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A comparison of sounds recorded from a catfish (orinocodoras eigenmanni, doradidae) in an aquarium and in the field.

Parvulescu (1) raised concerns regarding the suitability of a small glass aquarium for characterizing fish sounds based upon a theoretical consideration of sound echoes. Four out of eight authors who cited this paper most recently noted that small aquaria have complex acoustics, and the other four described the aquarium environment as yielding imprecise and poor quality sound recordings. Further advances in the study of sound production and communication in fishes require studies in controlled laboratory environments. Recently, Lugli (2) noted that waveforms and sound spectra were similar for field- and aquarium-recorded goby sounds. Okumura et al. (3) observed that artificially generated sounds recorded close to a hydrophone were free from acoustic artifacts. Whether more complex, natural fish sounds would also be artifactfree requires testing. We elicited sounds from a catfish and compared field and aquarium recordings which were specifically made close to the signal source.

We analyzed sounds produced by the swimbladder mechanism of a catfish in the disturbance context (fish are restrained by a human hand) underwater. Similar sounds were produced by the same fish in conflicts over resting sites (4). Many fishes that produce sounds in intraspecific behavioral contexts also "release" these sounds when restrained (5). We chose swimbladder sounds because they are a common mechanism of sound production for many fishes (6, 7).

We recorded sounds of nine individuals of a wild-caught neotropical catfish, the doradid Orinocodoras eigenmanni. Standard length ranged from 5.7 to 8.5 cm. Each individually recognizable fish was recorded twice in both recording environments. Recordings were conducted during 10 July-6 August 1992. Fish were positioned 7.5 cm from a hydrophone and 23 cm under the water surface. Fish were held with their left side toward and their swimbladder centered on the midpoint of the hydrophone. In the field (Jenkins Pond, Falmouth, MA) fish were recorded in a containment net. The net had a 60-cm diameter and 60-cm maximum depth. Water depth at the dock field site (Jenkins Pond) was 90 cm over a sand bottom. Aquarium recordings were conducted in a 10-gallon glass aquarium on a grass lawn near the pond. The hydrophone was suspended in the center of the water-filled aquarium. Fish were held in the same relative position to the hydrophone and water surface as in the field. Temperatures for recording dates in the aquarium a nd in the field were not different (24.7 [+ or -] 0.6 aquarium, 25.2 [+ or -] 0.3 field; n = 3). Sounds were recorded using a tape recorder (SONY Model WM-D6C: frequency response 40-15,000 Hz [+ or -] 3 dB). The hydrophone was pressure sensitive and had a frequency response range of 10 to 3,000 Hz (BioAcoustics, see 8 for specifications). The acoustic analysis software SIGNAL (Engineering Systems, Belmont, MA) was used to digitize and analyze sounds (sampling rate 25 kHz). We only analyzed sounds which had clear pulse structure. Both recording environments occasionally yielded some sounds with obscured pulse number and waveform patterns, due to spurious background noise or fish movements.

Spectrograms of over 800 sounds were evaluated (580 field, 275 aquarium). The catfish produced similar numbers of sounds in both recording environments. A minimum of ten sounds were produced by each individual on each sampling date. The same types of sounds were produced by individuals in both recording environments. Sound duration ranged from 30 ms to 2,400 ms.

In order to assess whether sounds were altered in the aquarium environment compared to the field, we compared waveforms visually and pulse durations statistically for sounds from both recording environments. Waveforms of sound pulses for field and aquarium showed the same shapes (Fig. 1). No artifacts were noted. Pulse duration was measured for one sound per individual (n = 9) for seven pulses in the center third of the sound where pulse peak amplitudes were consistent. Individual pulse durations ranged from 6 to 7 ms and were not significantly different between field and aquarium environments (one way ANOVA). For aquarium-recorded sounds, the pulse duration mean was 6.5 (SE 0.07, n = 63). For field-recorded sounds, the pulse duration mean was 6.5 (SE 0.07, n = 63).

Disturbance context swimbladder sounds of a catfish showed no differences in pulse waveform or pulse duration when recorded close to a hydrophone in both field and small aquarium recording environments. Kastberger (9) observed that for field recordings of doradid sounds, pulse pattern was unchanged for up to 30 cm. Many fishes initiate sound production in close proximity to con-specifics (10, 11). These results suggest that a small aquarium environment can provide sound recordings that accurately represent the sounds a fish produces in the field, yielding reliable acoustic measurements.

The research was supported by the SUNY-ESF Barbara Sussman fund and Sigma Xi. Thanks to John Beckerly for providing aquarium space, and Matt Bohling, Eric Horgan and David Mann for technical assistance. Supported in part by Army Research Office Grant DAAG-55-98-l-0304.

Literature Cited

(1.) Parvulescu, A. 1967. Pp. 7-14 in Marine Bia-acoustics, vol. 2. Pergamon Press, Oxford.

(2.) Lugli, M., G. Pavan, P. Torricelli, and L. Bobio. 1995. Environ. Biol. Fishes 43: 219-231.

(3.) Okumura, T., T. Akamatsu, and H. Y. Yan. 2001. Bioacoustics (in press).

(4.) Kaatz, I. M. 1999. Ph.D. dissertation, SUNY College of Environmental Science and Forestry, Syracuse, NY. Pp. 162-213.

(5.) Fish, M. P., and W. H. Mowbray. 1970. Pp. 1-207 in Sounds of the Western North Atlantic Fishes. The Johns Hopkins Press, Baltimore.

(6.) Schneider, H. 1967. Pp. 135-158 in Marine Bio-Acoustics, vol. 2. Pergamon Press, New York.

(7.) Tavolga, W. N. 1971. Pp. 135-205 in Fish Physiology, vol. 5. Academic Press, New York.

(8.) Kaatz, I. M., and P. S. Label. 1999. Biol. Bull. 197: 241-242.

(9.) Kastberger, G. 1977. Zool. Jahrb. Physiol. 81: 281-309.

(10.) Ladich, F. 1997. Mar. Freshw. Behav. Physiol. 29: 87-108.

(11.) Myrberg, A. A., Jr. 1981. Pp. 395-424 in Hearing and Sound Communication in Fishes, Springer-Verlag, New York.

[Figure 1 omitted]
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Author:Kaatz, Ingrid M.; Lobel, Phillip S.
Publication:The Biological Bulletin
Article Type:Brief Article
Geographic Code:1USA
Date:Oct 1, 2001
Words:986
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