1. Two experiments were carried out in a Scottish river to test the effects of electrofishing on endangered freshwater pearl mussels (Margaritifera margaritifera).
2. In the first experiment, two areas of mussel bed were marked out as treatment and control sites and the former was electrofished using standard equipment. The mussels were examined 10 min, 24 h and 35 days after treatment and their shell valve closure responses, burrowing capabilities and gravidities were recorded as signs of normal ‘functioning’.
3. In the second experiment, individual mussels were marked as treatments and controls and the former were electrofished. These mussels were examined as before.
4. No mortalities occurred and no significant differences in ‘functioning’ between treatments and controls were observed in either experiment.
5. Since no measurable treatment effect could be demonstrated, it appears that electrofishing did not adversely affect the short-term survival of M. margaritifera. Copyright © 2001 John Wiley & Sons, Ltd.