Winter activity of common bream (Abramis brama L.) in a European reservoir

Abstract

As temperatures drop and fish metabolism slows, cyprinids are generally assumed to form dense, static shoals or migrate to suitable sites up tributaries to reduce predation risk. Using telemetry, common bream Abramis brama (L.) were observed to remain active and (presumably) foraged throughout winter in an area in the middle of an 8‐m‐deep valley reservoir coinciding with a 3–5 m zone of warmer, oxygenated water below an inverse thermocline. Tagged bream appeared to avoid cold, shallow zones (<1.5 m) at the inlet and banks and the deepest zone (5–8 m) near the dam/outlet, possibly due to poor food availability. Under certain conditions, bream populations showed higher levels of winter activity (and feeding) than previously assumed, with implications for both reservoir fisheries management and future studies assessing cyprinid behaviour, energy budgets and diet in lakes and reservoirs.

Relationship between bream (Abramis brama) activity and water turbidity in a shallow lake under different season conditions

“…A recent telemetry study suggests that seasonal variation in bream habitat use could take place, e.g. Jurajda et al (2018) found that bream similar to the size of bream in this study, preferred depths between 3-5 meters during winter and avoided depths at 1-2 meter and 5-8 meters. However, if depth variation is the driver behind such seasonal variation, it seems unlikely to influence the results obtained from this study as Lake Loldrup is shallower and has a relative uniform depth profile.…”

“…However, if depth variation is the driver behind such seasonal variation, it seems unlikely to influence the results obtained from this study as Lake Loldrup is shallower and has a relative uniform depth profile. Moreover, the results from Jurajda et al (2018) could be biased by strong individual variability as the spatial behaviour of only eight bream were included in their study. still, if bream for some reason occasionally avoided the shoreline areas and the PIT antennae during summer, this could add an additional explanation to why we find no clear relationship between bream and FTU during summer.…”

“…As for ectotherms in general, bream activity, such as foraging intensity, is expected to be positively related to temperature. However, telemetry studies have shown considerable activity of lentic freshwater fish, such as bream, also during cold periods in autumn and winter (Jacobsen et al, 2002;Baktoft et al, 2012;Jurajda et al, 2018). This could in turn have implications for seasonal dynamics of water turbidity.…”

The effect of temperature on the dynamics of common bream Abramis brama migrations between the reservoir and its tributary

“…The length of observed common bream migrations between the reservoir and its tributary corresponded with its behaviour in riverine systems where the species migrates for comparably long distances and displays homing behaviours (Caffrey et al, 1996; Le Pichon et al, 2017; Lyons & Lucas, 2002; Molls, 1999; Whelan, 1983; E. R. Winter et al, 2021a). Similarly, the bream exhibited movements within the reservoirs and/or downstream migrations from the reservoirs (Jurajda et al, 2018; Knott et al, 2020). In our study, most individuals migrated between the reservoir and the tributary, some stayed in the tributary inflow to the reservoir and one individual was found in the reservoir.…”

Effects of physical parameters on fish migration between a reservoir and its tributaries

“…Abramis brama is an insectivorous, phytolithophilous, eurytopic Cyprinid species 34 , 35 that occurs in the whole longitudinal profile of rivers from an estuary into the sea to medium sized streams including their flood plain areas 36 – 38 , and also thrives in reservoirs 17 , 39 . Although A. brama shows homing and maintains stable home ranges, its ability to spread across various habitats and variability in food availability can be considered reasons for the species nomadism 8 .…”