Upstream passage of Galaxias maculatus and Galaxias brevipinnis: comparative behavioural assessment for improved fish pass design

Abstract
1. Customized fish passage solutions enhance the upstream passage of fish through low-head instream structures. These solutions are designed based on the behaviour of benchmark species, with the hope that they will also perform well for other species. Across species, suitability can be supported by establishing similarity in passage behaviour. However, for small-bodied fish species, such comparative behavioural assessments are largely missing. 
2. With respect to spoiler baffle-based passage design for Southern Hemisphere small-bodied fish species, Galaxias maculatus are typically considered as a benchmark species. In order to characterise the upstream passage of G. maculatus with a view to extending it to other species, here the behaviour of G. maculatus and Galaxias brevipinnis were recorded for three different spoiler baffle designs. Hydrodynamic preferences during upstream swimming and resting, including pathway assessment, were analysed.
3. Both species show increased preference to swim at locations with streamwise velocities similar to the known sustained swimming capacity threshold of G. maculatus, whilst resting locations align with minimal streamwise velocities. Preferred pathways were observed to be influenced by the streamwise water velocity and turbulent kinetic energy, with both species showing increased preference to move towards locations with similar streamwise velocities, by avoiding locations with higher turbulent kinetic energy. 
4. The study further shows that both species' passage behaviour is more dependent on space availability than individual behaviour alone. The spatial distribution of fine-scale hydrodynamics influences observed swimming and resting behaviour, with both species showing similar passage behaviour for all three tested designs. 
5. Synthesis and applications: Similarities, for both passage behaviour and pathway selection, suggest that spoiler baffle-based passage designs are a suitable management option for both species. Both species were observed to use different fine-scale hydrodynamic regions for resting and subsequent swimming. Among the patches, patch P2 provided increased resting and low-velocity swimming cells for both species, which are shown to be important ecological indicators of successful passage applications, supporting further evaluation for possible application of culvert retrofitting, allowing for varying flow rates, slopes and fish species.

摘要
1. 定制的鱼类通道解决方案能够有效提升鱼类通过低水头河道结构的上游通行能力。这些解决方案基于基准物种的行为模式进行设计，以期对其他物种亦能发挥良好作用。在物种间，可通过建立通行行为的相似性来支持其适宜性。然而，对于体型较小的鱼类物种，此类比较行为评估大多尚属缺失。
2. 针对南半球体型较小的鱼类物种的泄流板干扰器通道设计，通常将 Galaxias maculatus 视为基准物种。为了描述 G. maculatus 的上游通行行为并扩展至其他物种，本研究记录了 G. maculatus 和 Galaxias brevipinnis 在三种不同的泄流板干扰器设计下的行为。对上游游动和休息期间的水动力学偏好，包括路径评估，进行了分析。
3. 两种物种均表现出对游动于与 G. maculatus 已知持续游动能力阈值相似流速位置的偏好，而休息位置则与最小流速相一致。观察到，偏好路径受水流方向流速和湍流动能的影响，两种物种均倾向于向流速相似的位置移动，通过避免湍流动能较高的位置来实现。
4. 研究进一步表明，两种物种的通行行为更多地依赖于空间可用性，而非单一的行为特征。细尺度水动力学的空间分布影响了观察到的游动和休息行为，两种物种在所有三种测试设计中均表现出相似的通行行为。
5. 综合与应用：在通行行为和路径选择方面的相似性表明，基于泄流板的通道设计是两种物种适宜的管理选项。观察到，两种物种均利用不同的细尺度水动力学区域进行休息和随后的游动。在区域中，区域 P2 为两种物种提供了更多的休息和低速游动细胞，这些细胞被证明是成功通行应用的重要生态指标，支持进一步评估可能的应用于涵管改造，允许变化的水流速度、坡度和鱼类物种。