革胡子鲶出血性败血症病原菌的分离鉴定

从暴发性死亡的革胡子鲶(Clarias gariepinus)中分离出可疑病原菌株2010111403(简称1403),分别采用细菌全细胞脂肪酸鉴定系统、Biolog微生物自动鉴定系统及细菌16 S rDNA序列分析三种方法对其鉴定,结果表明菌株1403为嗜水气单胞菌(Aeromonas hydrophila)。分离菌株对健康革胡子鲶致病性测试表明其对革胡子鲶的半数致死剂量(LD50)为6.32×106菌落形成单位(CFU);实验感染革胡子鲶出现与自然发病相似症状,表明菌株1403是引起革胡子鲶发生暴发性死亡的主要致病病原。药敏试验表明,庆大霉素、四环素、阿奇霉素、氟哌酸、先锋霉素等9种抗生素对分离菌株有较强的抑制作用,但分离菌株对复方新诺明、克林霉素、罗红霉素等4种药物表现出耐药性。     

大力推广革胡子鲶的养殖

革胡子鲶又名埃及塘虱,它具有生长快、个体大、产量高、杂食性、效益好等优点。1986年江苏无锡市郊区养鱼技术服务站从埃及引进革胡子鲶后,经几年饲养证明,在一般饲养条件下,当年鱼体重可达1至1.5公斤,其生长速度相当于普通胡子鲶的5至6倍,而且对环境的适应能力强,疾病少,很适宜于小水体饲养和池塘混养,是一种值得推广养殖的高产养殖新品种。1991年     

革胡子鲶的鱼病防治

<正> 虽然革胡子鲶的抗病能力较强,但在高密度养殖时,要特别注意防病工作。现将革胡子鲶常见的几种鱼病介绍如下:1 “黑体病” 主要症状为鱼体变黑,消瘦,病鱼竖立浮于水面,头部向上,胸部和头背部有时可见白色绒毛状斑块,形似水霉,胸鳍内侧有一圆形红色血斑,此病由细菌性感染所引起,多发生在鱼苗阶     

革胡子鲶的秋季人工繁殖

由于革胡子鲶上市相对比较集中，在一定程度上影响了经济效益的提高和养殖规模的扩大，近几年我们成功地进行了革胡子鲶的秋季人工繁殖，培育出了大规格的越冬鱼种，走出了一条缩短养殖周期、增加养殖茬口，提高鱼池利用率和经济效益的养殖新路子，现将具体情况报道如下。一、试验条件1．亲鱼的强化培育。春季繁殖以后，亲鱼的能量消耗很大，因此必须抓住夏季高温，鱼类摄食旺盛的有利时机，加强亲鱼的培育，为秋繁的成功打好基础。首先要投饲充足，一般日投喂量可达鱼体重的8％～10％，日投喂3～4次，饲料以新鲜蚕蛹、猪下脚或专用配合饲料…     

革胡子鲶养殖试验

革胡子鲶是一种耐低氧的水生动物,因其具有生长速度快,耐低氧能力强(超过泥鳅),饲料来源广,养殖周期短,经济效益高,无任何病害等显著特点,深受广大养殖户的喜爱。我县从1996年引进以来,主要部分养殖户零星搭配饲养效果不太理想。如何发展革胡子鲶精养是我们急待探讨的课题。今年我们在果汁厂的大力支持下,在果汁厂院内成功地进行了革胡子鲶     

革胡子鲶养殖技术推广总结

革胡子鲶养殖技术推广总结庄业勤，唐卫红（湘潭市畜牧水产局４１１１００）革胡子鲶属淡水鱼品种中生长速度最快的鲶鱼优良品种，是以动物性饲料为主的杂食性鱼类，具有适应性强、生长迅速、耐低氧、疾病少、肉质细嫩、味道鲜美，适宜于集约化养殖等优点。１９９３年全市...     

革胡子鲶亲鱼的越冬技术

革胡子鲶是热带性鱼类，除我国南方的部分地区外，一般都不能在天然水体中自然越冬，因此，亲鱼的越冬必须在人工温室池内进行。1亲鱼越冬池的准备目前革胡子鲶亲鱼越冬池的保温方式主要用塑料薄膜、玻璃纤维瓦或玻璃等材料覆盖保温，也可用沼气池，防空洞等地下坑道保温。热源可用温泉水、深井水、工厂余热水以及用锅炉、电热器等设备加温。越冬地要建在避风向阳，靠近水源和热源的地方。越冬他一般用水泥池。建地时要求池壁上口略高于地平面，这样既能防止雨水流入，又能起到保温效果。越冬地面积为10－50m’，他深1．5－2m，要求有进水、…     

养革胡子鲶的三例经验

几年来,我做过多次养革胡子鲶的试验,现举三例效果较好的供大家参考。一、静水池养革胡子鲶1989年我用一口约9平方米的废弃粪池养革胡子鲶。4月初按常规清池消毒,干晒一周后,注水30厘米,施猪粪150公斤。4月下旬放2厘米大小的鲶鱼苗400尾,並在水上放水浮莲。开始半个月每天喂3次水溞、孑孓和水蚯蚓?竺绯さ?厘米以上,开始喂粪蛆、动物尸体和浮萍。一个月后增喂     

革胡子鲶的安全越冬技术

革胡子鲶的安全越冬技术鱼类是变温动物，体温随着水温的升降而变化。如果水温降到革胡子鲶生存的极限温度１０℃以下，将危及革胡子鲶的生命。革胡子鲶越冬期间，温度、溶氧和饵料是其生存的三大重要因素。那么怎样才能使革胡子鲶安全越冬呢？一、越冬方式及设备１．电厂...     

Artificial Spawning of African Catfish,Clarias gariepinus

Abstract

The effects of controlled reproduction of African catfish, Clarias gariepinuswere investigated in an experiment with carp pituitary (at the dose 4 mg/kg body weight) or Ovopel (1 pellet/kg body weight) used as ovulation stimulators. The application of the synthetic stimulator led to the significantly (P≤0.01) greater weight of eggs (expressed in grams and as percentage of female body weight) and to the significantly (P≤0.05) higher quality of eggs after 24-hour incubation as compared with the hypophysation effects. Two categories of females were used in the experiment, i.e., light (mean body weight of 3.75 kg) and heavy (mean body weight of 8.86 kg) fish. The results show that a significantly (P≤0.01) greater weight of eggs (expressed in grams) was obtained from heavier females. The quality of eggs expressed as the percentage of live embryos after 12- and 24-hour incubation was significantly (P≤0.01 and P≤0.05, respectively) higher for lighter females. The higher weight of obtained eggs and their better quality after Ovopel stimulation compared to the weight and quality of eggs obtained after hypophysation allow for the recommendation of this ovulation stimulator for the fish species investigated.     

Quantitative estimation of maximum daily feed intake of African catfish, Clarias gariepinus Burchell, fingerlings using radiography

Gastric evacuation rate, return of appetite and satiation time of African catfish, Clarias gariepinus Burchell 1822, fingerlings, fed with a commercial pelleted feed, were determined under experimental conditions. The gastric evacuation rate was described by an exponential function, which was found to be inversely related to the rate of ingestion (return of appetite). Satiation time remained constant over the experimental period. Based on these data the authors estimated maximum daily ration in relation to feeding schedule and feeding frequency for C. gariepinus fingerlings.     

Effect of feeding time and frequency on the growth and feed utilization of African catfish Clarias gariepinus (Burchell 1822) fingerlings

The effects of feeding time and frequency on the growth, feed utilization and survival of Clarias gariepinus (Burchell 1822; family Clariidae) fingerlings were evaluated in a 25-day study. Groups of African catfish with an initial individual weight of 0.98 ± 0.02 g were offered feeds continuously for 24 h, or during the day or night at different time intervals, with varying meal size. The growth rate was significantly affected by meal times. Widely practised day time feeding with three equal size meals a day gave the lowest growth and highest food wastage. The growth rates of fish fed continuously or during night time following their feed demand were significantly higher with lowest food conversion ratios and food wastage.     

Stunning of farmed African catfish (Clarias gariepinus) using a captive needle pistol; assessment of welfare aspects

The objective of this study was to assess whether high‐pressure injection of air into the brain of African catfish (Clarias gariepinus) could render the animal unconscious and insensible immediately and permanently. In the study, 48 African catfish with a live weight of 900–1900 g were restrained and equipped with EEG and ECG electrodes and then stunned. The catfish were stunned mechanically using a captive needle pistol. The pressure to shoot the needle was 8 bar and that to inject the air was 3 bar for 1.5 s. The catfish behaviour was observed during and after stunning. τ and δ waves and spikes, which precede a stoppage in brain activity as measured on the EEG, were used as indices for the measurement of immediate induction of unconsciousness and insensibility In 23 of 42 fish, an iso‐electric line was observed after an average of 13.4 s, while in the remaining fish the τ and δ waves and spikes remained on the EEG during the recording period. In all cases, the ECG showed an irregular heart rate with fibrillation and extra systolae. Moreover, the configuration showed ischaemia. Before the captive needle stunning, free‐swimming fish (n=7) explored the tank for an average of 21±12 s before lying down at the bottom. After stunning, they showed clonic uncoordinated swimming movements. The movements stopped after an average of 38±50 s. In another group (n=7) that was stunned and subsequently placed in ice water, clonic cramps were observed in two out of seven animals. When taking into account the number of animals with a reliable EEG (n=42) and using 95% confidence intervals, it was concluded that at least 93% of the catfish were effectively stunned using a correctly positioned captive needle pistol. Furthermore, it is recommended to immobilize the stunned fish by chilling, as the post‐stun clonic cramps may hinder gutting and filleting.     

Combined effects of photoperiod and temperature on growth and survival of African catfish (Clarias gariepinus,Burchell 1822) larvae under laboratory conditions

ABSTRACT

The effect of photoperiod (24L:00D, 12L:12D, and 00L:24D) and temperature (22 ± 1°C and 28 ± 1°C) on performance of Clarias gariepinus larvae was tested. Larvae weighing 3.2 ± 0.24 mg were cultured in aquaria at a stocking density of 20 fish L^?1 and fed twice a day on catfish starter diet (40% CP) at 10 % BW day^?1. Highest mean weight gain (31.00 mg), SGR (7.56% day^?1), and survival (83%) were achieved at photoperiod and temperature combination of 00L:24D and 28 ± 1°C. Percent survival of larvae differed significantly (p < .05) among treatments with optimal survival of (83%) in treatment combination of 28 ± 1°C and 00L:24D, while lowest survival (40%) in treatment combination of 22 ± 1°C and 24L:00D.     

The influence of food particle size on gastric emptying and growth rates of fingerling African catfish, Clarias gariepinus Burchell, 1822

This study investigates the effect of feed particle size on gastric evacuation and growth of fingerling African catfish, Clarias gariepinus . Fish (0.97 ± 0.07 g) held in 40-cm diameter tanks at a stocking density of 5 fish L^–1 (25 fish per tank) were presented with one of four sizes of food particles (1, 1.5, 2 and 3 mm diameter). Gastric evacuation rate could be described by an exponential function with small feed particles being evacuated more rapidly: values of 0.076, 0.054, 0.047 and 0.029 were observed for fish fed 1 mm, 1.5 mm, 2 mm and 3 mm food particles, respectively. Growth rates were highest for fish fed the 1.5 and 2 mm pellets. Based on these findings, recommendations are made on the optimum food particle size for C. gariepinus fingerlings.     

Steatitis in wild sharptooth catfish, Clarias gariepinus (Burchell), in the Olifants and lower Letaba Rivers in the Kruger National Park, South Africa

Large numbers of adult Nile crocodiles, Crocodylus niloticus (Laurenti), died from pansteatitis during autumn and winter 2008 in the lower Letaba and Olifants River gorge in the Kruger National Park, South Africa. Consequently, the health status of fish from these waters was investigated. The study presents the pathological findings in fish inhabiting these rivers within the boundaries of the Park. Changes typical of steatitis were diagnosed in many of the larger specimens of sharptooth catfish, Clarias gariepinus (Burchell), caught within the Olifants River gorge. These fish carried large amounts of mesenteric fat with characteristic small brown granulomata within the adipose tissue. Necrosis and inflammation of the adipose tissues, with characteristic ceroid accumulation within the resultant granulomata and the associated aggregation of ceroid‐containing macrophages, were demonstrated histologically and were typical of steatitis. Other changes included mild thickening and pallor of the gill tissues and swollen, orange, fatty livers. Focal hepatic lipidosis was demonstrated histologically, and special stains revealed storage of large amounts of iron in the livers. Blood smears revealed chromatin clumping in erythrocyte nuclei and nuclear and cell membrane irregularities. This is the first record of steatitis in wild‐caught C. gariepinus.     

Effect of Salinity on Embryonic Development,Hatchability, and Growth of African Catfish,Clarias gariepinus,Eggs and Larvae

Abstract

Effects of salinity on embryonic development and growth of African catfish, Clarias gariepinus, eggs and larvae were studied. Eggs were incubated at 27-29°C in 2,4,6,8, and 10 ppt sodium chloride. Rate of embryonic development was delayed in all salt solutions by 15, 15,28 and 30 minutes, in 2,4,6, and 8 ppt sodium chloride, respectively, when compared with the control group (0% salt); total mortality occurred at 12 hours after gastrula stage in the 10 ppt concentration. Percentage hatching was 45.1,47.7, 59.5,49.2, and 26.6% while percentage deformity was 10.4, 16.1, 52.0, 28.6, and 71.6% in 0, 2, 4, 6, 8, and 10 ppt salt treatments, respectively. There were significant differences (P <0.05) in the hatching percentage and in deformity percentage between 4, 6, and 8 ppt. Rate of yolk absorption was significantly faster in the control and 2 ppt salt treatments, but slower in 4, 6, and 8 ppt. Rate of increase in length was slower with increasing salinity. The optimum salinity for African catfish eggs and was between 0-2 ppt and acceptable up to 6 ppt. The results suggest that increasing salinity delayed hatching and development of African catfish eggs and larvae, respectively, as well as increased the deformity of the larvae.     

Characterization of the testicular semen of the African catfish, Clarias gariepinus (Burchell, 1822), and its short-term storage

Semen of the African catfish, Clarias gariepinus (Burchell, 1822), was investigated with respect to its cellular composition, sperm cell density, maturation grade, motility and fertility. Storage conditions were tested, whereby sperm viability was assessed by measurement of the motility after activation and by fertility tests. Testicular semen differed in its composition, i.e. the sperm density and numbers of spermatids, according to the maturity grade of the testis. Two semen types could be distinguished: semen type I was characterized by high sperm densities and low numbers of spermatids and semen type II had lower sperm densities and higher numbers of spermatids. Two semen types did not differ in motility and fertility (when adjusted for differences in sperm density). During storage, the sperm viability was influenced by the sodium concentration of the storage medium, temperature, membrane stabilizers as bovine serum albumen (BSA) or hen egg yolk, antibiotics and oxygen. Semen viability was maintained best when it was diluted at a ratio of 1:5 in storage solution (150 mmol L^?1 NaCl, 2.5 mmol L^?1 KCl, 1 mmol L^?1 CaCl₂, 1 mmol L^?1 MgSO₄, 20 mmol L^?1 Tris (pH 8.5) and 0.5% BSA or 0.5% hen egg yolk) and stored at 4 °C. Oxygen gassing and addition of antibiotics (1 mg mL^?1 gentamycine sulphate) to the storage solution affected the two semen types in different ways. Antibiotics had no effect on type I semen, but had a positive effect on type II semen. Oxygen gassing had a positive effect on type I semen but a negative effect on type II semen.     

Swim-up fry production in the African Catfish Clarias gariepinus (Burchell) broodstocks fed with differently heated soybean-based diets

Four hundred and eighty matured yearlings of Clarias gariepinus (Burchell) (female=182±10 g; males=208±5 g) distributed into groups of 30 specimens (sex ratio 1:1) were fed differently heated soybean‐based diets. Seven approximately iso‐nitrogenous (31% crude protein) and iso‐caloric (13.97 kJ g^?1) diets were prepared from either raw soybean (SAMSOY 2, TGX 636–02D) or soybean seeds autoclaved for 5, 10, 15, 20, 25 and 30 min. The untreated and the variously heat‐treated soybean meals were mixed with other ingredients to prepare diets designated as DSoy0, DSoy5, DSoy10, DSoy15, and DSoy20, DSoy25 and DSoy30 according to the treatment time of the soybean portion of the diets, and were fed to the fish broodstocks for 84 days. The fishmeal‐based diet (DFM) served as the reference diet. The duration of heating soybean component of the experimental diet significantly (P<0.05) affected the growth performance and the number of eggs produced by the broodstocks, the percentage number of eggs fertilized and hatched as well as the survival of the progenies. The progenies of the brood fish fed diets DFM and DSoy25 with a yolk sac size of 2.78±0.6 and 2.42±0.5 mm, respectively, had significantly (P<0.05) larger yolk sacs, which were also absorbed at a significantly faster rate of 0.61±0.02 and 0.51±0.03 mm day^?1, respectively, than progenies of broodstocks fed other experimental diets. Swim‐up fry survival rates were also better in hatchlings from broodstocks fed DFM (89.5%), DSoy25 (83.8%) and Dsoy 20 (80.5%) diets than progenies from other experimental diets. This study showed that soybean meal portion processed at 116°C and 1.2 kg cm^?2 pressure for 25 min in the diet, which ensures normal reproductive function and production of healthy progenies in C. gariepinus, could serve as a substitute for fishmeal in the broodstock diets.