Diurnal and seasonal behaviour of adult and juvenile European catfish as determined by radio‐telemetry in the River Berounka, Czech Republic

Abstract

The first telemetry study analysing behaviour of the largest freshwater predator in European rivers, Silurus glanis, was performed bimonthly during the years 2002-2004. Movement of juveniles and adults occurred mostly in the same time intervals. The only statistical differences occurred for nocturnal activity in spring and autumn. In spring and winter, activity was low with the peaks during daylight, and in autumn, maximal movement was recorded during dusk. In summer, the European catfish were active across the whole 24 h even during high-flow conditions. During all other seasons, movement was inversely related to flow rate. Maximal home ranges occurred in summer, being larger for adults. Juveniles and adults were spatially segregated. With increasing flow, fish were displaced, and individuals from both groups got closer to each other. Only juveniles migrated downstream from the upstream isolated river stretch suggesting a negative impact of lateral obstructions on the fish population structure.

Do You Eat or Not? Predation Behaviour of European Catfish (Silurus glanis) Toward Live Bait on a Hook

“…Among these 12 hooked fish, the angler caught 6. These results also confirm that European catfish is not only a nocturnal predator but can be also active across diurnal periods in rivers, see also [18]. Individual body size significantly differed between behaviour types (Kruskal-Wallis test, p < 0.01) with hooked individuals larger than individuals exhibiting Ignore behaviour (Mann-Whitney test, p < 0.01), Approach behaviour (p < 0.01), Taste behaviour (p < 0.01) and Spit behaviour (p < 0.01) (Fig.…”

“…We documented the feeding motivation of European catfish toward a live baited hook, by exposing the same type of bait in similar natural environmental conditions to catfish individuals and describing their behaviour toward the bait once they located the prey. Diel dualism in the activity of European catfish occurs in the wild and diel activity and energy consumption differs across the seasons [18]. In a Czech river, European catfish were active across the whole 24 h in summer [18].…”

Move or die: change in European catfish (Silurus glanisL.) behaviour caused by oxygen deficiency

“…In cold water during winter time, the activity of European catfish is minimal (Slavík et al, 2007;Copp et al, 2009). However, our telemetry study revealed the possibility of short-term high activity in winter in response to sub-optimal and/or potentially lethal environmental variables.…”

“…In our case, the tracked individuals displayed site fidelity at first. Each individual had its stable resting place, and the HR was minimal, which could have been bolstered by the low temperature (Slavík et al, 2007). Later on, a large aggregation of fish in two restricted areas took place.…”

“…It has a physiological optimum above 25 • C (Copp et al, 2009). In the temperate zone, cold water in winter leads European catfish to exhibit notably low activity (Lelek et al, 1964;Slavík et al, 2007). This paper presents data on a phenomenon accidentally observed during a long-term study, which was originally carried out to examine seasonal changes in the activity of European catfish.…”