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Oxygen Depletion Affects Kinematics and Shoaling Cohesion of Cyprinid Fish

1
Institute of Hydrobiology and Aquatic Ecosystem Management, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences, Vienna (BOKU), 1180 Vienna, Austria
2
Forest Research Centre (CEF), School of Agriculture, University of Lisbon, 1349-017 Lisbon, Portugal
*
Author to whom correspondence should be addressed.
Water 2019, 11(4), 642; https://doi.org/10.3390/w11040642
Received: 24 January 2019 / Revised: 18 February 2019 / Accepted: 25 March 2019 / Published: 27 March 2019
Numerous anthropogenic stressors impact rivers worldwide. Hypoxia, resulting from organic waste releases and eutrophication, occurs very commonly in Mediterranean rivers. Nonetheless, little is known about the effects of deoxygenation on the behavior of Mediterranean freshwater fish. To fill this knowledge gap, we assessed the impact of three different dissolved oxygen levels (normoxia, 48.4%, 16.5% saturation) on kinematics indicators (swimming velocity, acceleration, distance traveled) and shoaling cohesion of adult Iberian barbel, Luciobarbus bocagei, a widespread cyprinid species inhabiting a broad range of lotic and lentic habitats. We conducted flume experiments and video-tracked individual swimming movements of shoals of five fish. Our results reveal significant differences between the treatments regarding kinematics. Swimming velocity, acceleration, and total distance traveled decreased stepwise from the control to each of the two oxygen depletion treatments, whereby the difference between the control and both depletion levels was significant, respectively, but not between the depletion levels themselves. Shoaling cohesion showed dissimilarities between the treatments regarding the maximum distance between fish, as the high depletion treatment differed from each of the other two, indicating that under severe oxygen depletion some individuals move away from the shoal. Overall, our results show how oxygen depletion changes fish behavior, which may entail ecological responses, highlighting the need to maintain an unfragmented river network to ensure movement dispersal among habitats, thus providing conditions for species escapement from hypoxia. View Full-Text
Keywords: dissolved oxygen; anoxia; fish behavior; fish school; laboratory flume; video-tracking dissolved oxygen; anoxia; fish behavior; fish school; laboratory flume; video-tracking
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MDPI and ACS Style

Hayes, D.S.; Branco, P.; Santos, J.M.; Ferreira, T. Oxygen Depletion Affects Kinematics and Shoaling Cohesion of Cyprinid Fish. Water 2019, 11, 642.

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