title: Heterogeneity in prey distribution allows for higher food intake in planktivorous fish, particularly when hot.
abstract: When prey are scarce, planktivorous fish and other predators feeding on tiny prey should forage within prey-rich patches to attain a net food intake above the ambient mean food concentrations. If they can indeed locate prey-rich patches efficiently, then a patchy distribution of planktonic prey should lead to: (1) an increase in the overall per capita food intake, and (2) greater variability among predators in prey-capture rate due to differences in arrival times. Both phenomena were observed in 34 daily feeding sessions with a cohort of juvenile rudd held in twin experimental systems, each housing the same number of fish free to move in a loop of ten interconnected 200-L tanks. The fish were fed daily with equal numbers of planktonic prey (Artemia nauplii), offered either in a homogeneous or patchy distribution. To simulate low and high temperatures that represent potential global warming scenarios, the feeding protocol was replicated at 16, 21 and 26 °C, on each occasion following a 3-day period of fish acclimation. Up to 40-70 % of fish in the system with the patchy prey distribution assembled rapidly in the high-prey-density tank, the capture rate of first arrivals being up to 60 prey min(-1) at 26 °C, orders of magnitude greater than that of latecomers. The overall capture rates were higher in the system with patchy prey, regardless of the temperature. At the highest temperature (26 °C), the fish located the high-prey-density tank in less than half the time taken at the lowest temperature (16 °C, Q(10) > 2).
authors.affiliation: Department of Hydrobiology, Biology & Chemistry Research Center, University of Warsaw, Al. Żwirki i Wigury 101, 02-089, Warsaw, Poland. z.m.gliwicz@uw.edu.pl.
authors.forename: Z Maciej
authors.initials: ZM
authors.lastname: Gliwicz
authors.affiliation: Department of Hydrobiology, Biology & Chemistry Research Center, University of Warsaw, Al. Żwirki i Wigury 101, 02-089, Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Maszczyk
mesh_terms: D063147:Animal Distribution; D000818:Animals; D001156:Artemia / Q000502:physiology; D003080:Cold Temperature; D004435:Eating / Q000502:physiology*; D005399:Fishes / Q000502:physiology*; D057232:Global Warming; D006358:Hot Temperature; D010933:Plankton / Q000502:physiology; D011235:Predatory Behavior
keywords: Capture rate; Global warming; Learning; Patch exploitation; Top–down cascade