Acta Univ Latv (2006) 710: 17–28

The distribution and occurrence frequency of Gomphidae (Odonata: Gomphidae) in river Gauja

Abstract

The article contains data on four gomphid dragonfly species known in Latvia – Gomphus flavipes, Gomphus vulgatissimus, Onychogomphus forcipatus, Ophiogomphus cecilia and the latest data on their distribution, occurrence frequency and density of individuals. Gomphidae were obtained from macrozoobenthos samples in 1998. In total 280 quantitative und 65 qualitative samples were collected in the River Gauja from the town Taurene upstream to below Carnikava. For complete analyses, the observations of adult individuals used – bibliography, unpublished (personal) observations and data from 1933 to 2005. Three species of Gomphidae – G. vulgatissimus, O. forcipatus and O. cecilia were recorded. Data with regard to observations of larvae/exuviae/imago stages showed that all gomphid species are encountered in throughout Latvia. G. flavipes is infrequent for Latvia and this species has been recorded only in the Gauja. The occurrence frequency of gomphid was 13.2 % of obtained samples. G. vulgatissimus was found in 10 % of samples, O. forcipatus in 5 %, O. cecilia in 0.7 %. Ecological analysis of bottom substrate showed that O. forcipatus prefers a hard substrate situated in the rhitral stretches or in the rapids. The density of G. vulgatissimus reached 0.919 ind. m-2, and O. forcipatus 0.514 ind. m-2.