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White Bream (white + bream)
Selected AbstractsLeptodora kindti and Flexible Foraging Behaviour of Fish , Factors behind the Delayed Biomass Peak of Cladocerans in Lake HiidenvesiINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2003Laura Uusitalo Abstract In the eutrophic L. Hiidenvesi, the spring biomass maximum of cladoceran zooplankton is missing and the highest biomass takes place in July,August. The factors behind the delayed biomass peak were studied in four different basins of the lake with concomitant data on cladocerans assemblages, density of the predatory cladoceran Leptodora kindti and food composition of fish. In all the basins, the abundance of Leptodora peaked in June, being highest (up to 800 ind. m,3) in the two most shallow basins (max depth < 4 m). The duration of the high population density was short and in July-August Leptodora density stayed below 200 ind. m,3, although the water temperature was still favourable. The collapse of the Leptodora population coincided with the change in the feeding habits of fish. In early summer, fish predation was targeted mainly on copepods and zoobenthos, while in high summer Leptodora was one of the main preys of perch, white bream and bleak. The biomass of herbivorous cladocerans was below 10 ,g C l,1 in June, and climbed to a maximum in August in the two most shallow basins (34 and 76 ,g C l,1), in July in the deepest basin (27 ,g C l,1), and in September in the intermediate basin (55 ,g C l,1). In the two most shallow basins, the death rate of the dominating cladoceran, Daphnia cristata, closely followed the food consumption rate by the Leptodora population. In the deeper basins, the agreement was not so close, smelts (Osmerus eperlanus) and chaoborids being important predators of herbivores. The duration of the period of high Leptodora density thus depended on the predation pressure by fish, while the increased fish predation on Leptodora in July,August allowed the elevation of the biomass of herbivorous cladocerans. [source] Feeding efficiency of white bream at different inorganic turbidities and light climatesJOURNAL OF FISH BIOLOGY, Issue 2 2007Z. Pekcan-Hekim Experiments were conducted to test the effects of turbidity (10,50 NTU) and light (0,2 ,E m,2 s,1) on the feeding efficiency of white bream Abramis björkna preying on Chaoborus flavicans. Increased turbidity and low light levels did not have a significant impact on the feeding of white bream. In total darkness feeding was impeded indicating that white bream depends on vision for feeding. The dominance of white bream in temperate eutrophic lakes could be attributed to their success of feeding in turbid and low light environments. [source] Correlations between type-indicator fish species and lake productivity in German lowland lakesJOURNAL OF FISH BIOLOGY, Issue 4 2006X.-F. Garcia Morphotypes for 67 lakes in the German lowlands were derived, based on maximum depth and mixis type. A threshold of 11 m maximum depth was identified to be the best level to discriminate shallow from deep lake morphotypes. The fish communities in these two morphotypes were significantly different. Indicator species analyses based on fish biomasses found vendace Coregonus albula in deep lakes and ruffe Gymnocephalus cernuus, bream Abramis brama, white bream Abramis bjoerkna, roach Rutilus rutilus, pikeperch Sander lucioperca and small perch Perca fluviatilis in shallow lakes to be the most representative species of their communities. Lake productivity was closely related to biomass and in part abundance of the type-indicator species, with vendace declining with increasing chlorophyll a concentration in the deep lakes, whereas biomass of pikeperch, bream, white bream and ruffe increased and biomass of small perch decreased with increasing chlorophyll a. These results indicate that assessment of ecological integrity of lakes by their fish fauna is generally possible, if lakes are initially separated according to a depth-related morphotype before the assessment, and if eutrophication is considered to be the main anthropogenic degradation. [source] Morphological and molecular biological studies on intramuscular Myxobolus spp. of cyprinid fishJOURNAL OF FISH DISEASES, Issue 11 2002K Molnár Abstract The validity of Myxobolus species infecting the skeletal muscles of six cyprinid fish species was studied by morphological and molecular biological methods. Intracellularly developing Myxobolus spores identified as M. cyprini from the common carp, M. musculi from the barbel, and M. pseudodispar from the roach, rudd, common bream and white bream were very similar in their shape and size. Nonetheless, in species identified as M. pseudodispar, the occurrence of spores with an asymmetrical shape was higher than in M. cyprini, while asymmetrical spores were only occasionally found in M. musculi. The DNA sequence analysis of the polymerase chain reaction (PCR)-amplified 18S rRNA gene of Myxobolus spores from these fish showed a similar phylogeny to that of their host species. As morphological studies and DNA sequence analysis demonstrated slight but real differences in the spores infecting muscles of the six cyprinid species, it is suggested that M. musculi, M. pseudodispar and M. cyprini are valid species. [source] | ||||||||||