Turbidity amplifies the non‐lethal effects of predation and affects the foraging success of characid fish shoals

Abstract

Summary In aquatic systems, many species rely primarily on visual cues to choose optimal foraging sites, capture prey and avoid potential threats. Increases in the turbidity of water reduce visibility and impede animals in determining the precise location of both predators and food. How individuals balance foraging decisions with anti‐predator behaviour in turbid environments is not well understood. We tested the effects of turbidity and predation risk on the foraging behaviour and feeding of an invertivorous fish, Moenkhausia forestii (Characidae), using a mesocosm experiment with a 2 × 2 design, crossing water clarity (clear versus turbid) with predation risk as reflected by the presence or absence of the piscivorous wolf‐fish Hoplias aff. malabaricus (Erythrinidae). We predicted that turbidity and predator presence would interact additively to reduce foraging rates, and that increased turbidity or predator presence would result in disproportionate food partitioning among shoal members. The combination of high turbidity and predator presence resulted in a significant reduction in prey consumption. Foraging success exhibited a skewed distribution in the turbid treatment, i.e. there was a decreased evenness of food partitioning within shoals. Hence, both turbidity and predator presence affect the prey consumption and foraging behaviour of invertivorous fish, with turbidity amplifying the non‐lethal effects of predation risk on foraging success. Our results imply that turbidity‐induced visual obstruction amplifies the negative effects of predator presence on invertivorous fish feeding behaviour, resulting in higher prey survival. Also, our finding that food intake by an intermediate consumer decreased in turbid water with a top predator lends no support to the hypothesis that intermediate consumer fish reduce their anti‐predator behaviour in turbid water. From a management perspective, our findings suggest that the oligotrophication of aquatic systems could dramatically increase predation on basal prey organisms naturally adapted to turbid waters, and reduce within‐shoal differences in feeding behaviour.

Effects of Turbidity on Prey Selection and Foraging Rate of Hatchery‐Reared Juvenile Tiger Muskellunge

“…; Lunt and Smee ; Figueiredo et al. ). Turbidity is typically produced by small particles of silt, clay, fine sand, or detritus that are suspended by wind action, rain events, or fish disturbing the substrate (Carter et al.…”

“…Outcomes of predator-prey interactions are largely influenced by the ability of predators and prey to detect and respond to one another (Powers and Kittinger 2002;Chivers et al 2013). Water clarity, particularly turbidity, affects interactions between predator and prey in aquatic environments and also influences interactions between and within species, thereby shaping fish communities (Carter et al 2010;Lunt and Smee 2015;Figueiredo et al 2016). Turbidity is typically produced by small particles of silt, clay, fine sand, or detritus that are suspended by wind action, rain events, or fish disturbing the substrate (Carter et al 2010;Jonsson et al 2013;Li et al 2013) or by phytoplankton (Carlson 1977).…”

The effect of mussel farming on sediment dynamics in the Wadden Sea : case studies evaluating the local effects of mussel seed fisheries and mussel harvest on turbidity and sedimentation

“…The consequences are first seen in the reduction of primary producers (plants and algae) due to lack of light availability and photosynthesis (Henley et al 2000), followed by degradation of eel grass populations (Duarte 2002, Castorani et al 2015, the unsuccessful adaptation of benthic life to resuspension or sedimentation (Castorani et al 2015), the decrease of foraging success of piscivorous fish that rely on visibility to locate the prey (Figueiredo et al 2016), clogging/damaging of feeding and breathing equipment of filter feeders, loss of important nursery habitats and reductions in prey abundances (Lowe et al 2009). The increase in turbidity affects filter feeders because the elevated levels of suspended particulate matter (SPM, primary factor controlling turbidity in the water column) tend to clog feeding structures and reduce feeding efficiency, leading to reduction of growth rates, stress and death of these organisms (Newcombe & Macdonald, 2011).…”

Short-Term Interactive Effects of Experimental Heat Waves and Turbidity Pulses on the Foraging Success of a Subtropical Invertivorous Fish

“…Extreme rainfall events usually increase surface runoff from the catchment to water bodies, promoting terrestrial soil washout and increased turbidity in surface freshwater ecosystems [18]. Many floodplains, lakes and rivers, particularly in tropical and subtropical regions, experience sudden increases in inorganic turbidity following a pulse event in a tributary [19,20], which may have substantial effects on different aspects of predator-prey interactions [21]. As turbidity reduces the visual field of visually-oriented organisms [22], changes in turbidity may affect encounter, attack and predation rates [23,24].…”