Using knowledge of behaviour and optic physiology to improve fish passage through culverts

Abstract

Culverts reduce connectivity for aquatic animals by being both a hydraulic and physical barrier. However, altered light intensity may also be a behavioural barrier to fish movement, especially for diurnal species that have adapted to moving when it is light. We propose that knowledge of optical physiology and fish behaviour, two important mechanisms underpinning movement, can inform efforts to improve fish movement through culverts. We firstly review the sensory systems of fish with reference to visual sense and explore how this affects fish movement. We then highlight theoretical knowledge that can help us understand fish behaviour and the potential mismatch between the conditions under which fish have evolved and altered conditions within culverts. We describe potential knowledge gaps and directions for future research to improve our understanding of how culverts may affect fish movement. Finally, we explore the potential costs and ecological benefits of different mitigation options to identify those with the most promise for managing the light environment in culverts to facilitate movement. For researchers and managers exploring this subject, we suggest an approach that: (a) identifies light requirements for movement by different species, (b) tests movement under different light conditions and (c) considers an integrative assessment method for testing fish behaviour around culverts. Understanding how optical physiology, fish behaviour and culvert design influence fish movement can improve connectivity for a range of species.

Low light intensities increase avoidance behaviour of diurnal fish species: implications for use of road culverts by fish

“…Road-crossing pipe and box culverts located in the Brisbane region had maximum light intensities that were less than the minimum movement thresholds for fly-specked hardyhead and Australian smelt (<3 lx), therefore potentially posing a behavioural barrier to these species. Although the authors only measured light intensities on just 1 day at each culvert, they measured at the brightest time of day (Magurran, 1990;Morgan & Godin, 1985), schooling effects with conspecifics (Krause et al, 2000), an individual's personality (Hirsch et al, 2017), life-history stage, eye morphology or sensory plasticity (Jones & Hale, 2020). Movement motivation is also probably an important factor underpinning a fish's willingness to enter a darkened environment, and diadromous species may be more likely to pass through a darkened culvert because of an obligatory requirement compared with facultative migrators (Jones & Hale, 2020).…”

“…An emerging concern for fish passage is the potential for altered light intensities (i.e., low light during the day or artificial light at night) in and around anthropogenic structures to negatively influence fish movement and behaviour (Jones et al, 2017;Jones & Hale, 2020;Perkin et al, 2011). For most fish, vision is an important aspect of their sensory repertoire; visual systems are essential for orientation, breeding, foraging and predator avoidance.…”

“…Several studies have shown that artificial lighting at night (i.e., from street lights, transport networks and industry) can influence reproduction, community structure and movement in nocturnal fish (Becker et al, 2013;Riley et al, 2012;Ryer et al, 2009). Likewise, structures that limit natural light penetration can also alter the behaviour of diurnally active fish (Jones et al, 2017;Jones & Hale, 2020).…”

“…morning) and year (Austral summer), so if prohibitively low light intensities were detected under these conditions, they are likely to be light barriers at other times of year. The amount of ambient light present within the structure is dependent on a culvert's cross-sectional area, height and orientation relative to a light source(Franklin et al, 2018;Jones & Hale, 2020;Kozarek et al, 2017). Environmental factors such as season, water depth, clarity and surrounding riparian vegetation density will also affect the amount of light within a culvert, which means that the level of ambient light in a structure may vary considerably over daily and seasonal scales.…”

Physical modelling of pipe culverts to assist upstream fish passage

“…In terms of fish passage for a given targeted species, some parameters relevant to traversability include the culvert type, the barrel dimensions, cross‐sectional shape and invert slope, as well as the water discharge and fluid dynamics properties in the culvert structure (Larinier, 2002; Olsen & Tullis, 2013). For small‐bodied and juvenile fish species, the excessive barrel velocities are often a major hinderance, because small‐body‐mass fish tend to have weak swimming capabilities (Hurst, Kay, Ryan, & Brown, 2007; Pavlov, Lupandin, & Skorobogatov, 1994; Tudorache, Viaene, Blust, Vereecken, & De Boeck, 2008), notwithstanding that swimming performance data can exhibit substantial variability in natural populations (Jones & Hale, 2020). In laboratory, the testing protocol and equipment may impact the data outcomes (Katopodis & Gervais, 2016; Kern, Cramp, Gordos, Watson, & Franklin, 2018), leading to “ inconsistent metrics ” (Kemp, 2012).…”