Potential effects of artificial light associated with anthropogenic infrastructure on the abundance and foraging behaviour of estuary‐associated fishes

Abstract

Summary1. Urbanization has been identified as a global threat to biodiversity. Human population growth in coastal areas, including estuaries, is expected to increase considerably in coming decades, which will result in a proliferation of infrastructure such as jetties, wharfs and marinas. This infrastructure is often associated with artificial night lighting, yet the implications of these unnatural lighting regimes for the fish fauna in coastal ecosystems are unknown. 2. We conducted novel, night-time surveys of the fish community directly adjacent to an artificial structure using an acoustic camera (DIDSON). By manipulating the artificial lighting conditions (lighting either 'on' or 'off'), we tested the effects of artificial light on fish abundance and behaviour. 3. Clear differences in the abundance of fish were observed between the two light treatments. The occurrence of large-bodied predators (>500 mm TL) increased when the artificial lights were on. The behaviour of these fish also differed as they attempted to maintain their position within the illuminated area adjacent to the associated anthropogenic structure. The abundance of small shoaling fish also increased when the lights were on. 4. It is possible that the conditions created by artificial lighting benefit piscivores through the concentration of prey and enhanced foraging capabilities in the case of visual predators. This has the potential to create unnatural top-down regulation of fish populations within urban estuarine and coastal waters. 5. Synthesis and applications. As a consequence of a positive phototaxic response, the findings of this study suggest that artificial light often associated with man-made structures has the potential to alter fish communities within urban estuarine ecosystems by creating optimal conditions for predators. Future coastal developments should consider the ecological implications of lighting on aquatic communities. We recommend that lighting be minimized around coastal infrastructure and the use of red lights, which have limited penetration though water, be considered.

Artificial Light at Night Affects Organism Flux across Ecosystem Boundaries and Drives Community Structure in the Recipient Ecosystem

“…Our results suggest that the Treatment site produced more aquatic insect biomass or that the rate of larval survival was higher. Increased illumination is generally associated with increased predation risk (Cerri and Fraser, 1983), as diurnally active piscivorous fish can extend their hunting activity at night, increasing predation pressure on smaller, invertivorous fish (Becker et al, 2013). Lee et al (2013) attributed reduced emergence in Cloeon dipterum (the most abundant species in our emergence traps) to increased fish predation in a wetland.…”

The biological impacts of artificial light at night: the research challenge

“…[50,79,80]), the manner in which such influences ramify through communities remains poorly understood [11]. Bennie et al [68] report experimental evidence of bottom-up, but not top-down, effects in simple plant-herbivore-predator communities.…”

European Wilderness in a Time of Farmland Abandonment

“…But artificial light has also strong ecological impacts (Longcore and Rich 2004;Navara and Nelson 2007;Hölker et al 2010b;Gaston et al 2013), affecting invertebrates (Davies et al 2012, see Chap. 6), fish (Becker et al 2013), mammals (Boldogh et al 2007) and bird populations (Montevecchi et al 2006). Direct mortality (Hölk-er et al 2010b), impacts on trophic relations and community structure (Perkin et al 2011), disruption of migratory routes (Gauthreaux Jr et al 2006) by night light lead to profound modifications of ecosystems functions (Hölker et al 2010a).…”