Ecological consequences of food partitioning for the fish population structure in a eutrophic lake

Abstract

In the highly eutrophic lake, Frederiksborg Slotsso, the diet composition of the bream (Abramis brama L .) and roach (Rutilus rutilus L.) populations was examined during three periods with different food availability . The length range of bream and roach was 9-34 cm (TL) and 5-18 cm (TL), respectively . The relative food composition was examined for 2 cm and 1 cm length intervals of bream and roach, respectively. During all three periods, bream shifted from benthic cladocerans (Alona sp.) to zooplankton and chironomids within a transitional length of 15 .0-20 .0 cm . These foodshifts were coupled with a change in feeding behaviour from particulate to filter feeding . The biomass of chironomids was too low to sustain the consumption of larger bream (>20 .0 cm) which initiated feeding in the pelagic zone even in periods when the mean length and biomass of the preferred zooplankton, Daphnia cucullata, were low . In contrast to bream, roach fed mainly on zooplankton . With increasing size, roach progressively shifted to larger zooplankton species due to the increasing mesh size of their branchial system . The importance of benthic animals in the diet of roach was minor due to low feeding efficiency on prey buried in the sediment . Detritus appeared in the diet of bream and roach in periods of low availability of animal food items . Feeding on detritus may provide an energetic advantage to bream and roach and increase the carrying capacity for these species in lakes, where detritus is highly abundant . Especially for the larger fish due to the decrease in their relative metabolic demands . However, the ability of bream to filter feed and with increasing size to retain food items smaller than those retained by roach may be the main mechanism for the dominance of bream over roach in highly eutrophic lakes .

Diel Migration and Spatial Distribution of Fish in a Small Stratified Lake

“…The length of juvenile roach corresponded to that backcalculated for Estonian small lakes (Eesti ja¨rved, 1968) and for Finnish lakes (Horppila & Nyberg, 1999) and its length frequency distributions was similar to that in the eutrophic lake Frederiksborg Slotssø (Michelsen et al, 1994). Age composition showed a similar scarceness of 2-to 3-year-aged roach both in the pelagic and littoral zones, being obviously catchable as a refugee in reeds (Herzig et al, 2002), the biotope not explored in lake Verevi.…”

“…A similar composition of fish is characteristic of mesotrophic lakes in southern Finland (Olin et al, 2002). In highly eutrophic lakes, the proportion of other cyprinids and percids, such as bream, white bream (Blicca bjoerkna) and ruff, increased (Michelsen et al, 1994;Olin et al, 2002). During the past years L. Verevi, especially its epilimnion, has changed from hypertrophic to mesotrophic with oligotrophic features while bream and ruffe have disappeared by now.…”

The food of roach, Rutilus rutilus (Actinopterygii: Cypriniformes: Cyprinidae), in a biomanipulated water supply reservoir

“…While it might be expected that results would be similar in shallow reservoirs, in a relatively shallow eutrophic lake in Denmark (mean depth 3.1 m), roach fed mainly on zooplankton (Michelsen et al 1994). Zoobenthos were of minor importance and detritus appeared only in periods of low animal-food availability.…”

Individual and population‐level food consumption by cyprinids and percids in a mesotrophic lake

“…The ability of roach and bream to consume detritus is one of the characteristics that gives them a competitive advantage over species like perch under eutrophic conditions (Persson 1983) and makes it possible for cyprinids to maintain dense populations despite shortage of high-value invertebrate food (Michelsen et al 1994). Persson (1983) observed that during the whole ice-free period, detritus made up a high proportion of the stomach contents of 3-to 4-year-old roach in a Swedish lake.…”