The feeding ability of the alien species topmouth gudgeon (Pseudorasbora parva, Schlegel 1842) under different water velocities
The topmouth gudgeon (Pseudorasbora parva, Schlegel 1842) is a non-native fish species in the european continent, who was dragged into Europe with imports of herbivorous fish from Asia already in the sixties. At present its occurencce is reported from many countries trough the whole European region. In Europe the topmouth gudgeon occurs almost in all types of still and running waters except in the trout and grayling zones. High abundance occures in nursing ponds and connecting channels of aquacultural facilities and in natural waters it is observed mainly in smaller lentic and lotic water bodies where it often forms very numerous populations.
Studies concerning the feeding pattern of Pseudorasbora parva (Asaeda
et al., 2001, Asaeda et al., 2002, Priyadarshana et al., 2001) were concentrated
only on observations in still waters, informations from feeding patterns
in running water are still unknown. Therefore the main aim of this study
is to obtain more detailed knowledges about the feeding behaviour of topmouth
gudgeon at different water velocities.
The experiments were performed in an artificial circulating stream channel.
Individuals were starved 24 h before the begginning of experiments. Groups
of 4 fish (TL 31- 40 mm) adapted for experimental conditions at least
15 h before each experiment were used and a single fish was filmed using
zooming technique during a 3 min observation interval. Two synchronized
video cameras were used to get information in a 3 dimnensional environment.
Daphnia magna, Straus 1820 (carapace lenght 1,03 ± 0,1 mm),
were used as prey items. Prey density was 0,2 ind.l-1, prey was introduced
into the experimental channel by a tube delivery system. Experiments were
replicated five times using different fish groups. The recordings were
analyzed with image analysis software Optimas®.
Habitat selection by fish depends
also on the income of energy and nutrients (Wooton, 1998) which is generated
by its feeding activities providing for fish the growth and reproduction.
Fig. 1: Experimental setup showing the two video cameras (horizontal and vertical recording), the spatial division of the stream channel and the video-recorders.
contacts
Dipl. Ing. Jirí Musil
University of South Bohemia
Ceské Budejovice, Department of Fisheries, Faculty of Agriculture,
Studentská 13, 370 05 Ceské Budejovice
E-mail: musil_jiri@quick.cz
Doc. RNDr. Zdenek Adámek
CSc., University of South Bohemia
Ceské Budejovice, Department of Fisheries, Faculty of Agriculture,
Studentská 13, 370 05 Ceské Budejovice
Research Institute of Fish Culture and Hydrobiology, Vodnany, Czech republic
- Laboratory Pohorelice, Vídenská 717, 691 23 Pohorelice
E-mail: adamek.zdenek@quick.cz