WILLIAM N. TAVOLGA
142
moving fish, and even the currents of water flow in rivers and seas are
essentially acoustic phenomena, and a line of demarcation between such
energy and that of a distinctly audible hoot of a toadfish is difficult to
draw. Some investigators have referred to these extremely low frequency
or steady state displacements and pressures as “unsound or “pseudosound” ( Parvulescu, 1964, 1967; Ffowcs-Williams, 1967).
It is apparent, therefore, that in water the usual definitions of sound
are not entirely applicable, and the distinction between rheotaxis and
hearing is not clear, As evidenced by the problems and discussions at a
recent conference on the lateral line of fishes (Cahn, 1967), the concern
over underwater bioacoustics has extended far below what is ordinarily
considered the audiofrequency range.
C. Sonic Mechanisms in Fishes
There appears to be little relationship between the morphology of
sound-producing mechanisms and phylogenetic position in fishes. At the
present time, however, only a few hundred out of more than 20,000
species have been clearly identified as sound producers. Many species,
such as certain deep-sea forms (N. B. Marshall, 1967), appear to possess
the means for sound production but have not yet been recorded. Three
general types of sonic mechanisms are present in fishes: stridulatory, hydrodynamic, and swim bladder. Stridulatory sounds are produced by
friction of teeth, fin spines, or bones. Hydrodynamic sounds result from
swimming movements, especially during rapid changes of direction or
velocity. The swim bladder acts as a sound projector when it is vibrated
by contiguous or attached muscles.
1. STRIDULATORY MECHANISMS
A large majority of teleost fishes possess opposing patches of denticles
in the pharynx and are at least potentially capable of sound production
during feeding. Some species stridulate pharyngeal denticles in connection with other activities such as alarm and territoriality. The best known
sound producers of this type are members of the family Pomadasyidaethe grunts (Fig. 3 ) . Burkenroad (1930) described the sounds and the
mechanism in some detail for the white grunt, Haemulon plumieri. He
also noted that if the swim bladder were deflated, the character of the
sound became “dry” and lost its “gruntlike” quality. He concluded that
the swim bladder acts as a “resonator.” A similar arrangement has been
described for other members of the family, and the margate fish,
Haemulon album, has been observed to emit sounds, probably produced
142
moving fish, and even the currents of water flow in rivers and seas are
essentially acoustic phenomena, and a line of demarcation between such
energy and that of a distinctly audible hoot of a toadfish is difficult to
draw. Some investigators have referred to these extremely low frequency
or steady state displacements and pressures as “unsound or “pseudosound” ( Parvulescu, 1964, 1967; Ffowcs-Williams, 1967).
It is apparent, therefore, that in water the usual definitions of sound
are not entirely applicable, and the distinction between rheotaxis and
hearing is not clear, As evidenced by the problems and discussions at a
recent conference on the lateral line of fishes (Cahn, 1967), the concern
over underwater bioacoustics has extended far below what is ordinarily
considered the audiofrequency range.
C. Sonic Mechanisms in Fishes
There appears to be little relationship between the morphology of
sound-producing mechanisms and phylogenetic position in fishes. At the
present time, however, only a few hundred out of more than 20,000
species have been clearly identified as sound producers. Many species,
such as certain deep-sea forms (N. B. Marshall, 1967), appear to possess
the means for sound production but have not yet been recorded. Three
general types of sonic mechanisms are present in fishes: stridulatory, hydrodynamic, and swim bladder. Stridulatory sounds are produced by
friction of teeth, fin spines, or bones. Hydrodynamic sounds result from
swimming movements, especially during rapid changes of direction or
velocity. The swim bladder acts as a sound projector when it is vibrated
by contiguous or attached muscles.
1. STRIDULATORY MECHANISMS
A large majority of teleost fishes possess opposing patches of denticles
in the pharynx and are at least potentially capable of sound production
during feeding. Some species stridulate pharyngeal denticles in connection with other activities such as alarm and territoriality. The best known
sound producers of this type are members of the family Pomadasyidaethe grunts (Fig. 3 ) . Burkenroad (1930) described the sounds and the
mechanism in some detail for the white grunt, Haemulon plumieri. He
also noted that if the swim bladder were deflated, the character of the
sound became “dry” and lost its “gruntlike” quality. He concluded that
the swim bladder acts as a “resonator.” A similar arrangement has been
described for other members of the family, and the margate fish,
Haemulon album, has been observed to emit sounds, probably produced