大菱鲆复合生物保鲜剂的优化及保鲜效果研究

为了延长大菱鲆的货架期,选取乳酸链球菌素(Nisin)、乳酸钠和海藻酸钠进行单因素试验,利用响应面Box-Behnken试验设计对复合生物保鲜剂进行复配优化,建立以第9天的鱼肉挥发性盐基氮(TVB-N)含量为响应值的二次多项式回归模型,并通过测定大菱鲆肌肉菌落总数、pH值、TVB-N含量、巯基含量、持水力,以及用低场核磁技术测定水分迁移和光学显微镜观测肌肉组织结构变化,验证最优配比复合保鲜剂的保鲜效果。结果表明,经方差分析和回归拟合,得到3种生物保鲜剂的最佳添加量为Nisin 0.04%、乳酸钠5.92%、海藻酸钠1.06%,经保存9 d的大菱鲆TVB-N有最小值(18.37 mg·100g^-1), 且Nisin与乳酸钠对大菱鲆的保鲜具有显著的交互作用(P<0.05),响应面模型与实际情况拟合较好。经复合保鲜剂处理过的4℃冷藏大菱鲆,货架期可延长至14 d。本研究为制备高品质水产品可食性涂膜提供了理论依据和技术支持。     

Density‐independent and density‐dependent factors affecting temporal changes in spatial distributions of eastern Bering Sea flatfish

The general warming of the eastern Bering Sea (EBS) and the wide range of abundance exhibited by several eastern Bering Sea flatfish motivated an examination of how density‐dependent and density‐independent factors may influence the spatial distributions of EBS flatfish. In this study, EBS trawl survey data from 1982 to 2006 were used to examine how temporal changes in the distributions of six flatfish species groups [yellowfin sole (Limanda aspera), rock sole (Lepidopsetta sp.), flathead sole (Hippoglossoides sp.), Alaska plaice (Pleuronectes quadrituberculatus), arrowtooth flounder (Atheresthes sp.), and Greenland turbot (Reinhardtius hippoglossoides)] are related to temporal changes in the location of the ‘cold pool’ (bottom water < 2°C), and how the area occupied by flatfish are related to the cold pool and population abundance. Rock sole and flathead sole distributions have generally moved northwest since 1982 and are significantly correlated with the movement of the cold pool, whereas arrowtooth flounder avoid the cold pool and their area occupied is inversely related to the size of the cold pool. The area occupied by arrowtooth flounder and rock sole are also significantly related to stock abundance. Multivariate statistical models indicate that the location of rock sole is more strongly related to stock abundance than to the cold pool, whereas the area occupied by arrowtooth flounder is more strongly related to the area of the cold pool rather than abundance. The temperatures occupied by several flatfish stocks indicate a substantial variability in suitable temperatures. These results suggest that a complex suite of density‐dependent and density‐independent factors may determine the response of EBS flatfish spatial distributions to increasing temperatures.     

Experimental infection of turbot, Psetta maxima (L.), with strains of viral haemorrhagic septicaemia virus isolated from wild and farmed marine fish

The susceptibility of turbot, Psetta maxima, to infection with two strains of viral haemorrhagic septicaemia virus (VHSV) obtained from wild Greenland halibut, Reinhardtius hippoglossoides, and from farmed turbot was examined. A marine VHSV strain known to be highly pathogenic for turbot was also utilized for comparative purposes. Fish were infected by intra-peritoneal (i.p.), immersion or cohabitation, and maintained at two different temperatures (8 and 15 degrees C). Infection trials showed that the three VHSV isolates were pathogenic for turbot fingerlings by i.p. injection at both temperatures, with high levels of mortality. Virus was recovered from most pools of dead fish i.p. challenged, but not from surviving fish. Although clinical signs were not induced following waterborne exposure, viral growth was obtained from some pools of surviving fish challenged by immersion with strain GH40 from Greenland halibut, which indicates that the virus can survive in sea water and infect other fish via horizontal transmission. Furthermore, although low, the clinical signs and mortality observed in fish cohabitating with turbot challenged with strain GH40 confirms horizontal transmission and indicates that the passage through fish increases the virulence of this strain for turbot. These findings indicate that Greenland halibut, as other wild fish, may play an important role in the epizootiology of VHSV and suggest a potential risk for the turbot farming industry.