欧洲鳎的生物学特性及其育苗和养殖

近年来，由于比目鱼类，如牙鲆、大菱鲆和大西洋大比目鱼的养殖成功，我国掀起了海水养殖比目鱼的高潮。欧洲鳎是欧洲水产市场上的传统产品。很受欢迎。下面将欧洲鳎的育苗和养殖研究情况作一简单介绍。     

牙鲆养殖的常见疾病及其防治方法

<正> 牙鲆俗称比目鱼、偏口,系高档经济鱼类。目前在国内外市场极受欢迎,由于牙鲆养殖经济效益很高,许多养殖单位把它作为重要的养殖品种,目前发展很快。但在人工养殖条件下,由于生活环境、鱼体密度、饵料质量等因素的影响,各种疾病随之发生。现将近年来牙鲆主要常见疾病及防治方法介绍如下。 1 病毒性疾病 1.1 弹状病毒病     

比目鱼类补充机制：总结过去展望未来

本文总结过去十年比目鱼类补充机制研究的进展,重点关注了1990和1993年两次比目鱼类研讨会许多论文展示的共同特征。在浮性鱼卵和仔鱼阶段,补充量变异性主要由非密度制约因子作用的结果。这种变化过程的效应在其分布区域边缘呈扩大的趋势,并与非生物条件因子有关。当比目鱼类高度特化至底栖食性时,密度制约的反馈过程看见了底层幼鱼时期。有证据表明,密度制约的反馈过程在未开发或轻度开发利用种群的成鱼时期也有发生。这次研讨会提出的比目鱼类补充机制的未来研究领域包括:1.根据生态等值概念,对比目鱼种群分类,包括连续生活吏阶段的栖息地需求;2.补充过程中种间和种群间的比较研究;3.决定浮性鱼卵和仔鱼存活率的环境因子分析;4.与生长和死亡有关的底层幼鱼受密度制约的栖息地选择;5.对比目鱼按种类浮性鱼卵、仔鱼,底栖幼鱼和成鱼的栖息地特征分析,包括鱼卵和仔鱼的漂移,从产卵场向育幼场的运输和成鱼洄游;6.相关种群动力过程的模拟研究,定量揭示各种动力过程的重要性以及确定这些过程的必要精度。     

鱼肉采取设备

本文介绍的是从已切出鱼片的骨骼上获取鱼肉的方法和设备，适用于加工黑线鱼、鳕鱼、比目鱼、箬鳎鱼等。     

欧洲鳎鱼的育苗和养殖简述

近年来,由于比目鱼类,如牙鲆、大菱鲆和大西洋大比目鱼的成功养殖,世界上掀起了海水养殖比目鱼的高潮。欧洲鳎鱼和塞内加尔鳎鱼是欧洲水产市场上的传统产品,很受欢迎。目前在欧盟市场的价格是9～13．5欧元／kg。这两种鱼类主要靠海洋捕捞上市,而欧盟对其捕捞配额限制越来越严格,因此非常支持这两种鱼类大规模商品化养殖的研究。笔者曾于2003年作为国家公派访问学者赴荷兰渔业研究所进行了为期一年的访问留学,在学习期间曾参加了欧洲鳎鱼育苗和养殖项目的研究工作。     

沙蚕在半滑舌鳎亲鱼培育中的重要作用

<正>一般情况下,比目鱼的人工繁殖相对其他鱼类来说难度较大,其主要原因是比目鱼对环境、营养等条件要求苛刻,尤其是对高不饱和脂肪酸的要求较高。在人工养殖条件下,人工饲料难以满足比目鱼亲鱼对营养的需要。人们培育半滑舌鳎亲鱼过程中发现,在投喂人工饲料的同时,辅助投喂多毛类环节动物(沙蚕类)可以促进     

养殖比目鱼的新设备

日本一家渔业公司制成了一种养殖比目鱼的新型设备。使用它饲养比目鱼,效益要比普通设备提高2倍左右。 这种养鱼新设备的主要特点是:饲养槽水位较浅,两端呈圆形,便于水流循环;槽内设置的喷水管向槽的四壁喷射水流,能进一步加快水的循环流动;循环水流能使鱼类排泄物和饲料残渣经槽底排水沟自行排除。由     

玛拉巴石斑鱼苗种生产技术

介绍了玛拉巴石斑鱼从亲鱼培育到幼鱼出池的人工繁殖及苗种培育技术。讨论了人工繁殖和苗种培育过程中影响仔、稚、幼鱼成活率的三个主要因素,并提出了相应的预防措施。     

日本培育成功生长快的比目鱼新品种

最近日本长崎县水产养殖研究所试验成功比普通比目鱼生长快1．4倍的比目鱼新品种。     

玉环县捕获特大比目鱼

1月7日,浙江省玉环县大麦屿渔民捕到一条特大比目鱼。这条鱼体长100厘米,体重22.5斤。比目鱼学名牙鲆,体呈长卵圆形,两眼均在头的左侧,口大,齿尖锐,鳞细小。比目鱼属底层鱼类,产量以黄海中、北部为高。它喜欢生活在底质泥沙的     

Effect of diets containing low levels of methionine and oxidized oil on body composition, retina structure and pigmentation success of Japanese flounder

Diets reduced in methionine (Met) and with oxidized oil were formulated to induce visual deficiencies in Japanese flounder, Paralichthys alivaceus (T. & S.), in an attempt to link vision with pigmentation development. Even though Met-deficient diets have proved to be cataractogenic in salmonids, no cataracts were formed in flounder eye. However, both diets produced an abnormal morphology in the retinal pigment epithelium and the photoreceptor outer segments of the fish retina. The high presence of dead nuclei in the photoreceptor inner segment suggests a loss in the visual capability of fish fed these two diets, which produced lower pigmentation success than the control. A significant correlation was also found between pigmentation success and fatty acid composition (docosahexaenoic acid and arachidonic acid) of the head polar lipid fraction. The results suggest that a deficient intake of amino acids and fatty acids produces a change in retinal structure and composition, leading to reduced visual capability and suppression of the development of normal pigmentary pattern in flatfish.     

Effects of Rotifer and Artemia Fatty-Acid Enrichment on Survival, Growth and Pigmentation of Summer Flounder Paralichthys dentatus Larvae

Abstract— Enrichment of live food for marine fish larvae with highly unsaturated fatty acids (HUFA) has been shown to improve survival, growth and stress resistance in many species and to decrease pigmentation abnormalities in flatfish. In order to aid the developing summer flounder industry, we conducted an experiment in which summer flounder larvae were fed diets differing in HUFA composition to determine whether enrichment with a commercially available product would increase survival and growth and reduce the incidence of abnormal pigmentation. We also examined whether growing unenriched rotifers on different species of algae would affect the survival, growth and pigmentation of the flounder larvae to which they were fed. Growth of summer flounder larvae was significantly better when they were fed HUFA-enriched Mtifers and Artemia rather than unenriched and, among the unenriched treatments, was significantly better when the larvae were fed rotifers raised on Isochrysis galbana rather than on Tetraselmis suecica . The percentage of larvae that failed to complete metamorphosis during the experiment was significantly higher in the unenriched treatments than in the enriched treatments. Neither survival nor percentage of individuals with pigmentation abnormalities were significantly different among the treatments.     

A sensitive period during first feeding for the determination of pigmentation pattern in Atlantic halibut, Hippoglossus hippoglossus L., juveniles: the role of diet

Six groups of Atlantic halibut, Hippoglossus hippoglossus L., larvae were offered calanoid cope-pods at different periods from days 11 to 25 after first feeding (1.13-3.20 mm myotome height) in order to establish at which stage normal pigmentation was determined. Artemia nauplii enriched with an oil emulsion were used prior to and after the copepod period. Control groups were fed on copepods or Artemia only. The Artemia diet initiated an earlier intake of food and higher initial growth compared to the copepod diet. After 50 days of feeding, the average dry weights of the fish fed on Artemia and copepods were quite similar to the copepod-fed fish, while the Artemia-fed fish were the smallest in size. The lowest frequency of normally pigmented juveniles was found in the Artemia-fed group (66.4%), while the copepod group showed almost 100% normal pigmentation. A significantly higher frequency of pigmentation was found in juveniles given a copepod diet close to the initiation of metamorphosis than those provided with an earlier copepod period of equal duration. A high degree of eye migration was found in all groups, but was lowest in the Artemia-fed group. The initial stage of eye migration was found to occur at a larger body size in fish given Artemia and copepods, or a copepod diet than in fish fed on Artemia alone. There was no significant correlation between eye migration and growth rates prior to metamorphosis, although the largest individuals exhibited the most complete eye migration. High pigmentation frequencies were obtained in fish with a low 22:6n-3:20:.5n-3 (DHA:EPA) ratio (< 1.0).     

Progression of staining-type hypermelanosis on the blind side in normally metamorphosed juveniles and pigmentation progression in pseudoalbino juveniles of the Japanese flounder Paralichthys olivaceus using individual identification

Abnormal flounder coloration frequently occurs in flounder hatcheries and diminishes the commercial value of the fish. To understand hypermelanosis, the progression of staining-type hypermelanosis in normally metamorphosed juveniles and ocular-side pigmentation in pseudoalbino juveniles were examined in the Japanese flounder Paralichthys olivaceus. Sixty-five days post hatching, juveniles (total length, 6 cm) were individually identified by color-marker implantation, and the darkened area of the body surface was examined for 10 weeks by image analysis of digital photographs of the fish taken from above or below the transparent tank. Staining was observed to mainly begin at the upper and lower bases of the tail fin, expanded anteriorly along the peripheral part of the trunk, and ceased after 2 months. The individuals in which staining occurred earlier expressed severe staining and small body size by the end of the experiment. Further, pigmentation of the ocular side in pseudoalbino juveniles ceased after 2 months, but the order of pigmentation was different from that on the blind side. In this case, darkening began from the posterior, but expanded from the center to the periphery of the trunk. Even at the end of the experiment, ctenoid scales were exclusively found within the darkened area, together with cycloid scales.     

Growth of early juvenile winter flounder (Pseudopleuronectes americanus Walbaum)

Metamorphosis is a critical developmental stage in marine fish species, but mortalities are also elevated at the settling phase. Our objective was to evaluate the effects of different rearing systems and larval diets on survival, general condition and pigmentation of newly settled winter flounder (Pseudopleuronectes americanus) juveniles. At settlement, winter flounder juveniles were reared in two different types of tanks (plankton kreisel and rectangular raceway). The early juveniles were followed for 1 month and their condition was evaluated using biochemical indices. Juveniles did not show signs of fin rot and pigmentation was well developed, but they had different RNA/DNA ratios. This study highlights the fact that rearing conditions at the onset of the juvenile stage may be critical for successful juvenile production.     

Pigmentation and eye migration in Atlantic halibut (Hippoglossus hippoglossus L.) larvae: new findings and hypotheses

Atlantic halibut juveniles, which have been fed Artemia during larval development, frequently demonstrate malpigmentation and impaired eye migration. This is in contrast to the high percentage of normally developed larvae fed copepods, reared under similar conditions. Nutrition is therefore an important component influencing larval development. Analyses of the nutrient composition of Artemia and copepods show that Atlantic halibut larvae fed Artemia probably receive sufficient amounts of vitamin A by converting canthaxanthin, while iodine may be deficient, possibly leading to interrupted thyroid hormone synthesis. An unbalanced fatty acid composition, such as high levels of arachidonic acid and low levels of docosahexaenoic acid, can be another limiting factor in Artemia. Vitamin A, fatty acids and thyroid hormones have all been shown to affect pigmentation in flatfish. They are ligands to nuclear receptors, thyroid hormone receptors, retinoic acid receptors, retinoic X receptors and peroxisomal proliferator‐activated receptors, which are members of the superfamily of steroid hormone receptors. The receptors interact with each other to promote gene expression that modulates proliferation and differentiation of cells. Our hypothesis is that these interactions are important for development during flatfish metamorphosis. Very little data exist on the topic of impaired eye migration. However, energy limitation, iodine deficiency and an unbalanced fatty acid composition have been proposed as possible explanations. Here, we review the literature on development of pigment cells and the possible mechanisms behind the effects of vitamin A, fatty acids and thyroid hormone on pigmentation and eye migration during development of Atlantic halibut larvae.     

Effects of arachidonic acid on pigmentation and fatty acid composition of Japanese flounder, Paralichthys olivaceus (Temminck and Schlegel)

The dietary effect of arachidonic acid (20:4n-6, AA) on the composition of the head and the body, and on the pigmentation of Japanese flounder, Paralichthys olivaceus (T. & S.), was studied by means of microbound diets. Increasing levels of this essential fatty acid produced higher growth and pigmentation success in juveniles after 45 days of feeding. The role played by AA in the composition of phosphatidylinositol and eicosanoid synthesis is discussed in relation to the normal function of the neural system and the production of hormones involved in the metamorphosis and pigmentation of flatfish.     

Pseudoalbinism and ambicoloration in hatchery-reared pleuronectids as malformations of asymmetrical formation

Morphological abnormalities in eye location and/or body coloration are commonly observed in hatchery-reared juveniles of many pleuronectid species, and have become one of the most serious problems in juvenile production for stock enhancement. In this study, these morphological abnormalities of six pleuronectid species—barfin flounder Verasper moseri, slime flounder Microstomus achne, stone flounder Platichthys bicoloratus, starry flounder Pl. stellatus, cresthead flounder Pseudopleuronectes schrenki, and marbled sole Ps. yokohamae—were successfully classified into four morphological types [normal, two types of pseudoalbinism (normal-eye position or top-eye position), and ambicoloration], following the same classification scheme proposed for other two pleuronectids. Based on our results, the characteristics of each morphological type are quite similar among species. It is confirmed that the normal type has the same ocular side and blind side characteristics as those of wild fish, not only in eye position and body coloration, but also in scales or dentition. The pseudoalbino types have the blind side characteristics of wild fish on both sides, with top-eye type in all characteristics, and normal-eye type in all other characteristics other than eye position. The ambicoloration type has all the ocular side characteristics of wild fish on both sides. Therefore, the pseudoalbinism and ambicoloration of hatchery-reared juveniles of pleuronectid species can be considered malformations of asymmetrical formation. Since this process normally occurs during metamorphosis, the term “metamorphosis-related malformation” is proposed for the abnormal formation of juveniles in pleuronectid species.     

Skeletal and Pigmentation Defects following Retinoic Acid Exposure in Larval Summer Flounder, Paralichthys dentatus

Supplementation of larval diets with vitamin A (VA) is routinely and successfully used to stimulate pigmentation development in hatchery‐reared flatfishes. However, excess dietary VA can lead to high levels of its metabolite retinoic acid (RA) and has been associated with the occurrence of skeletal deformities, presumably via RA toxicity. We reared summer flounder larvae, Paralichthys dentatus, in water containing 0‐ to 20‐nM RA to assess its effects on postmetamorphic pigmentation and on skeletal development. RA exposure disrupted pigmentation development: treated tanks had a smaller percentage of normally pigmented fish than did controls, with increased numbers of both hypo‐ and hyperpigmented individuals. Exposure also affected the development of several skeletal features: RA treatment correlated with a significant increase in the severity of defects in jaws, fins, hypurals, and vertebrae compared with control groups.     

Diet and Light Intensity Effects on Survival, Growth and Pigmentation of Southern Flounder Paralichthys lethostigma

Interest in the culture of flatfishes has increased globally due to high consumer demand and decreased commercial landings. The Southern flounder Paralichthys lethostigma inhabit South Atlantic and Gulf of Mexico waters and support important commercial and recreational fisheries. In spring, 1996, a two-part larval rearing study was performed with Southern flounder to examine the effects of three larval diets and two light intensities on survival, growth, and pigmentation. The first part of the study consisted of feeding 6 d post-hatch (dph) (3.0 ± 0.1 mm TL) larvae three diets: 1) rotifers Brachionus plicatilis at a rate of 10/mL from day 1–9 and Artemia nauplii (3/mL) from day 7 through metamorphosis; 2) rotifers fed day 1 through metamorphosis and Artemia fed day 7 through metamorphosis; or 3) same diet as treatment 1 plus a commercial larval diet added day 13 through metamorphosis. The second part of the study examined the effects of two light levels: low-light (mean 457 lux) and high-light (mean 1362 lux). At 24 C, metamorphosis began on day 23 (mean fish size 8.2 ± 0.6 mm TL) in all treatments and was completed by day 30. Analysis of survival, size, and pigmentation data indicated there were no significant differences among feed treatments or between light treatments. Overall survival was 33.4% (±15.9) and mean length was 11.5 mm TL ± 1.3. Only 35% of the larvae were normally pigmented. Reexamination of the pigmentation on day 37 indicated fish reared at the low light intensity through metamorphosis (day 30) but exposed to high light intensity for 1 wk post-metamorphosis had become significantly more pigmented.