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

Abstract

Inadequately designed culverts can be physical barriers to fish passage if they increase the velocity of water flow in the environment, alter natural turbulence patterns or fail to provide adequate water depth. They may also act as behavioural barriers to fish passage if they affect the willingness of fish species to enter or pass through the structure due to altered ambient light conditions. To understand how reduced light intensity might affect fish behaviour in culverts, the authors performed a behavioural choice experiment quantifying the amount of time individual fish spent in dark and illuminated areas of a controlled experimental channel. They found that behavioural responses were largely reflective of the species' diel activity patterns; the diurnal species Craterocephalus stercusmuscarum and Retropinna semoni preferred illuminated regions, whereas the nocturnal/crepuscular Macquaria novemaculeata preferred the darkened region of the channel. Bidyanus bidyanus were strongly rheotactic, and their behaviour was influenced more by water flow direction than ambient light level. The authors then determined that a threshold light intensity of only c. 100-200 lx (cf. midday sunlight c. 100,000 lx) was required to overcome the behavioural barrier in c. 70% of the diurnally active C. stercusmuscarum and R. semoni tested. When these values were placed into an environmental context, 15 roadcrossing (3.4-7.0 m long) box (c. 1 m × 1 m, height × width) and pipe (c. 1 m diameter) culverts sampled in Brisbane, Australia, recorded light intensities in the centre of the structure that were below the threshold for C. stercusmuscarum and R. semoni movement and could potentially be a barrier to their passage through the structure. Attention is required to better understand the impacts of low light intensity in culverts on fish passage and to prioritize restoration.

Environmental enrichment in fish aquaculture: A review of fundamental and practical aspects

“…), but they both present an integrative view of what resources fish want and how much they want it. It is also important to consider that some EE features may be actively avoided and may represent a behavioural barrier preventing fish to access specific areas of the environment, 299 and thus should also be taken into account for welfare purposes. The implementation of EE based on preferences and avoidances of fish is challenging, because fish are known to have considerable individual variability of preference responses 298,300 .…”

Physical enrichment research for captive fish: Time to focus on the DETAILS

“…Light, the intensity, wavelength and amount (photoperiod), is an important factor that is often overlooked in studies of PE. Light levels can have a large impact on fish behaviour, playing a crucial role in their behavioural ecology (Cerri, 1983; Keep et al ., 2020; McCartt et al ., 1997; Santon et al ., 2020), and can drive the use of shelter and shade. Light levels can impact levels of aggression (Valdimarsson & Metcalfe, 2001), which in turn can have significant impacts on fish welfare (da Silva et al ., 2020).…”

Rapid Colonization of Upstream Habitats by Oncorhynchus Mykiss Following Culvert Modification

“…Improperly designed culverts can disrupt connectivity and serve as physical barriers to fish movement by creating insufficient water depth, causing excessive water velocities (at either the inlet or outlet), or forming drops or jumps too tall for passage (Kahler and Quinn 1998;Keep et al 2021). Because of their low cost relative to other stream-crossing structures such as bridges, culverts are globally widespread in lotic environments (Gibson et al 2005).…”