Treatment of vibriosis in European sea bass larvae, Dicentrarchus labrax L., with oxolinic acid administered by bath or through medicated nauplii of Artemia franciscana (Kellogg): efficacy and residual kinetics

European sea bass larvae were challenged by bath with Listonella anguillarum strain 332A, 2.5×10(7) CFUmL(-1) for 1h. Fish either received no treatment or oral treatment with Artemia franciscana (Kellog) nauplii enriched with oxolinic acid, or bath treatments with oxolinic acid. Medication commenced 1day following challenge and was performed on days 1, 3 and 5 post-challenge at a dosage of 20mgL(-1) for 2h for bath treatments, while two doses each of 750 nauplii per fish were administered daily for five consecutive days in oral treatments. Cumulative mortality reached 96% for the unmedicated challenged group, 32% in the group receiving bath treatments and 17% in the group receiving medicated nauplii. Pharmacokinetic parameters of oxolinic acid were calculated in sea bass larvae, for both treatments. Steady-state concentrations of oxolinic acid of 48.0 and 75.2μgg(-1) were achieved for bath treatment and oral treatment, respectively, while the elimination half-life was calculated to be 25.1h for bath treatment and 21.7h for oral treatment.     

Enhancement of non-specific disease resistance in Atlantic salmon, Salmo salar L., by a glucan from Saccharomyces cerevisiae cell walls

Abstract. An insoluble polysaccharide from the cell wall of Saccharomyces cerevisiae , called M-Glucan, has been shown to enhance the non-specific disease resistance of Atlantic salmon, Salmo salar L., when injected intraperitoneally. M-Glucan consists only of glucose units which presumably are linked through β -1,3 and β -1,6 linkages. Enhanced resistance was demonstrated against Yersinia ruckeri , the causal agent of enteric redmouth disease, against Vibrio anguillarum , the causal agent of classical vibriosis and against Vibrio salmonicida , which causes cold water vibriosis or 'Hitra-disease' in salmon. At a dose of 2mg M-Glucan per fish (20g mean weight), maximal resistance developed in the fish 3 weeks after injection. Injection of different glucan doses and challenge one week later with Vibrio anguillarum , showed that 50-200μg glucan per fish resulted in the highest level of resistance. The level of resistance in Atlantic salmon obtained with M-Glucan was strikingly higher than that obtained with another glucan which was prepared from Saccharomyces cerevisiae by a different procedure.     

Bioencapsulation and pharmacokinetic study of oxolinic acid in rotifers (Brachionus plicatilis), Artemia franciscana nauplii and metanauplii

The uptake of oxolinic acid by the rotifer Brachionus plicatilis, Artemia franciscana nauplii and metanauplii was studied as a function of its concentration in the enrichment medium and the duration of the enrichment period. An emulsion containing 5, 10, 20 or 30% (w/w) oxolinic acid was administered and the enrichment period lasted 4, 8, 12 or 36 h. Highest incorporation of oxolinic acid was achieved using a 20% emulsion and a 12 h enrichment for rotifers (205.05 ± 17.1 μg g^?1 dry weight), a 24 h enrichment for nauplii (2528.8 ± 254.6 μg g^?1 dry weight), and an 8 h enrichment for metanauplii (1236.58 ± 22.9 μg g^?1 dry weight). Higher concentrations of oxolinic acid in the enrichment emulsion or longer enrichment times resulted in decreased survival. Two hours post enrichment the contents of the drug appeared significantly decreased. The concentration data of oxolinic acid were best fit to a two phase exponential elimination model, the first phase elimination half‐life (t_1/2α) being 1.86, 1.08 and 1.74 and the terminal phase elimination half‐life (t_1/2β) 26.83, 29.67 and 17.48 in rotifers, nauplii and metanauplii correspondingly. Enrichment with an emulsion containing 20% oxolinic acid is recommended employing a duration of 12, 24, or 8 h enrichment for rotifers, nauplii and metanauplii respectively, while enriched carriers should be used shortly after enrichment.     

恶喹酸与诺氟沙星对异育银鲫体内嗜水气单胞菌的抑菌效果比较

在水温(25±2)℃下,给体质量150~200g的异育银鲫分别口灌3种剂量(20、30、40mg/kg)的诺氟沙星和恶喹酸,结合这两种药物对嗜水气单胞菌AH10的体外药效学研究和对异育银鲫单次口灌不同剂量的诺氟沙星、恶喹酸的体内药代动力学,研究诺氟沙星、恶喹酸对异育银鲫体内嗜水气单胞菌AH10的抑菌效果。试验结果表明,恶喹酸和诺氟沙星对嗜水气单胞菌AH10的最小抑菌质量浓度分别为1μg/mL和0.5μg/mL。口灌上述3种剂量恶喹酸、诺氟沙星后,异育银鲫血浆中恶喹酸的最大药物质量浓度分别为4.1μg/mL、6.0μg/mL和8.89μg/mL;诺氟沙星的最大药物质量浓度分别为11.5μg/mL、15.1μg/mL和18.9μg/mL;恶喹酸的最大药物质量浓度/最小抑菌质量浓度分别为4.1、6.0和8.89;诺氟沙星的最大药物质量浓度/最小抑菌质量浓度分别为23、30.2和37.8;恶喹酸0~24h内药—时曲线下面积/最小抑菌质量浓度分别为21.6214、33.1449、39.1846;诺氟沙星0~24h内药—时曲线下面积/最小抑菌质量浓度分别为274.75、451.55、578.35。综合0~24h内药—时曲线下面积/最小抑菌质量浓度、最大药物质量浓度/最小抑菌质量浓度这两个指标可知,诺氟沙星对异育银鲫体内的嗜水气单胞菌AH10抑制效果强于恶喹酸。     

The effect of vitamins C and E in (n-3) highly unsaturated fatty acids-enriched Artemia nauplii on growth, survival, and stress resistance of fresh water walleye Stizostedion vitreum larvae

This study aimed to evaluate the effect of enriching Artemia nauplii with vitamin C (ascorbyl-6 palmitate) or vitamin E (α-tocopherol acetate), 20% w/w, together with a mixture of concentrated eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) on the growth, survival, and stress resistance of fresh water walleye Stizostedion vitreum larvae. Either cod liver oil (CLO) or EPA/DHA ethyl esters concentrate was used as lipid sources in the Artemia enrichment. Walleye larvae were fed ad libitum for 40 days. At day 40, submersion in salt water (25 g L⁻¹) was performed to evaluate larvae resistance to stress. EPA and DHA levels in walleye juveniles fed EPA/DHA-enriched Artemia increased significantly, by an average of 650% compared with fish fed non-enriched Artemia . A significant increase was found for vitamins C (71.8 ± 1.0 and 42.7 ± 1.2 μg g⁻¹ wet weight (WW)) and E (17.0 ± 3.7 and 6.5 ± 0.9 μg g⁻¹WW) concentrations in fish fed enriched and unenriched Artemia , respectively. Growth was comparable throughout treatments, whereas survival was significantly higher in fish fed CLO-enriched Artemia nauplii compared with fish fed Artemia nauplii enriched with EPA/DHA concentrate. The addition of vitamin C increased fish survival by 1.4-fold compared with fish fed Artemia enriched with only EPA/DHA concentrate. The survival of the latter was similar to control fish ( Artemia without enrichment). The supplementation of vitamin E did not affect fish survival significantly. Stress tests revealed that the resistance of walleye larvae to salinity changes increased when Artemia enrichment was supplemented with vitamin C. However, walleye larvae fed CLO-enriched Artemia had the best performances in the stress test.     

The in vitro susceptibility of Aeromonas salmonicida and other fish-pathogenic bacteria to 29 antimicrobial agents

Abstract. The minimum inhibitory concentrations (MICs) of 29 antimicrobial agents were determined for some representative Aeromonas salmonidda, Yersinia ruckeri and Vibrio isolates. Eleven of them, including three widely used in clinical practice, were further tested against 28–36 recent field isolates of A. salmonidda. The fluoroquinolones were inhibitory at very low concentrations with 50% of A. salmonidda isolates having a MIC of enro-floxacin ≤0·02μg ml-1. The distribution of MICs to the fluoroquinolones and to oxolinic acid were similar indicating possible cross resistance. Amoxycillin, florfenicol, minocycline, rifampicin and the potentiated sulphonamides had a single peak MIC distribution with values of ≤1·25μg ml-1. Minimum inhibitory concentrations of the fluoroquinolones were four or more times greater at 10°C compared with 22°C; this was not so with amoxycillin, florfenicol or the sulphachlorpyridazine-trimethoprim (S-TP) combination. A. salmonicida was rapidly killed at 22°C by the fluoroquinolones and S-TP whereas oxolinic acid and amoxycillin killed within 24h. Florfenicol was bacteriostatic. The therapeutic potential of some of these antibiotics is considered.     

Fluoroquinolones display rapid bactericidal activity and low mutation frequencies against Aeromonas salmonicida

Abstract. Oxolinic acid and five new fluoroquinolones, sarafloxacin, enrofloxacin, PD127, 391, PD117, 596 and C1934, were evaluated for in vitro activity against Aeromonas salmonicida. Sarafloxacin, enrofloxacin, PD127, 391 and PD117, 596 were significantly more active than cither oxolinic acid or C1934 in terms of their bactericidal activity against both oxolinic-acid-resistant and sensitive strains of A. salmonicida , killing 99% of the bacteria after 1h exposure. Resistant mutants developed at lower frequency to the fluoroquinolones than to oxolinic acid or oxytctracycline at 5, 10 and 20 times the MIC. However, mutants selected with one quinolone were cross-resistant to all the other quinolones tested.     

Pharmacokinetics and bioavailability of flumequine and oxolinic acid after various routes of administration to Atlantic salmon in seawater

The present preclinical study was performed to investigate the pharmacokinetics of flumequine in Atlantic salmon (Salmo salar L.) in seawater after administration of different doses and dosage formulations. Flumequine was administered intravenously (dose 4.9 mg/kg fish) and orally from the drug delivery system Aqualets as Apoquin 5 g/kg (dose 25 mg/kg) and 10 g/kg (dose 50 mg/kg), respectively. Experiments were carried out with oxolinic acid administered in the same way for the purpose of comparing the two compounds. The seawater temperature was 5±0.2°C in all experiments.

The pharmacokinetic calculations showed that the distribution half-life for flumequine was and for oxolinic acid . The drugs were absorbed rapidly, and flumequine reached a plasma concentration of C_max = 2.26 μg/ml after a single oral dose of 25 mg/kg, whereas oxolinic acid reached C_max = 0.99 μg/ml. The apparent bioavailability of flumequine was found to be 40–45%, whereas the apparent bioavailability of oxolinic acid varied from 25% at a dose of 50 mg to 40% at a dose of 25 mg/kg body weight of fish. The distribution profile of flumequine in the various compartment of fish appeared to be different from that of oxolinic acid. After a single oral dose (25 mg/kg) the areas under the concentration-time curves showed that flumequine was 2.3 times more concentrated in plasma and 2.6 times more concentrated in liver compared to oxolinic acid. In muscle the difference was less pronounced, flumequine being 1.4 times more concentrated than oxolinic acid.     

A single-dose pharmacokinetic study of oxolinic acid and vetoquinol,an oxolinic acid ester,in cod,Gadus morhua L., held in sea water at 8 degrees C and in vitro antibacterial activity of oxolinic acid against Vibrio anguillarum strains isolated from diseased cod

The pharmacokinetic properties of the antibacterial agent oxolinic acid and vetoquinol, the carbitol ester of oxolinic acid, were studied after intravenous (i.v.) and oral (p.o.) administration to 100-150 g cod, Gadus morhua L., held in sea water at 8 degrees C. Following i.v. injection, the plasma drug concentration-time profile showed two distinct phases. The distribution half-life (t1/2alpha) was estimated at 1.3 h, the elimination half-life (t1/2beta) as 84 h and the total body clearance (Cl(T)) as 0.047 L kg(-1) h(-1). The volume of distribution at steady state, Vd(ss) was calculated to be 5.5 L kg(-1), indicating good tissue penetration of oxolinic acid in cod. Following p.o. administration of oxolinic acid or vetoquinol, the peak plasma concentrations (C(max)) of oxolinic acid and the time to peak plasma concentrations (T(max) were estimated to be 1.2 and 2.5 microg mL(-1) and 24 and 12 h, respectively. The bioavailabilities of oxolinic acid following p.o. administration of oxolinic acid and vetoquinol were calculated to be 55 and 72%, respectively. The in vitro minimum inhibitory concentration (MIC) values of oxolinic acid against three strains of Vibrio anguillarum isolated from diseased cod were 0.016 microg mL(-1) (HI-610), 0.250 microg mL(-1) (HI-618) and 0.250 microg mL(-1) (HI-A21). Based on a MIC value of 0.016 microg mmL(-1) a single p.o. administration of 25 mg kg(-1) of oxolinic acid maintains plasma levels in excess of 0.064 microg mL(-1), corresponding to four times the MIC-value, for approximately 12 days. The analogous value for a single p.o. dose of 25 mg kg(-1) of oxolinic acid administered as vetoquinol was 13 days.     

Bioencapsulation of Therapeutic Quantities of the Antibacterial Romet-30 in Nauplii of the Brine Shrimp Artemia and in the Nematode Panagrellus redivivus

Nauplii of the brine shrimp, Artemia , and cultures of the soil nematode, Panagrellus redivivus , were fed a suspension of the water-insoluble antibacterial Romet-30 (sulfadimethoxine plus ormetoprim) to determine if they could be used as a mechanism for delivery of the drug to larval penaeid shrimp.
Romet-30 was added to groups of brine shrimp nauplii and nematodes in 1 L beakers to achieve a concentration of 3 mg of drug per ml of seawater. After a 4 h uptake period, predetermined numbers of organisms were assayed for antibiotic content using the micro-plate diffusion method and a Romet-30 sensitive strain of Vibrio alginolyticus as the indicator. The resulting zones of inhibition were compared to that of a standard Kirby-Bauer sensitivity disc containing 25 μg of the drug that was placed on each plate as standard control. Negative controls consisted of equal numbers of nauplii and nematodes that were not exposed to the antibiotic. Artemia nauplii and nematodes accumulated approximately 0.1 μg of the drug per nauplius and approximately 0.25 μg per nematode. They exhibited no signs of toxicity from exposure to the drug and contained the antibiotic in sufficient quantity to provide a theoretical therapeutic dose of the drug when fed to penaeid larvae.
In subsequent tests, normal and diseased larval Penaeus stylirostris readily accepted Romet-30 enriched Artemia . Diseased larvae fed the drug in this manner exhibited a statistically greater overall survival and a greater survival to the post-larval stage by Student's t -test at the 5% significance level.     

Tissue distribution and depletion of sarafloxacin hydrochloride after in feed administration in gilthead seabream (Sparus aurata L.)

Tissue distribution and depletion of sarafloxacin was studied in gilthead seabream, under experimental field conditions at 25 and 18 °C, after in-feed administration of sarafloxacin hydrochloride for 5 days (10 mg/kg body weight/day). Ten fish per sampling point were examined during and after treatment. Muscle plus skin (n=10), liver, kidney and vertebra (pooled) were collected and analyzed by HPLC. Sarafloxacin concentrations in these tissues increased during the medication period, and then decreased rapidly. The highest sarafloxacin concentrations were recorded in liver (335.2 and 49.8 μg/g at 25 and 18 °C, respectively). In muscle plus skin, sarafloxacin concentrations were 193.0 and 42.0 μg/kg at 25 and 18 °C, respectively. Sarafloxacin residues were eliminated rapidly; at 36 h post treatment, the levels in muscle plus skin were 10.2 and 8.5 μg/kg at 25 and 18 °C, respectively. Elimination half-lives (t_1/2) were 17.8 and 32.5 h at 25 and 18 °C, respectively. Withdrawal period for the Maximum Residue Limit (MRL) of 30 μg/kg sarafloxacin in muscle plus skin (95% tolerance limit) at 25 °C was 42.2 h. The slow elimination from vertebra, relative to other tissues, suggests that vertebra behaves as a reservoir in gilthead seabream.     

Effect of poly-β-hydroxybutyrate on Chinese mitten crab, Eriocheir sinensis, larvae challenged with pathogenic Vibrio anguillarum

This study investigated the protective effect of poly-β-hydroxybutyrate (PHB) on Chinese mitten crab, Eriocheir sinensis, zoea larvae challenged with pathogenic Vibrio anguillarum. PHB was delivered to the crab larvae through rotifer and Artemia bioencapsulation. Zoea 3 larvae were challenged with V. anguillarum at a final concentration of 10(5) CFU mL(-1). PHB-enriched rotifers and Artemia nauplii were added to the culture water 24 h prior to, upon and 24 h after challenge. The results confirmed that PHB could enhance the survival and growth of unexposed E. sinensis larvae. Moreover, PHB protected larvae from the pathogen as the larvae fed PHB-enriched live food showed the highest survival and development rate in all challenged groups (P < 0.05). Furthermore, larval performance was the best when PHB was delivered to the larvae 24 h before challenge (P < 0.05). In conclusion, our results indicate that PHB can be used as part of an effective strategy to protect E. sinensis larvae from V. anguillarum resulting in higher survival and better growth, especially when applied before the challenge.     

Bioencapsulation of erythromycin using adult brine shrimp, Artemia franciscana (Latreille)

Live adult brine shrimp, Artemia franciscana (Latreille), were enriched with erythromycin to determine if Artemia could accumulate therapeutic levels for subsequent feeding to young fish. Three trials were conducted to determine the erythromycin incorporation and survival rates of enriched Artemia when fed either liposomes containing erythromycin or various erythromycin suspensions. Erythromycin concentration in Artemia fed a liposome suspension was low (∼ 5 μg mL⁻¹) relative to Artemia fed the direct suspension (> 100 μg mL⁻¹) over the same time period. When enriched with suspensions up to 1 g erythromycin L⁻¹ sea water for 14 h, Artemia survival was not significantly affected ( P > 0.05) relative to controls. Using a suspension of 1 g L⁻¹, tissue erythromycin concentrations of 109 ± 16 μg erythromycin mL⁻¹  Artemia homogenate (mean ± SEM) were achieved after 12 h. Concentrations above 170 μg mL⁻¹ were obtained using suspensions of 2–5 g L⁻¹, but Artemia survival significantly ( P < 0.05) decreased.     

Effects of oral vaccination against vibriosis in turbot, Scophthalmus maximus (L.), and sea bass, Dicentrarchus labrax (L.)

Abstract. Turbot, Scophthalmus maximus (L.), and sea bass, Dicentrarchus labrax (L.), are susceptible to vibriosis, a septicaemia caused in France by Vibrio anguillarum 408. A bacterin produced with this strain by Rhône–Merieux has been tested orally in both species and, as a comparison, by intraperitoneal injection. During a challenge carried out 4 weeks later by intraperitoneal inoculation, the protection observed in orally vaccinated fishes was significant (72 % in sea bass and 70 % in turbot). Eleven weeks after vaccination, this protection is still significant. The mean titre of serum agglutinins was weakly increased in orally vaccinated fishes. Bacteriostatic antibodies have also been searched for in serum, but compared to agglutination, the applied technique leads to lower titres and it has not been possible to prove the presence of such antibodies after oral vaccination. Passive immunizations using serum from orally vaccinated fishes (2 months after vaccination) confers some protection against a challenge carried out by inoculation of virulent vibrio. Therefore, the production of serum factors following oral vaccination of sea bass and turbot may be involved in generalized protection of fish.     

Cytophaga johnsonae: a putative skin pathogen of juvenile farmed barramundi, Lates calcarifer Bloch

Abstract Cytophaga johnsonae , a gliding filamentous Gram-negative rod, was isolated from diseased farmed juvenile barramundi, Lates calcarifer Bloch. Infected fish had extensive but superficial erosion of the skin, mainly involving the posterior flanks, but also affecting the pectoral fins and lower jaw in some individuals. Minimum inhibitory concentrations of a number of antibacterial agents for C. johnsonae were determined; acriflavine and oxolinic acid inhibited growth between 0.78 and 1.5 μg ml⁻¹, while polymyxin B, trimethoprim and sulphamethazine failed to inhibit growth at 100 μg ml⁻¹.     

图们江陆封型马苏大麻哈鱼的个体繁殖力

为研究马苏大麻哈鱼(Oncorhynchus masou)资源保护策略和人工繁殖技术,对人工养殖的图们江陆封型马苏大麻哈鱼繁殖力进行了研究。选取122尾不同养殖区域卵巢发育Ⅳ-Ⅴ期的马苏大麻哈鱼样本(其中延吉42尾、山东35尾、北京45尾)进行统计分析。试验马苏大麻哈鱼体重209~845 g,平均为(512±206)g;体长17.0~39.5 cm,平均为(26.81±6.53)cm。结果表明,大麻哈鱼的绝对繁殖力410~3 075粒,平均为(1 485±797)粒;体重相对繁殖力1.93~3.64粒/g,平均为(2.72±0.47)粒/g;体长相对繁殖力23.60~77.85粒/cm,平均为(51.35±17.60)粒/cm;Ⅴ期卵巢性腺指数14.85%~27.93%,平均为(20.97±3.57)%;繁殖力随着体重、体长、性腺指数增加而提高(P0.01)。通过人工驯养和移植培育,改变了马苏大麻哈鱼在自然环境下雌鱼卵巢发育不成熟的现象,而且繁殖力明显提高。移植到北京和山东后,其繁殖力极显著高于原产地(P0.01)。国产陆封型马苏大麻哈鱼具有规模化人工繁育的优势,能够为野生种群资源增殖提供苗种补充。     

Leaching of four different antibacterials from oil- and alginate-coated fish-feed pellets

Leaching of oxytetracycline, oxolinic acid, amoxycillin and the potentiated sulphonamide trimethoprim/ sulphamethoxazote (TMP/SMX) from surface-coated fish-feed pellets, surrounded with either cod liver oil or with calcium-alginate, was investigated. Despite the low water temperature (12°C), losses of amoxycillin, oxytetracycline and TMP/SMX from the oil-coated feed were high with 41.6-67.3% of the drugs lost after 15 min immersion. By contrast, less than 20% of oxolinic acid was lost within the same interval. When calcium-alginate was used, leaching rates were found to be considerably lower. Losses of TMP/SMX. amoxycillin and oxytetracycline ranged from 6.3 to 24.1% within 15 min. Leaching of oxolinic acid was completely prevented by the alginate.     

Pharmacokinetics of oxolinic acid and oxytetracycline in kuruma shrimp, Penaeus japonicus

The pharmacokinetics of oxolinic acid and oxytetracycline were examined in kuruma shrimp (Penaeus japonicus) after intra-sinus (10 and 25 mg/kg, respectively) and oral (50 mg/kg) administration. The shrimp were kept in tanks with recirculated artificial seawater at a salinity of 22–23 ppt. The water temperature was maintained at 25±0.6 °C. The hemolymph concentrations of both drugs after intra-sinus dosing were best described by a two-compartment open model. The distribution and elimination half-lives (t_1/2 and t_1/2β) were found to be 0.59 and 33.2 h for oxolinic acid and 0.45 and 24.7 h for oxytetracycline, respectively. The apparent volume of distribution at a steady state (V_ss) and total body clearance (CL_b) were estimated to be 1309 ml/kg and 28.8 ml/kg/h for oxolinic acid and 748 ml/kg and 22.7 ml/kg/h, respectively. The hemolymph concentration–time curves after oral administration did not fit by the nonlinear least squares method using one- and two-compartment model with first-order absorption in either of the drugs. The peak hemolymph concentration (C_max), the time to peak hemolymph concentration (t_max) and the elimination half-life were found to be 17.8 μg/ml, 7 h and 34.3 h for oxolinic acid and 24.3 μg/ml, 10 h and 33.6 h for oxytetracycline, respectively. The bioavailability (F) after oral administration was 32.9% for oxolinic acid and 43.2% for oxytetracycline. The hemolymph protein binding in vivo was determined to be 36.7±8.5% for oxolinic acid and 22.9±4.8% for oxytetracycline.     

Assessment of marine thraustochytrid <Emphasis Type="Italic">Schizochytrium limacinum</Emphasis> OUC88 for mariculture by enriched feeds

ABSTRACT:   In the present study, Schizochytrium limacinum OUC88, a thraustochytrid with high content of docosahexaenoic acid (DHA, 22:6 n −3), was used as feed for rotifer Brachionus plicatilis and Artemia franciscana . The rotifer and Artemia were harvested at 3, 6, 9, 12, 18, and 24-h intervals, analyzed for fatty acid composition, and compared with the control which fed on yeast only. The highest DHA content resulted from an enrichment period of 12 h for both fed organisms, reached 13.4 and 10.9% of the total fatty acids (TFAs) in rotifers and Artemia nauplii, respectively, and the DHA level reduced sharply if enrichment time was longer than 12 h. The pseudoalbinism rate of turbot Scophthalmus maximus juveniles fed enriched rotifers and Artemia nauplii reduced greatly (40% lower than in control group). Thus, enrichment of rotifers and Artemia nauplii by DHA-rich Schizochytrium limacinum OUC88 may provide a practical strategy for feeding fish juveniles in aquaculture.     

Lipid Nutrition and Feeding of Cobia Rachycentron canadum Larvae

This study examined the fatty acid composition of cobia Rachycentron canadum eggs and yolksac larvae, as well as the ovaries of wild caught females as an initial guide to lipid nutritional requirements. A 2-wk feeding study also was conducted to investigate the effectiveness of four dietary treatments on the growth and survival of cobia larvae. Cobia eggs in the tailbud stage contained 31.4 ± 1.3 μg lipid/egg. After hatching, the amount of lipid decreased significantly (P < 0.05) from 28.3 ± 0.3 to 23.2 ± 0.1 μg lipid/larvae during the yolksac larval stage (days 1 to 3 after hatching). Ovaries from wild caught adults and captive spawned eggs and yolksac larvae contained high levels of PUFAs with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) accounting for approximately 80% of the total suggesting that cobia larvae may have a high dietary requirement for these fatty acids. For the feeding study, larvae were fed: 1) Artemia only; 2) enriched rotifers for 1 d only + microparticulate diet (day 313); 3) enriched rotifers for 3 d (day 3–5) + Artemia (day 3–13); and 4) enriched rotifers for 6 d (day 3–8) + Artemia (day 3–13). Cobia larvae began feeding on rotifers 3 d after hatching and on newly hatched Artemia nauplii by the fifth day following the onset of exogenous feeding (day 7). On day 7, no differences in larval growth were found among larvae fed rotifers for 3 versus 6 d, whereas larvae fed only Artemia or rotifers for I d followed by microparticulate diet were significantly smaller (P < 0.05) and did not survive beyond day 9 and 13, respectively. The results of the feeding study indicate that cobia larvae require rotifers for a minimum of 4 d following the onset of exogenous feeding.