耗氧率则随之下降;在盐度(0~32‰)范围内,耗氧率随着盐度的升高而下降。本文从耗氧率的角度探讨温度和盐度对鱼尾楔蚌呼吸功能的影响。     

内刺盘管虫耗氧率的研究

通过实验生态学方法研究内刺盘管虫在饥饿状态下,其耗氧率在不同温度、盐度和pH值下的变化。结果表明,温度、盐度、pH对内刺盘管虫的耗氧率有极显著影响（F〉F0.01）,在12～24℃范围下,随温度升高,内刺盘管虫的耗氧率明显增大,在24℃达到最高,随着温度进一步升高,耗氧率反而下降;在盐度S16～36范围内,内刺盘管虫耗氧率与盐度呈正相关;pH值8时内刺盘管虫代谢最为旺盛。     

温度、盐度和 pH 对鲻幼鱼耗氧率、排氨率以及窒息点的影响

采用封闭流水式实验方法,研究了不同温度(12、16、20、24、28、32℃)、盐度(5、10、15、20、25、30)和pH(7.2、7.7、8.2、8.7、9.2、9.7)对体质量(0.21±0.03)g的鲻(Mugil cephalus)幼鱼耗氧率和排氨率的影响.结果表明,温度(X)对鲻幼鱼耗氧率(Yo)和排氨率(YN)的影响显著,其两两间的相关关系可分别用一元二次方程Yo=-0.0256x2+0.2191X-0.1054(P＜0.05)和YN=-0.0054X2+0.044 1X-0.0082(P＜0.01)表示.随着温度的升高,鲻的耗氧率和排氨率呈现相同的变化趋势,均为先升高后降低,在24℃时,耗氧率和排氨率都达到最大值.经单因素方差分析得出盐度对鲻幼鱼耗氧率的影响极显著(P＜0.01),当盐度在5～30时,随着盐度的升高,耗氧率先下降再升高,然后再下降;排氨率则先升高后降低.经方差检验,盐度对鲻幼鱼排氨率的影响差异极显著,两者之间的相关关系式为YN=-0.0013X2+0.0027X+0.047(P＜0.01).pH对鲻幼鱼耗氧率的影响差异极显著,随着pH的升高,耗氧率呈先升高后下降的趋势,两者之间的关系可用一元二次方程Yo=-0.02583X2+0.198X+0.0775(P＜0.01)表示;pH对鲻排氨率的影响差异极显著,两者之间的相关关系式为YN=-0.0032X2+0.0217X+0.003(P＜0.01).温度和pH对鲻幼鱼窒息点的影响极显著(P＜0.0),盐度对鲻幼鱼窒息点的影响显著(P＜0.05),但对鲻的窒息时间没有显著影响(P＞0.05).     

半滑舌鳎幼鱼耗氧率和窒息点的研究

采用Winkler法对75d(0.2～0.3g)和35d(0.02～0.03g)的半滑舌鳎幼鱼进行了在不同温度(17、20、23℃)、不同盐度(20、25、30、35)下的耗氧率和窒息点测定。结果表明,75d组的相对耗氧率低于35d组;在同一体重组,盐度一定时,耗氧率取决于温度,即温度增高,耗氧率增大。而温度一定时,所测4个试验组中,盐度25时耗氧率最低,盐度20、30稍高,盐度35最高。75d组的窒息点高于35d组,高温度组窒息点较高,盐度25和30组的窒息点高于20和35组。     

温度和盐度对不同规格甲虫螺(Cantharus cecillei)耗氧率和排氨率的影响

采用静水法测定了温度和盐度对两种规格甲虫螺(Cantharus cecillei)耗氧率和排氨率的影响.结果显示,(1)温度、规格均对甲虫螺的耗氧率和排氨率有显著影响(P＜0.05),但其二者的交互作用对甲虫螺的耗氧率和排氨率没有显著影响(P＞0.05).当温度为12-24℃时,甲虫螺的耗氧率和排氨率随温度的升高而逐渐增加,温度为24℃时,达到最高值.之后随着温度的继续升高,各组耗氧率和排氨率均有明显的下降.在温度为12-28℃条件下,大规格组(A组)甲虫螺的单位体重耗氧率和排氨率均小于小规格组(B组).当温度为12-28℃时,甲虫螺的氧氮比值O/N比值范围在8.17-17.31之间.温度为20℃和24℃时,各实验组均有最大的O/N比值.温度升至28℃时,O/N比值明显下降.(2)盐度、规格对甲虫螺的耗氧率和排氨率有显著影响(P＜0.05),但其二者的交互作用对甲虫螺的耗氧率和排氨率没有显著影响(P＞0.05).当盐度为20-30时,两种规格甲虫螺的耗氧率和排氨率随盐度的升高而逐渐增加,盐度为30时,达到最高值.之后随着盐度的继续升高,各组耗氧率和排氨率均有明显的下降.在盐度为20-40条件下,大规格组(A组)甲虫螺的单位体重耗氧率和排氨率均小于小规格组(B组).当盐度为20-40时,甲虫螺的O/N比值范围在10.80-22.71之间.盐度为30时,各实验组均有最大的氧氮比值,盐度升至35和40时,氧氮比值明显下降.研究表明,甲虫螺生存的最适温度为24℃,最适盐度为30.以期为甲虫螺的人工繁殖以及贝螺混养技术提供科学的依据.     

褐菖鲉的耗氧率与温度、盐度和体重的关系

本文就体重、温度、盐度对褐菖鲉耗氧率的影响进行了初步研究.结果表明,褐菖鲉的耗氧量和耗氧率与体重(w)之间的关系可用幂函数Q=awb表示,其中,耗氧量随体重的增加而升高,耗氧率随体重的增加而降低.温度为11℃～20℃的范围内,褐菖鲉的耗氧率随温度的升高而升高,在温度为20℃时耗氧率达到最高值,超过这一温度耗氧率开始降低.盐度对其耗氧率的影响表现出低盐和高盐条件下耗氧率高的现象.     

不同个体大小和环境因子对瘤背石磺水中耗氧率及皮肤特性的影响

本研究设定了3种不同规格,以及温度(15℃、20℃、25℃和30℃)、盐度(5、15、25、35和45)和pH(7.5、7.8、8.1和8.4)3种主要环境因子,通过测定瘤背石磺(Onchidium struma)耗氧率和呼吸器官组织结构的变化研究了其对瘤背石磺呼吸的影响。结果显示,个体较小的瘤背石磺的耗氧率显著高于个体较大的瘤背石磺,且温度、盐度和pH对瘤背石磺的呼吸均有显著影响(P0.05)。在低于25℃时,瘤背石磺的耗氧率和黏液腺长短径随温度的升高而增大,并在25℃时出现峰值;高于25℃后,耗氧率和黏液腺长短径随之减小;表皮厚度的变化趋势与其相反;每0.1 cm~2皮肤所含颗粒腺数目及长短径变化规律不明显。盐度组各项指标的变化规律或趋势与温度组相似,峰值出现在盐度15。pH实验组中,耗氧率和黏液腺长短径随着pH的增加而增加,表皮厚度和颗粒腺长短径却在减小,每0.1 cm~2皮肤所含颗粒腺数目先增大,在pH 8.1时达到最高值,随后急剧减少。随着时间的增加,各影响因子对瘤背石磺的呼吸强度均减小。由此得出,在水下,环境因子对瘤背石磺皮肤呼吸具有显著影响,在25℃、盐度15和pH 8.1时,呼吸代谢良好;而在15℃、盐度45和pH 7.5时,呼吸代谢受到严重胁迫,这为深入揭示瘤背石磺呼吸机制、物种保护和人工增养殖奠定基础。     

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.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.     

Effects of metomidate anaesthesia or transfer to pur sea water on plasma parameters in ammonia-exposed Atlantic salmon (Salmo salar L) in sea water

Atlantic salmon (Salmo salar L) postsmolts weighing 150 ± 53 g were exposed to 14–15 mg l^–1 TA-N (total ammonia-N) in sea water in 1 m³ tanks for 24h. Blood samples were then taken A) immediately after the fish were netted from the exposure tanks and stunned by a blow to the head; B) 2–20 min after the fish were transferred to 15 l of an anaesthetic solution of metomidate in ammonia-free sea water; or C) 2–20 min after the fish were transferred to 15 l of ammonia-free sea water. Plasma TA-N level was 18% lower in the anaesthetised fish compared to in the fish sampled directly from the exposure tanks (p 0.05), and accordingly 16% lower in the fish transferred to pure sea water although this difference was not significant (p = 0.07). Plasma glucose level was higher in the fish transferred to pure sea water than in the fish receiving the two other treatments (p 0.05), but plasma urea, osmolality, Na^{+, Cl–, Ca2+ or Mg2+} levels did not vary significantly between the different treatments. Plasma TA-N level increased with time in the fish in the metomidate solution (p 0.02).