Oxygen Depletion Affects Kinematics and Shoaling Cohesion of Cyprinid Fish

Abstract

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.

Longitudinal river zonation in the tropics: examples of fish and caddisflies from the endorheic Awash River, Ethiopia

“…The effects of deforestation, intensification of agriculture and other land-use changes, hydropower, river engineering, and water pollution threaten aquatic biodiversity (e.g. Clausen & York, 2008;Fitzgerald et al, 2018;Hayes et al, 2018Hayes et al, , 2019Meulenbroek et al, 2019). These trends can even have visible impacts on largescale ecosystem processes (Darwall et al, 2018).…”

STRESS RESPONSES OF THREE SPECIES OF CYPRINID: COMMON CARP (Cyprinus carpio), BONYLIP BARB (Osteochilus hasselty), AND TORSORO (Tor soro) SUBJECTED TO OXYGEN DEPLETION

“…In the wild, fish might try to escape from unfavorable conditions (Hayes et al, 2019). Barbel and some fish species usually reduce their swimming activity and adopt a "sit and wait" strategy (Domenici et al, 2013).…”

“…A study showed that oxygen depletion levels affected the behavior and ecological responses of Luciobarbus bocagei (Hayes et al, 2019). Studies related to oxygen consumption in barred loach reported Stress responses of three species of cyprinid: common carp ..... (Wahyulia Cahyanti) that oxygen consumption under hypoxic conditions decreased significantly compared to normoxic conditions marked by decreased swimming activities (Iswantari et al, 2019).…”

Differential gene expression indicates modulated responses to chronic and intermittent hypoxia in corallivorous fireworms (Hermodice carunculata)

“…The term “hypoxic” is context-specific and can either refer to the level at which an organism responds to low oxygen conditions or to the environment in which the organism resides. For the purpose of this study, we characterize DO concentrations of 4.5 mg O 2 L −1 as Mild hypoxia 25 , 26 , 2.5 mg O 2 L −1 as Moderate hypoxia, and 1 mg O 2 L −1 as Severe hypoxia. Our previous studies indicate that previous exposure to the Moderate hypoxia increases H. carunculata ’s metabolic rate in the long-term 27 .…”

“…However, based on climate change models, chronic hypoxic events are more likely in the future 1 – 3 , 57 . In addition, due to unique physiological and behavioral responses at different levels of hypoxia 25 , 26 , gene expression associated with chronic Mild and Moderate DO should be investigated to understand organismal response. While it has been suggested that amphinomids may thrive in lowered DO conditions 58 – 60 , no studies have yet determined direct gene expression responses to this stressor.…”