Effects of brown and turbid water on piscivore–prey fish interactions along a visibility gradient

Abstract

Summary 1. Environmental changes such as eutrophication and increasing inputs of humic matter (brownification) may have strong effects on predator–prey interactions in lakes through a reduction in the visual conditions affecting foraging behaviour of visually oriented predators. 2. In this experiment, we studied the effects of visual range (25–200 cm) in combination with optically deteriorating treatments (algae, clay or brown humic water) on predator–prey interactions between pike (Esox lucius) and roach (Rutilus rutilus). We measured effects on reaction distance and strike distance for pike and escape distance for roach, when pike individuals were exposed to free‐swimming roach as well as to roach held in a glass cylinder. 3. We found that reaction distance decreased with decreasing visual range caused by increasing levels of algae, clay or humic matter. The effect of reaction distance was stronger in turbid water (clay, algae) than in the brown water treatment. 4. Strike distance was neither affected by visual range nor by optical treatment, but we found shorter strike distances when pike attacked roach using visual cues only (roach held in a cylinder) compared to when pike could use multiple senses (free‐swimming roach). Escape distance for roach was longer in turbid than in brown water treatments. 5. Changes in environmental drivers, such as eutrophication and brownification, affecting the optical climate should thus have consequences for the strength of predator–prey interactions through changes in piscivore foraging efficiency and prey escape behaviour. This in turn may affect lake ecosystems through higher‐order interactions.

Growth of rainbow trout (Oncorhynchus mykiss) in warm-temperate lakes: implications for environmental change

“…However, excessive primary productivity can become detrimental to certain fish species. Foraging of visual predators may be impaired by high turbidity in eutrophic lakes (Beauchamp et al 1999;Ranåker et al 2012), and the volume of cool habitat in the hypolimnion may be reduced by low dissolved oxygen (DO) concentrations (Plumb and Blanchfield 2009). In warm, productive lakes, growth rate potential of coolwater species decreases with increasing chlorophyll a (chl a) concentrations (Budy et al 2011).…”

Water Browning Influences the Behavioral Effects of Ultraviolet Radiation on Zooplankton

“…The light regime also influences predator escape efficiency, mostly through visual predator avoidance (Brewer et al, 1999). In this case, water browning should decrease the chances of spotting a predator-or, vice versa, prey (Ranåker et al, 2012;Lindholm et al, 2016). In our experiments, D. magna individuals generally increased exploration activity with increasing DOM levels, suggesting that encounter rates with predators could increase.…”

The effect of turbidity and prey fish density on consumption rates of piscivorous Eurasian perch Perca fluviatilis

“…Perch consumption in turbid waters may also be linked to changes in individual prey behaviour. For instance, roach escape distance has shown to be severely reduced in turbid waters (Ranåker et al, 2012). Further, it is well acknowledged that anti-predator behaviours, such as schooling and refuging, weaken at low visibility (Abrahams and Kattenfeld, 1997), which might increase the number of individual encounters.…”

“…For instance, degraded visibility could increase prey chance of avoiding predation, while it may decrease predator foraging efficiency (De Robertis et al, 2003). The consequences of visibility conditions for predator-prey interactions depend on effects on detection, attack and escape abilities (Ranåker et al, 2012).…”

“…Antipredator behaviour in prey can be abandoned in low visibility conditions (Abrahams and Kattenfeld, 1997) with consequences for prey distribution and encounters. At the same time, reduced visibility decreases detection distance for both predators and prey, making predictions of predator-prey encounters in poor visibility complicated (Turesson and Brönmark, 2007;Wellington et al, 2010;Ranåker et al, 2012).…”