Interannual spatial variability of krill (Euphausia superba) influences seabird foraging behavior near Elephant Island, Antarctica

We investigate the influence of krill (principally Euphausia superba ) patchiness on the foraging distributions of seabirds to understand how variation in krill influences patch dynamics between krill and birds. At sea-surveys were conducted near Elephant Island, Antarctica, for 3 yr (2004–2006) during the annual U.S. Antarctic Marine Living Resources (AMLR) program. Standardized strip-transect surveys were used to map seabirds, and a combination of acoustic and net surveys was used to map krill. We measured patch size of krill and seabirds and elucidated how krill patch dynamics influence foraging seabirds. The spatial association between krill and predators was influenced by the size and arrangement of krill patches. We found a negative relationship between abundance and patchiness of krill and predators, indicating that when krill is less abundant, its predators are less abundant and concentrated. We conclude that annual patch dynamics of krill strongly influences the local abundance and distribution of seabirds. Such information should be used to interpret potential interactions between seabirds and krill fisheries operating near Elephant Island.     

The Forms of Fluoride in Antarctic Krill (Euphausia superba) Oil Extracted with Hexane and its Removal with Different Absorbents

Krill oils (KOs) were prepared using different extraction methods (hexane and supercritical carbon dioxide), different materials (heat-dried krill powder, freeze-dried krill powder, and freeze-dried krill tail meat powder), and different standing times during hexane extraction. The fluoride concentrations in the KOs were positively correlated with the protein concentrations. Absorbents were employed to remove fluoride from KO. Activated clay achieved the highest fluoride removal rate (70.66%), followed by calcium oxide (14.49%), activated carbon (11.97%), calcium chloride (9.32%), activated alumina (0.94%), and chitosan (0.52%). Meanwhile, the protein removal rates of the above absorbents were positively correlated with the fluoride removal rates.     

不同水平南极磷虾粉等量替代鱼粉对大口黑鲈生长性能及部分生理生化指标的影响

为研究不同水平南极磷虾粉等量替代饲料中进口鱼粉对大口黑鲈幼鱼生长性能、全鱼营养成分组成、血液部分生理生化指标的影响,本试验共设4组利用不同水平南极磷虾粉等量替代饲料中鱼粉的试验饲料(分别记为:0%(D1组)、3%(D2组)、6%(D3组)、9%(D4组),每组饲料设3个重复组,每个重复放养初始体重约为(12.43±0.16)g/尾的大口黑鲈(LargemouthBass)30尾,在室内循环水养殖系统中饲养8周。结果表明:(1)与对照组相比,试验组大口黑鲈的增重率(WGR)、特定生长率(SGR)和蛋白质效率(PER)均显著提高,SGR分别提高14.0%、15.8%、20.5%,PER分别提高9.1%、16.8%、27.3%,饲料系数(FCR)显著降低(P<0.05),其中以9%南极磷虾粉替代组效果最佳;(2)各试验组全鱼的水分、粗蛋白质和粗灰分含量没有显著差异(P>0.05),南极磷虾粉替代组的粗脂肪含量均高于对照组,其中6%南极磷虾粉替代组较对照组提高13.8%(P<0.05);(3)南极磷虾粉等量替代组试验鱼血液中的白细胞数目(WBC)较对照组分别提高66.1%、61.1%、56.5%(P<0.05),而红细胞数目(PBC)较对照组分别提高25.2%、25.2%、20.7%(P<0.05),而红血蛋白(HGB)、白蛋白(ALB)各组间差异不显著(P>0.05);(4)各替代组试验鱼血清超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性随着南极磷虾粉替代鱼粉含量的上升而上升,其中9%替代组分别较对照组提高45.0%、36.4%(P<0.05),各替代组试验鱼血清中谷胱甘肽过氧化物酶(GSH-Px)活性显著高于对照组(P<0.05),各试验组血清中丙二醛含量与对照组没有显著差异(P>0.05);(5)各替代组血清中甘油三酯(TG)的含量均显著高于对照组(P<0.05),总胆固醇(TC)的含量随着南极磷虾粉替代鱼粉含量的上升而上升,其中9%替代组较对照组提高21.5%(P<0.05),各组血清谷丙转氨酶(ALT)、谷草转氨酶(AST)和碱性磷酸酶(ALP)活性差异均不显著(P>0.05)。综上,南极磷虾粉是大口黑鲈配合饲料中的优质蛋白源,适当替代鱼粉可以提高大口黑鲈幼鱼的生长性能,抗氧化功能以及免疫功能,本试验中以6%、9%南极磷虾粉等量替代饲料中鱼粉的效果最佳。     

基于多元变量的南极磷虾拖网作业状态影响因素分析

拖网作业过程中的网位、网身状态、拖网整体状态是评价拖网性能优劣的重要指标。以南极磷虾拖网为例,通过测量拖网不同部位(上纲、第3~4节网身连接处和网囊口上部中点)深度,以部位间深度差表示拖网作业状态,分析捕捞操作、海洋环境和渔获量对拖网作业状态的影响,确定中层拖网作业过程中状态的变化趋势。结果表明:上纲与第3~4节网身连接处深度差范围为-0.20~8.02 m,上纲与网囊口上部中点深度差范围为6.49~30.16 m;曳纲长度、拖速、风速、150 m水层流速对磷虾拖网上纲深度影响显著,上纲深度与曳纲长度和150 m水层流速呈正相关关系,与拖速呈负相关关系,随风速增加,上纲深度先减小后增大;拖速、200 m水层流速和浪高对上纲与第3~4节网身连接处深度差影响极显著;上纲与第3~4节网身连接处深度差具有随拖速和200 m水层流速的增加,先增大后减小的趋势,其中拖速为2.6 kn以及200 m水层流速为0.3 kn时,上纲与网囊口上部中点深度差最大,2 m浪高时,深度差最小;渔获量与上纲和网囊口上部中点深度差呈正相关关系;曳纲长度是影响拖网作业状态的最重要因素,其次是拖网速度、风速、浪高和水流速度。