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While fixed visual cues provide reliable reference points for navigation in static water, it remains unclear whether fish energetically benefit from their presence in flowing water. Furthermore, benefits of visual feedback from fixed sources may be less for group members that can gain additional information from others. Using an open-channel flume, this study investigated how the response of fish to stationary visual stimuli is influenced by flow and group membership under two treatments: vertical black and white stripes placed on (1) both side walls of the channel or (2) one side wall only compared to a control where both walls were uniform white. The responses were compared in flowing and static water, and between individuals and groups of five. Fish exhibited a positive affiliation for the visual cues, travelling more slowly and spending more time closer to the striped walls. Fish were more edge oriented under flowing conditions, presumably utilizing the lower velocities at the wall boundary to reduce energy expenditure. When only one wall presented visual cues, individual fish spent more time associated with it in flowing water, suggesting some energetic benefit in lotic conditions. This may result from a greater ability to maintain station or control position relative to a reference point and/or the use of visual stimuli as a proxy indicator of physical structure which may provide drag-reducing refuge. A lesser association with the striped wall in static water suggests that visual cues provide other nonhydrodynamic benefits, such as physical refuge from predators or opportunities for crypsis. Conversely, less association of shoals with the striped walls may reflect a greater dependence on information provided by conspecifics or increased security associated with being part of a group. This study indicates that fixed visual cues likely provide several benefits that vary depending on flow and group membership. • Minnows associated strongly with static visual cues (vertical stripes). • Association increased in flowing water and decreased when in a group. • Visual cues likely provide a reference point from which to control position. • Strong individual association may reflect a sheltering or refuge seeking response. • Reduced use of visual cues by groups may reflect security or information transfer. [ABSTRACT FROM AUTHOR]

To mitigate negative impacts of delayed migration it is necessary to understand the causes of avoidance exhibited by animals at behavioural barriers. For downstream migrating juvenile salmon, avoidance of velocity gradients at anthropogenic structures may compromise fitness. Building on previous experimental investigations on salmonid response to velocity gradients, this study aimed to quantify impacts of behaviour on subsequent passage in the presence and absence of visual cues. In an experimental flume, downstream moving juvenile Chinook salmon, Oncorhynchus tshawytscha, encountered either a high or a low velocity gradient created by an orifice weir, under light (95lx) or dark (infrared illumination only) conditions. The majority of fish exhibited an observable response on encountering accelerating velocity, with avoidance behaviour elevated when light (45%) in comparison to when dark (12%). More time was spent facing the flow when the velocity gradient was high. Fish that exhibited avoidance were delayed by approximately eight-fold, travelled 3.5 times further, and experienced a higher mean cumulative velocity gradient across the body length (spatial velocity gradient) prior to successful downstream passage. This study highlights the impact of variation in behaviour on fish passage, and the potential for combined multimodal signals (in this instance visual and mechanosensory) to be used to repel fish, for example from hazardous areas such as turbine intakes. Conversely, by limiting information available, undesirable delay, for example at entrances to downstream fish bypasses, may be reduced. [Copyright &y& Elsevier]