我国大菱鲆产业价值链实证研究

随着规模的扩大,大菱鲆养殖产业逐渐从高利时代步入常利时代,各种深层次问题开始显现,产业升级已势在必行.着眼于产业内部,进行产业链优化整合可以提高产业运行效率、总利润和各环节的福利,是实现产业升级的切入点.基于实证调研,分析了我国大菱鲆产业链构成及产业价值链,初步研究结果表明,各环节价值增值量依次为:餐饮＞养殖＞育苗＞综...     

Fishmeal replacement by mixed plant proteins and maggot meal on growth performance,target of rapamycin signalling and metabolism in juvenile turbot (Scophthalmus maximus L.)

Fishmeal could only be replaced by plant proteins at limited levels in aquafeeds, especially for carnivorous fish. In this study, an experiment was designed to evaluate the possibility of improving the utilization of plant proteins by maggot meal supplementation in turbot diet. Five diets were formulated: a reference diet (FM) containing 63% fishmeal and four experimental diets (35(0%), 35(3%), 40(0%), 40(3%)) in which fishmeal was substituted at different levels by plant proteins with 0–3% maggot meal. Turbot (4.90 ± 0.03 g) was fed with these diets for 9 weeks. Fishmeal was successfully replaced by plant proteins in turbot diet without growth reduction at 35% but not 40%. However, maggot supplementation (3%) at 40% plant protein replacement level achieved comparable growth performance with that of fishmeal. Maggot meal supplementation improved apparent digestibility coefficients, plasma hydroxyproline levels, intestine trypsin activities and activated target of rapamycin (TOR) signalling, all of which were decreased or down‐regulated after high plant protein replacement. Therefore, this study demonstrated maggot meal, a potential valuable protein source for turbot.     

Estimation of genetic parameters for early growth trait of turbot (Scophthalmus maximus L.) using molecular relatedness

In this study, a data set of 1140 progenies from 19 families that were composed of 13 half‐sib and six full‐sib families was used in the estimation of the genetic parameters of weight for juvenile turbot at 100 days post hatch. Sixty progenies were randomly selected from each family, and 20 of these individuals were genotyped at 12 microsatellite loci. Two sorts of relatedness, including pedigree relatedness (PR) from a complete pedigree and average molecular relatedness (AMR) from molecular markers, were compared to explore the feasibility of AMR in selective breeding when only parents were known. Two different animal models, Model 1 and Model 2 which were without and with the addition of maternal and common environmental effects, respectively, were used to estimate the variance component and breeding values for weight using restricted maximum likelihood (REML) method. Thereafter, cross‐validation was applied to investigate predictive ability of model and accuracy of breeding values. Pearson correlation analysis showed that AMR was highly correlated (0.91) with PR. According to conditional Akaike Information Criterion, the best models for AMR and PR methods were Model 2 and Model 1 respectively. Heritability estimates from AMR and PR methods based on their best models were 0.19 (±0.06) and 0.66 (±0.17). Cross‐validation showed that AMR was comparable to PR in terms of predictive abilities and accuracies of breeding values based on the same model. This study therefore suggests that the AMR can be applied as alternative of PR when only parents were known.     

循环水养殖条件下水温对大菱鲆氨氮排泄、转氨酶及免疫因子的影响

在高密度工业化封闭循环海水养殖条件下（养殖密度为14?2±0?48 kg／m2）,选取大菱鲆（371?68±43?15 g）360尾,随机均分4组,设置4个水温梯度14℃、16℃、18℃和21℃,旨在探寻水温对大菱鲆氨氮排泄、转氨酶及血清免疫因子的影响,试验期为56 d。结果表明：（1）养殖水体总氨氮浓度随水温升高呈先升后降,18℃时总氨氮浓度极显著高于14℃、21℃时;大菱鲆氨氮排泄率随水温升高而升高,且二者呈指数关系。（2）大菱鲆肝脏GPT、GOT活力随水温升高呈先升后降,均在18℃达最大值;而血清两种指标变化趋势与之相反,均在21℃达最大值。（3）血清LZM、SOD活力及皮质醇含量均随水温升高呈先升后降,均在18℃达最大值;血氨含量则逐渐下降,14℃时极显著高于18℃、21℃时;鳃丝Na＋?K＋?ATPase活力随水温升高而升高,但组间差异不显著。综上,封闭循环水养殖大菱鲆的适宜水温为16～18℃。     

Pathology of Edwardsiella tarda infection in turbot, Scophthalmus maximus (L.)

Macroscopic and histopathological changes in cultured turbot, Scophthalmus maximus (L.), in Spain caused by infection with Edwardsiella tarda are described. Eye tumefaction, inflammation, haemorrhages, ascites and the presence of a purulent fluid were the main macroscopic lesions observed. Histopathological lesions were found in the kidney, spleen and liver. In the kidney and spleen these were characterized by a severe apostematous inflammatory reaction, with a large number of abscesses. The liver was affected to a lesser degree and only some phagocytes loaded with bacteria were observed. Ultrastructural observations indicated that macrophages were the main cell type implicated in the inflammatory response. Most of the bacteria observed within the phagocyte cytoplasm showed no degenerative changes and some were dividing. Degenerative changes observed in macrophages indicate their failure in preventing the infection.     

Characterization of Edwardsiella tarda strains isolated from turbot, Psetta maxima (L.)

The biochemical, serological and molecular characteristics of a group of 21 Edwardsiella tarda strains isolated from turbot, Psetta maxima, in two different areas of Europe were analysed and compared with a total of 13 strains of this bacterial species with different geographical and host origins. All the turbot isolates were biochemically identical to the E. tarda strains included as reference. The use of different techniques including microagglutination, dot blot and Western blot of lipopolysaccharides allowed us to determine that all the turbot isolates constitute an homogeneous and distinctive serological group. Genetic analysis by randomly amplified polymorphic DNA (RAPD) analysis demonstrated that although the E. tarda strains from turbot were compiled in a unique group using the primers P3 and P6, two clonal lineages could be detected when oligonucleotides P4 and P5 were employed.     

Susceptibility of marine fish species to a megalocytivirus, turbot iridovirus, isolated from turbot, Psetta maximus (L.)

Turbot iridovirus (TBIV), a member of the genus Megalocytivirus in the family Iridoviridae, was isolated from diseased turbot, Psetta maximus (L.), in Korea in 2003. In this study, experimental infection of turbot, Japanese flounder, Paralichthys olivaceus (Temminck & Schlegel), and rock bream, Oplegnathus fasciatus (Temminck & Schlegel), with TBIV was performed to evaluate the viral susceptibility of these fish species. After virus exposure, the mortalities of turbot reared at 22 and 25 degrees C were 60% and 100%, respectively, suggesting that TBIV is the causative agent of the mass mortality of turbot that occurred in Korea in 2003. Moreover, TBIV was detected in Japanese flounder and rock bream by polymerase chain reaction after experimental infection (26 days post-inoculation) despite no viral pathogenicity in these fish, suggesting that these two fish species are also susceptible to the virus. It is possible that horizontal transmission of TBIV occurs among these three fish species because turbot is routinely cultured with Japanese flounder and rock bream in Korea.     

Reassortant betanodavirus infection in turbot (Scophthalmus maximus)

In this study, the susceptibility of turbot juveniles to two betanodavirus strains was assessed, a RGNNV/SJNNV reassortant (Ss160.03) and a SJNNV strain. The reassortant isolate exhibits a slightly modified SJNNV CP, with two amino acid substitutions in the C‐terminal domain (positions 247 and 270). To analyse the role of these residues as virulence and host determinants in turbot, three recombinant strains (rSs160.03₂₄₇, rSs160.03₂₇₀, rSs160.03_247+270) harbouring site‐specific mutations in the CP sequence were also tested in experimental trials. Moderate mortalities (up to 50%) were recorded at 18 °C in the fish challenged with the Ss160.03 strain, whereas low mortalities (17%) were observed in the group challenged with the SJNNV strain. A slight decrease (around 10%) was observed in the mortalities caused by the mutants rSs160.03₂₄₇ and rSs160.03₂₇₀, whilst the mutation of both positions reduced mortality by more than half of that observed in fish challenged with the wild strain. These results are confirmed by the replication in brain tissues, because whereas the wild strain was detected from 5 to 30 dpi and reached the highest viral load, the recombinant virus harbouring both mutations was not detected in the brain until 20 dpi and with a moderate viral load.