Original paper
Recruitment of a freshwater mussel with a planktonic life-stage in running waters - Studies on Dreissena polymorpha in the River Rhine
Kern, Regine; Borcherding, Jost; Neumann, Dietrich
Archiv für Hydrobiologie Volume 131 Number 4 (1994), p. 385 - 400
21 references
published: Nov 11, 1994
DOI: 10.1127/archiv-hydrobiol/131/1994/385
ArtNo. ESP141013104000, Price: 29.00 €
Abstract
The seasonal abundance and size of larvae of the freshwater mussel Dreissena polymorpha were studied at nine stations along the River Rhine from Schaffhausen (High Rhine) to Grietherort (Lower Rhine) in 1991 and 1992. In both years the larvae appeared between April and October, with maximum numbers occurring in spring (e.g. the maximum peak at Karlsruhe was about 315 larvae/l at the end of May 1991). However, in 1991 the total amount of larvae (e.g. about 1015 larvae in 1991, at Cologne) was about three times higher than in 1992. For nearly all samples, the average larval shell length was ca. 100 µm. Generally, far less than 0.1 % of the larvae were about 200 µm in length and were, thus, at a stage near to settlement. In 1991, larval growth was studied under controlled laboratory conditions. Studies for two "fließende Welle" -inventories were also carried out. Growth rates ranged from 3.7 to 15.0 µm/day, assuming that no larvae originating from the river bed itself had the chance to complete their development before reaching the North Sea. Thus, the search for parent populations concentrated on those parts of the river system where the current is slower, thereby enabling the larvae to pass their main developmental period before being introduced into the "fließnde Welle" of the River Rhine. By combining all information on the larvae and knowing the time it takes for a water column to flow between two points one can roughly estimate the places of origin of a larval age group which is drifting downstream. In 1991 and 1992, the places of probable major importance were the 'Rest Rhine' between Basel and Breisach, the other dammed up parts of the Upper Rhine and the River Main (a major tributary).
Keywords
freshwater mussel • Rhine • Schaffhausen