Effects of fish size and water temperature on the acute toxicity of boron to Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> and red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

ABSTRACT:     The acute toxicities of boron were examined for Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major in terms of fish size and water temperature. Japanese flounder of 0.1–70.0 g and red sea bream of 0.6–20.3 g were exposed to different concentrations of boron for 96 h at 20°C under semi-static conditions. In both fish species, the median lethal concentration (LC₅₀) for 96 h of boron increased linearly with increasing fish size, ranging from 108 to 252 mg B/L for the flounder, and from 97 to 172 mg B/L for the sea bream. The effect of water temperature on acute toxicity was examined for Japanese flounder of 0.6 and 1.5 g at 10, 15, 20 and 25°C, and for red sea bream of 0.6 and 2.4 g at 12, 15, 20 and 25°C. The toxicity of boron for the flounder increased linearly with increasing water temperature. The 96 h LC₅₀ values ranged from 299 to 108 mg B/L for the 0.6 g flounder and from 350 to 113 mg B/L for the 1.5 g flounder. A similar trend was shown for the 2.4 g red sea bream; however, the relationship for the 0.6 g red sea bream was not significant.     

Lymphocystis disease virus persists in the epidermal tissues of olive flounder, Paralichthys olivaceus (Temminch & Schlegel), at low temperatures

Olive flounder artificially infected with lymphocystis disease virus (LCDV) were reared at 10, 20 and 30 °C for 60 days, to compare LCD-incidence. In the fish reared at 20 °C, lymphocystis cells appeared on the skin and fins at 35 days post-challenge, and the cumulative LCD-incidence was 80% at 60 days. High levels of LCDV, with a mean polymerase chain reaction (PCR) titre of 10⁶ PCR-U mg⁻¹ tissue, were detected in the fins and skin of LCD-affected fish at 20 °C, but were not detected in the spleen, kidney, brain and intestinal tissues of these fish. No LCD clinical signs were observed in the fish reared at 10 °C and 30 °C; however, a low level of LCDV (10³ PCR-U mg⁻¹ tissue) was detected in the fins and skin of these fish. By increasing the rearing temperature from 10 to 20 °C, lymphocystis clusters appeared on the skin and fins of the fish with no previous LCD clinical signs within 33 days after the temperature change. It was shown that permissive cells for LCDV infection exist in the epidermis of olive flounder. At low temperatures, small amounts of LCDV were able to persist over a period extended for a further 45 days in the fish epidermis, even though the fish showed no LCD clinical signs. The optimum growth temperature of LCDV is near 20 °C.     

Effects of temperature changes on the endogenous rhythm of oxygen consumption in the Japanese flounder <Emphasis Type="Italic">paralichthys olivaceus</Emphasis>

ABSTRACT:   The effects of temperature changes on the endogenous rhythm of oxygen consumption in the Japanese flounder Paralichthys olivaceus which were acclimated to 3, 14 or 20°C in advance were investigated. The oxygen consumption rate (OCR) of individuals (total length >28 cm) that were acclimated to 3°C, maintained a relatively low value of 6.9 ± 2.3 mL (mean ± SD) O₂/kg ww (wet weight)/h till 5.8°C, which is considered a 'minimum' rate. Thereafter, the OCR gradually increased up to 18.7 mL O₂/kg ww/h at the temperature of 10.6°C. The OCR of individuals acclimated to 14°C stabilized with 124.2 ± 24.1 mL O₂/kg ww/h, when tested at the relatively constant temperature of 14.4 ± 0.17°C. Maximum entropy spectral analysis revealed that the peak OCR occurred at 23.9 h intervals, which could be a circadian rhythm. The mean OCR showed a peak at 06.00–08.00 hours. For the temperature above 25°C in which the fish were acclimated to 20°C, the rhythmic patterns of OCR were observed until the experimental temperature reached 26.4°C. For the temperature above 28.4°C, the metabolic activity rhythm of the OCR was dampened and then the OCR abruptly rose again. It is assumed that the oscillator of the endogenous rhythm lost the governing of normal metabolic activity in Japanese flounders above 28.4°C. These results suggest that the temperatures of around 5.8, 26.4 and 28.4°C are the 'lower limit temperature', 'upper incipient lethal temperature', and the 'critical thermal maximum', respectively, for the endogenous rhythm of oxygen consumption in the Japanese flounder.     

Optimum dietary phosphorus level of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> reared in the recirculating system

ABSTRACT:   An 8-week feeding trial was conducted to determine the optimum dietary phosphorus level of juvenile Japanese flounder Paralichthys olivaceus reared in the recirculating system. The basal diet containing 0.33% total phosphorus (TP) was supplemented with NaH₂PO₄·H₂O to provide 0.33, 0.51, 0.71, 0.94, 1.10 and 2.12% TP for the experimental diets. Fish averaging 2.0 ± 0.04 g (mean ± SD) were fed in triplicate groups with the experimental diets for 8 weeks. After 8 weeks, fish fed the 0.51% TP diet showed significantly higher weight gain (WG), feed efficiency (FE), specific growth rate (SGR), and protein efficiency ratio (PER) than those fed the 0.33% and 2.12% TP diets ( P  < 0.05). Meanwhile, no difference was observed in WG, FE, SGR and PER of fish fed the 0.51, 0.71, 0.94 and 1.10% TP diets. Fish fed the 0.33% TP diet showed phosphorus deficiency symptoms such as poor growth and a deformed head by the end of 8 weeks. Ash and phosphorus contents of bone increased with the increase of dietary phosphorus concentrations. anova test, the quadratic regression analysis, and the broken line analysis suggested that the optimum dietary phosphorus level could be between 0.45 and 0.51% TP for maximum WG in juvenile Japanese flounder.     

Temperature-dependent index of mitotic interval τ0 in greenling Hexagrammos otakii

ABSTRACT:   The aim of this study was to establish effective procedures for chromosome manipulation in greenling Hexagrammos otakii Jordan et Starks, which has enormous aquacultural potential. To accomplish this, temperature-dependent measurements of the mitotic intervals (τ₀) were carried out. The τ₀ in this fish was determined by averaging the duration of the first and third embryonic divisions at temperatures ranging 5–25°C. At higher temperatures, eggs developed faster and underwent more identical development. For greenling, τ₀ were 341.1 ± 3.60 min at 5°C, 275.5 ± 4.53 min at 10°C, 189.7 ± 6.93 min at 15°C, 99.2 ± 8.27 min at 20°C and 34.2 ± 8.74 min at 25°C. There were strong, negative correlations between the τ₀ and water temperatures at all temperatures studied ( Y  = −79.3 X  + 425.3, R ² = 0.9968, where Y is the mitotic interval and X is the temperature).     

Effect of taurine supplemented practical diet on growth performance and taurine contents in whole body and tissues of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

ABSTRACT:   The effect of dietary taurine on juvenile Japanese flounder was determined by feeding three taurine-supplemented experimental diets (TAU) and a commercial diet (CD) to evaluate a practical diet for juvenile Japanese flounder. Juvenile Japanese flounder were reared on the three experimental diets supplemented with taurine at 0, 0.5, 1.0% and CD. These diets were fed to juvenile Japanese flounder of an initial mean body weight of 0.2 g for 6 weeks at 20°C and the taurine contents of the whole body and tissues were analyzed. The final average body weight of juvenile Japanese flounder fed the 1.0% TAU was significantly higher than that of the other groups. Taurine contents in the whole body and tissues increased with the increase in dietary taurine level. These results indicate that juvenile Japanese flounder require at least 15 mg/g taurine in the diet, even though a combined mix of fish, krill and squid meal was the main protein source in the experimental diets.     

Effects of Fish Size and Water Temperature on the Acute Toxicity of Copper for Japanese Flounder,Paralichthys olivaceus,and Red Sea Bream,Pagrus major

The acute toxicities of copper were examined for Japanese flounder, Paralichthys olivaceus, and red sea bream, Pagrus major, in terms of fish size and water temperature. Artificial seawater of low pH of 5.4–6.7 was used as testing water to keep dissolved copper concentration at 0.04–41 mg Cu/L. Japanese flounder of 0.3–17 g and red sea bream of 0.5–13 g were exposed to different concentrations of copper for 96 h at 20 C under semistatic condition. Median‐lethal concentration for 96 h of Japanese flounder and red sea bream were 8.7–12.2 and 2.0–5.2 mg Cu/L, respectively. No significant relationships were observed between median‐lethal concentrations for 96 h and fish size for Japanese flounder, while the value decreased significantly with increasing fish size for red sea bream. Effect of water temperature on the acute toxicity was examined for Japanese flounder of 0.3 and 0.4 g at 10, 15, 20, and 25 C and red sea bream of 0.5 and 1.0 g at 12, 15, 20, and 25 C. Ninety‐six‐hour median‐lethal concentrations for Japanese flounder and red sea bream were 5.1–11.2 and 1.0–5.3 mg Cu/L, respectively. No significant relationships were observed between median‐lethal concentrations for 96 h and water temperature for both fish species.     

Effect of water temperature on the growth performance and digestive enzyme activities of Chinese longsnout catfish (Leiocassis longirostris Günther)

The present study was carried out to investigate the influence of water temperature on the growth performance and digestive enzyme (pepsin, trypsin and lipase) activities of Chinese longsnout catfish. Triplicate groups of Chinese longsnout catfish (35.6±0.48 g, mean±SE) were reared at different water temperatures (20, 24, 28 and 32 °C). The feeding rate (FR), specific growth rate (SGR) and feed efficiency ratio (FER) were significantly affected by water temperatures and regression relationships between water temperature and FI, SGR as well as FER were expressed as FR=−0.016 T ²+0.91 T −10.88 ( n =12, R ²=0.8752), SGR=−0.026 T ²+1.39 T −17.29 ( n =12, R ²=0.7599) and FER=−0.013 T ²+0.70 T −8.43 ( n =12, R ²=0.7272). Based on these, the optimum temperatures for FR, SGR and FER were 27.66, 26.69 and 26.44 °C respectively. The specific activities of digestive enzymes at 24 or 28 °C were significantly higher than that at 20 or 32 °C. In addition, there was a significant linear regression between FR or SGR and specific activities of pepsin and lipase, which indicated that pepsin and lipase played important roles in regulating growth through nutrient digestion in Chinese longsnout catfish.     

Growth and Survival of Larval Red Sea Bream Pagrus major and Japanese Flounder Paralichthys olivaceus Fed Microbound Diets

To establish the practical use of microbound diets (MBD) for larval fish in mass seedling production, rearing experiments of larval red sea bream, Pagrus major , and Japanese flounder, Paralichthys olivaeeus , were conducted. A mixture of various protein sources was used, and dietary amino acid patterns were approximated to those of larval whole body protein. Two thousand red sea bream larvae and 1,000 Japanese flounder larvae, all 10 days old, were placed in 100 liter tanks with running sea water under ambient water temperature, which ranged from 18 to 20C. The particle size of MBD was 125 μm at the beginning of the experiment and adjusted as fish size increased thereafter. Employing MBD together with a small amount of live food could sustain the growth and survival of larval red sea bream and Japanese flounder. Thus, data from the present study indicates that substitution of artificial feeds for live foods is possible for larval fish production, although improvements in MBD diets may be necessary before they are adequate for large scale seedling production.     

Annual changes in ovarian development and plasma estradiol-17β level in reared female common Japanese conger, <Emphasis Type="Italic">Conger myriaster</Emphasis>

ABSTRACT:   Annual changes in the gonadosomatic index (GSI), oocyte diameter, gonadal histology and plasma estradiol-17β (E₂) levels were investigated in female common Japanese conger Conger myriaster in captivity. Juveniles were caught in September 1999 and reared in seawater at temperatures ranging from 10–20°C for 3 years. All fish were immature when captured in September 1999. GSI and oocyte diameter increased from October 2000, peaked between summer and autumn 2001, and bottomed-out in winter 2001. Plasma E₂ level also increased from October 2000, but remained high. The ovarian developmental stage was at the peri-nucleolus stage or the oil droplet stage until September 2000. Vitellogenesis started in October 2000 and oocytes progressed to the tertiary yolk globule stage by summer 2001. However, vitellogenic oocytes regressed in all females after autumn 2001. The neogenetic oocytes began to increase after November 2001 and ovarian development progressed in 2002 as they did in 2001, although maximum GSI in 2002 was half its 2001 value. These data indicate that ovarian development in the common Japanese conger has an annual periodicity, and that these congers may be able to spawn in multiple years under rearing condition.     

Growth, stress tolerance and non-specific immune response of Japanese flounder Paralichthys olivaceus to probiotics in a closed recirculating system

ABSTRACT:   Effects of probiotics on growth, stress tolerance and non-specific immune response in Japanese flounder Paralichthys olivaceus were evaluated in a closed recirculating system. Survival and growth of flounder treated by supplying commercial probiotics either in the diet (the probiotic diet group), or into the rearing water (the water supply group), were higher compared to the untreated group (the control group). Water quality parameters, pH, NH₄-N, NO₂-N and PO₄-P showed lower concentration in the probiotic diet group compared with the control group and the supply group. Plasma lysozyme activity in the probiotic diet group and the water supply group was significantly higher ( P  < 0.05) than that in the control group. In heat shock stress tests, flounder in the probiotics-treated groups showed greater heat tolerance (measured by 50% lethal time, LT50) than the control group. Pathogen challenge tests with Vibrio anguillarum (2 × 10⁷ c.f.u./mL) resulted in significantly higher survival in the probiotics-treated groups than the control group. Results indicated that probiotics supplied in the rearing water and the diet of fish enhanced the stress tolerance and the non-specific immune system of Japanese flounder, providing them a higher resistance against stress conditions and pathogens.     

Effects of Dietary Chlorella ellipsoidea Supplementation on Growth, Blood Characteristics, and Whole-Body Composition in Juvenile Japanese Flounder Paralichthys olivaceus

The study was conducted to investigate the effects of dietary Chlorella powder (C) supplementation on growth performance, blood characteristics, and whole-body composition in juvenile Japanese flounder Paralichthys olivaceus . Four experimental diets were supplemented with C at 0, 1, 2 and 4% (C₀, C₁, C₂, and C₄) on a dry-weight basis. Three replicate groups of fish averaging 1.13 ± 0.02 g (Mean ± SD) were randomly distributed in each aquarium and fed one of four experimental diets for 12 wk. After 12 wk of the feeding trial, fish fed C₂ diet had higher weight gain (WG), feed efficiency (FE), and protein efficiency ratio (PER) than did fish fed C₀ and C₁ diets ( P 0.05); however, there was no significant difference among fish fed C₁ and C₄ diets, and among fish fed C₂ and C₄ diets ( P > 0.05). Fish fed C₂ and C₄ diets had a lower serum cholesterol level than did fish fed C₀ and C₁ diets ( P 0.05). Fish fed C₂ and C₄ diets had a lower body fat than did fish fed C₀ ( P 0.05). These results indicate that dietary supplementation of 2% Chlorella powder in the commercial diets could improve growth, feed utilization, serum cholesterol level, and whole-body fat contents in juvenile Japanese flounder.     

Determining the optimum doses of Kurasan (ethoxiquinolin) and butylhydroxytoluol (BHT) in dry pellets: effect of both anti-oxidants on some haematological and condition parameters of rainbow trout, Salmo gairdneri Richardson

Abstract. Kurasan and BHT were tested at doses of 100, 200 and 400mg kg^-1 incorporated in dry pellets. The administration of these antioxidants did not influence the red blood count of rainbow trout, Salmo gairdneri Richardson, at body weights of 100 to 400g, reared in flow-through tanks at water temperatures of 7 to 13°C and in cage culture at water temperatures of 15 to 2O°C. In laboratory experiments at a water temperature of 14°C, the highest Kurasan dose increased the red blood cell (RBC) count insignificantly by 14% (1.06 vs 0.93 10¹²1^-1) after 80 days, haematocrit (PCV) was increased by 27% (0.410 vs 0.32511^-1), and haemoglobin (Hb) by 16% (72 vs 62gl^-1), This was seen in the cage culture experiment, but not in the experiments in the flow-through tanks. A trend of diminishing haematological parameters of the red blood count and total blood serum protein (TP) of the fish fed with BHT-stabilized diet was recorded only under laboratory conditions at the water temperature 9°C, The decline of RBC count in the experimental group with 0.04% BHT represented 14% (0.90 vs 1.05 10¹²1^-1), the decline in PCV amounted to 18% (0.328 vs 0.39811^-1), Hb to 17% (57 vs 69g 1^-1), and TP to 11% (39 vs 44g 1^-1).     

Effects of temperature, density and early weaning on the survival and growth of Atlantic ditch shrimp Palaemonetes varians larvae

This investigation examined the effects of temperature, density and early weaning on the survival and growth of Palaemonetes varians larvae. Survival of larvae raised at 17.5 °C was not significantly different (average + standard deviation) (94 ± 5%) from the survival of those raised at 19.5 °C (95 ± 5%) and at 21.5 °C (94 ± 4%). However, the duration of the larval stage was significantly longer for shrimp reared at 17.5 °C (17.3 ± 0.8 days) compared with shrimp reared at 19.5 °C (14.3 ± 0.7 days) and at 21.5 °C (11.3 ± 0.6 days). No significant differences ( P >0.05) were found in the survival rate, final weight and length of larvae reared at the densities of 5, 10, 20 and 50 larvae L⁻¹. The survival of P. varians larvae fed solely on Artemia was significantly higher ( P <0.05) than larvae weaned with an artificial practical diet from Zoea II stage (94 ± 4% and 82 ± 1%, respectively, for Artemia and artificial diet-fed larvae), but no significant differences ( P >0.05) were observed in the final larval weight or length between these two treatments. The survival and growth of the larvae fed with the practical diet tested is a promising step ahead in the development of the culture of this species as it eliminates both the need for Artemia throughout all larval stages, and the need for more expensive artificial diets.     

Changes in growth,higher salinity tolerance and behavioral traits in Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> after repeated cross-breeding

ABSTRACT:     To improve stock enhancement strategies, the influences of repeated cross-breeding on several traits were studied in hatchery-reared juveniles of the Japanese flounder. Ten families (seven caught in the wild and three from cross-bred brood fish) were produced by artificial fertilization. Ninety-four days after hatching, we investigated settlement, burying in the sand and escape behavioral traits, and then measured tolerance of high salinity and six morphological traits. Juveniles from the repeatedly cross-bred brood fish showed significantly higher growth and tolerance than those from the wild-caught brood fish. Among the behavioral traits, a significantly lower settling speed and incidence of burying in the sand were observed in the juveniles from the repeatedly cross-bred families. Heritability ( h ²) of growth traits was more than 0.2 in both origins, while that of other traits was close to zero. These results suggest that repeated cross-breeding of Japanese flounder under hatchery conditions improves growth performance and leads to the loss of certain behavioral traits that are considered essential to survival in wild environments.     

Growth and feeding responses of a hatchery population of brown trout (Salmo trutta L.) at low temperatures

Abstract— Feed intake, specific growth rate and changes in body composition were studied in age 1+ (140-190 g) brown trout ( Salmo trutta L.) reared at three temperatures (2, 4 and 6°C) under continuous light conditions. Feed in take increased from 35.7 kJ-kg⁻¹.day⁻¹ at 2°C to 95.7 kJ-kg⁻¹-day⁻¹ at 6°C, and the growth rate increased from 0.19%-day⁻¹ to 0.42%-day⁻¹ over the same temperature range. The estimated lower temperature limits for feeding and growth were slightly above 0°C. For all groups of fish, the majority (about 75%) of the weight gain comprised water and protein, but lipid deposition tended to increase with increasing temperature. The deposition of lipid accounted for about 50% of the body energy gain at all temperatures.     

Effects of organic acids on growth and phosphorus utilization in red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

ABSTRACT:   A feeding experiment was conducted to investigate the effects of various organic acids and supplements on the growth, phosphorus (P) utilization, and environmental loading of nitrogen (N) and P in red sea bream Pagrus major. Seven diets designated as PA (0.5% inorganic P as Ca[H₂PO₄]₂), PO (no inorganic P), CA (1% citric acid), MA (1% malic acid), LA (1% lactic acid), MHA (1% methionine hydroxy analog) and LTE (1% liquid trace elements) were formulated. Duplicate groups of 25 fish were fed four times daily to near satiation for 75 days. Fish fed CA and LTE diets showed significantly better weight gain and feed conversion ratio compared to fish fed diet PO. Absorption of P was significantly improved in all organic acid-supplemented groups compared to the PA and PO groups. The P retention in CA and LTE groups were significantly higher compared to PA and PO diets. The P excretion was also significantly decreased in all organic acid-supplemented groups. Thus, use of organic acids, in particular CA and LTE, in red sea bream diets can reduce the use of inorganic phosphorus and contribute to the development of much-desired eco-friendly diets.     

Utilization of glucose and starch by the grouper Epinephelus malabaricus at 23°C

ABSTRACT : The aim of the present study was to investigate carbohydrate utilization by the grouper Epinephelus malabaricus reared at 23°C. Two isoenergetic semipurified diets were prepared with two carbohydrate sources (glucose and starch). Each diet was fed to triplicate groups of grouper in a recirculating rearing system for 8 weeks. Water temperature was held constant by a thermal controller at 23 ± 1°C. Weight gain, feed efficiency (FE) and protein efficiency ratio (PER) of fish fed the starch diet were significantly higher ( P  < 0.05) than those of fish fed the glucose diet. Body lipid content of the starch-fed group of fish was higher than that of glucose-fed group of fish. Hepatic hexokinase and glucose-6-phosphate dehydrogenase activities were higher in fish fed the starch diet than fish fed the glucose diet. Fish fed the glucose diet had higher hepatic glucose-6-phosphatase activity than fish fed the starch diet. These results suggest that starch is better utilized by grouper than glucose when the water temperature is 23°C.     

Anaesthetic efficacy and physiological responses to clove oil-anaesthetized kelp grouper Epinephelus bruneus

The efficacy of clove oil as an anaesthetic and at producing a physiological response (plasma cortisol and glucose) was evaluated in the kelp grouper, Epinephelus bruneus . To acquire complete anaesthesia in less than 3 min and recovery in <10 min, three doses of clove oil were tested at 18, 22 and 26 °C. Although higher anaesthetic doses resulted in shorter induction times and longer recovery times, and a lower temperature resulted in longer anaesthesia induction and slower recovery, we found the optimal dose and administering temperature of clove oil to be 250–300 mg L⁻¹ at water temperature of 18 °C, 150–200 mg L⁻¹ at water temperature of 22 °C and 50–100 mg L⁻¹ at water temperature of 26 °C respectively. Following the administration of 150 mg L⁻¹ of clove oil at 22 °C, the plasma cortisol level was highest (4.24 ± 1.571 μg dL⁻¹) after 12 h and the plasma glucose was highest (92.7 ± 9.61 mg dL⁻¹) after 2 h. These results should be useful to the aquaculture industry, where anaesthesia is necessary for a range of activities.     

Characteristics of burnt meat in cultured yellowtail <Emphasis Type="Italic">Seriola quinqueradiata</Emphasis>

ABSTRACT:   In order to understand the characteristics of burnt meat in cultured yellowtail Seriola quinqueradiata , fish were kept at two different temperatures (13 and 30°C) and slaughtered by either spinal cord destruction (SCD) or suffocation in air (SA). Early postmortem changes during storage at 32°C were analyzed by rheological, biochemical, and histological methods. The burnt meat (with lightness parameter, L* ≥ 55) was observed at 1-h storage in the SA 30°C group, at 2 h in SCD 30°C, and at 4 h in SA 13°C; meat was normal for the SCD 13°C group until 6 h of storage. Breaking strength scores were higher for the normal meat (200 g/cm²) than burnt meat (70 g/cm²) at 4 h of storage. Expressible water content was higher for the burnt meat than for the normal meat. Adenosine triphosphate concentrations for the SCD groups were higher than for the SA counterparts. Moreover, pH decrease was much faster in the 30°C groups, showing pH 5.6 at 2 h of storage. A negative correlation between the pH and lactic acid contents in muscle ( P  < 0.001) was found. Histological analysis evidenced a larger pericellular area (40%) in the burnt samples than in the normal samples (16%). It was confirmed that a higher fish-keeping water temperature and a stressful slaughter method (faster glycolytic process) were determinative factors that influence the occurrence of burnt muscle in yellowtail, and that the effect of the former is larger than the latter.