0+ perch predation on 0+ bream: a case study in a eutrophic gravel pit lake

Abstract

SUMMARY 1. We studied the population dynamics of 0+ fish in a eutrophic gravel pit lake in which predation of 0+ Eurasian perch on other 0+ fish was suspected to influence perch growth and the structure of the fish community, with effects on the lake food web. 2. The adult fish community was dominated by piscivorous species, especially perch, and the 0+ fish community was dominated by perch and bream. Bream grew to a total length of 80 mm between May and the end of August, gradually decreased in numbers during the summer, and completely disappeared in autumn. Stomach analysis revealed that 0+ perch ≥28 mm fed on 0+ bream. 3. The initially unimodal cohort of 0+ perch gradually broadened and became bimodal by the end of July. Fish of the larger, piscivorous cohort grew faster (1.4 mm day−1) than the smaller, zooplankton‐consuming fish (0.6 mm day−1). Although individuals of both cohorts later consumed zooplankton and grew at similar rates (0.5 mm day−1), only perch of the large cohort (mean TL 125 mm) were found by mid‐October. Intraspecific competition for food or cannibalism of older perch may have contributed to the disappearance of the smaller perch. 4. Early piscivory of the fast‐growing 0+ perch apparently resulted in the disappearance of 0+ bream by the end of the growing season and precocious maturation of male perch. In contrast to findings in other studies, these large 0+ perch thus avoided the juvenile bottleneck by switching to piscivory early during their ontogenetic development. 5. The observations of this study suggest that early piscivory of 0+ perch can have a long‐lasting impact on fish communities in eutrophic lakes, particularly if prey fish are abundant and the structural complexity of the lake is low. Furthermore, early piscivory of 0+ perch may help prevent the expected increase in 0+ cyprinids following reduction of adult cyprinids, which is considered important to ensure the long‐term success of biomanipulation experiments.

Prey or predator: 0+ perch (Perca fluviatilis) in the trade-off between food and shelter

“…Some authors demonstrated that growth of 0+ fish increases significantly when they switch from zooplanktivorous or benthivorous feeding to piscivory (Van Densen 1985;Buijse and Houthuijzen 1992;Olson 1996;Borcherding et al 2000). As recently shown by Beeck et al (2002), early piscivory of 0+ perch, starting with a mean size of 28 mm in total length (TL), not only increases individual growth, but also leads to a bimodal size distribution, with fast-growing piscivores and slow-growing zooplanktivores.…”

“…Persson 1993). In addition to the aforementioned food of 0+ perch, there have also been a few reports of piscivorous 0+ perch (Clemens et al 1924;Smyly 1952;Mehner et al 1996;Beeck et al 2002). Some authors demonstrated that growth of 0+ fish increases significantly when they switch from zooplanktivorous or benthivorous feeding to piscivory (Van Densen 1985;Buijse and Houthuijzen 1992;Olson 1996;Borcherding et al 2000).…”

Resource heterogeneity, diet shifts and intra-cohort competition: effects on size divergence in YOY fish

“…Variation in the timing of diet shifts can thus be hypothesised to result in diVerent degrees of size variation within cohorts depending on the relative size-dependent resource proWtability in diVerent niches, ultimately leading to bimodal size distributions (e.g. Beeck et al 2002). Furthermore, variation in YOY Wsh densities has been shown to aVect resource densities (Byström and Garcia-Berthou 1999;Persson et al 2000a).…”

A Comparative Study on the Feeding Competition of the European Perch Perca Fluviatilis L. And the Ruffe Gymnocephalus Cernuus (L.) in Lake Piediluco (Umbria, Italy).

“…The perch's improved growth in Lake Piediluco, in comparison with the years in which the lake was mesotrophic, is also due to the fact that the diet of this species is currently broader and includes more fish than formerly (GIOVINAZZO, 1988). Indeed, an increase in fish-eating is strongly correlated with an improvement in growth (THORPE, 1977;BEECK et al, 2002;HOLMGREN, 2003).…”