欧洲舌齿鲈和花鲈生长期营养需求特点综述

鱼类的生长期(幼鱼和成鱼阶段)相对于仔稚鱼阶段在养殖生产中持续时间较长,是养殖生产的重要阶段和保证产品质量的关键时期。鱼类生长期饲料使用量大、所占养殖成本高。该时期营养需求特点不同于仔稚鱼期和亲鱼期,有其阶段特殊性,因此,针对鱼类生长期营养需求特点的研究有其必要性。花鲈(Lateolabrax japonicus)作为我国的名优海水鱼,得到大规模养殖,市场广阔。欧洲舌齿鲈(Dicentrarchus labrax)作为引进新品种,与花鲈的生活习性、营养需求和生长特点颇为相似。在现有文献基础上,较系统地综述和比较了欧洲舌齿鲈和花鲈对蛋白质、氨基酸、脂肪、脂肪酸、维生素、矿物质等营养物质的需求量范围和需求异同点,并提出了今后的研究方向和重点,以期为专用配合饲料研发、更好地满足养殖生产提供参考。     

不同光周期下欧洲舌齿鲈幼鱼生长、摄食和肌肉营养成分的比较

选取450尾欧洲舌齿鲈（）幼鱼，体长（13.50±0.52）cm，体重（46.04±0.61）g，监测其在5种光周期（0L：24D、8L：16D、12L：12D、16L：8D、24L：0D，L表示光照时间，D表示黑暗时间）下的生长、摄食及肌肉营养成分等相关指标。实验周期为60 d。结果表明，8L：16D处理组的欧洲舌齿鲈的日增重系数显著高于其他各组（<0.05）；0L：24D和8L：16D处理组粗脂肪含量分别较16L：8D处理组分别提高了19.70%和21.67%（<0.05）。5种光周期下的欧洲舌齿鲈幼鱼肌肉中均检测到17种氨基酸，其中8L：16D和12L：12D处理组的肌肉中氨基酸总含量较0L：24D组分别提高11.60%和9.16%（>0.05）；肌肉中二十碳五烯酸（EPA）与二十二碳六烯酸（DHA）总含量在8L：16D处理组中最高，为14.21%，在0L：24D处理组中最低，为12.30%。不同光照周期对欧洲舌齿鲈幼鱼生长、摄食和肌肉营养品质均产生了不同程度的影响，综上所述，8L：16D和12L：12D光照环境更适宜欧洲舌齿鲈的生长。     

LED光谱对舌齿鲈幼鱼摄食、生长和能量分配的影响

在海水循环水养殖系统中,分别设置白光(λ_(400～780 nm))、红光(λ_(630 nm))、黄光(λ_(595 nm))、绿光(λ_(530 nm))、蓝光(λ_(455 nm))5组不同LED光谱处理组,研究5种不同LED光谱对舌齿鲈幼鱼[(29.91±0.39) g、(13.78±0.35) cm)]摄食、生长和能量分配的影响。结果显示,不同LED光谱对舌齿鲈幼鱼摄食、生长和能量分配具有显著性影响。红光谱下舌齿鲈幼鱼生长较好(41.09±5.70) g,蓝光谱下舌齿鲈幼鱼生长较差(36.02±4.18) g;蓝光谱下舌齿鲈幼鱼DGC(daily growth coefficient)显著低于其他各组,其他各组之间差异不显著;5组LED光谱处理组舌齿鲈幼鱼摄食率存在显著性差异,其中红光谱摄食率最高。类胰岛素生长因子IGF-1和IGF-2测定结果表明,白光谱下IGF-1的mRNA表达量最高;黄光谱下IGF-2的mRNA表达量最高。能量分配方面,红光谱下舌齿鲈幼鱼排粪能和代谢能较低,摄食能和生长能较高;蓝光谱下舌齿鲈幼鱼排粪能较高,摄食能和代谢能较低,生长能最低。对舌齿鲈幼鱼肌肉和肝脏RNA/DNA比值测定结果表明,蓝光谱下,舌齿鲈幼鱼肝脏RNA/DNA比值显著高于其他各组;蓝光谱和白光谱下舌齿鲈幼鱼肌肉中RNA/DNA比值存在显著性差异,其他各组之间不具有显著性差异。研究表明,红光谱下舌齿鲈幼鱼摄食、生长均表现较好,且红光谱下舌齿鲈幼鱼具有较高的摄食能和生长能;蓝光谱下舌齿鲈幼鱼摄食、生长表现较差,排粪能较高,生长能较低。因此,红光谱对舌齿鲈幼鱼摄食、生长具有积极影响;蓝光谱对舌齿鲈幼鱼摄食、生长具有不利影响。     

淞江鲈幼鱼自残行为特征分析

为研究淞江鲈幼鱼的自残特征和自残原因,对在淞江鲈繁育过程中收集到的自残鱼进行测量分析,结果发现,其体长和体质量的关系为:y=0.015e0.809 8x,R2=0.824 4;自残吞食鱼与被吞食鱼的体长比为1.28∶1,体质量比为2.56∶1,吞食鱼个体大于被吞食鱼。文章总结了淞江鲈自残行为学特征,提出淞江鲈育苗过程中降低自残率的预防措施。     

循环养殖系统中密度对舌齿鲈性能的影响

舌齿鲈按以下四种密度在基于养殖水池的再循环系统进行了为期63天的养殖：10,40,70,100kg／m^3。对鱼的性能,应激指标（血浆皮质醇,蛋白血（症）加上血液参数——Na^＋,K^＋,葡萄糖,pH,总CO2）和水质进行了监测。在63天的饲养末期,采用诺达病毒激发反应研究了舌齿鲈的抗感染能力。对最低和最高两种密度（10和100kg／m^3）和一个中等密度（40kg／m^3）的鱼进行为期25天的测试。对于不同的密度,～直高达70kg／m^3,日摄食（DFI）和单位生长率（SGR）没有明显差异。     

舌齿鲈循环养殖系统中泡沫分离去除颗粒物质和异养细菌的效率

本研究调研泡沫分离在去除封闭的舌齿鲈再循环系统中的颗粒物质和异养细菌的效率。该系统有10个养殖池,1个充当泡沫分离系统的撇沫器（SKIM）,1个生物过滤器装置和1个紫外线装置。     

野生花鲈幼鱼对人工鱼礁模型的趋集性研究

以花鲈为目标对象,研究其野生幼鱼对人工鱼礁模型的行为反应和选择性,为花鲈的资源养护技术研发提供参考。试验池(4.5 m×4.0 m×2.0 m)均分为72个平面观测网格单元(0.5 m×0.5 m),池中心网格为礁模型放置区。笔者试制6种人工鱼礁模型(棱台形、方形和星形框架×有、无牡蛎),通过室内模拟试验,分析比较花鲈幼鱼在礁区放置不同模型时的趋集行为和分布特征。试验结果显示,未放鱼礁时,花鲈幼鱼在试验池中呈分散均匀分布,单个观测网格的最高分布率为6.65%,空白礁区的平均分布率为1.19%;放入礁体,花鲈幼鱼经短暂巡游试探后集群入礁,鱼群主体分布在礁区,礁区的平均分布率>20%、集群出现率>75%。相较于无牡蛎礁型,有牡蛎礁型中花鲈幼鱼响应和聚集时间长,礁区平均分布率(32.2%～49.9%)更高,集群优势更明显,其中以结构最简单的方形牡蛎礁组内的礁区分布率最高,个体离礁距离和群体重心离礁距离最短,集鱼效果最明显。方差分析结果显示,花鲈幼鱼的趋集行为参数和聚集效果在6种礁型间的差异未达到显著水平(P>0.05)。试验结果表明,野生花鲈幼鱼具有一定的趋礁性,放置礁体可...     

鲈幼鱼对饲料中苏氨酸的需要量

以初始体质量(8.00±0.20)g的鲈为实验对象,在海水网箱(1.5 m×1.5 m×2.0 m)中进行为期8周的摄食生长实验,研究鲈对饲料中苏氨酸的需要量。通过在半精制基础饲料中添加晶体L-苏氨酸使饲料中苏氨酸含量分别达到0.75%、1.03%、1.36%、1.67%、2.04%和2.31%,配制成6水平等氮等能饲料(41.83%粗蛋白质,19.68 kJ/g总能)。每种饲料设3个重复,每个重复随机放养30尾鲈。实验采用表观饱食投喂方式,每天投喂2次(06:00和17:30),实验期间水温为26～32℃,盐度为22～28,溶解氧含量在7 mg/L左右。实验结果表明,各饲料处理组成活率(94.4%～98.9%)无显著差异。随着饲料中苏氨酸含量的增加,鲈的增重率显著升高(150.3%～256.9%)(P<0.05),且在1.67%苏氨酸饲料组达到最大值(256.9%),然而,随着饲料中苏氨酸含量的进一步增加,增重率有下降的趋势。鲈的氮累积率随着饲料中苏氨酸含量的增加而显著升高(13.18%～26.36%)(P<0.05),且在1.67%苏氨酸饲料组达到最大值(26.36%),随着饲料中苏氨酸含量的进一步增加,氮累积率有下降的趋势。饲料苏氨酸含量对鲈鱼体粗蛋白、粗脂肪和灰分含量无显著影响。以增重率和氮累积率为评价指标经二次回归分析得出,鲈对饲料中苏氨酸的需要量分别为1.77%和1.88%,占饲料蛋白质的4.21%和4.47%。     

盐度对澳洲宝石鲈幼鱼３个免疫因子活力的影响

实验室条件下测定了在盐度0、5、8、11、13、16下胁迫20d,澳洲宝石鲈(Scortum barcoo)幼鱼内脏组织中超氧化物歧化酶(SOD)、碱性磷酸酶(AKP)及酸性磷酸酶(ACP)共3个免疫相关因子的活力变化.结果表明,盐度胁迫对澳洲宝石鲈3个免疫因子均有一定的影响,在不同盐度的胁迫下,随着盐度的升高,其SOD活性先下降、再升高;碱性磷酸酶(AKP)活性在低盐度胁迫下有短暂升高的过程,然后随着盐度的升高,其活性又明显下降;而酸性磷酸酶(ACP)则是随盐度的升高逐渐增大.试验结果说明低盐度胁迫能引起宝石鲈的应激反应,适当提高其免疫力,而大幅度升高盐度可显著影响其免疫力.     

European seabass (Dicentrarchus labrax) ability to discriminate between diets made with different dietary fat sources

The aim of this work was to determine whether juvenile and adult European seabass (Dicentrarchus labrax L.), fed ad libitum manually and with self‐feeding demand feeders, respectively, were able to discriminate between a fish oil‐based diet and a series of diets made with vegetable oils (soybean, linseed, rapeseed and sunflower oil), as well as a fat‐free diet. Adult D. labrax (443.6 ± 108.8 g) selected diets made from soybean (SYO) and rapeseed (RO) in proportions similar to fish oil (FO). Demand levels for the other two diets, sunflower (SUO) and linseed (LO) oils, were significantly lower than FO, whilst juveniles (56.4 ± 11.2 g) displayed a preference for SYO and FO. The lowest demand levels were associated with a fat‐free diet (FF). Selection percentages of the diets for adult and juvenile fish were, respectively, FF—22.96% and 39.76%, SYO—43.02% and 53.26%, LO—36.48% and 36.19%, SUO—39.87% and 37.32%, and RO—46.38% and 40.94%. The animals’ size and feeding method did not significantly affect dietary selection. However, a statistical difference in specific growth rate (1.37% ± 0.26% day^?1) for juveniles was only observed for FO+FF combination. For juveniles, no differences were observed in the conversion index. The juvenile group (FO + FF) had the highest food intake (2.00 ± 0.35 g 100 g^?1 body weight). Moreover, the groups fed FO + SUO and FO + RO consumed the least. In conclusion, this study shows D. labrax can discriminate between diets where the only difference is the lipid source. These findings should be used to understand the acceptance or rejection of different source oils, which are increasingly being used in aquaculture such as aquafeeds for European seabass.     

A shortcut method for sexing juvenile European sea bass, Dicentrarchus labrax L.

The objective of this study was to develop a rapid and effective method of sexing juvenile sea bass with minimum labour and material. To this end, the gonad squash mount technique was applied along with macroscopic techniques for sexing a large number of experimental fish at the age of 215–275 days post fertilization (p.f.). At this age, 90% of the 3894 fish could be unambiguously sexed by macroscopic examination of their gonads, whereas the remaining proportion was identified using squash mount preparations (10%). The accuracy of the observations was measured up to classical histology procedures. Undifferentiated fish accounted for 0.1% of the total population only. The application of the squash mount technique holds out the prospect of considerable improvement in the efficiency and rapidity of current sexing techniques in sea bass.     

Effects of successive size grading on the growth of juvenile European sea bass (Dicentrarchus labrax L.) at three temperatures

Juvenile European sea bass from the same fish stock were selected by successive size grading processes using 2, 3 and 4 mm bar graders at 79, 96 and 99 days post hatching, thus forming three groups (n=300) consisting of similar‐sized fish that differed by time of each group formation. The growth patterns of fish groups were studied at three temperatures during 5 weeks of rearing. Three‐way anova followed by the Tukey multiple comparison test (P<0.05) showed a high dependence of growth on the temperature applied. The smallest size and weight of fish were detected in all groups reared at 19 °C compared with fish held at 21 and 23 °C respectively. Differences in coefficients of variation of lengths were small and insignificant between groups and temperatures. Growth in the length of sea bass juveniles during the test period was a linear function of time and no differences were observed in growth rate among groups at a particular temperature. Growth rates of fish were 0.71 ± 0.02, 0.62 ± 0.01 and 0.52 ± 0.02 mm day^?1 at 23, 21 and 19 °C respectively. These results indicated that the variations in body size of juveniles in the test period were not the result of differences in the growth potential of individuals.     

Settling velocity and total ammonia nitrogen leaching from commercial feed and faecal pellets of gilthead seabream (Sparus aurata L. 1758) and seabass (Dicentrarchus labrax L. 1758)

The physico-chemical characteristics of particulate wastes of Sparus aurata and Dicentrarchus labrax were investigated. Changes in the dimensions, settling velocity and total ammonia nitrogen (TAN) leached from commercial feed pellets were investigated after soaking. Also, the settling velocity and TAN leached from faecal pellets of these fish were assessed at 15 and 25 °C. The settling velocity of feed pellets was influenced positively by pellet weight and negatively by immersion length as a result of changes in pellet dimensions after soaking. The settling velocity of faecal pellets was determined by pellet weight. The experimental design did not allow identification of any consistent effect of water temperature on settling velocity. Total ammonia nitrogen leaching over time from feed and faecal pellets was successfully explained by means of a first-order kinetic equation. For feed pellets, water temperature significantly affected the speed of the process and the time at which the maximum TAN leached was reached, but did not influence the maximum TAN leached. Leaching was related to feed pellet size, and so the smaller the pellet, the higher the leaching. Total ammonia nitrogen leaching from faecal pellets was greater per unit weight than in feed pellets. However, neither water temperature nor fish species influenced TAN leaching from faeces.     

Post-haemorrhagic anaemia in sea bass,Dicentrarchus labrax (L.), caused by blood feeding of Ceratothoa oestroides (Isopoda: Cymothoidae)

The effects of the fish parasitic isopod, Ceratothoa oestroides (Risso), on haematological parameters of its cage-cultured sea bass host, Dicentrarchus labrax (L.), were studied. Analyses of blood parameters (cell counts, haemoglobin content and haematocrit) were carried out on parasitized and unparasitized sea bass from a fish farm in Turkey. Parasitized fish had significantly lowered erythrocyte counts, haematocrit and haemoglobin values and significantly increased leucocyte counts. Blood feeding by C. oestroides thus produces a post-haemorrhagic anaemia and the fish appear to mount an immune response to the presence of parasites.     

Effects of 2-phenoxyethanol on survival of normal juveniles and malformed juveniles having lordosis or nonfunctional swimbladders of European sea bass (Dicentrarchus labrax L., 1758)

The objectives of this study were to evaluate the effects of 2‐phenoxyethanol (2‐PE), which is an anaesthetic, on survival rates of normal juveniles and malformed juveniles having lordosis or nonfunctional swim bladders of European sea bass (Dicentrarchus labrax L., 1758) and to establish the LC₅₀ (the concentration lethal to 50% of test animals at concentrations of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 and 4.5 mL L⁻¹) and LT₅₀ (the time lethal to 50% of test animals after 10‐, 20‐, 30‐, 40‐, 50‐ and 60‐min time periods) of 2‐PE at 19±0.5°C, salinity 38 g L⁻¹, pH 7.4–7.8 and dissolved oxygen >8 mg L⁻¹. Between concentrations of 0.05 and 0.25 mL L⁻¹, 2‐PE did not cause any mortality or toxicity on normal, lordosis and nonfunctional swimbladder juveniles of sea bass during the 60‐min exposure period. On the other hand, significance in each group fish in their mortality rates between concentrations of 0.30 and 0.45 mL L⁻¹ was observed (P<0.05). The nonfunctional swimbladder juveniles showed lower LC₅₀ than normal and lordosis juveniles respectively. Also, nonfunctional swimbladders juveniles showed lower LT₅₀ than normal and lordosis juveniles respectively. At concentrations of 0.30, 0.35, 0.40 and 0.45 mL L⁻¹, induction times were found to be significantly different among the three groups (P<0.05). Recovery times were not found to be significantly different in two groups at concentrations of 0.30 and 0.40 mL L⁻¹ (P>0.05). The toxic effect of 2‐PE on sea bass juveniles increased depending on the exposure times (P<0.05). The most suitable concentrations of 2‐PE were 0.30–0.35 mL L⁻¹ between minutes 10 and 30, although the normal juveniles can resist to 0.45 mL L⁻¹ of 2‐PE concentration for 20 min. The 2‐PE showed toxicity in relation to the concentrations and exposure time combinations among the three groups in the order; nonfunctional swimbladder fish >lordosis fish >normal fish.     

A pharmacokinetic study of flumequine in sea bass, Dicentrarchus labrax (L.), after a single intravascular injection

The pharmacokinetic properties of flumequine following a single intravascular injection (10 mg kg^–1 fish) were studied in sea bass, Dicentrarchus labrax (L.), 120 g held at 18 °C. The absorption half life ( t _1/2α) and the elimination half life ( t _1/2β) of the drug were calculated to be 1.05 and 10.71 h, respectively. Tissue penetration of flumequine seemed to be moderate because both the apparent volume of distribution of the drug at steady-state ( V _d(ss)) and the extensive apparent volume of the central compartment ( V _c) were found to be small (1.51 and 0.626 L kg^–1). The mean residence time ( MRT ) was short (09.73 h) and the total clearance (CL_T) of the drug was rapid (0.156 L kg^–1 h^–1).