Graduation Year

2005

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Marine Science

Major Professor

David A. Mann, Ph.D.

Keywords

Agonistic, Territorial, Gas bladder, Sebastes nebulosus, Fish

Abstract

Rockfishes of the genus Sebastes are trophically important in most nearshore environments of the west coast of North America, and support important commercial and recreational fisheries. Though the 72 northeast Pacific species have drumming muscles along their swim bladders, little is known about sound production in the genus. Sounds produced by nearshore rockfish were recorded using fixed hydrophones and underwater video in aquaria, and acoustical dataloggers in the field. Sounds were analyzed from six species: Sebastes nebulosus, S. atrovirens, S.carnatus, S. chrysomelas, S. caurinus, and S.maliger. These six species are closely related, mostly bottom dwelling species with similar drumming musculature. No sounds were recorded from twelve other species in response to diver harassment or agonistic interactions. All the sound production observed was close range, agonistic and relatively quiet (estimated source level 122 dB re 1uPa). Sounds were recorded at all times of the day in the field, presumably from S. nebulosus. While courtship type behavior was observed and video-recorded for only two species, no sounds were produced during courtship. Analysis of the sounds (duration, number of pulses, pulse rate, peak frequency, interpulse interval) from the six species showed considerable overlap between call characteristics, although S. carnatus and S.chrysomelas produced some longer calls with more pulses than the other species. It appears that these agonistic sounds are designed for short-range communication and that they are not species-specific.

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