We studied the dragonfly fauna along a 15 km stretch of the floodplain of the regulated, first-order river Tisza, Hungary. Data on captured and observed adults, larvae and exuvia were recorded. Observations were made from May to October 1998 and 1999 on 34 species, which is 52% of the Hungarian fauna. Classification on the basis of faunistic similarity revealed that habitat-level differences, associated with various degrees of physical anthropogenic impact on bank vegetation, can exceed variation among the water bodies of different types (backwater, pond, marsh, canal, river). The richest sites were dominated by structurally diverse macrophyte vegetation, while flowing waters (river and canal) were poorest in species. Odonata were found to be reliable indicators of small-scale habitat patterns, reflecting vegetation differences even within single water bodies where the sampling spots were arranged just a few hundred metres apart. Along a gradient of utilisation intensity, the species number of Odonata assemblages and the summed relative abundance of the five rarest species of the study area decreased linearly with increasing fragmentation of the marginal vegetation. Sports fisherman activities, implying disruption of the littoral marsh zone by establishment of clearings and excessive trampling of the banks, can also be monitored by dragonfly faunistic investigations. Our results demonstrate that conservation of these varied floodplain water bodies requires the control of sports fishing activity, suggesting that (i) to maintain the representative odonate fauna of the water bodies, some nonfragmented shores must be provided; and (ii) permanent fishing stands should not exceed 8 m mean width and should be separated by at least 12 m of intact riparian sections.
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