1. Studies suggest the migratory behaviours of potamodromous fishes can be highly variable in barrier-free systems, where differing movement types enable populations to exploit a wide range of food and space resources. This intra-population diversity in spatial and temporal resource use is important to our ecological understanding of fish distribution patterns and population structure. Despite this, freshwater ecosystems are increasingly characterised by high levels of fragmentation and degradation that restrict mobile fauna, and limit opportunities to study natural, unconstrained movement behaviour.
2. Common bream Abramis brama (bream) is a potentially strong model species for testing the importance of diverse migration patterns in lowland rivers, but existing studies have been largely restricted to spatially confined and/or anthropogenically modified systems. This study's principal focus was to examine the diversity of bream movement behaviour in a highly connected, lowland system using passive acoustic telemetry, which provided continuous, multi-year data on the movements of 181 bream across a tidally influenced, lowland wetland in eastern England (c. 60 km of continuous river length plus numerous interconnected shallow lakes and dykes). Tracked bream were grouped according to their initial location and timing of tagging.
3. Bream migratory behaviours varied considerably between tagging groups, but with greater consistency within groups. There was little mixing of groups outside of spawning periods, with season and tidal phase being significant predictors of movement. Rates of movement and swimming speeds were highest in spring, with movements also generally occurring in the direction of tidal flows.
4. For fish sampled just prior to spawning, there was considerable diversity in their post-spawning behaviour, with some remaining in the immediate vicinity of the sampling location and others that moved to areas c. 25 km away. These spatially discrete patterns remained until the following spawning period.
5. These results suggest that this lowland fish population is comprised of several distinct, semi-independent subpopulations that only share space resources in their spawning period. This indicates the importance of connectivity in lowland freshwater systems for enabling and maintaining high phenotypic diversity in the movement behaviours of potamodromous fishes.

中文翻译：

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鳊在高度连通的低地湿地中的运动揭示了具有不同迁徙策略的亚种群

1. 研究表明，在无障碍系统中，马鲛鱼的洄游行为变化很大，不同的运动类型使种群能够利用广泛的食物和空间资源。这种时空资源利用的种群内多样性对于我们对鱼类分布模式和种群结构的生态理解很重要。尽管如此，淡水生态系统的特点是高度破碎化和退化，限制了移动动物群，并限制了研究自然、不受约束的移动行为的机会。
2. 普通鳊Abramis brama ( bream ) 是一种潜在的强大模型物种，用于测试低地河流中不同迁徙模式的重要性，但现有研究主要限于空间受限和/或人为改造的系统。本研究的主要重点是使用被动声学遥测技术检查高度连接的低地系统中鲷鱼运动行为的多样性，该系统提供了关于 181 条鲷鱼在英格兰东部受潮汐影响的低地湿地运动的连续多年数据。c . 60 公里的连续河流加上众多相互连接的浅湖和堤坝）。被追踪的鲷鱼根据它们的初始位置和标记时间进行分组。
3. 鳊迁移行为在标记组之间差异很大，但在组内具有更大的一致性。在产卵期之外几乎没有群体混合，季节和潮汐阶段是运动的重要预测因素。春季的运动速度和游泳速度最高，运动也通常发生在潮汐流方向。
4. 对于在产卵前采样的鱼，它们产卵后的行为存在相当大的差异，一些留在采样位置附近，而另一些则移动到区域c。25 公里。这些空间离散的模式一直持续到下一个产卵期。
5. 这些结果表明，这种低地鱼类种群由几个不同的、半独立的亚种群组成，它们仅在产卵期共享空间资源。这表明低地淡水系统中的连通性对于实现和维持河豚运动行为的高表型多样性的重要性。