First record of migrating silver American eels (Anguilla rostrata) in the St. Lawrence Estuary originating from a stocking program

In fall 2009, six migrating silver American eels (Anguilla rostrata) originating from a stocking program were caught in the brackish waters of the St. Lawrence Estuary. These maturing eels were all females with gonads developed at a similar stage as other migrating eels in the estuary. Fluorescent oxytetracycline marks observed on the otoliths allowed us to assert without any doubt that they came from glass eels caught in Nova Scotia and stocked 4 years earlier in the Richelieu River, 500 km upstream from the recapture location. Their length varied between 570 and 668 mm, which is within the size range of naturally recruited female silver eels in Nova Scotia, while silver eel are most generally longer than 80 cm in the St. Lawrence estuary. Their growth rate was also exceptionally fast. This direct observation is the first evidence that American eels stocked as glass eels can migrate seaward at least as far as the estuary in synchrony with naturally recruited female silver eels en route to their spawning grounds in the Sargasso Sea.     

转谷氨酰胺酶对鳗鱼冷冻鱼糜凝胶性能的影响

为了改善鳗鱼冷冻鱼糜的凝胶性能,提高其经济价值,添加转谷氨酰胺酶(TGase),通过SDS-PAGE凝胶电泳测定鱼糜凝胶形成过程中蛋白质的变化,研究TGase对鳗鱼冷冻鱼糜凝胶性能的影响。结果表明:TGase在鱼糜凝胶化过程中起着重要作用,并且不同浓度的TGase均可使鳗鱼冷冻鱼糜凝胶的破裂强度、凹陷深度及凝胶强度增加,而对其颜色和白度无影响;TGase的最佳使用浓度为0.5%,在此条件下,鱼糜的凝胶强度达到550.4g·cm,是对照样品的3倍多,而且电镜分析表明,TGase的加入可使冷冻鱼糜形成致密、均匀的凝胶网络结构。     

速酿塔制醋工艺中主要生物污染物的清除

醋鳗、醋虱是发酵制醋工艺中造成醋液品质下降,产生异味,导致醋液产量降低的主要生物污染物。因此清除醋鳗、醋虱污染是食醋酿造工艺中必须解决的关键问题,本实验着重研究速酿塔制醋工艺中这两大主要生物污染物的清除,所采用的方法尚未见报道。     

Are Biometric Parameters Helpful to Assess the Health Risk of Consuming Organochlorine Compounds Contaminated Silver European Eel (Anguilla anguilla)?

Several organochlorine compounds (OCs) were measured in European eels from the Tevere river (Italy). It followed that some of them are still important chemical contaminants. Concentrations of dichlorodiphenyltrichloroethanes (DDTs) are hazardous for the consumer health; those of the 6 indicator polychlorinated biphenyls (PCBs) are often close to the current European maximum residue limit and always higher than the former limit. The relationship between OC concentrations, biometric parameters and the lipid content was then investigated. A strong positive correlation with eel size emerged for the indicator PCBs and DDTs concentrations expressed on wet weight basis. This is explained by the corresponding higher lipid percentage that characterizes bigger eels and the absence of a dilution effect for compounds of main concerns. On the basis of the PCB‐TDI threshold for a 70 kg person, we suggest that 1 should consume no more than 2 eels per week each weighing about 100 g. Thus, we conclude that eel consumption should be limited and restricted to eels relatively shorter and lighter.     

400 MPa级超细晶粒钢板焊接热影响区的组织和力学性能

超细晶粒钢的强度和韧性比普通晶粒钢有大幅度的提高，其焊接性是该钢能否获得广泛应用的关键。通过采用实际焊接和焊接热模拟方法，研究了焊接热输入对超细晶粒钢组织和力学性能的影响。研究结果表明，超细晶粒钢的奥氏体晶粒长大倾向与普通晶粒钢相近，在热影响区和母材之间存在一再结晶软化区，板厚小于3mm时，粗晶热影响区的裂纹扩展吸收能大于母材，板厚大于5mm时，粗晶热影响区韧性比母材有较大幅度降低。对影响粗晶热影响区韧性的机理进行了探讨。     

高效液相色谱-串联质谱联用(Finnigan TSQ Quantum)测定鳗鱼中孔雀石绿、隐性孔雀石绿残留量

利用高效液相色谱串联质谱（LC／MS／MS）方法快速．准确的同时测定鳗鱼中孔雀石绿．隐性孔雀石绿残留量。鳗鱼样品经乙腈．乙酸铵缓冲溶液提取，液相色谱分配到二氮甲烷层，MCX阳离子固相革取小柱净化，浓缩定容。以甲醇和甲酸缓冲溶液为流动相，经C18柱分离后，并用串联质谱在电喷雾（ESI＋）-选择反应监测离子（SRM）的模式下，氘代隐性孔雀石绿为内标，进行质谱定性和定量。该方法无需采用传统PbO2氧化柱，检测限（LOD）为0．2μg／Kg，定量下限为0．5μg／Kg，完全可以达到出口欧盟和日本残留限量要求。     

Rag1 and Rag2 Gene Expressions Identify Lymphopoietic Tissues in Larvae of Rice-Field Eel (Monopterus albus)

In immature lymphocytes, recombination activating genes 1 and 2 are necessary for antigen receptor V (D) J recombination, representing immature lymphocyte biomarkers. Herein, we cloned and sequenced rice-field eel rag1 and rag2 genes. Their expressions in the thymus, liver, and kidney were significant from 0 days post hatching (dph) to 45 dph, peaking at 45 dph in these three tissues. In situ hybridization detected high rag1 and rag2 expressions in the liver, kidney, and thymus of rice-field eel from 2 to 45 dph, suggesting that multiple tissues of rice-field eel contain lymphocyte lineage cells and undergo lymphopoiesis. Tissue morphology was used to observe lymphopoiesis development in these three tissues. The thymus primordium began to develop at 2 dph, while the kidney and liver have generated. Our findings verified that the thymus is the primary lymphopoietic tissue and suggested that, in rice-field eel, lymphocyte differentiation also occurs in the liver and kidney.     

The N-Linked Glycosylation Site N191 Is Necessary for PKA Signal Transduction in Eel Follicle-Stimulating Hormone Receptor

The follicle-stimulating hormone receptor (FSHR) contains several N-linked glycosylation sites in its extracellular region. We conducted the present study to determine whether conserved glycosylated sites in eel FSHR are necessary for cyclic adenosine monophosphate (cAMP) signal transduction. We used site-directed mutagenesis to induce four mutations (N120Q, N191Q, N272Q, and N288Q) in the N-linked glycosylation sites of eel FSHR. In the eel FSHR wild-type (wt), the cAMP response was gradually increased in a dose-dependent manner (0.01–1500 ng/mL), displaying a high response (approximately 57.5 nM/10⁴ cells) at the Rmax level. Three mutants (N120Q, N272Q, and N288Q) showed a considerably decreased signal transduction as a result of high-ligand treatment, whereas one mutant (N191Q) exhibited a completely impaired signal transduction. The expression level of the N191Q mutant was only 9.2% relative to that of the eel FSHR-wt, indicating a negligible expression level. The expression levels of the N120Q and N272Q mutants were approximately 35.9% and 24% of the FSHG-wt, respectively. The N288Q mutant had an expression level similar to that of the eel FSHR-wt, despite the mostly impaired cAMP responsiveness. The loss of the cell surface agonist-receptor complexes was very rapid in the cells expressing eel FSHR-wt and FSHR-N288Q mutants. Specifically, the N191Q mutant was completely impaired by the loss of cell surface receptors, despite treatment with a high concentration of the agonist. Therefore, we suggest that the N191 site is necessary for cAMP signal transduction. This finding implies that the cAMP response, mediated by G proteins, is directly related to the loss of cell surface receptors as a result of high-agonist treatment.     

从烤鳗下脚料中提取测定牛磺酸的研究

建立了用光度法测定烤鳗下脚料中牛磺酸的含量,加标回收试验的结果表明,该法的回收率达93%,相对标准偏差为2.4%,可用于水产品中牛磺酸含量的准确测量。从下脚料中提取牛磺酸的工艺流程设计合理,方法简便。从烤鳗下脚料中提取牛磺酸的方法不仅为烤鳗下脚料的综合利用研究提供了新的途径,而且可作为其它水产原料中牛磺酸提取测定的方法。      

Assessing migratory bottlenecks and escapement of silver eel (Anguilla anguilla) in the highly urbanized North Sea Canal basin,the Netherlands

Habitat fragmentation and migration barriers have attributed to the decline of European eel (Anguilla anguilla). The migration of silver eels through pumping stations, ship locks, and migration facilities within the North Sea Canal basin using acoustic telemetry and overall escapement by mark–recapture was studied. A network of 61 acoustic receivers and three PIT-tag stations was built, and 305 silver eels were tagged with acoustic transmitters and 3923 with PIT-tags. Of all the silver eels that were detected, 55% passed barriers between the polders and the canal and 46% also passed the barrier complex at IJmuiden to sea, mainly via the ship locks. Overall, silver eel escapement to the North Sea per year averaged 81,629 silver eels and 14.3% suffered mortality in the pumping station at IJmuiden. Migration speed was lower for silver eels that initiated their migration upstream compared with silver eels further downstream, higher for silver eels passing barriers later in the migration period, and highest at sea. This study of silver eel movement and escapement in the North Sea canal basin indicated several bottlenecks. Passage success along barriers varied strongly between sites and types of barriers. While at two smaller locations, silver eels migrated through the pedal valves in the ship lock gates, a small passage facility and the pedal valves in a ship lock at complex IJmuiden did not enhance silver eel migration. The barriers and unnatural canal system caused additional delay during silver eel migrations. Mitigation measures for management could include installing fish-friendly pumps, using pumping stations only during the day, and in addition opening ship locks and pedal valves at the beginning of the night.