Differences between male, female and juvenile haddock (Melanogrammus aeglefinus L.) sounds

Abstract

Female and juvenile haddock make sounds, as well as males. Examination of the sounds from different sexes indicates that the sound waveform is a function of fish maturity and it is gender-specific. Immature fish sounds were found to be made up of two pulses with similar frequencies and opposite polarities. Females produced two pulses with the same polarity, the first pulse having a higher frequency than the second. The acoustic characteristics of juvenile, female and male haddock sounds are compared. Sexual dimorphism in the mass of the drumming muscle mass has also been investigated. Female haddock possess less well-developed drumming muscles than males throughout the whole year. A significant difference in drumming muscle mass was observed not only in males but also in females at different seasons. A positive relation between drumming muscle mass and fish size has been highlighted in both male and female fish. The physical parameters of the sound units emitted by juveniles, females and males, which are likely affected by physiological condition and maturity stage, are discussed in relation to the sound-producing mechanism.

Keywords:

• Melanogrammus aeglefinus
• drumming muscle
• sounds
• hydrophone

Acknowledgements

The behavioural observations were carried out at the former Fisheries Research Services Marine Laboratory, Aberdeen, Scotland with funding from the Scottish Executive. The laboratory is now part of Marine Scotland Science, a division of Marine Scotland (a Scottish Government department). We thank B. Williamson for help with the provision of aquarium facilities and other colleagues at the Marine Laboratory who assisted with the experiments. The authors are grateful to G. Pierce (University of Aberdeen) for his valuable feedback at all stages of the research.