Functional role of environmental stimuli for the spawning migration in Danube nase Chondrostoma nasus (L.)

Abstract

– In spring 2004 and 2005, an online monitoring by horizontal split‐beam hydroacoustics complemented by trap net catches and electro fishing was conducted to investigate the spawning migration of nase Chondrostoma nasus (L.) into the Fischa River, a tributary of the Danube River east of Vienna, Austria. Upstream‐moving adult nase could be counted hydroacoustically based on their dominance (93%) of fish in the range 45–55 cm total length. Significant correlations were observed between the number of migrants and three environmental factors (water temperature, water level and turbidity), with special focus on their fluctuations. Thresholds of water temperature, water level and turbidity were revealed as general environmental cues on a seasonal scale. On a fine temporal scale, the fluctuations of the environmental factors over days, especially in the main river, represent relevant stimuli; they initiate and control the fine‐scaled temporal pattern as well as the intensity of the spawning migration. In addition, a combination of increasing water temperatures and decreasing water levels, corresponding to the period after a flood peak, offers high predictability of favourable spawning conditions at the spawning place and acts as a stimulus for the right timing for upstream migration in Danube nase.

There and back again: migration in freshwater fishes

“…Spawning migrations are seasonal and most likely evolved in scenarios whereby the optimal habitat for growth and survival differs between juveniles and adults. Many freshwater fish undertake spawning migrations, for example, the nase (Chondrostoma nasus (L., 1758)) that migrates from rivers into tributaries to spawn (Rakowitz et al 2008). There are also examples in the literature of refuge migrations, where individuals migrate to reduce the risk of predation, often at times of the year when growth potential is reduced (i.e., during winter: Brönmark et al 2008;Skov et al 2011).…”

Occurrence of cyprinids in fish ladders in relation to flow

“…It appears that the response of migrating fish on flow variability becomes significant, provided the analyses of the relationship between flow and cyprinid migrations are sufficiently widespread, i.e., reflects local variability in environmental conditions. As disclosed by Rakowitz et al (2008), descending flows after a flood peak and also ascending flows before a peak together with an increase in turbidity were the key stimuli for migrations of nase Chondrostoma nasus (L., 1758). Furthermore, authors described significant correlations between the number of migrant and fluctuations in three environmental factors (water temperature, water level and turbidity).…”

Two methods to improve the accuracy of target-strength estimates for horizontal beaming

“…1). Two of these branches contain riffles with high current velocity and are regularly frequented by the same nase individuals from year to year (Keckeis, 1998;Rakowitz et al, 2008). Individuals of this species occur in this river system only during spawning season, from March to early June (Keckeis, 1998).…”

“…Recently, 36 fish species were identified here. In spring, the river is characterised by a sequence of single-species spawning events starting with pike Esox lucius L. and dace Leuciscus leuciscus (L.), followed by nase Chondrostoma nasus (L.), ide Leuciscus idus (L.) and barbel Barbus barbus (L.) (Rakowitz et al, 2008). Two nase spawning sites are located 4.5 km upstream the mouth, where the Fischa splits into several smaller branches, creating a local floodplain area (Fig.…”