鱼类下脚料中鱼油的提取工艺研究

鱼油所含的磷脂是动物脑、神经组织、骨髓、心、肝和脾中不可缺少的组成部分,既有助于脂的消化吸收、转运和形成,又是生物膜的重要结构物质。目前金枪鱼下脚料的利用主要是提取活性多肽、胶原蛋白、生产鱼骨粉等。金枪鱼加工中产生大量的下脚料,如果用于提取鱼油,可以创造可观的经济效益。重点研究了酶解工艺条件对鱼油提取率的影响,结果表明,胰蛋白酶提取鱼油的酶解工艺参数为:酶解温度45℃,酶添加量1.5%,料液质量比为1:1,酶解时间4h,酶解pH值8。在此条件下,粗鱼油的提取率为4.32%。     

Mesoscale eddies modulate the dynamics of human fishing activities in the global midlatitude ocean

Frequent fishing activities are causing overfishing, destroying the habitat of marine life, and threatening global marine biodiversity. Understanding the dynamics of fishing activities and their drivers is crucial for designing and implementing effective ocean management. The fishing activities in the open sea are reported to be characterized by high spatial variability in local waters; however, it is still unclear whether their high spatial variability is random or regulated by oceanographic variations. Mesoscale eddies are ubiquitous swirling currents that dominate locally biogeochemical processes. Previous case studies presented an ongoing debate regarding how eddies exert impacts on high trophic organisms, which imposes limitations on understanding the dynamics of fishing activities based on the bottom-top control hypothesis from eddies to fish and fishing activities. By combining global fishing activities from deep learning and oceanic eddy atlases from satellite monitoring, we showed that the spatial variations in fishing activities were closely related to mesoscale eddies in the global midlatitude ocean, confirming that fishing activities primarily targeting tuna, were aggregated in (repelled from) anticyclonic (cyclonic) eddy cores. This eddy-fishing activity relationship was opposite to satellite-observed primary production but corresponded well with the temperature and oxygen content in deeper water. By integrating existing evidence, we attribute eddy-related fishing activities to a reasonable hypothesis that warm and oxygen-rich deeper water in anticyclonic eddies relieves the thermal and anoxic constraints for diving predation by tuna while the constraints are aggravated in cold and oxygen-poor cyclonic eddies.     

中西太平洋围网黄鳍金枪鱼渔场分布与溶解氧垂直结构的关系

溶解氧垂直结构是影响黄鳍金枪鱼(Thunnus albacares)垂直活动的重要因素,为了解中西太平洋围网黄鳍金枪鱼渔场溶解氧的分布特征及其对围网渔业生产的影响,基于WOA18溶解氧三维数据集和中西太平洋2008-2017年间围网黄鳍金枪鱼渔业的生产数据,分析渔场区溶解氧浓度的垂直结构特征及其与渔获量(catch p...     

Modeling environmental influence on Atlantic bluefin tuna bycatch by Mexican longliners in the Gulf of Mexico

Atlantic bluefin tuna (ABFT) stocks have been considered overfished over the last decades, especially the western stock, whose main spawning grounds are in the Gulf of Mexico (GoM). Despite the current measures implemented, spawner bycatch by the longline fleet targeting yellowfin tuna (YFT) may explain the lack of recovery of local stocks. This situation demands the implementation of appropriate spatiotemporal management strategies to minimize bluefin bycatch in the GoM, which involves knowledge in depth of its distribution and environmental forcing. Using catch and effort data from the Mexican commercial longline fleet with 100% scientific observer coverage from 1999 to 2012 and satellite derived environmental data, this study investigated the influence of environmental conditions on catch per unit effort (CPUE) of ABFT and YFT. General additive models (GAMs) were fitted using a negative binomial distribution and applying Akaike information criterion (AIC) to select the best model. Bluefin CPUE exhibited a marked seasonality, reaching higher values in February and March while YFT catches occurred throughout the year. Two main locations were identified with higher ABFT bycatch rates, Campeche Bay and the western‐central area of the GoM. Higher ABFT CPUE was significantly associated with areas with negative sea level anomalies and low sea surface temperatures, characteristic of cyclonic eddies. Instead, YFT CPUE showed a lesser environmental influence in its distribution. To our knowledge, the patterns shown in this study provide the first in‐depth approach to understand ABFT bycatch in Mexican waters, which will help in further development of adequate management strategies.     

Environmental associations of Pacific bluefin tuna (Thunnus orientalis) catch in the California Current system

We investigate the impact of oceanographic variability on Pacific bluefin tuna (Thunnus orientalis: PBF) distributions in the California Current system using remotely sensed environmental data, and fishery‐dependent data from multiple fisheries in a habitat‐modeling framework. We examined the effects of local oceanic conditions (sea surface temperature, surface chlorophyll, sea surface height, eddy kinetic energy), as well as large‐scale oceanographic phenomena, such as El Niño, on PBF availability to commercial and recreational fishing fleets. Results from generalized additive models showed that warmer temperatures of around 17–21°C with low surface chlorophyll concentrations (<0.5 mg/m³) increased probability of occurrence of PBF in the Commercial Passenger Fishing Vessel and purse seine fisheries. These associations were particularly evident during a recent marine heatwave (the “Blob”). In contrast, PBF were most likely to be encountered on drift gillnet gear in somewhat cooler waters (13–18°C), with moderate chlorophyll concentrations (0.5–1.0 mg/m³). This discrepancy was likely a result of differing spatiotemporal distribution of fishing effort among fleets, as well as the different vertical depths fished by each gear, demonstrating the importance of understanding selectivity when building correlative habitat models. In the future, monitoring and understanding environmentally driven changes in the availability of PBF to commercial and recreational fisheries can contribute to the implementation of ecosystem approaches to fishery management.     

应用贝叶斯状态空间剩余产量模型框架评估印度洋大眼金枪鱼的资源状况

根据1950―2016年的渔获量数据及1955―2016年的单位捕捞努力量(Catch Per Unit Effort,CPUE)数据,采用贝叶斯状态空间剩余产量模型框架JABBA(Just Another Bayesian Biomass Assessment)对印度洋大眼金枪鱼(Thunnus obesus)的资源状况进行评估,分析了渔船效应、CPUE数据尺度对评估结果的影响。结果表明,模型拟合效果对于不同时间跨度下CPUE数据的选择比较敏感。当选用时间跨度为1979―2016年的CPUE数据且考虑渔船效应时,模型拟合效果最好。2016年大眼金枪鱼的资源量为812 kt,最大可持续产量(Maximum Sustainable Yield,MSY)为163 kt,远高于同年渔获量86.81 kt,其资源量具有82.50%的概率处于"健康"状态。当总允许可捕量为69.45～104.17 kt时(2016年渔获量的80%～120%),未来10年大眼金枪鱼的资源量仍高于B_(MSY)(达到MSY所需的生物量)。回顾性分析结果表明,该资源评估结果存在一定程度的回顾性问题,捕捞死亡率和资源量分别存在被低估和高估的现象。将来需要在模型结构设定、CPUE数据选择及模型参数的先验分布设置等方面进一步优化。     

东太平洋大眼金枪鱼自由鱼群栖息地偏好的时空分布特征

摘 要：本研究基于美洲间热带金枪鱼委员会收集的2015-2017年东太平洋金枪鱼围网金枪鱼自由鱼群捕捞数据和相匹配的卫星遥感数据，使用二阶提升回归树模型(Boosted regression trees, BRTs)建立了该鱼群的栖息地，以探究其时空分布特征。研究结果表明，相对于环境因子，空间因子对大眼金枪鱼自由鱼群的丰度有更大的影响。环境因子方面，纬度、经度、混合层深度、月份和海表面温度是影响大眼金枪鱼捕捞成功概率的主要影响因子，而影响丰度的主要因子为经度和海表面叶绿素浓度。空间上，大眼金枪鱼主要处于10°S以南， 95°W以西的海域。在2016年7-9月和2017年2-4月中，BRTs模型预测的空间分布显示一些高度密集的自由鱼群分别栖息在远离海岸，经度为150°W，纬度为0°的赤道海域和经度为120°W，纬度为10°S附近的海域。时间序列上，大眼金枪鱼丰度月平均值的年际间变化差异很小，月间差异较大，在7月达到最高值，但在8月份立刻下降到最低值。本研究的结果可以为东太平洋大眼金枪鱼的资源养护和管理提供参考依据。     

The cause of death of juvenile Pacific bluefin tuna (Thunnus orientalis) reared in sea net cages

Although the survival rate of juvenile Pacific bluefin tuna Thunnus orientalis (PBT) during 30 days after stocking in sea net cages has been as low as approximately 50%, the reason for this high mortality is not clear. The dead fish were collected and counted during 30 days after stocking in a sea net cage, and the growth performance, stomach contents, and bone injury were investigated. Nearly half (47.9%) had died within the first 4 days. The total length and body weight of the dead fish were significantly smaller than those of the live fish, and the weight of the dead fish did not increase during the first 7 days. Approximately one-third of the dead fish (21.9–42.9% per day) had ingested inorganic matter such as wood or Styrofoam waste during the first 7 days, and 25.0–45.0% of the dead fish sampled per day showed poor growth. The daily ingestion rate of inorganic matter decreased dramatically from the eighth day, when the daily mortality rate decreased. The percentage of dead fish with bone injuries due to collision or contact was low (less than 15%). These results suggest that one of the causes of high mortality during several days after stocking in a sea cage was accidental ingestion of inorganic matter by juvenile PBT. Improvement in feeding method can increase the survival rate of juveniles in sea net cages.     

A rapid latex agglutination test for gender identification in the Atlantic bluefin tuna,Thunnus thynnus (Linnaeus)

A rapid, one‐step agglutination assay has been developed, based on latex particles sensitized with antibodies against vitellogenin (Vtg), aimed at Atlantic bluefin tuna, Thunnus thynnus (Linnaeus) (ABFT), gender identification. The egg‐yolk precursor protein Vtg was used as a gender marker for the assay as it is a female‐specific protein synthesized during reproductive maturation. The presence of Vtg in the plasma was revealed in 60–120 s through an agglutination reaction by mixing small volumes of ABFT plasma and an anti‐Vtg antibody‐latex suspension on a microscope slide. The effectiveness of the present test was restricted to the months of May and June, concomitant with high circulating Vtg levels. Because of its rapidity and ease of performance in the field, the present gender identification assay could be useful for broodstock management in the aquaculture industry as well as in tagging studies on wild populations.     

3种不同脱水方式处理对金枪鱼碎肉挤压产物品质的影响比较

为了获得品质最佳的金枪鱼挤压产物,本试验以金枪鱼碎肉为原料,探讨了炒制、热泵干燥和真空干燥3种脱水方式对挤压产物品质的影响。结果表明,3种脱水方式对挤压产物的色差、膨化率、硬度和咀嚼度无显著影响。经炒制制得的挤压膨化产物,其组织化度最高,为1.62,蛋白质体外消化率最高、酸价最低,分别为84.41%和18.09 mg·g-1。而经热泵和真空干燥处理得到的挤压产物,其组织化度为0.97和1.03,蛋白质体外消化率为81.77%和78.42%,酸价为32.76 mg·g-1和26.36 mg·g-1。相比其他2种脱水方式,炒制脱水有利于提高金枪鱼碎肉挤压膨化产物的组织化度,保持蛋白质的营养价值,并降低产物中脂肪的氧化程度。本研究为金枪鱼碎肉的挤压膨化提供了一定的理论依据。