Since 2015, the European Union gradually implemented the landing obligation (LO). This prohibits at-sea discarding of species under total allowable catch management. Spatiotemporal avoidance strategies and increasing fishing gear selectivity are two complementary levers that could help fishers in reducing the amount of discards. The objective of this paper is to analyse discarding practices of demersal mixed fisheries in the central part of the Celtic Sea to inform on potential spatial avoidance strategies of unwanted catches in a multi-species context. This study provides the first international and fine scale discard maps based on combined observer at-sea data from Ireland, France and the UK, the main countries fishing in the area. Using a suite of multivariate analyses, we identified areas with similar discard profiles, accounting for the multi-species nature of the fisheries. The maps were also derived separately for the three countries to examine national versus general patterns. Strong spatial segregation in effort between the countries, combined with nationally distinct quotas constraints, fisheries targets and market preferences, resulted in limited differences in the species composition of discards, but considerable differences in spatial discard patterns between countries. In theory, the maps based on discards below and above the minimum conservation reference size could inform fishers on areas to avoid but in practice, the spatial ubiquity of some species involved and strong technical interactions between fishing gears limit the possibility of avoiding discards. Some species trade-offs could be identified that might help to minimize adverse impacts of the implementation of the LO.

中文翻译：

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混合渔业中丢弃物的空间分布：物种权衡、潜在的空间回避和国家对比

2015年以来，欧盟逐步实施了登陆义务（LO）。这禁止在总允许捕捞量管理下在海上丢弃物种。时空规避策略和增加渔具选择性是两个互补的杠杆，可以帮助渔民减少丢弃物的数量。本文的目的是分析凯尔特海中部底层混合渔业的丢弃做法，以了解多物种背景下不想要的渔获物的潜在空间规避策略。该研究根据爱尔兰、法国和英国（该地区主要捕鱼国）的海上观察员综合数据，提供了第一张国际精细尺度丢弃物地图。使用一套多变量分析，我们确定了具有相似丢弃概况的区域，考虑到渔业的多物种性质。这三个国家的地图也分别派生出来，以检查国家与一般模式。国家间努力的强烈空间隔离，加上国家不同的配额限制、渔业目标和市场偏好，导致丢弃物的物种组成差异有限，但国家之间的空间丢弃模式差异很大。理论上，基于低于和高于最低保护参考尺寸的丢弃物的地图可以告知渔民应避免的区域，但在实践中，所涉及的某些物种的空间普遍性和渔具之间强大的技术相互作用限制了避免丢弃物的可能性。