Data from North Sea - International Bottom Trawl Survey (IBTS)

ibts surveys (international bottom trawl survey) are carried out within an international framework. main countries bordering the north sea participate to it according to the european community regulations (ec n°1543/2000 and n° 1639/2001) which specify that countries from e.u. have to carry out surveys at sea in order to evaluate abundance and stocks distribution, independently of commercial fisheries data. the first target of the ibts survey is to have a diagnosis on the main commercial fish stock and to calculate abundances index by age for these species. this survey started in the years 70’s and gradually standardised. since the years 80’s, a common protocol is implemented and used by all participants. the same fishing gear and the same working methods are used. in addition, to calculate an index for herring and sprat larvae (0 groups), each participating vessel operates with a mik net during the night (methot isaac kidd). for 20 years, the southern part of the north sea has been allocated to the french vessel and since 2007, the eastern channel has been integrated to the whole sampled area. as interactions and circulation of stock between these two areas are important, eastern channel is often associated the north sea for stock assessment. herring for example which is exploited all the year in the north sea comes into the channel during november and december for reproduction. more precise information on larvae indices will be obtained when this area is sampled. in order to study the whole marine ecosystem of the north sea and english channel, some additional studies are carried out during the survey on the r/v thalassa. for example, the continuous underwater fish eggs sampler device (cufes) is used to study fish spawning areas. abundance and distribution of the winter planktonic community (phyto and zoo plankton) and a monitoring study on the structure and distribution of the benthic macroinvertebrates community are also carried out. at last, more samples are done for the marine strategy framework since 2015.

国际底层拖网调查（International Bottom Trawl Survey，简称 IBTS）是在国际框架下进行的。根据欧洲共同体法规（EC No. 1543/2000 和 No. 1639/2001），北海周边的主要国家参与其中。这些法规明确规定，欧盟国家必须在海上进行调查，以评估鱼群的丰富度和分布，这一评估独立于商业渔业数据。IBTS 调查的首要目标是进行主要商业鱼类资源的诊断，并计算这些物种的年龄丰度指数。该调查始于 20 世纪 70 年代，并逐渐标准化。自 20 世纪 80 年代起，实施并采用了一个共同的协议，所有参与者均遵循相同的捕捞工具和工作方法。此外，为了计算鳀鱼和鲱鱼幼鱼（0 组）的指数，每艘参与船只夜间使用 Mik 网进行作业（采用 Isaac Kidd 方法）。在过去 20 年中，北海南部区域由法国船只负责，自 2007 年起，东海峡已纳入整个采样区域。由于这两个区域的种群相互作用和流通至关重要，东海峡通常与北海一起用于种群评估。例如，全年都在北海捕捞的鳀鱼，在 11 月和 12 月会进入海峡进行繁殖。当对该区域进行采样时，将获得更精确的幼鱼指数信息。为了研究北海和英吉利海峡的整个海洋生态系统，调查期间在 R/V Thalassa 上进行了一些附加研究。例如，使用连续水下鱼卵采样器（CUFES）来研究鱼类产卵区。还对冬季浮游生物群落（包括植物和动物浮游生物）的丰富度和分布进行了监测研究，并对底栖大型无脊椎动物群落的结构和分布进行了监测研究。最后，自 2015 年以来，为了海洋战略框架，进行了更多的样本采集。