Development of successful fish passage structures for downstream migrants requires knowledge of their behavioural response to accelerating flow

Abstract

Fish have evolved intrinsic flight responses, allowing pre-emptive avoidance of potentially threatening situations. To direct downstream migrant fish away from deleterious conditions at dams and other barriers, mechanical devices such as travelling screens and fish bypass systems are often installed. However, field observations suggest that if these structures create areas of rapidly accelerating flow, they do not effectively guide the fish. We studied the avoidance behaviour of actively migrating fall Chinook salmon ( Oncorhynchus tshawytscha ) smolts in controlled experiments of low-, medium-, and high-flow accelerations. We measured the response velocity (VR) and the velocity gradient (VG) over body length. Although VR varied significantly with flow conditions and increased with increasing water temperature, the median VG at the instant at which smolts displayed an avoidance response was similar over the range of accelerating flows tested. Results from this study present the first quantitative information about the avoidance behaviour of fish to flow acceleration and should provide data needed to help engineers and biologists develop effective systems to alleviate anthropogenically altered flow regimes. Furthermore, the devised experimental setup provides a valuable means to test the effects of accelerating flow on any downstream migrant fish species.

Linking individual behaviour and migration success inSalmo salarsmolts approaching a water withdrawal site: implications for management

“…Thus, it is possible that passage time can be reduced by management measures that induce these behaviours. Recent studies have demonstrated behavioural avoidance in smolts related to hydraulic conditions (Haro et al 1998;Enders et al 2009), in-stream structures (Kemp and Williams 2008), overhead cover and absence of visual clues (Kemp et al 2005;Kemp and Williams 2009). Moreover, fish guidance may be accomplished using strobe lights (Johnson et al 2005), bubble curtains and sounds (Welton et al 2002;Sonny et al 2006) and deep, mid-channel furrows (Svendsen et al 2007).…”

“…Smith 1982). More recent studies have however, demonstrated smolts responding behaviourally to in-stream structures (Kemp and Williams 2008) and visual clues (Kemp and Williams 2009), avoiding rapidly accelerating currents (Haro et al 1998;Enders et al 2009) and overhead cover (Kemp et al 2005), and preferring certain areas while migrating downstream (Davidsen et al 2005;Svendsen et al 2007). The present study corroborates the conclusion that smolt migration includes active components and depends on behavioural decisions.…”

Fish navigation of large dams emerges from their modulation of flow field experience

“…Our approach is based on the simple notion that animals sensitive to gravity are generally also sensitive to other acceleratory and inertial stimuli (22). Decades of work have identified fish sensitivity to relative water velocity and acceleration fields over short ranges, as well as inertial stimuli (17,(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36). To explore how water acceleration may shape fish movement and identify why fish avoid some flow field regions, we need descriptions of water velocity and acceleration throughout the environment.…”

Impact of Tide Gates on the Migration of Adult European Eels, Anguilla anguilla

“…The role of behavioural avoidance is likely to be important in understanding the causes of delay at tide gates. While tide gates physically block migrating fish when closed, the narrow apertures through which water is discharged when open, and culvert entrances, may create a hydrodynamic barrier in the form of a rapid acceleration of flow which acts as a repellent (Pacific salmonid smolts: Enders et al 2009;Kemp et al 2005b, silver European eels: Piper et al in prep.). Indeed, eels have been observed to exhibit non-passive exploratory behaviour at other riverine structures (silver American eels, Anguilla rostrata: Brown et al 2009;Castro-Santos 2000, silver European eels: Behrmann-Godel andEckmann 2003;Travade et al 2010) during which they may reject an area approached, to either approach again, or find an alternative route (e.g.…”