6533b851fe1ef96bd12a8c02

RESEARCH PRODUCT

Attempts to re-colonise water insects in German brooks

subject

description

Attempts were made to reintroduce water insects (five stonefly species and one mayfly species) into several third order streams in Rhineland-Palatine and Hessen, Germany. All these streams had been strongly affected by waste water and rubbish and had lost most of their macroinvertebrates. As a consequence of the installation of several purification plants in the past three decades, water quality has improved. Since no stoneflies returned, 700–1300 eggs of three different species (Isoperla goertzi, I. oxylepis, and I. grammatica) were exposed in the Selz brook (1997). In February 1998 a few larvae and in 1999 about 10,000 eggs of Perla marginata were added in the Walluf brook, and in 1998, 500 larvae of Oligoneuriella rhenana each in the Ruwer, Alf and Elz brooks. After 10 years, I found only one single larva of Perla marginata in the Walluf brook. In the laboratory, the total number of eggs produced per female could be determined by rearing. On that basis coupled with the assumption of about 3% survival c...