Visual performance impaired by elevated sedimentary and algal turbidity in walleye Sander vitreus and emerald shiner Notropis atherinoides

Abstract

The objectives of this study were to determine the effects of different forms of elevated turbidity on the visual acuity of two native Lake Erie fishes and to assess the response of fishes from different trophic levels to elevated turbidity. Additionally, the role of visual morphology (e.g., eye and optic lobe size) on visual acuity was evaluated across visual environments. Reaction distance, a behavioural proxy for measures of visual acuity, was measured for a top predator, walleye Sander vitreus and a forage fish, emerald shiner Notropis atherinoides. In both S. vitreus (n = 27) and N. atherinoides (n = 40) reaction distance across all types of turbidity (sedimentary, algal, sedimentary + algal; 20 NTU) was approximately 50% lower relative to the clear treatment. Reaction distance was further reduced in algal compared with sedimentary turbidity for wild‐caught S. vitreus. Eye and brain morphology also influenced reaction distance across turbidity treatments, such that larger relative eye and brain metrics were positively correlated with reaction distance. This study provides evidence for disrupted visual acuity as a potential mechanism underlying fish responses, such as decreased foraging efficiency, to increased turbidity and further indicates that algal turbidity will probably be more detrimental to visual processes than sedimentary turbidity. With the increasing occurrence and severity of harmful algal blooms due to cultural eutrophication globally, this could have significant implications for predator–prey relationships in aquatic systems.

Elevated algal and sedimentary turbidity alter prey consumption by emerald shiner (Notropis atherinoides)

“…Across turbidity type, we found that higher levels of turbidity (40 NTU) resulted in decreased consumption of prey items, likely indicating that at this level of turbidity, visual perception is compromised such that prey are more difficult to detect. Previous work indicates disruptions to visual acuity at high levels of both sedimentary and algal turbidity in emerald shiner (Nieman & Gray, ).…”

“…Visual morphological structures (i.e. the left eye and the brain) were removed and measured following Nieman and Gray (). Briefly, the left eye of each fish and brain were placed under a stereo microscope and photographed.…”

“…turbidity levels elevated above natural levels due to human activities in or around water; e.g. Becker, Brooks, & Gabor, ; Bonner & Wilde, ; Nieman & Gray, ; Salonen, Urho, & Engström‐Öst, ) can disrupt fish vision and thus negatively influence visual foraging (e.g. De Robertis, Ryer, Veloza, & Brodeur, ; Nieman, Oppliger, McElwain, & Gray, ).…”

“…Turesson & Brönmark, ). For example, emerald shiner ( Notropis atherinoides Rafinesque 1818) exhibit decreased reaction distance (a behavioural measure of visual acuity; Vogel & Beauchamp, ) by approximately 50% in both sedimentary and algal turbidity (Nieman & Gray, ). Bonner and Wilde () found that emerald shiner in stream habitats exhibit a 73% decrease in prey consumption in waters with elevated sedimentary turbidity compared with individuals found in clearer waters.…”

“…Juvenile yellow perch, for example, display reduced consumption of zooplankton in algal compared to sedimentary turbidity (Wellington, Mayer, Bossenbroek, & Stroh, ). In another example, algal turbidity was found to disrupt visual processes at lower levels than sedimentary turbidity in both walleye and their favoured prey, emerald shiner (Nieman & Gray, ; Nieman et al, ). Further, elevated algal turbidity can result in both decreased prey consumption and selectivity of prey in many species, for example the three‐spine stickleback (Sohel, Matilla, & Lindström, ).…”