Two transmitter masses (2 and 6% of the fish's mass) were selected to examine the interference of tags with the behaviour of Sarpa salpa using a computerized video tracking system based on digital imaging techniques. The study demonstrated that light transmitters had no effect on the behavioural variables studied, and a substantial bias in behaviour is introduced if heavier (6%) tags are used.

During observations of the River Ourthe, Belgium, 70 spawning attempts were recorded during the reproductive period of the European grayling. Thirty‐six per cent of the spawning attempts proceeded to completion, while interference by another male may explain some of the incomplete acts. Sneaking behaviour was observed and one spawning act included two males and one female.