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Foraging efficiency and prey selectivity in a visual predator: differential effects of turbid and humic water

Jönsson, Mikael LU ; Ranåker, Lynn LU ; Nilsson, Anders LU and Brönmark, Christer LU (2013) In Canadian Journal of Fisheries and Aquatic Sciences 70(12). p.1685-1690
Abstract
Predators exert strong regulating forces on lower trophic levels through predation. As most fish are visual foragers, visual conditions in the water may alter the strength of this regulation. We evaluated effects of turbidity and humic water on foraging efficiency and prey-size selectivity in Northern pike (Esox lucius) feeding on roach (Rutilus rutilus). Encounter rates decreased in both turbid and humic water but were not counteracted by increased searching activity. Capture success was unaffected by turbidity but was nonlinearly affected by humic water by being high in clear and highly humic water but low in less humic water. In highly humic water, the visual range approached pike's strike distance and, together with its cryptic... (More)
Predators exert strong regulating forces on lower trophic levels through predation. As most fish are visual foragers, visual conditions in the water may alter the strength of this regulation. We evaluated effects of turbidity and humic water on foraging efficiency and prey-size selectivity in Northern pike (Esox lucius) feeding on roach (Rutilus rutilus). Encounter rates decreased in both turbid and humic water but were not counteracted by increased searching activity. Capture success was unaffected by turbidity but was nonlinearly affected by humic water by being high in clear and highly humic water but low in less humic water. In highly humic water, the visual range approached pike's strike distance and, together with its cryptic colours, pike may have initiated its attack before the prey detected it, limiting the possibility for prey evasive manoeuvres. Prey-size selectivity towards small prey in clear water disappeared in turbid water but was maintained in humic water. Owing to its optical properties, turbidity degrades the quality of the visual information more through scattering than humic water does through absorption. We show that the effect of visual degradation on foraging depends on the cause of visual degradation, which has not previously been acknowledged in the visual foraging literature. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Canadian Journal of Fisheries and Aquatic Sciences
volume
70
issue
12
pages
1685 - 1690
publisher
National Research Council Canada
external identifiers
  • wos:000328273100003
  • scopus:84888354391
ISSN
1205-7533
DOI
10.1139/cjfas-2013-0150
language
English
LU publication?
yes
id
8fb1274a-9dd4-46e9-9c0d-728f4254a355 (old id 4272774)
date added to LUP
2014-02-11 14:11:32
date last changed
2019-10-16 01:16:38
@article{8fb1274a-9dd4-46e9-9c0d-728f4254a355,
  abstract     = {Predators exert strong regulating forces on lower trophic levels through predation. As most fish are visual foragers, visual conditions in the water may alter the strength of this regulation. We evaluated effects of turbidity and humic water on foraging efficiency and prey-size selectivity in Northern pike (Esox lucius) feeding on roach (Rutilus rutilus). Encounter rates decreased in both turbid and humic water but were not counteracted by increased searching activity. Capture success was unaffected by turbidity but was nonlinearly affected by humic water by being high in clear and highly humic water but low in less humic water. In highly humic water, the visual range approached pike's strike distance and, together with its cryptic colours, pike may have initiated its attack before the prey detected it, limiting the possibility for prey evasive manoeuvres. Prey-size selectivity towards small prey in clear water disappeared in turbid water but was maintained in humic water. Owing to its optical properties, turbidity degrades the quality of the visual information more through scattering than humic water does through absorption. We show that the effect of visual degradation on foraging depends on the cause of visual degradation, which has not previously been acknowledged in the visual foraging literature.},
  author       = {Jönsson, Mikael and Ranåker, Lynn and Nilsson, Anders and Brönmark, Christer},
  issn         = {1205-7533},
  language     = {eng},
  number       = {12},
  pages        = {1685--1690},
  publisher    = {National Research Council Canada},
  series       = {Canadian Journal of Fisheries and Aquatic Sciences},
  title        = {Foraging efficiency and prey selectivity in a visual predator: differential effects of turbid and humic water},
  url          = {http://dx.doi.org/10.1139/cjfas-2013-0150},
  volume       = {70},
  year         = {2013},
}