Differential effects of turbidity on prey consumption of piscivorous and planktivorous fish

Abstract

Contrast degradation theory predicts that increased turbidity decreases the visibility of objects that are visible at longer distances more than that of objects that are visible at short distances. Consequently, turbidity should disproportionately decrease feeding rates by piscivorous fish, which feed on larger and more visible prey than particle-feeding planktivorous fish. We tested this prediction in a series of laboratory feeding experiments, the results of which indicated that prey consumption by two species of planktivorous fish (juvenile chum salmon (Oncorhynchus keta) and walleye pollock (Theragra chalcogramma)) is much less sensitive to elevated turbidity than piscivorous feeding by sablefish (Anoplopoma fimbria). Planktivorous feeding in the turbidity range tested (0–40 nephelometric turbidity units (NTU)) was reduced at high light intensity, but not at low light intensity. Comparatively low (5–10 NTU) turbidity decreased both the rate at which sablefish pursued prey and the probability of successful prey capture. These results suggest that turbid environments may be advantageous for planktivorous fish because they will be less vulnerable to predation by piscivores, but will not experience a substantial decrease in their ability to capture zooplankton prey.

Developmental plasticity in vision and behavior may help guppies overcome increased turbidity

“…Since decreasing baseline activity is often a response to stressors (Walls et al 1990;Schreck et al 1997), it is possible that novel assay conditions were stressful for fish. In turbid water, encounter rate with an organism's environment (e.g., habitat, conspecifics, prey) is likely decreased, since the visual range of fish in these environments is diminished (Vinyard and O'brien 1976;De Robertis et al 2003). By increasing activity in turbid water (as observed in turbid water developmental treatment fish), a fish could maintain a certain encounter rate with salient factors in its environment (Gerritsen and Strickler 1977), as has been observed in chinook salmon (Oncorhynchus tshawytscha; Gregory and Northcote 1993), perch (Perca fluviatilis; Granqvist and Mattila 2004), and Atlantic cod (Gadus morhua; Meager and Batty 2007).…”

Context‐dependent planktivory: interacting effects of turbidity and predation risk on adaptive foraging

“…2 by multiplying zs in the numerator and zhs in the denominator by (e ÀbT ) 2 , where b represents the exponential rate of decay of our intermediate consumer's R with increasing T. Importantly, the exponents a and b represent the same phenomenon, differing only in that they characterize T's effect on the visual detection of the prey by our top predator and intermediate consumer, respectively. Because increased turbidity has a greater negative effect on the visual capabilities of piscivores than planktivores (De Robertis et al 2003), we assume a . b in our model.…”

“…We suspect, however, that turbidity and predation risk interact to modify the behavior of intermediate consumers. This expectation is driven by our synthesis of many unrelated studies, which in general show that (1) turbidity reduces foraging efficiency of visual consumers in the absence of predation risk (Gardner 1981, De Robertis et al 2003, Wellington et al 2010) and (2) visual consumers at intermediate trophic levels that are exposed to predation risk exhibit fewer anti-predator behaviors (Gregory 1993, Miner and Stein 1996, Abrahams and Kattenfeld 1997, as well as more aggressive foraging behavior (Lehtiniemi et al 2005), in turbid versus clearer water. Based on these observations, we hypothesized that, in the presence of a predator, turbidity would lessen the risk of predation perceived by an intermediate consumer, and in turn, lead to increased consumption of the basal prey resource.…”

‘Selfish herds’ of guppies follow complex movement rules, but not when information is limited

“…As errors may be exacerbated by environmental conditions [19], we explore the impact of increasing environmental turbidity on the selfish herd responses of our guppy shoals. In aquatic systems, increasing turbidity degrades the visual environment, shortening response distances to conspecifics [24,25], predators [26,27] and prey [28][29][30] in many species including guppies [24,25]. We predict that increasing turbidity will result in either (i) a switch from more complex to simpler rules as fewer shoalmates can be detected or (ii) increased error in evaluation of the position of shoalmates, leading to increased error in following any rule.…”