Refine
Has Fulltext
- no (2)
Year of publication
- 2002 (2) (remove)
Document Type
- Article (2)
Language
- English (2)
Is part of the Bibliography
- yes (2)
Institute
Juvenile roach (Rutilus rutilus L.) fed on the cyanobacterium Aphanizomenon were able to maintain liver glycogen and muscle protein concentrations. In contrast, internal energy stores of fish fed on the cyanobacterium Microcystis were degraded. However, liver glycogen was higher than in starved fish, suggesting that roach was able to obtain some nutrients (probably carbohydrates) from the mucus cover of Microcystis. Weak assimilation of radiolabeled Microcystis by roach was detectable, and assimilation rates increased with increasing proportion of Aphanizomenon in a mixture of both cyanobacteria. We conclude that the incomplete digestion of Microcystis was the main reason for the negative growth rates of roach when fed on this cyanobacterium species.
1. The ability of roach to use cyanobacterial food is generally believed to be one reason for the dominance of roach over perch in eutrophic European lakes. The aim of this study was to test whether cyanobacteria really are a suitable food for juvenile roach. Special attention was paid to differences between the two cyanobacteria species Aphanizomenon and Microcystis which are common in eutrophic lakes and are ingested by roach there. 2. We performed growth and behaviour experiments with juvenile roach fed with zooplankton and the different cyanobacteria. Growth rate with Aphanizomenon was lower than with Daphnia but significantly higher than without food, whereas growth rate with Microcystis was as low as without food. 3. In cultivation experiments of roach faeces, Microcystis was found not to have been digested and grew exponentially after passing through the gut whereas Aphanizomenon stayed at low biomass. Differences in growth were not related to the toxin content of cyanobacteria. Investigations of roach motility showed no differences whether fed Aphanizomenon or Microcystis. 4. In contrast to Microcystis, Aphanizomenon can be regarded as a suitable food source for juvenile roach probably due to its better digestability. We conclude that the ability to feed on cyanobacteria is not a general competitive advantage for roach, but the outcome depends on the species composition of the cyanobacteria.