Experimental rearing of juvenile New Zealand turbot Colistium nudipinnis (Waite 1910): a potential new aquaculture species

Investigations into factors affecting the growth of the first hatchery-produced juvenile New Zealand turbot Colistium nudipinnis (Waite 1910) showed that this endemic flatfish can be reared in raceways and tanks. After initial high mortality (> 60%) in the post-weaning period (to 120 days post-hatch), the juveniles showed high survival over the grow-out period. Growth of the juveniles was better at lower (16–18 °C) than at higher (> 20 °C) water temperatures, and better in a deep tank than in shallow raceways. Under the experimental rearing conditions, growth (to mean weight of 0.2 kg in 20 months) was relatively slow and food conversion (FCRs > 1.4) relatively high, both factors being related to the feeding behaviour of this species. C. nudipinnis feeds directly from the bottom, and this behavioural characteristic influences aspects of fish farming practice, such as stocking density and feeding strategy, that are critical to its economic viability. There is potential to improve the growth by optimizing the rearing conditions, so that it may not be unrealistic to achieve the maximum growth reached in these trials commercially and produce marketable farmed turbot, of over 400 g weight, within 2 years.     

Reproduction, gamete supply and larval rearing of New Zealand turbot Colistium nudipinnis (Waite 1910) and brill Colistium guntheri (Hutton 1873): a potential new aquaculture species

New Zealand turbot Colistium nudipinnis (Waite 1910) and brill Colistium guntheri (Hutton 1873) were studied to assess their potential for aquaculture development. The reproductive cycle of wild fish showed a long spawning season from winter to summer, during which it is possible to obtain gametes. Both species have a diurnal ovulatory cycle, and gamete collection, by stripping and fertilizing at sea, was most successful within 2–3 h before and after sunset. Male reproductive anatomy suggests that these flatfish spawn in close proximity and that pair formation is highly likely. The eggs of both species have multiple oil droplets, turbot eggs being slightly larger (0.99 mm diameter) with more droplets (18–55) than brill eggs (0.97 mm, 13–26 droplets). Hatching occurred approximately 84 h after fertilization at 14 °C. Newly hatched turbot averaged 2.2 mm in length, and brill averaged 2.1 mm. First feeding began 4 days post-hatch (DPH). During larval rearing, rotifers were replaced by Artemia nauplii at 10 DPH. Metamorphosis commenced at 12–15 DPH and was completed and the larvae settled by 45 DPH. Weaning to inert foods began at 20–22 DPH (50 mg weight) and was completed by 57 DPH. Survival of turbot was 22.8% from fertilized egg to hatching, 7.3% through incubation to 22 DPH and 2.1% through incubation to fully weaned juveniles. Weaning success for turbot from metamorphosis to 57 DPH was 31.5%.     

盐度对大菱鲆幼鱼耗氧率和排氨率的影响

研究了大菱鲆(Scophamusmaximus)幼鱼由盐度34向低盐(盐度28、23、18、12、6)以及向高盐(盐度40)适应过程中代谢率的变化。结果表明:盐度改变后,各突变组大菱鲆幼鱼的耗氧率和排氨率都呈现出不同程度的逐渐升高趋势,随着盐度突变范围的增大,变化趋势更为明显。在突变后24h左右,各突变组大菱鲆幼鱼耗氧率出现高峰值,48h后恢复到突变前的水平,此时各实验组大菱鲆的耗氧率没有显著的差异性(P>0.05)。在突变后9～15h排氨率出现高峰值,48h后各组大菱鲆幼鱼的排氨率恢复到突变前的水平,此时各实验组大菱鲆的排氨率没有显著的差异性(P>0.05)。     

Effects of dietary organic trace mineral mixture levels on survival,growth performance,body composition and antioxidant capacity of juvenile turbot (Scophthalmus maximus)

A 70‐day feeding trial was conducted to investigate effects of dietary organic trace mineral (OTM) mixture levels on survival, growth performance, body composition and antioxidant capacity of juvenile turbot (Scophthalmus maximus). The commercial diet with 0.03% inorganic trace mineral (ITM) premix was used as the control, and other four experimental isonitrogenous (50% crude protein) and isolipidic (12% crude lipid) diets were formulated to contain 0.0375%, 0.075%, 0.1125% and 0.15% OTM mixture respectively. Results showed that there were no significant differences in survival among dietary treatments. However, the growth was not significantly different between the control and OTM supplementation diets. Especially, turbot fed the diet with 0.075% OTM had significantly higher specific growth rate than 0.15%, 0.1125% and 0.0375% OTM treatments (p < .05). Moisture, crude protein, crude lipid and ash of the whole fish body showed no significant differences among dietary treatments. Activities of superoxide dismutase in serum of turbot fed diets with 0.1125% and 0.15% OTM were significantly higher than 0.0375% OTM treatment (p < .05). Activities of total antioxidant capacity and catalase in serum were the highest, while the malondialdehyde content was the lowest when the turbot were fed the diet with 0.075% OTM. In summary, results of the present study suggested that the supplementation of 0.0375% or more OTM in diets could obtain similar performance to the commercial diet with ITM premix, and the optimal amount of OTM supplementation in diets of turbot was approximately 0.075% on basis of growth performance and antioxidant capacity.     

Effects of salinity on the growth and lipid composition of Atlantic salmon (Salmo salar) and turbot (Scophthalmus maximus) cells in culture

The direct effects of osmotic pressure (salinity) on growth performance and lipid composition were investigated in fish cells in culture. Cell lines from a relatively stenohaline marine species, turbot (Scophthalmus maximus) (TF) and an anadromous species, Atlantic salmon (AS) were cultured in media supplemented with NaCl to produce osmotic pressures varying from 300 to 500 mOsm kg⁻¹. The growth rates of the two cell lines were affected in a similar manner by the salinity of the media with the rank order for both peak cell numbers and growth rates up to the day of peak cell number being 300 > 350 > 400 > 450 > 500 mOsm kg⁻¹. Cell death occurred in both cell lines in older cultures at all salinities with the greatest loss of viable cells in media of 300 and 350 kg⁻¹. However, there were quantitative and qualitative differences between the cell lines in their lipid metabolism in response to the salinity of the media. The lipid content expressed per cell showed a positive correlation between lipid per cell and salinity in TF cells, but this was less apparent in AS cells. The percentage of total polar lipid classes increased with increasing salinity in TF cells due mainly to graded increases in the percentages of choline phospholipids. In contrast, there were no significant differences in the proportions of polar and neutral lipid classes with salinity in AS cells. The only significant effect of salinity in AS cells was a decreased proportion of dimethylacetals in total lipid at the highest salinity. The same significant effect of salinity on dimethylacetal content of total lipid was observed in TF cells. However, in addition there was a graded decrease in the percentage of 18:2n-9 in TF cell total lipid with increasing salinity. This was accompanied by increased percentages of total n-3 and n-6 PUFA with higher proportions of both groups of PUFA at 450 and 500 compared with 300 mOsm kg⁻¹. The results show that environmental salinity, in the absence of hormonal or other physiological stimuli, has direct effects on the growth and lipid metabolism of fish cells and that these effects differ in cells from different fish species.     

Growth, feed utilization and growth heterogeneity in juvenile turbot Scophthalmus maximus (Rafinesque) under different photoperiod regimes

Juvenile turbot (45 g, SE = 1.3) were reared under three photoperiods, 08L:16D, 12L:12D and 20L:04D at slightly elevated ambient temperature for Ireland. Over the 297‐day experimental period, the overall growth rate of the 12L:12D (0.82% d^?1) treatment was higher than for both 08L:16D (0.80% d^?1) and 20L:04D (0.77% d^?1). Overall relative feed intake (FI = % consumption*day^?1) was higher for the 20L:04D (FI = 0.81% d^?1, SE = 0.06) treatment than for the 08L:16D (0.63% d^?1, 0.04) and 12L:12D (0.64% d^?1 0.04) treatments, whereas feed conversion efficiency (FCE = weight gain* consumption^?1) was lower in the 20L:04D (FCE = 0.67, SE = 0.08) group when compared with the 08L:16D (0.88, 0.06) and 12L:12D (0.88, 0.06) treatments. Present results show that the long‐term extended fixed photoperiod may act as an irritant, inducing stress, suppressing growth and reducing feed utilization. It is hypothesized that the progression of size‐dependent hierarchies over time can be divided into two distinct phases herein referred to as ‘hierarchy resolution’ and ‘hierarchy stabilization’ phases (or phases 1 and 2) characterized by increasing and decreasing growth heterogeneity respectively. Growth heterogeneity is measured as coefficient of variation of weight and rank correlation of initial weight of a phase and corresponding growth rate.     

温度对大菱鲆幼鱼生长、成活率和体内蛋白酶活性的影响

通过温度的变化研究不同温度对大菱鲆幼鱼生长、成活率和消化器官内蛋白酶活性的影响,结果表明,A在温度达到0℃时,幼鱼成活率为30%;4℃以上至20℃时成活率为100%,22~24℃为80%;26℃为40%;当水温达到28℃时,幼鱼成活率为0(20d)。养殖水温在8℃以下时,幼鱼基本不摄食,体重没有增长。12~16℃时,其生长速度随温度的升高而加快,当养殖水温达到20℃时,其生长速度与16℃条件下的生长速度相比较开始下降,达到24℃时,幼鱼生长速度已经明显下降,与12℃条件下的体重增长速度相接近。在8℃之前,幼鱼胃、肠和肝脏等消化器官中的蛋白酶活力单位含量较低。随温度的增加,酶活力单位显著增加,其中胃中的消化酶活力增加最快。     

Ambient salinity and osmoregulation,energy metabolism and growth in juvenile yellowtail kingfish (Seriola lalandi Valenciennes 1833) in a recirculating aquaculture system

The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption and conversion and growth performance of yellowtail kingfish (Seriola lalandi) were evaluated. Fish (11.6 ± 0.6 g) were kept for 29 days at 14, 18, 22, 26 (experimental) and 30 g L^?1 (control) salinity in independent, pilot‐scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L^?1 (7.61 ± 0.19, 7.61 ± 0.01 and 7.61 ± 0.13% day^?1, respectively) had higher growth rates than fish at 26 and 30 g L^?1 (7.10 ± 0.05 and 6.97 ± 0.06% day^?1 respectively). The higher growth rate at lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on‐growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture species.     

Effect of dietary protein and lipid levels on growth and body composition of juvenile turbot (Scophthalmus maximus L) reared under optimum salinity and temperature conditions

Effect of dietary protein and lipid levels on growth and body composition of juvenile turbot was determined at optimum salinity and temperature conditions of 17 g L^?1 and 19.2 °C, respectively, by using 3 × 2 (protein levels: 550, 600 and 650 g kg^?1; lipid levels: 69 and 168 g kg^?1) factorial design with three replications of each. Fish were hand‐fed to satiety twice daily throughout the feeding trial. Weight gain and specific growth rate of fish were significantly (P < 0.05) increased with increased dietary lipid level, but not by dietary protein level. Daily feed intake was significantly (P < 0.05) affected by both dietary protein and lipid levels. Feed efficiency ratio and protein efficiency ratio were significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Moisture content of whole body was significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Crude lipid content of whole body was significantly (P < 0.05) affected by dietary lipid level, but not by dietary protein level. Significantly higher 20:5n?3, 22:6n?3 and n?3 highly unsaturated fatty acids were observed in turbot fed the low lipid diet than fish fed the high lipid diet in all protein levels, but significantly lower 18:2n?6 was observed in fish fed the former compared with the latter. In considering results of growth, specific growth rate and efficiency of feed, optimum dietary protein and lipid levels for juvenile turbot seemed to be 550 and 168 g kg^?1 of the diet, respectively, under optimum salinity and temperature conditions.     

Combined effects of salinity and potassium concentration on juvenile mulloway (Argyrosomus japonicus, Temminck and Schlegel) in inland saline groundwater

This paper reports on experiments conducted to examine the combined effects of salinity and potassium concentration on survival and growth of juvenile mulloway (Argyrosomus japonicus, Temminck and Schlegel) in inland saline groundwater. Three separate experiments were conducted in 20 (±1)°C water. In the first experiment, mulloway were held in 60 L aquaria (triplicate) with salinities of 5, 15, 25 or 35 g L^?1 and potassium concentrations of 20%, 40%, 60% or 80% of the concentration present in oceanic water of the equivalent salinity in a 4 × 4 factorial combination for 7 days. Response surface contour diagrams were generated from survival data to estimate optimal conditions. The results showed that maximum survival of juvenile mulloway occurred at salinities of >14 g L^?1 and potassium concentrations of >38%. Survival was lowest at salinities of <7 and >33 g L^?1 and potassium concentrations of <25%. The second experiment was conducted with mulloway held in 60 L aquaria at salinities of 15, 25 or 35 g L^?1 and potassium concentrations of 40%, 60%, 80% or 100% in a 3 × 4 factorial combination for 44 days. Optimal conditions for maximum survival and growth of mulloway were within a salinity range of 15–35 g L^?1 and potassium concentration above 40%. The third experiment was conducted in three 500 L tanks to record the survival and growth of mulloway fingerlings held at 20 (±1)°C, 23 g L^?1 salinity and potassium concentrations of 50% for 8 months. Survival and growth of mulloway fingerling in inland saline groundwater were similar to those reported from a semi‐intensive floating tank system in inland saline water and sea cage trials in oceanic water.     

饲料中赖氨酸和精氨酸含量对大菱鲆幼鱼生长、体成分和肌肉氨基酸含量的影响

为研究饲料中精氨酸(Arg)、赖氨酸(Lys)水平及其相互作用对大菱鲆生长、体成分和肌肉氨基酸含量的影响,本实验以初始体质量为(18.48±0.16)g的大菱鲆作为研究对象,采用3×3双因素设计,在基础饲料中分别添加Arg(0%、0.9%和2.0%)和Lys(0%、1.19%和2.39%),配制成9种等氮等能的实验饲料,每个处理设3个重复,每重复30尾鱼,养殖周期为8周。实验结果表明,当饲料中Lys添加量为1.19%时,大菱鲆增重率和特定生长率较其他两种添加量组显著升高(P < 0.05),但精氨酸的添加对其影响不显著且与赖氨酸之间不存在交互作用(P > 0.05)。饲料效率、蛋白质效率、蛋白质保留率和鱼体蛋白质含量受饲料中Lys和Arg添加量的交互影响(P < 0.05),在Arg和Lys添加量分别为0.9%和1.19%时,数值最高,显著高于赖氨酸未添加组和高添加组(P < 0.05)。全鱼粗脂肪、水分、灰分和形体指标不受Arg和Lys的交互作用影响(P > 0.05)。粗脂肪和水分随Lys的添加量升高而显著降低(P < 0.05);肝体比和脏体比均随饲料中Arg和Lys添加量的升高而显著降低(P < 0.05)。肌肉中大多数氨基酸含量受饲料Arg和Lys添加量的交互作用,显著性最低值均出现在Arg和Lys添加量分别为0.9%和2.39%组(P < 0.05)。以上结果表明,Arg和Lys的交互作用显著影响了大菱鲆幼鱼的饲料效率、鱼体蛋白质沉积和肌肉氨基酸含量;Arg和Lys添加量分别为0.9%和1.19%时,大菱鲆有最大生长和饲料利用效率;与Arg相比,Lys为主要影响因素,适量添加Lys可以促进生长,而添加量过高Lys会与Arg产生拮抗作用,抑制生长、饲料利用和肌肉氨基酸沉积。     

Effect of salinity on growth, survival and oxygen consumption of juvenile brown shrimp, Farfantepenaeus californiensis (Holmes)

The brown shrimp, Farfantepenaeus californiensis (Holmes), is a species native to north‐west Mexico, where its culture potential is presently being addressed. Because of the climatic conditions prevailing in the region, salinities over 40 g L^?1 is a commonly encountered problem. In the present study, the effect of salinity on the growth and mortality of juvenile F. californiensis is described. The change in short‐term routine metabolism at different salinities was also evaluated in order to define the adaptive capacity of the shrimp and to provide insight into the changes in the pathways of energy distribution. Groups of shrimp were exposed to increasing salinity (25, 35, 45 and 55 g L^?1), and growth and survival rates after 75 days were determined in duplicate 1.8‐m³ tanks for each salinity level. Significant differences were found in final weight, growth rate and mortality of shrimp as a result of salinity level. Final mean shrimp weights at increasing salinity levels were 10.0, 9.4, 8.6 and 7.8 g. Corresponding mortality was 24.4%, 15.1%, 33.6% and 55.7%. Oxygen consumption was found to depend significantly on salinity and was equivalent to 0.0027, 0.0037, 0.0043 and 0.0053 mg g^?1 min^?1 respectively for the increasing salinities. The increased rate of oxygen consumption at high salinities reflects the response of the organism to osmoregulatory and ionic imbalances. Increased energy requirements to fulfil basic metabolic function as salinity increased resulted in a reduction in the energy that could be diverted to growth. Consequently, the culture of the brown shrimp at salinities over 35 g L^?1 would probably result in reduced yields.     

Influence of several non‐nutrient additives on nonspecific immunity and growth of juvenile turbot,Scophthalmus maximus L.

The effects of three non‐nutrient additives on nonspecific immunity and growth of juvenile turbot (Scophthalmus maximus L.) were studied in this feeding experiment. The five treatments are basal diet alone, basal diets containing three different additives [0.4 g kg^?1 of xylo‐oligosaccharides (XOS), 1.3 g kg ^?1 of yeast cell wall and 0.8 g kg ^?1 of bile acids] individually or in combination. Two hundred and twenty‐five turbots (average initial weight 151.3 ± 11.3 g) were randomly allotted in five treatments with three replicates within each treatment in a 72‐day period. Comparing with basal diet group, activities of C3, C4, phagocyte, lysozyme, specific growth rate and feed conversion rate in yeast cell wall, XOS and the combined groups was enhanced significantly (P < 0.05); however, these parameters in bile acid groups were increased slightly (P > 0.05) except for phagocyte (P < 0.05); superoxide dismutase activity in additive groups was not significantly increased (P > 0.05) except for the combined group (P < 0.05). In conclusion, supplementation of yeast cell wall and XOS enhanced the nonspecific immunity of juvenile turbot. Synergistic or additive effect of the three additives was not observed.     

Physiological and morphological effects of severe hypoxia,hypoxia and hyperoxia in juvenile turbot (Scophthalmus maximus L.)

We studied the physiological status of juvenile turbot (Scophthalmus maximus L.) under severe hypoxia (1 and 2 mg/L dissolved oxygen, DO), hypoxia (3 and 5 mg/L DO), hyperoxia (11 and 14 mg/L DO) and normoxia (7 mg/L DO, control) conditions. The respiratory rates, haematology parameters, acid–base balance status and gill structure were analysed to find the effects of different DO concentration on turbot. Fish mortality was only observed under severe hypoxia conditions. Severe hypoxia caused an increase in respiratory rates and red blood cell counts, as well as an increase in haemoglobin and haematocrit levels in the fish. In fish exposed to hypoxia conditions, the respiratory rate increased overall as the DO concentration decreased. Lower pCO₂ and HCO₃^? levels led to a high blood pH, while the pO₂ remained stable. In hyperoxia groups, respiratory rate decreased as the DO concentration increased. The levels of pCO₂ and HCO₃^? significantly increased (P < 0.05), while the pO₂ level and blood pH did not change obviously. The gill structure was damaged after prolonged exposure to hyperoxia, but no obvious damage was found in hypoxia groups. The fish that survived the hypoxia or hyperoxia treatment were able to restore the structural integrity of the gills after 14 days' recovery. The results suggest that juvenile turbots can tolerate a wide range of DO concentrations. However, even mild hyperoxia condition (11 mg/L DO), which is widely used in fish culture, has adverse effects on juvenile turbot physiology.     

盐度变化对军曹鱼稚鱼相关免疫因子及其生长的影响

研究了盐度(5、10、20、30及对照37)对军曹鱼(Rachycentron canadum)稚鱼生长及其血清溶菌酶、碱性磷酸酶(ALP)、旁路途径补体(ACP)溶血活性(ACH50)和总免疫球蛋白(T-Ig)含量等免疫因子的影响。实验周期为14 d。结果表明,在逐渐达到设定盐度后养殖14 d,盐度30组稚鱼特定生长率(SGR)最高(5.77%/d),而盐度5和10组的SGR(分别为4.24%/d和4.38%/d)显著低于其他组(P<0.05)。在低盐度环境中血清溶菌酶活性在第7天各组都有不同程度升高,其中以盐度20组升高最为显著,其次为盐度10和30组,但第14天各组溶菌酶活性又都回落至对照组水平;而稚鱼在低盐度环境中血清ALP活性受到明显抑制,且活性与盐度呈一定正相关;各组间ACP活性在第7天各盐度组间无明显差异,但实验结束时盐度5和10两组出现显著升高;而T-Ig含量在盐度10组中始终明显高于其他组。研究显示,军曹鱼稚鱼在盐度20~37范围内都可正常生长,尽管稚鱼有较强的低盐度耐受能力,但过低盐度明显影响其生长率并导致体色变黑、蛀鳍和应激增强等异常表现。此外,盐度变化还影响稚鱼多种免疫相关因子。[中国水产科学,2007,14(1):120-125]     

盐度对大菱鲆幼鱼生长和肌肉营养成分的影响

将平均体质量为(7.16±0.07)g的大菱鲆幼鱼分别饲养在不同盐度(12、18、24、30和36)的水体中60 d,以探讨盐度对幼鱼特定生长率、生长激素、成活率、摄食率、饲料效率和肌肉营养成分的影响。结果表明:大菱鲆幼鱼在盐度分别为18、24、30和36的水体中均生长良好,成活率为100%,特定生长率分别为1.97、1.87、1.87和2.00 %/d;在盐度为12的水体中,幼鱼的成活率和特定生长率均显著低于盐度30组(对照组)(P<0.05),分别为80.77%和1.45 %/d。生长激素为0.41～1.66 ng/mL时,盐度18和36组均显著高于盐度30组(P<0.05),而盐度12组显著低于盐度30组(P<0.05)。饲料效率为1.12%～1.38%时,盐度18、24和36组均显著高于盐度30组(P<0.05),而盐度12组显著低于盐度30组(P<0.05)。摄食率为1.19～1.28 %/d时,盐度12和24组均显著低于盐度30组(P<0.05),其它盐度组之间均无显著差异(P>0.05)。幼鱼特定生长率随血清生长激素和饲料效率的升高而增大,与盐度的相关性不显著。幼鱼肌肉中的粗蛋白质含量随水体盐度的升高而降低,除盐度12和18组之间无显著性差异外(P>0.05),其余各盐度组之间均存在显著性差异(P<0.05);盐度12组幼鱼肌肉中的粗脂肪低于其它盐度组,灰分显著高于其它盐度组(P<0.05),其余各盐度组之间粗脂肪和灰分均无显著性差异(P>0.05);各盐度组之间幼鱼肌肉中的水分均无显著性差异(P>0.05)。综上所述,适当降低盐度可改善大菱鲆幼鱼生长和肌肉品质,其适宜盐度为18。     

Larval growth of turbot, Scophthalmus maximus (L.) produced with fresh and cryopreserved sperm

The present paper assesses the fertilization and hatching rates, as well as the growth, of larvae obtained from four artificial fertilizations (AF) using fresh and cryopreserved sperm of the turbot Scophthalmus maximus (L.). Larvae growth in both sperm groups, measured in terms of length and weight at culture days 0, 7, 14 and 31, are compared, as well as their growth rates. The two groups' fertilization and hatching rates were not significantly different. Likewise, no significant differences in length and wet weight of 7‐ and 14‐day‐old larvae were found using fresh and cryopreserved sperm; however, significant differences were found in 31‐day‐old larvae, which were more attributable to the variability inherent in larval turbot culture, and to variability in the reproductive specimens used in our study, than to the type of sperm employed. These results indicate that the type of sperm used in artificial fertilization, i.e. fresh or cryopreserved, is not a determining factor, either for fertilization and hatching, or for subsequent larval development. Our results also confirm once again the high quality of cryopreserved turbot sperm, and its usefulness in commercial hatcheries.     

不同放养量与水交换率对大菱鲆幼鱼的养殖效果及水质条件的影响

经过 6 0d的试验养殖 ,在每日 2、 4、6个循环水量的条件下 ,研究放养量从 0 .74～ 1.99kg/m2 大菱鲆 (Scophthalmusmaximus)幼鱼的平均体重增长、养殖成活率、饵料系数和养殖水中的溶解氧、氨氮含量等养殖生态状况。结果表明 ,日水循环量为 2个全量时 ,放养量为 1.5 4kg/m2 的实验组的平均体重增重与放养量低的实验组 (0 .75kg/m2 、1.0 1kg/m2 、1.31kg/m2 )平均体重增重无显著差异 (P >0 .0 5 ) ,而与高于此实验组 (1.74kg/m2 、1.99kg/m2 )的增重比较则差异显著 (P <0 0 5 ) ;水循环量的增加可以改善水质条件 ,加快幼鱼的生长速度 ,但对幼鱼的饵料系数影响不大。     

盐度对三疣梭子蟹生长、蜕壳及能量利用的影响

在实验室条件下,研究了盐度(15,20,25,30,35)对三疣梭子蟹(Portunus trituberculatus)幼蟹生长、蜕壳和能量利用的影响,探讨了三疣梭子蟹生长的最适盐度、蜕壳与生长的关系以及不同盐度水平下蟹的蜕壳同步性。实验时间为50 d,结果显示:1、盐度显著影响三疣梭子蟹的摄食、生长和能量利用。盐度20、25和30组,三疣梭子蟹的日摄食率(FId)较小,但其食物转化效率(FCEd)较高,其中盐度30组蟹的食物转化效率显著高于盐度15和35组(P<0.05),与盐度20和25组差异不显著(P>0.05)。盐度20、25和30组的能量吸收效率(K1)和净生长效率(K2)显著高于盐度15和35组。实验结束时,盐度30组三疣梭子蟹获得了较高的湿重、相对增重率和特定生长率,且显著高于盐度15和35组(P<0.05),而与盐度20和25组间的差异不明显(P<0.05)。回归分析表明,当水体盐度为26.3时,三疣梭子蟹特定生长率(SGRd)最大。2、不同盐度下,三疣梭子蟹幼蟹从Ⅶ期生长到Ⅹ期的蜕壳周期为18.9~23.5 d,各盐度组间的差异不明显(P>0.05),但盐度30组三疣梭子蟹蜕壳周期较其他盐度组缩短了3.1~4.6d。低盐(15)下,三疣梭子蟹出现MDS(蜕壳未遂)死亡,蜕壳受到抑制;而高盐(35)则抑制三疣梭子蟹新壳的硬化,盐度20和25组三疣梭子蟹的蜕壳同步性较好。实验结果初步表明,养殖生产中水体盐度控制在25左右有利于三疣梭子蟹的蜕壳同步及生长。     

不同水循环率对大菱鲆生长和水质的影响研究

研究了封闭循环水养殖系统中不同水循环率对大菱鲆(Scophthalmus maximus)生长和水质变化的影响。试验设置4个水循环率梯度12,24,36,48次/d,大菱鲆初始平均体重为200.36 g。经43 d养殖,12次/d组大菱鲆最终平均体重为277.98 g/尾,而48次/d组达到了296.24 g/尾;12次/d组水体氨氮(TAN)和亚硝酸盐氮(NO2--N)浓度分别为0.41~1.50 mg/L和0.12~0.38 mg/L,而48次/d组分别为0.33~0.56 mg/L和0.05~0.09 mg/L。试验结果显示,提高水循环率可降低系统中氨氮和亚硝酸盐氮的积累速度,优化养殖水质,减小水中有害物质对大菱鲆的胁迫作用,从而加快大菱鲆的生长速度,但对化学需氧量(COD)的去除没有显著影响。