Gradual frequency rises in interacting black ghost knifefish, Apteronotus albifrons.

The present paper highlights the relationship between social status and production of gradual frequency rises in interacting Apteronotus albifrons. The gradual frequency rise production was mathematically inferred and a discrete classification deliberately avoided. The results showed little gradual frequency rise production before the hierarchy settlement. Afterwards, only the dominant fish kept this gradual frequency rise production at low levels, while the subdominant fish drastically increased it in all following interaction contexts. The hypothesis of gradual frequency rises being involved in communication as submissive signals was thus strengthened.