Abstract
Background. Roach, Rutilus rutilus (Linnaeus, 1758), is an omnivorous fish species that is able to utilise a range of food resources. Both juvenile and older roach can negatively affect zooplankton abundance in freshwater bodies of water; hence populations are often reduced (biomanipulated) in order to increase zooplankton populations. The aim of this study was to assess the roach diet after large-scale removal of cyprinids (bream, roach) from a reservoir. The study was done to clarify the roach diet after three years of intensive reduction of cyprinid fish and also to find out how the roach feeding behaviour impacts the quantity of filtering zooplankton. As such, this study may help to explain more general relations within the aquatic food web and specify the roach diet during the vegetative season (from spring to autumn). Materials and methods. This study was undertaken at the Hamry water supply reservoir in the Czech Republic. Samples of macrozoobenthos, periphyton, and zooplankton were collected as representative food resources. Fish were caught using a 100-m littoral beach seine during the April to October growing season in 2011. Supplementary fish were caught using a pelagic Nordic gillnet in August and September 2012 and a 15-m beach seine in June and August 2012. Gut contents were preserved in 4% formaldehyde for later laboratory analysis (frequency of occurrence, index of preponderance, index of gut fullness). Results. ‘Detritus’ was the major component found in roach guts, with no difference observed in age category or locality (littoral vs. open water areas). Significant differences were observed, however, between younger (0+ and 1+, 36–92 mm) and older (>3 years, >92 mm) fish. The 0+ and 1+ age groups also fed on zooplankton (P < 0.008), accompanied by Chironomidae (1+), while diet of older roach (3–4+; 6–8+) included macrophytes and periphyton, together with Cladocera (fish from open water; P < 0.008). Conclusion. The results demonstrate that detritus was the main ‘dietary’ component of roach during the growing season, with macrophytes and periphyton as complementary dietary items. Zooplankton was an important dietary component of mainly younger roach age classes. Roach appear to be an important component in ichthyo-eutrophication of the Hamry Reservoir, mainly through transfer of phosphorous from plants to water.
Highlights
Roach, Rutilus rutilus (Linnaeus, 1758), is an omnivorous fish species that is able to utilise a range of food resources
These two criteria are combined in order to express an index of preponderance (IP) using the following formula: IP = 100(Wi · FOi) · Σ(Wi · FOi)–1 where: Wi is the weight percentage of a particular food component i and FOi is the frequency of occurrence of that food component
Bacillariophyceae were dominant in the periphyton assemblage throughout the year (Fig. 4)
Summary
Rutilus rutilus (Linnaeus, 1758), is an omnivorous fish species that is able to utilise a range of food resources. Both juvenile and older roach can negatively affect zooplankton abundance in freshwater bodies of water; populations are often reduced (biomanipulated) in order to increase zooplankton populations. The 0+ and 1+ age groups fed on zooplankton (P < 0.008), accompanied by Chironomidae (1+), while diet of older roach (3–4+; 6–8+) included macrophytes and periphyton, together with Cladocera (fish from open water; P < 0.008). The results demonstrate that detritus was the main ‘dietary’ component of roach during the growing season, with macrophytes and periphyton as complementary dietary items. Roach appear to be an important component in ichthyo-eutrophication of the Hamry Reservoir, mainly through transfer of phosphorous from plants to water
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
