Comparisons of Uptake and Depuration of 2-Methylisoborneol in Male, Female, Juvenile, and 3MC-induced Channel Catfish Ictalurus punctatus

The occurrence of off-flavors in farm-raised channel catfish is a major burden to the catfish culture industry, causing millions of dollars worth of market-ready fish to be rejected each year. Off-flavors are believed to be the result of exposure and subsequent accumulation of certain volatile microbial metabolites such as 2-methylisoborneol. In this study, the uptake and elimination of [¹⁴C]-2-methylisoborneol equivalents were examined in juvenile and mature channel catfish. The described method is presented as a simple and inexpensive procedure for comparing treatment effects on off-flavor elimination rates. In addition, the effects of the cytochrome P4501A inducing agent 3-methylcholanthrene on 2-methylisoborneol depuration was studied in juvenile fish. Uptake was determined during a 24–h static exposure to waterborne 2-methylisoborneol (7.6 ± 3.7 μg/L). Uptake equilibrium had been established in all groups by 12 h, with total uptake higher in juvenile fish. Depuration rates were not different between untreated groups (t_½ a = 12.r122.4 h; t_½β= 91.3–143.7 h); however, the depuration half-lives for 3-methylcholanthrene treated juveniles were significantly longer than those of controls.     

斑点叉尾(鱼回)病害防治研究进展

斑点叉尾(鱼回)(Ictalurus punctatus)又称美洲鲶、沟鲇,属鲶形目、(鱼回)科,原产于美国,其商业化养殖占美国有鳍鱼类总养殖产量的50%～85%,我国湖北省水产科学研究所于1984年从美国引进后,因其具有生长速度比较快、肉质细嫩、销售价格较高的特点,受到了广大消费者和水产养殖业者的欢迎.2000年我国斑点叉尾(鱼回)开始出口美国,2005年1月就占美国市场6%,并且有逐年加大的趋势,更是加快了我国斑点叉尾(鱼回)养殖业的发展.     

Effects of Dietary Vitamin E Enrichment on Frozen Channel Catfish, (Ictalurus punctatus) Fillets

The storage quality of channel catfish (Ictalurus punctatus), following long term frozen storage, fed diets containing 5 and 10 times the normal level of vitamin E for 45 or 60 days prior to harvest, was evaluated. There were no unusual effects of treatment on fish weight, survival or feed conversion ratios. Muscle vitamin E content was higher (P < 0.05) from fed diets containing supplemental vitamin E than in the control. Oxidation as measured by TBARS and sensory analysis values did not differ (P > 0.05) in response to vitamin E supplementation. Lipid oxidation increased as storage time increased. Lack of change in phospholipid and neutral lipid fractions during storage indicated that autoxidations was the major cause of oxidation in catfish. Vitamin E levels up to 10 times the normal amount did not improve the overall quality of catfish fillets.     

Sensory Evaluation of the Off-Flavors Geosmin and 2-Methylisoborneol (MIB) in Farm-Raised Catfish

Individuals responsible for tasting catfish in quality control settings sometimes report sensations of sensory adaptation, sensory fatigue and flavor carry-over between samples containing earthy/muddy off-flavors due to geosmin and/or 2-methylisoborneol (MIB). If these experiences are real, sensory evaluation of flavor quality may not be as straightforward as many fish processors and researchers would wish. To determine the influence of these compounds on the sensory evaluation of fish, a series of controlled experiments was conducted. These studies indicate that trained panelists were unable to recognize and evaluate, with precision, the intensity of off-flavor compounds such as geosmin and MIB. However, panelists were precise in evaluating other natural off-flavors, such as fishy. In evaluating two MIB samples in succession, the second sample was perceived as having a lower MIB intensity. The addition of off-flavor compounds to catfish caused the panelists to perceive the desirable flavor chickeny to be lower in intensity, indicating masking. Based on these experiments, a simplified off-flavor quality rating system, consistent with available data, is proposed.     

Multi-Locus DNA Fingerprinting of Channel Catfish Ictalurus punctatus

Abstract.— Similarities among multi-locus DNA fingerprints of five channel catfish Ictalurus punctatus strains and the ability to identify the strain of a fish based on its fingerprint pattern were investigated. Five restriction enzymes and 13 multi-locus DNA probes were screened to identify enzyme-probe combination useful for DNA fingerprinting channel catfish. Restriction enzymes Hinf I and Dpn II, in combination with probes (CAC)n, (CGC)n, (CTC)n, (ATCC)n, and (GATA)n, produced useful fingerprints (20–30 resolvable bands for each enzyme-probe combination). Thirty individuals (3 pools of 10 individuals each) from each of five channel catfish strains (albino, Mississippi normal, USDA-102, USDA-102 select, and USDA-103) were fingerprinted with all useful enzyme-probe combinations. Band sharing among samples was higher within strains than among strains and band sharing among strains was higher for strains whose breeding history indicated a high degree of relatedness. Individual fingerprints of 18 fish from each of the USDA-102 select and USDA-103 strains revealed no strain-specific bands, but several diagnostic bands (present at high frequencies in either USDA-102 select or USDA-103 strains and at a low frequencies in other strains) were identified. Band sharing at diagnostic bands was used to correctly identify fish as USDA-102 select or USDA-103 strains with 82% accuracy from fingerprints of 17 USDA-102 select strain fish, 18 USDA-103 strain fish, and 38 fish collected from three commercial farms.     

美国红鮰鱼人工繁殖试验

从人工饲养的成鱼中挑选体色单纯、红色较深的个体作后备亲鱼进行强化培育，待其性腺发育成熟后，注射LHRH—A2催熟催产。催熟剂量为每千克鱼体重2～3μg(雄鱼不催熟)，催产剂量为8μg(雄鱼剂量减半)。试验结果，雌鱼的催产率达70．6％；共获受精卵大约18万粒；孵化出鱼苗约16万尾，平均孵化率88．9％；经培育，共获体长3．5cm的鱼种14．82万尾，鱼种的平均培育成活率达92．6％。试验结果表明，亲鱼培育是美国红鮰鱼人工繁殖取得成功的关键，而要获得遗传性状稳定的红鮰鱼鱼种，亲鱼的筛选至关重要；美国红鮰鱼生长快，抗病力强，产量高，肉质鲜嫩，是优良的养殖品种，可以在国内推广养殖。     

斑点叉尾鮰全基因组微卫星分布特征分析

为了解斑点叉尾鮰(Ictalurus punctatus)全基因组中完整型微卫星的分布特征,本研究使用生物信息学软件MISA对其全基因组微卫星进行了搜索并分析。结果显示,在斑点叉尾鮰29条染色体中,筛选到完整型微卫星共510 256个,总长度达11 036 941 bp。其中,微卫星数量最多的是2号染色体(25 284个),其次分别是3号、1号和5号染色体,29号染色体的微卫星数量最少,只有11 591个。每条染色体长度与位于其上的微卫星的数量均显著相关(SPSS, r=0.98, P<0.01)。27号染色体的微卫星相对丰度最大(785.03个/Mb),11号染色体的微卫星相对丰度最小(615.89个/Mb)。6种重复拷贝类型的微卫星中,单碱基的数量最多,占总数的45.31%,随后依次是二碱基(38.53%)、三碱基(8.73%)、四碱基(6.93%)、五碱基(0.46%)和六碱基(0.04%)。斑点叉尾鮰全基因组微卫星中,前10种优势重复拷贝类别为A、AC、AG、AT、AAT、AAAT、C、AAC、AAAC和AAG,表现出明显的A、T碱基优势。本研究结果可为进一步研究斑点叉尾鮰全基因组特征提供参考,并为今后进行斑点叉尾鮰分子标记辅助育种及遗传信息评估等工作提供基础资料。     

Enzymic Lipid Peroxidation System in Channel Catfish (Ictalurus punctatus) Muscle Microsomes

A lipid peroxidation enzyme system of channel catfish (Ictalurus punctatus) muscle microsomes was identified and characterized. The enzyme system preferred NADH to NADPH as a cofactor to catalyze lipid oxidation. High levels of ADP and NADH, but not ferric ion, were inhibitory in the system. Ferrous ion had a greater promoting effect on lipid peroxidation than ferric ion in catfish muscle microsomes. ATP was more effective than ADP in activating the enzyme system, but AMP had little effect on activating lipid oxidation. The optimal temperature for activity was 30°C and the optimal pH was around 6.9. MnCl2 , p-hydroxymercuribenzoate (pHMB), KCN, and sodium benzoate had a complete inhibitory effect on the lipid peroxidation enzyme system.     

Behavioral Interactions in Juvenile Channel Catfish,Ictalurus punctatus

Behavioral interactions among juvenile channel catfish, "Ictalurus punctatus," were observed, and fixed action patterns were described and anlyzed. Dominant fish engaged regularly in aggressive activities and never in submissive activities, whereas subordinate fish were observed in submissive activities on a regular basis and rarely in those that were aggressive. Activity levels were significantly higher in dominant fish; however, there was no difference in activity levels between pairs of equal and unequal size fish. A factor analysis indicated that there were three general categoris of behavior in juvenile channel catfish. In addition, two behaviors (which appeared to be displacement activities) were functioning in agnostic encounters. Plasma cortisol concentrations measured in sigle fish and pairs of fish in aquaria and individuals from a holding tank indicated that the least amount of stress occurred in fish that were not interacting with any other individuals. Cortisol levels, however, were lower that those associated with stress levels in fish from other studies.     

Effects of Water Temperature on Sock Grading of Sub-Marketable Channel Catfish,Ictalurus punctatus,in Earthen Ponds

Abstract

The passive sock grading method used by commercial channel catfish, Ictalurus punctatus, farmers to grade and reduce the number of under-sized fish delivered to processing plants was assessed on an experimental scale. The assessment was conducted at the Aquaculture Research Station at the University of Arkansas, Pine Bluff in 0.1-ha earthen ponds. A rectangular holding sock was fabricated with dimensions of 0.9 m in width, 2.4 m in length, and 1.2 m in depth. The mesh size of the sock was 4.4 cm and the mesh material was nylon netting, 0.64 cm in diameter. Seventeen groups of channel catfish, were graded, with group weights ranging from approximately 115 to 370 kilograms. Fish were held in the sock for approximately three hours (±0.27 hours). The water temperature during the trials ranged from 7.3°C to 28.7°C. The percent removal of fish less than 0.45 kg during the three-hour holding period ranged from 27.6% to 73.3%. Overall, sock grading efficiency increased with increasing water temperature and at water temperatures above 15°C a greater percentage of fish less than 0.45 kg were not retained in the socks.     

Wading Bird Depredations on Channel Catfish Ictalurus punctatus in Northwest Mississippi

We interviewed farm managers about their perceptions of wading bird problems and conducted preliminary surveys of wading bird populations at 67 randomly selected channel catfish Ictalurus punctatus pond complexes in northwest Mississippi during December 1995. At a subsample of 24 complexes and 10 other complexes previously surveyed in 1990, we surveyed wading bird populations bimonthly throughout the year in 1996 and observed great blue herons Ardea herodias and great egrets Ardea alba feeding at catfish ponds. Seventy-five percent of farm managers questioned felt that wading birds were causing losses to their fish stocks, and 74% believed the problem was increasing. Consistent with interview results, 88% of the pond complexes surveyed had one or more wading birds present. Despite reported harassment programs by producers, great blue heron densities at 10 complexes previously surveyed in 1990 had increased by more than eightfold in 1996. Great blue heron densities varied with location, season and time of day, but the average 127-ha farm supported about 78 herons and 56 great egrets. Despite similar populations, the potential impact of these two species was quite different. Live catfish, averaging 10.3 cm in length (circa 10 g) comprised only 8% of the egret diet by weight, and most of the fish were obtained from fingerling ponds during periods when these fingerlings may be weakened by the bacterial disease, enteric septicemia of catfish. In contrast, live catfish, averaging 16 cm in length (circa 34 g), comprised 44% of the great blue heron diet by weight. Herons foraged from both fingerling and food fish ponds, primarily in the early morning and evening. Based on average population densities and foraging rates, herons at the average 127-ha farm in northwest Mississippi consumed 114,000 (circa 3,900 kg) catfish, annually. However, further studies are recommended to document production losses.     

Performance of Albino and Normal Channel Catfish (Ictalurus punctatus) in Different Water Temperatures

Experiments to determine effects of skin colour on growth in different water temperatures were conducted with albino and normally pigmented channel catfish (Ictalurus punctatus). In Experiment 1, fish were reared in 29°C, 27°C, or 22°C water from hatching to 40 weeks of age. Two additional groups were initially reared in 27°C water for either 12 or 16 weeks and in 22°C water for either the remaining 28 or 24 weeks, respectively. Results indicated that: (1) albino fish reared in 29°C water were superior in growth to normal fish; (2) albino fish did not differ from normal fish in growth when reared in either 27°C or 22°C water; (3) albino fish were inferior in growth to normal fish when reared in 27°C water for either 12 or 16 weeks of the 40-week growth period; (4) genetic differences between families and the age of fish strongly influenced relative growth of both colour types; and (5) both albino and normal catfish were able to compensate in growth at a later age. Experiment 2 began when fish were 48 weeks old and included both albino and normal fish which were either full-siblings or not genetically related. Results indicated that: (1) albinos and normal catfish did not respond differently to a 5°C water temperature change; (2) genetically related and randomly selected albino and normal fish produced consistent results concerning water temperature, skin pigmentation, and sex effects on growth; (3) increasing water temperature from 22°C to 27°C for 19 weeks resulted in increased weight and length of the fish by 144 and 80%, respectively; and (4) growth increase during the first 19-week period resulting from the higher water temperature was followed by a significant increase in the subsequent 10-week growth when the fish were in the lower water temperature.     

Environmental Assessment of Channel Catfish Ictalurus punctatus Farming in Alabama

An environmental assessment was made of Alabama channel catfish Ictalurus punctatus farming which is concentrated in the west‐central region of the state. There are about 10,000 ha of production ponds with 10.7% of the area for fry and fingerlings and 89.3% for food fish. Food fish production was about 40,800 tons in 1997. Watershed ponds filled by rainfall and runoff make up 76% of total pond area. Water levels in many of these ponds are maintained in dry weather with well water. The other ponds are embankment ponds supplied by well water. Harvest is primarily by seine‐through procedures and ponds are not drained frequently. The main points related to Alabama catfish farming and environment issues are as follows: 1) catfish farming in Alabama is conservative of water, and excluding storm overflow, about two pond volumes are intentionally discharged from each pond in 15 yr; 2) overflow from ponds following rains occurs mostly in winter and early spring when pond water quality is good and stream discharge volume is high; 3) total suspended solids concentrations in pond effluents were high, and the main sources of total suspended solids were erosion of embankments, pond bottoms, and discharge ditches; 4) concentrations of nitrogen and phosphorus in effluents were not high, but annual effluent loads of these two nutrients were greater than for typical row crops in Alabama; 5) ground water use by the industry is about 86,000 m³/d, but seepage from ponds returns water to aquifers; 6) there is little use of medicated feeds; 7) copper sulfate is used to control blue‐green algae and off‐flavor in ponds, but copper is rapidly lost from pond water; 8) although sodium chloride is applied to ponds to control nitrite toxicity, stream or ground water salinization has not resulted from this practice; 9) fertilizers are applied two or three times annually to fry and fingerling ponds and occasionally to grow‐out ponds; 10) hydrated lime is applied occasionally at 50 to 100 kg/ha but this does not cause high pH in pond waters or effluents; 11) accumulated sediment removed from pond bottoms is used to repair embankments and not discarded outside ponds; 12) sampling above and below catfish pond outfalls on eight streams revealed few differences in stream water quality; 13) electricity used for pumping water and mechanical aeration is only 0.90 kW h/kg of production; 14) each metric ton of fish meal used in feeds yields about 10 tons of dressed catfish. Reduction in effluent volume through water reuse and effluent treatment in settling basins or wetlands does not appear feasible on most farms. However, some management practices are recommended for reducing the volume and improving the quality of channel catfish pond effluents.     

斑点叉尾(鮰)养殖技术及病害防治

我国自美国引进斑点叉尾(鮰),并深入进行了养殖技术研究,已在全国20多个省、市、自治区推广应用,十几年来产值达数十亿元.斑点叉尾(鮰)病害及防治技术的研究,解决了养殖中重大技术难点,它的应用取得了巨大经济效益和社会效益.     

利用mtDNA控制区序列分析斑点叉尾(鮰)的遗传多样性

利用m tDNA控制区序列对1984、1997年引进的斑点叉尾鮰群体遗传多态性进行了分析。通过PCR产物测序法,测定了40尾斑点叉尾鮰线粒体DNA的一段包括部分Cytb基因、tRNAThr、tRNAPro、D-loop控制区和部分tRNAThe长度为1256 bp的核苷酸序列,经过比对分析得到7个序列单元型。7个单元型中共有13个碱基转换位点,全部发生在控制区,其序列相似度平均为99.58%。群体总的序列单元型多态性比例为17.5%,其中1997年群体的单元型多态性比例为35%,是1984年群体单元型多态性比例(15.0%)的2倍多。初步表明1984年引进的群体遗传多样性较低。     

斑点叉尾鮰胚胎及卵黄囊期仔鱼发育研究

探索研究了斑点叉尾鮰(Ictalurus punetatus)的早期牛活史及其发育生物学.运用解剖镜观察、记录、测量、描述、绘图等方法,连续规察了6个批次斑点叉尾鮰的胚胎及卵黄囊期仔鱼发育情况.结果表明:(1)在水温23～25℃时,斑点叉尾鮰胚胎期约需186 h,有效积温4 490～4 6lO qC·h;水温24～27℃时,班点叉尾鮰卵黄囊期约需6 d,有效积温3 620～3 710℃·h.(2)斑点叉尾鮰胚胎在出膜之前可见血液循环、胸鳍突起、眼球色素、直肠和肛门,卵黄囊耗尽期时各鳍鳍条明显且尾鳍已分叉.(3)斑点义尾鮰胚胎发育的温度上限是28～29℃.     

Biochemical Oxygen Demand in Channel Catfish Ictalurus punctatus Pond Waters

A study of the biochemical oxygen demand (BOD) of waters from ten channel catfish ponds at Auburn, Alabama, revealed that the 5-d BOD (BOD₅) seldom exceeded 8 mg/L and that the ultimate BOD (BOD_u) was usually less than 30 mg/L. Water samples from catfish ponds usually needed to be diluted only 2 or 3 times to permit BOD₅ measurements, and nitrification occurred even during a 5-d incubation period. Catfish pond waters were not extremely high in ammonia nitrogen concentration, and ammonia nitrogen introduced in the ammonium chloride-enriched dilution water caused an appreciable increase in BOD of some samples. Plankton respiration is a major component of carbonaceous BOD (CBOD) in catfish pond waters. Thus, the BOD is not expressed as rapidly during 5-d incubations as in typical waste-water. The ultimate BOD (BOD_u) would be a good measurement of oxygen demand for catfish pond effluents, but it is difficult to measure. Data from this study suggest that BOD_u can be estimated from BOD₅, but the correlation is not strong ( R ²= 0.62). An alternative is to develop a short-term BOD measurement specifically for effluents from channel catfish and other aquaculture ponds. This study suggests that a 10-d BOD conducted without nitrification inhibition or addition of ammonia nitrogen in dilution water might be a better alternative to standard BOD₅ or BOD_u measurements normally used in wastewater evaluation.     

Effects of Stocking Sac-Fry and Hatchery-Fed Fry on Production of Fingerling Channel Catfish Ictalurus punctatus

Abstract.— Channel catfish Ictalurus punctatus fry are typically held under hatchery conditions for 7 to 14 d after hatching to allow feeding and growth before they are stocked into nursery ponds to produce fingerling catfish. In an attempt to reduce hatchery operating costs, several catfish fingerling producers in Louisiana presently stock fry within 2 d after hatching before yolk absorption is complete. Fry at this stage of development are commonly referred to as "sac-fry." Although research has shown that fry can be stocked at the onset of yolk absorption with no detrimental effects on subsequent fingerling production, stocking sac-fry has been reported to result in reduced fingerling survival. To further investigate this topic, production trials were conducted in experimental outdoor pools over the course of two growing seasons to evaluate the effect of stocking fry of three different ages (2-, 7-, and 14-d post-hatch, DPH) on survival, growth (weight and length), condition factor (K), yield, feed consumption, and feed conversion ratio (FCR) of fingerling catfish. Results from both trials indicated that the age at which fry were stocked had no effect on production characteristics with the exception of growth. Specifically, fingerlings reared from fry stocked at 2 and 7 DPH were significantly larger than fingerlings reared from fry stocked at an age of 14 DPH. These findings suggest that the practice of stocking sac-fry may be a suitable alternative to the traditional procedure of holding and feeding fry under hatchery conditions prior to stocking. However, in order to fully evaluate the effects of early-age stocking of catfish fry on fingerling production, additional studies must be conducted under pond conditions. Furthermore, these studies must be coupled with a rigorous economic analysis before the practice of stocking sac-fry can be recommended to the catfish industry.