Juvenile Döbel (Leuciscus cephalus), Haseln (Leuciscus leuciscus), Rotaugen (Rutilus rutilus) und Brachsen (Abramis brama) sind die häufigsten Cyprinidenarten im Litoral des Bodensees. In kleinen flachen Seen nutzen diese Arten vor allem sublitorale Habitate mit dichten Makrophytenbeständen (SAV). Im Bodensee hingegen präferieren diese Arten vor allem die ufernächsten Flachwasserzone zwischen 0 und 50 cm Wassertiefe.
In kombinierten Aquarien- und Mesokosmosversuchen wird untersucht, welches der zwei Habitate "tiefe SAV-Zone" oder "Flachwasser" - von juvenilen Cypriniden primär bevorzugt wird, wenn keine weiteren externen Stimuli vorhanden sind. Zusätzlich werden die Effekte von Prädationsrisiko, Temperaturschichtung, SAV-Bewuchs und Wellenschlag auf das Habitatwahlverhalten der einzelnen Arten getestet.
Juvenile bream (Abramis brama), chub Leuciscus cephalus, roach Rutilus rutilus, and dace Leuciscus leuciscus are most common cyprinid species in the littoral zone of Lake Constance. In the early summer they dominate the near-shore community and aggregate in high densities in the shallow areas < 50 cm water depth (Fischer 1997a,b). In July and August, age-0 bream and roach pass through a significant change in body morphometry. While chub and dace remain their torpedo-like body shape which is typical for many rheophil species, bream and roach then become laterally compresses and high backed. During this phase of morphometric changes, bream emigrates from the very shallow littoral areas and moves to deeper habitats with dense stands of submerged aquatic vegetation (Fischer 1994b).
Changing habitat preferences due to changes in the ontogenetic development of fish are a common phenomenon in many species (Copp 1990; Copp 1992). In this work, we test the hypothesis that the habitat shift of bream (and roach) is due to the changed body shape associated with a relocation of the center of gravity. This relocation modifies the behaviour against the shear rates and the perceptibility to currents of waves so that the species are forced to switch in deeper zones with SAV as an alternative habitat.
Copp, G. H. (1990). Shifts in the microhabitat of larval and juvenil roach, Rutilus rutilus (L.), in a floodplain channel. Fish. Bull. 36: 683-692.
Copp, G. H. (1992). Comparative microhabitat use of cyprinid larvae and juveniles in a lotic floodplain channel. Env. Biol. Fish. 33: 181-193
