Ontdekking van een populatie Rivierrombout (Gomphus flavipes) op het Albertkanaal (België), een van de drukst bevaren kanalen van Europa, en een overzicht van de status in West- en Midden-Europa

De Knijf G., T. Adriaens, R. Vermylen & P. Van der Schoot 2014. Discovery of a population of Gomphus flavipes on the Albert Canal (Belgium), one of the busiest channels in Europe, with an overview of its status in Western and Central-Europe. Brachytron 16(1/2): 3-17.

Gomphus flavipes, a typical river species, disappeared in many parts of western and central Europe as a result of deterioration of the water quality. Since the beginning of the 1990s G.flavipes has been rediscovered in several rivers, first in the Netherlands and Germany. The first observation of G.flavipes from Belgium dates from 2000 and originates from the river Meuse, where it forms the border between Belgium and the Netherlands. Several observations were made there, but exuviae have never been found. Although the species has been observed several times since 2002 in the province of Antwerp, these observations were all considered to refer to vagrant individuals from the river Meuse the Netherlands or the river Rhine in Germany. In July 2012 a population of G.flavipes was discovered along the Albert Canal in the province of Antwerp, Flanders, Belgium. A freshly emerged individual was found on 28 July 2012 and the following days along the Albert Canal in Broechem. The first exuvium was found on 6 August. The subsequent search (6-12 August 2012) resulted in the discovery of 70 exuviae, all found along the Albert Canal between the sluices of Wijnegem and the bridge over the canal in Grobbendonk, over a distance of 9.5 km. The average density of exuviae found per trajectory with larval skins present was 1.2 (minimum 0.1, maximum 3.3) per 100 meter. Sex-ratio was 1:0.6 in favour of females, which is reported normal in Gomphid populations but can also be explained by the late sampling date, as in dragonflies males are mostly the first to emerge. Emergence
substratum was highly artificial. Most exuviae were found on the concrete sheet piling of the bank, to a lesser extent also on poles or vertical walls. Based on long-term research in other parts in Europe, we estimated the population along the Albert canal at a minimum of 200 individuals. This discovery of a population of G.flavipes in one of the busiest channels in Europe is unique and sheds new light on the potential range of the species in Flanders and suitable habitat in large parts of Europe. G.flavipes is also known to reproduce in small irrigation canals (< 5m wide) between the rice paddies in northern Italy, but although also artificial these
cannot be compared with the Albert Canal. This local shift in habitat preference from rivers towards canals with concrete banks, is probably a result of the recent range expansion of G.flavipes in western Europe.