The growth of turbot (Scophthalmus maximus (L.)) in recirculating systems

O-group wild turbot (Scophthalmus maximus (L.)) were used in a number of feeding experiments designed to assess the usefulness of readily available species of industrial fish as feed for the ongrowing stage of cultivation (10–500 g). Sprats (Sprattus sprattus (L.)) and sandeels (Ammodytes marinus Raitt) were the most successful in that feeding rates of 2% live weight per feed gave conversion efficiencies which were generally better than 3:1. A regular regime of two feeds a day should give growth rates approaching 2% per day resulting in an ongrowing period of about 200 days at 16°C. The turbot were maintained in closed recirculating systems using a simple design for the treatment units. These provided a stable environment in which to conduct the experiments the average water quality conditions being given. There were few health problems and the taste and texture of the fish produced appeared to be good.     

Growth of 0-group turbot (Scophthalmus maximus L. 1758) fed on artificial diets

Group-0 turbot Scophthalmus maximus L. were fed on artificial diets for 13 months, at 15° C. Partially defined diets containing about 40% protein were used and fish were fed once per day with moist pellets.The mean weight of the fish, at the beginning of the experiment, was 3.5 g. During the first 6 months, a fish gained 15 g weight on average, and 40 g in the following 6 months. The final mean weight was 62 g, and the final mean total length, 15.3 cm. The daily growth rate was 0.7% and the protein efficiency ratio (P.E.R.) ranged between 1.4 and 2.1.For fish fed on natural food at 15° C, the results were similar for the first 9 months. Subsequently, these fish grew faster than those fed artificial diets.     

Experiments of the rearing of larval turbot, Scophthalmus maximus L.

Experiments on the live food requirements of cultured turbot larvae are described. A mixture of six species of unicellular algae did not sustain early larvae, but the growth and survival of larvae fed with rotifers were considerably improved when the rotifers were feeding on Isochrysis galbana rather than on Dunaliella tertiolecta. Oyster (Crassostrea gigas) larvae offered alone or with rotifers, did not produce higher larval growth or survival than rotifers alone. Black tanks were found to be more suitable than white tanks for rearing larval turbot.     

Growth and gonadal development in diploid and triploid turbot (Scophthalmus maximus)

This study determined the effect of triploidy on the survival, growth and gonadal development of turbot from 6 to 48 months of age. From 6 to 24 months of age (first sexual maturity), survival was similar in both ploidies (P > 0.05). From 24 to 48 months of age, after the first sexual maturity, survival was 91.9% in diploids and 100% in triploids, which did not exhibit the post-spawning-associated mortality. Growth was similar for both ploidies during the first year of life. After that, triploids grew significantly (P < 0.05) more that diploids, with more marked differences after each spawning season. From 24 to 48 months, the average weight difference between both ploidies was 11.4 ± 1.9%, ranging from 4.3 to 23.0%. At 47 months of age, the biomass of triploids was 10.3% greater in total weight and 14.3% greater in eviscerated weight. Gonads of triploid males were similar to that of diploids, whereas in triploid females, they were significantly smaller and rudimentary. A histological analysis carried out at 47 months of age showed complete sterility of triploids in both sexes. Sex ratio was 1 male (M):0.6 female (F), for diploids, significantly (P < 0.05) different from 1:1, and 1 M:3.3 F for triploids, significantly (P < 0.05) different from 1:1 and from the diploids. Since females grow more than males, culture of triploids benefited from the high female ratio, which helped to reduce size dispersion. In addition, their sterility allowed better performance by avoiding the reduction in growth that takes place during the spawning periods. Together, these observations indicate that triploidy induction can be an interesting option for turbot aquaculture, especially for the production of large-size fish of more than 2 years of age.     

大菱鲆选育家系雌、雄群体的生长发育差异

采用全长/体长、体高/体长、全长/体高和体质量为评价指标,分别对9~33月龄大菱鲆雌、雄群体在生长发育过程中体型的动态变化及生长性能差异进行了比较。大菱鲆雌、雄群体形态比较结果显示,雌、雄群体的全长/体长、体高/体长、全长/体高在不同发育阶段呈现特有的变化,但在雌、雄群体间,除33月龄的体高/体长和全长/体高差异达到显著水平外,3项指标在不同阶段没有差异或差异不显著,即可以认为,对于统计初始体质量相同或相近的大菱鲆雌、雄群体,全长/体长、体高/体长和全长/体高3个形态比例指标是随发育时间序列同步变化。基于Logistic模型对大菱鲆雌、雄群体生长性能的比较结果显示,雌性群体的拐点月龄、拐点体质量和最大月增重均大于雄性群体;对于雌性和雄性群体的瞬时增长率,除在9~13月龄雌性群体稍低于雄性群体外,13~33月龄的雌性群体均高于雄性群体,且随着生长发育和体质量差异的增大,雌、雄瞬时增长率的差异也呈增大趋势;雄性群体进入快速生长期的始速点和进入缓慢生长期的终速点均比雌性群体提前,雄性群体的快速生长期时间区间长度小于雌性群体,其对应的体质量区间长度也小于雌性群体,雌性群体在快速生长期的月增重显著高于雄性群体。研究表明,大菱鲆雌、雄群体在生长发育过程中存在着显著的生长差异,而形态差异不显著。     

Characterisation of the environmental impact of a turbot (Scophthalmus maximus) re-circulating production system using Life Cycle Assessment

The environmental impacts of a water re-circulating system for fish farming were studied through the case study of an inland turbot farm located in Brittany (France). Life Cycle Assessment methodology was used to evaluate the potential environmental impact through the following indicators: Eutrophication Potential, Acidification Potential, Global Warming Potential, Net Primary Production Use and Non Renewable Energy Use. Two methods were used to assess the farm's nitrogen, phosphorus and solids emissions: nutrient measurement accounting and nutrient balance modelling. The two methods gave similar results for solids and phosphorus emissions, while for nitrogen the measurement-based approach resulted in half the emissions predicted by the model. The uncertainty regarding the potential gaseous nitrogen emissions led us to assess impacts according to three scenarios, differing with respect to emissions of N₂, N₂O and NH₃. This approach illustrates that the uncertainty concerning nitrogenous emissions to the atmosphere leads to uncertainty with respect to the production system's Eutrophication Potential and its Global Warming Potential. The comparison of our results with similar results for large rainbow trout production in a flow-through system points out the impacts associated with the high level of energy consumption in the studied re-circulating system (i.e. Non Renewable Energy Use, Global Warming potential, Acidification Potential). The nitrogenous gas emissions of re-circulating systems require further studies, in order to precisely identify the substances involved and the technological solutions allowing reduced impacts.     

The effect of ammonia on the growth of juvenile Dover sole, Solea solea (L.) and turbot, Scophthalmus maximus (L.)

The growth of sole and turbot was followed in groups of fish exposed to constant unionised ammonia concentrations at pH levels both at and below that of normal sea water. Low pH levels were produced by the addition of carbon dioxide. Results for both species showed evidence for a threshold level of unionised ammonia below which little or no effect on growth was evident. This level was determined to be 0.066 mg N/l for sole and 0.11 mg N/l for turbot at 16°C, 34‰ salinity. The different pH conditions did not have any marked effect on these threshold levels.Above the threshold levels growth appeared to be depressed in a linear manner with increased unionised ammonia. The rate at which growth was depressed was greatest at the low pH levels for both species. The level at which growth ceased thus decreased from 0.77 to 0.38 mg N/l for sole and from 0.9 to 0.3 mg N/l for turbot, over the pH range from 7.9 to 6.9.The absence of disease and gill damage in the experimental populations is discussed. It is suggested that this and the tolerance shown by the fish, which is higher than is generally accepted for fish in high density culture, may be due to the clean environment in which the fish were held while under test.     

Accuracy of pairwise methods in the reconstruction of family relationships, using molecular information from turbot (Scophthalmus maximus)

Many estimators and algorithms have been developed to infer the genealogical relationships from molecular marker data when there is no pedigree information. Most pairwise methods provide estimates in a continuous range that needs to be converted into genealogical relationships (namely full-sibs, half-sibs and unrelated) if there is a previous knowledge of the population structure. Transformations are usually based on arbitrary thresholds, but the possibility of correcting the coancestry estimates via explicit pedigree reconstruction methods has been suggested. Using molecular data for ten highly polymorphic microsatellite loci on a population of turbot (Scophthalmus maximus) with a known genealogy, the behaviour of four pairwise marker-based coancestry estimators and the molecular coancestry has been evaluated. The population consisted on 138 families with 4 full-sib individuals each and one family with 8 full-sib individuals (up to 15 half-sib families were also present due to the sharing of parents between some of the full-sibs families). Our results suggested that transforming the pairwise estimators and the molecular coancestry to family relationships through the establishment of thresholds performs slightly better than the explicit pedigree reconstruction method, when accuracy is measured in a pairwise basis. However, if joint relationships between more than two individuals were tested at a time, the threshold methods led to a high percentage of incongruous triads of full-sib individuals, with Mendelian incompatibilities appearing in congruous full-sib families (more than 70% and 60% in our study, respectively). The explicit pedigree reconstruction approach, due to its nature, is free from such problems. Therefore, the pedigree reconstruction approach seems to be a valuable tool to provide a congruent and compatible pedigree when the pairwise marker-based coancestry matrices or the molecular coancestry need to be transformed.     

大豆浓缩蛋白替代鱼粉对大菱鲆摄食、生长及体组成的影响

研究了大豆浓缩蛋白(SPC)替代鱼粉对大菱鲆生长及生理生化指标的影响。5种饲料分别含有0、12.0%、25.0%、37.0%和49.5%的SPC以替代相应的鱼粉,并分别添加0、0.83%、1.65%、2.48%和3.30%的必需氨基酸混合物(L-lysine∶DL-methionine∶L-leucine∶Lvaline∶L-threonine=18∶6∶3∶2.5∶2)以平衡各组饲料的氨基酸组成。每种饲料投喂3个水族箱(300 L),每个水族箱放养实验鱼16尾,实验鱼初始体质量为(31.1±0.1)g。经过9周生长实验,结果显示随着饲料中SPC替代水平的升高,大菱鲆摄食率、特定生长率均显著下降(P0.001)。然而,当使用0~37.0%的SPC替代鱼粉时,各处理组饲料效率和蛋白质效率未出现显著差异(P0.05)。饲料中SPC替代鱼粉对大菱鲆鱼体水分、粗蛋白、粗脂肪及灰分含量均无显著影响(P0.05)。各处理组干物质和粗蛋白的表观消化率之间也未出现显著差异(P0.05)。研究表明,在本实验条件下SPC不能作为大菱鲆饲料中替代鱼粉的有效蛋白源,造成SPC替代效果较差的主要原因是其对大菱鲆饲料适口性的显著影响。     

The effect of dietary water content and feeding rate on the growth and food conversion efficiency of turbot (Scophthalmus maximus L.)

The effect of dietary water content and feeding rate on the growth and food conversion efficiency of turbot was investigated using diets which contained identical amounts of dry nutrient material but different quantities of water, ranging from 0 to 74%. The dietary water content did not significantly influence the growth, composition, condition factor or food conversion efficiency of the turbot. It appeared that, as long as the basic nutrients were formulated so as to produce an adequate diet, the water content was immaterial. The over-riding factor governing growth was the rate of food intake. Comparisons at feeding rates which in energy equivalents ranged from 24 to 72 calories per gram of fish a day, showed that the higher the energy intake the more rapid the growth. At the highest feeding rate, fast growth was accompanied by a marked increase in the condition factor and an elevated lipid content of the fish. The percentage protein content, however, was relatively stable in relation to the feeding rate. Food conversion efficiency was also relatively stable. On average, 40.3% of the dietary protein and 36.3% of the ingested energy was converted into turbot.     

Microinjection of the antifreeze protein type III (AFPIII) in turbot (Scophthalmus maximus) embryos: Toxicity and protein distribution

Fish embryo cryopreservation has not been achieved. Different methods and alternative cryoprotective agents (CPAs) should be explored in order to succeed in this purpose. Antifreeze proteins (AFPs) are naturally expressed in sub-arctic fish species, and they inhibit the growth of ice crystals as well as recrystallization during thawing. Therefore, their introduction into embryos can be highly beneficial for vitrification purposes. In this study, AFP type III was introduced into turbot embryos, by microinjection into the yolk sac and the perivitelline space at F stage (tail bud).Toxicity and distribution of protein in microinjected embryos were established before testing the protein effect on embryo cryopreservation. AFP-FITC distribution within the embryo was analyzed by confocal microscopy at 5 min and 24 h after microinjection in F stage embryos. To test the sensitivity of microinjected embryos to CPAs, embryos were subjected to a protocol for the incorporation of a vitrifying solution that was specially designed for turbot embryos. Hatching rates after CPA incorporation were determined. Results indicate that embryos at late developmental stages are more resilient to microinjection, with embryo survival rates between 60 and 82%. Confocal microscopic images demonstrated that the protein was homogeneously distributed within the microinjected embryo compartment, but did not enter any other compartment. On the other hand, microinjected embryos successfully surmounted their incubation in the CPAs. This study explores new alternatives for cryopreservation suggesting the use of natural cryoprotectants (AFPs) in the protection of intra-embryo compartments, which are usually unprotected with the conventional cryopreservation protocols for fish embryos.     

Effect of dietary protein,lipid and energy content on the growth of turbot (Scophthalmus maximus L.)

Juvenile turbot were fed diets containing various proportions of protein and lipid. The fastest growth occurred on a diet rich in protein and low in lipid. The addition of extra lipid to the diet gave poorer growth but improved protein conversion efficiency. The protein sparing action of the lipid was most pronounced when the turbot were fed to about three-quarters of satiation on a diet supplemented with 6% lipid. Under these conditions 42% of the dietary protein was converted into fish protein, compared with 32% conversion on the basic diet which contained 0.5% lipid. There was a general decline in food conversion efficiency and protein sparing was marginal at the satiation feeding rate. Not all the dietary lipid was used in a protein sparing role, much of it was deposited as lipid reserves. In contrast, there was very little increase in the lipid content of fish fed on a high protein-low lipid diet.     

皂角苷对大菱鲆非特异免疫的增强作用

为评价皂角苷增强鱼类非特异免疫效果,分别用浓度为0、15和35 mg/L的皂角苷浸泡大菱鲆,分析了浸泡后6、12、24、48和72 h时大菱鲆白细胞的吞噬活力、血清补体旁路途径溶血活性、血清与黏液中溶菌酶活性、抑菌活性与碱性磷酸酶(AKP)活性及血清总蛋白浓度。结果显示,皂角苷低浓度组(15 mg/L)与高浓度组(35 mg/L)大菱鲆白细胞吞噬活力分别在浸泡后12与24 h出现显著的增高(P0.05)。实验组大菱鲆血清中补体旁路途径溶血活性除低浓度组在12与24 h较对照组低外,其他检测时段均高于对照组(P0.05)。血清溶菌酶活性最高值出现在低浓度组浸泡后6 h时,黏液中未能检测出。不同时间点各组大菱鲆黏液抑菌活力变化幅度较大,两实验组黏液抑菌活力在浸泡后6与12 h时较对照组提高,两个实验组间无差异(P0.05)。血清中AKP活力高峰值出现在浸泡后6与12 h,该时段AKP的活力显著高于对照组,且实验组间存在差异(P0.05),而黏液中AKP高峰值出现在12 h,该时段AKP的活力显著高于对照组(P0.05),实验组间无差异。浸泡皂角苷后6 h高浓度组血清中蛋白浓度达到最高值,除12 h时各组差异不显著外(P0.05),24~72 h高浓度组中血清蛋白含量均高于低浓度及对照组(P0.05)。研究表明,皂角苷具有提高鱼类非特异免疫水平的效果。     

Morphogenese de l'appareil digestif et de la vessie gazeuse du turbot, Scophthalmus maximus L.Morphogenesis of the digestive system and swim bladder of the turbot, Scophthalmus maximus L.

The study is based on serial sections made on turbots raised at 18 ± 0.5°C from day 1 (post-hatching) to day 20. Histological changes of the digestive system and swim bladder were observed on a daily basis.At day 1, specimens (total length, Lt = 3.0–3.1 mm) present a digestive tract undifferentiated along its length and closed anteriorly. They belong to the embryonic period in spite of the presence of associated digestive glands (liver and pancreas).The larval period extends from day 2 to day 14–15 (Lt = 3.5–7.0 mm): the swim bladder differentiates and inflates, then the pneumatic duct binding the swim bladder to the stomach degenerates; regional differences appear along the digestive tract which starts to be functional.From day 15–16 (Lt = 6.9–7.7 mm) the juvenile period begins with the formation of gastric glands and the onset of gastric digestion. Two pyloric caeca are clearly visible and the number of intestinal folds and goblet cells increases progressively.     

Survival and growth of turbot larvae Scophthalmus maximus L. Reared on different food organisms with special regard to long-chain polyunsaturated fatty acids

Turbot larvae reared on rotifers (Brachionus plicatilis) and Artemia (San Francisco brand) nauplii (A) were compared with those fed on different copepod (Eurytemora affinis) stages (B). In one trial, growth and survival of larvae from hatching to day 21, their fatty acid pattern and that of their food organisms were examined. At the age of 21 days larvae of group A measured 11·1 ± 1·6 mm total length (TL) compared with 14·8 ± 1·1 mm TL for group B. From day 3 to 8 survival was 29% (A) and 38% (B). Long-chain polyunsaturated fatty acid composition of turbots resembled that of their corresponding diets. Artemia and Artemia fed larvae were lacking 22 : 6 n-3 fatty acid.In a further study, survival of larvae from day 11 to 21 fed on Artemia nauplii (C) or copepods (D) was found to be greater with the latter diet (73 versus 93%) whereas growth during this experiment was similar in both groups. Before the start of this trial they had been reared on a mixture of copepod nauplii and Brachionus. No influence on weaning success was observed. 22 : 6 n-3 fatty acid is seen to be essential for turbot larvae: elongations of fatty acids by the larvae were not found.     

Effects of dietary energy level and dietary energy source on growth,feed conversion and body composition of turbot (Scophthalmus maximus L.)

Seven diets containing 350 g protein/kg and with energy levels varying from 1 860 to 3 150 kcal/kg were fed to groups of turbot at a rate of 25 g diet/kg biomass/day for 18 weeks.An additional group of turbot was similarly fed a diet containing 500 g protein and 2 895 kcal/kg. Weight gain, food conversion and body composition of these eight groups of fish were compared.At a constant dietary protein level, weight gain and protein utilization increased with increasing dietary energy level. The body fat content of the experimental fish did not exceed that of wild fish even at the highest dietary energy level.At comparable dietary energy levels (about 3 000 kcal/g) protein utilization of turbot given diets containing 350 g protein/kg was superior to that of turbot given diets containing 500 g protein/kg. Weight gains of the two groups were similar.     

Analyses sanguines de turbots d'elevage immatures (Scophthalmus maximus L.)Blood analysis of immature cultured turbot (Scophthalmus L.)

A study of cultured healthy turbot haemochemistry is based on blood data of 107 twelve- to fifteen-month-old fish. Six successive samplings were carried out in the Centre Oceanologique de Bretagne (COB) and in two aquaculture experimental stations in Brittany. Turbot were not fed 36 h before sampling.Thirteen parameters were studied: in the blood, haematocrit and haemoglobin, and in the plasma, glucose, total protein, total cholesterol, triglycerides, phospholipids, sodium, potassium, chloride ion, calcium, magnesium and mineral phosphorus. Moreover, electrophoresis of plasma proteins was systematically carried out. Indicative haemochemistry standards are proposed from these results.A parallel is drawn between the present results and previously known haemochemistry data in turbot and other flat-fish.     

Factors influencing the survival and growth of turbot larvae, Scophthalmus maximus L., during the change from live to compound feeds

In a series of 14 trials the survival of turbot larvae during transfer from a live to an inert food ranged from 45% to 95%. The time taken for up to 50% of each batch to establish feeding was also highly variable, ranging from 1 to 11 days. The potential to accept inert food was probably established during the initial stages of weaning or even earlier. Final survival could reliably be predicted from survival and feeding response during the first few days of weaning. Evidence was presented which suggests that the quality of the live food (Artemia salina L.) influenced the subsequent acceptance of an inert diet. For example, larvae reared on San Francisco Bay nauplii accepted an artificial diet less readily than those reared on Artemia which had first been fed on the unicellular alga Isochrysis for 2 days. Dietary water content was not an important factor governing weaning success.     

饲料中大豆黄酮对大菱鲆生长、消化酶活力、抗氧化力及肠道结构的影响

为研究大豆黄酮在大菱鲆幼鱼中的营养生理作用,本实验在以鱼粉为主要蛋白源的基础饲料中添加不同剂量的大豆黄酮(0、5、10、20和100 mg/kg)来配制5种等氮等脂的实验饲料,并通过12周的投喂养殖实验评估饲料中不同剂量的大豆黄酮对大菱鲆幼鱼生长性能、消化酶活力、抗氧化力以及肠道结构的影响。结果表明:与对照组相比,饲料中添加不同剂量的大豆黄酮对大菱鲆幼鱼的存活率(98.89%~100.00%)、终末体质量(21.24~24.42 g)、特定生长率(1.81~1.98%/d)、饲料效率(1.01~1.11)、摄食率(1.43~1.51%/d)及形体指标均没有产生显著性影响;饲料中添加大豆黄酮显著降低了大菱鲆幼鱼鱼体的粗蛋白(15.41%~15.59%)和粗脂肪(3.19%~3.93%)含量,但对鱼体的水分(77.41%~79.70%)和灰分(3.46%~3.81%)含量未产生显著性影响;饲料中添加10~100 mg/kg大豆黄酮显著提高了大菱鲆幼鱼的胰蛋白酶活力(35.26~40.66 U/g prot),但胃蛋白酶(31.75~49.56 U/mg prot)、肠蛋白酶(10.00~14.79U/mg prot)、胃淀粉酶(0.10~0.25 U/mg prot)和肠淀粉酶(0.05~0.17 U/mg prot)的活力在各处理组间没有显著性差异。饲料中添加5、10和20 mg/kg的大豆黄酮显著降低了血清丙二醛(10.67~11.17 nmol/mL)的含量,并显著提高了大菱鲆幼鱼血清超氧化物歧化酶(51.05~53.36U/mL)和谷胱甘肽过氧化物酶(551.40 U/mL)的活力;饲料中添加不同浓度的大豆黄酮对大菱鲆幼鱼后肠肠道结构完整性没有显著性影响,但10~20 mg/kg大豆黄酮显著促进了肠道组织结构的发育和成熟,提高了大菱鲆幼鱼后肠肠绒毛的高度(391.26~401.48μm)。研究表明,大豆黄酮(5~100 mg/kg)对大菱鲆的生长没有显著性的影响,但饲料中适量的大豆黄酮(10~20mg/kg)可以显著提高大菱鲆幼鱼的消化酶活力和抗氧化能力,并促进肠道绒毛的发育。