Collaborative research: Development of a manual on elasmobranch handling and release best practices in tropical tuna purse-seine fisheries     

《Marine Policy》2014

The reduction of by-catch mortality is an objective of the ecosystem approach to fisheries and a request made by consumers. Elasmobranchs, an important component of the French tropical tuna purse seine fishery by-catch, are currently thrown back into the sea. Fishers interact with various types of elasmobranchs that range widely in size, weight and shape, and could pose various degrees of danger to the crew. A diversity of discarding practices within the fleet were reported, some practices were considered suitable, others needed to be adapted and improved and others simply had to be banned. The majority of the crews were likely to improve their handling practices if they were presented with practical suggestions that were quick and easy. Combining scientific observations and empirical knowledge from skippers and crew, a manual, providing appropriate handling practices to ensure crew safety and increase the odds of survival for released animals has been developed and disseminated. Bringing these good practices onto the decks of fishing vessels should contribute to the reduction of the fishing mortality of some vulnerable species. It would be positively viewed by consumers as an act that reduces fishing's footprint on the environment and promoting animal welfare which would improve the image of fishing industry. Mitigation research is by definition an iterative process and different complementary methods must be carried out at different levels of the fishing process to significantly reduce the mortality of the by-catch.  相似文献   

大泷六线鱼仔鱼饥饿试验及不可逆点的研究     

菅玉霞 《海洋科学》2014,(1)

摘要：利用人工孵化得到的大泷六线鱼（Hexagrammos otakii Jordan et Starks）初孵仔鱼,在水温16±0.5℃,盐度31条件下,研究了饥饿对大泷六线鱼前期仔鱼生长的影响,并确定仔鱼的初次摄食饥饿不可逆点（PNR）。结果表明,仔鱼3日龄开口摄食,卵黄于7日龄消耗完毕,油球于8日龄消耗完毕,混合营养期为5-6天,饥饿对仔鱼卵黄吸收速度影响显著（P＜0.05）,对油球的吸收在仔鱼开口前影响不显著（P＞0.05）,仔鱼开口后影响显著（P＜0.05）。摄食仔鱼生长呈线性增加,饥饿仔鱼生长呈现先升高后降低的趋势。仔鱼饥饿不可逆点出现在8日龄和9日龄之间。  相似文献   

Fish Canyon Tuff榍石He扩散及(U- Th)/He年代学研究     

喻顺  田云涛 《地质学报》2023,97(1):278-290

榍石富含U和Th,是(U-Th)/He定年的理想矿物之一。本文以Fish Canyon Tuff榍石为例,开展了榍石He扩散行为和榍石(U-Th)/He定年实验方法研究。榍石分步加热扩散实验结果表明He扩散系数ln(D/a²)与温度倒数呈负相关,与期望的热活化扩散过程一致。测试Fish Canyon Tuff榍石(U-Th)/He年龄分布在28.3～24.6 Ma之间,平均值为26.7±1.2 Ma (1σ),Th/U分布在4.6～5.5之间,平均值为5.2±0.2,在误差范围内与国际上已出版数据一致,表明建立的榍石(U-Th)/He定年实验方法可靠。本次测试15粒榍石碎片外表层(～20μm)存在不同程度的磨蚀(即不完整晶体),且榍石表层磨蚀厚度随着等效半径的增加而增大。榍石碎片(U-Th)/He年龄介于完整晶体(U-Th)/He年龄和真实(U-Th)/He年龄之间,且随着榍石等效半径及表层磨蚀厚度(<20μm)的增大,(U-Th)/He年龄更接近真实年龄,这表明榍石(U-Th)/He年龄不确定度与等效半径大小和表层磨蚀厚度有关。  相似文献   

Numerical simulation of the effects of fish behavior on flow dynamics around net cage     

《Applied Ocean Research》2017

The computational fluid dynamics study is performed to analyze the impact of the cultured fish on the flow field through net cage and the deformation of net cage. The shear stress turbulent k-omega model is applied to simulate the flow field through the net cage, and the large deformation nonlinear structure model is adopted to conduct the structural analysis of the flexible net cage. To validate the net-fluid interaction model of the net cage in current, a series of physical model tests are conducted, which indicate that the numerical model can accurately simulate the flow field around the net cage and the deformation of the net cage. A fish model is used to simulate the effect of fish behavior on the flow pattern around the net cage and the deformation of the net cage. In addition, the flow fields around the net cage in current are investigated considering different fish group structures, fish swimming speeds, fish distributions and fish stocking densities. The results indicate that the circular movement of fish in the still water leads to a low pressure zone at the center of net cage, which causes a strong vertical flow along the center line of the net cage. The drag force on the net cage is significantly decreased with the increasing fish stocking density, but the most severe deformation of net cage occurred in the case of medium fish stocking density.  相似文献   

Are Territorial Use Rights in Fisheries (TURFs) sufficiently large?     

《Marine Policy》2017

Territorial Use Rights in Fisheries (TURFs) are gaining renewed attention as a potential tool for sustainable fisheries management in small-scale fisheries. This growing popularity comes despite the fact that there are still unresolved questions about the most effective TURF designs. One of the key questions is the role of TURF size in their efficacy both from ecological and social standpoints. This study explores the expected effects of existing TURF sizes on yields for TURF systems in Chile, México and Japan. The expected effect of larval dispersal and adult movement on yields was simulated for TURFs in each system. The results show that the analyzed TURF systems fall into three main categories: (a) TURFs that are of adequate size to eliminate the expected negative effects of both adult and larval movement, (b) TURFs that are large enough to eliminate the expected negative effects of adult movement, but not the effects of larval dispersal, and c) TURFs that are too small to eliminate the expected impacts on yield of both adult and larval movement. These analyses suggest that either existing models of TURF performance are incomplete or that there is significant scope for improved performance with altered TURF designs. Considering these alternatives, empirical evidence from the TURFs deemed too small suggests that complementary management tools can enhance TURF performance when natural or social constraints prevent the construction of TURFs of optimal size.  相似文献   

中国近海洄游日本鳗鲡(Anguilla japonica)玻璃鳗肠道微生物菌群分析          下载免费PDF全文

姜之信  李慷  巴旭冰  曾祥标  刘利平 《海洋与湖沼》2023,54(6):1728-1736

为研究长江口日本鳗鲡玻璃鳗肠道菌群的结构与多样性特征,初步探究野生鳗鲡仔鱼的营养需求,分别采集浙江台州市、舟山市以及江苏盐城市邻近海域的玻璃鳗样品,利用16S rDNA扩增子测序技术,分析三个采样点玻璃鳗肠道优势菌群及营养代谢相关的功能差异。结果显示,三个采样点的玻璃鳗肠道菌群均以变形菌门(Proteobacteria, 68.7%～82.0%)和放线菌门(Actinobacteria,4.2%～19.0%)为主要优势菌门。在属分类水平上,不动杆菌属(Acinetobacter, 12.4%～17.3%)和假单胞菌属(Pseudomonas, 8.07%～13.03%)丰度较高,属固定优势菌属。此外,每个采样点样本中都含有丰富的独特细菌群,包括台州市的气单胞菌属(Aeromonas)、舟山市的内生单胞属(Endozoicomonas)和丙酸杆菌属(Cutibacterium)以及盐城市的嗜冷杆菌属(Psychrobacter)和稳杆菌属(Empedobacter),推测是受采样点不同水环境因素影响。不动杆菌、假单胞菌、内生单胞菌等菌属在多种鱼类肠道中有着消化蛋白质的功能,气单胞菌虽属于...  相似文献