Full Description

"Males generally produced non harmonic, multiple-pulsed sounds that lasted for several seconds (3.5 ± 1.3 s) with a pulse period of ca. 100 ms. Juvenile and female sounds were recorded for the first time in ophidiids. Female sounds were harmonic, had shorter pulse period (±3.7 ms), and never exceeded a few dozen milliseconds (18 ± 11 ms). Moreover, unlike male sounds, female sounds did not have alternating long and short pulse periods. Juvenile sounds were weaker but appear to be similar to female sounds."

"Multiple-pulsed sounds (Figure 6) were isolated from tank and field recordings. In both cases, the mean call duration was between 3.5 s and 4 s (Table 1), and was significantly (p < 0.05) correlated to pulse number (r2 = 0.86 and r2 = 0.59, respectively). The pulse period duration increased progressively in the first part of the sound before alternating between long and short durations. The alternation started at the 15th ± 3 (N = 26) pulse in captivity and 14th ± 2 (N = 20) in the field. In tank recordings, the number of pulses in a call fluctuated between 3 and 55 (median: 31 ± 10.3, N = 29) and field recordings varied from 31 to 53 (median: 40.5 ± 6.3, N = 20). Call duration and alternation start were not significantly different (p > 0.05) between the field and the tank sounds but pulse number, pulse period, and pulse duration were (Table 2). However, means and standard deviations of all temporal variables were similar in both recording situations (Table 1). Power spectra of male multiple-pulsed sounds revealed no harmonic patterns (Figure 7) as evidenced by sound energy that was generally concentrated in two peaks with no consistent mathematical relationship between them. In captivity, the means were 541 ± 493 Hz (N = 27) and 884 ± 570 Hz (N = 28). It was 191 ± 7 Hz (N = 19) and 355 ± 59 Hz (N = 19) in the field. Despite the higher frequencies present in some sounds recorded in captivity, shapes of power spectra from field and tank sounds are quite similar (Figure 7). In captivity, peaks present at high frequencies could be due to tank resonance."

"Some sounds (blue ellipses in Figure 8) recorded in aquaria possessed high frequency peaks (>500 Hz). The remaining sounds, however, possessed a similar distribution of frequency peaks as sounds in the field: 1st main frequency 195 ± 40 Hz (N = 17) and 2nd main frequency 347 ± 55 Hz (N = 14). Single pulse sounds (Figure 6 and 9) were recorded in captivity but not in the field. Their waveform was similar to the waveform of pulses isolated from multiple-pulsed sounds (Figure 9). In addition, the pulse duration was 12.4 ± 6.3 ms (N = 17) in single pulse sounds while it was 16 ± 13 ms (N = 921) for multiple-pulsed sounds in captivity. Spectral data showed high variability for 2nd main frequency (1068 ± 417 Hz, N = 17). However, the 1st main frequency (180 ± 48 Hz, N = 17) was less variable and closer to the 1st main frequency in the field (191 ± 7 Hz, N = 19). The power spectrum of a single pulse sound was shown in Figure 7."

"Sounds produced by 4 adult females were first identified in tanks (Figure 6). They were produced spontaneously during nighttime but associated fish behaviors remain unknown."

"Females emitted shorter calls (18 ± 11 ms, N = 56 in captivity and 20 ± 10 ms, N = 20 in the field) than males. Mean call duration of female sounds was similar to the mean duration of individual pulses from male calls. However, female sounds were described as multiplepulsed sounds because they were composed of a highly variable number of repeated units that had a relatively stereotyped waveform (Figure 6). This was not observed in male pulses (Figure 9). The number of pulses in female sounds varied from 2 to 12 in captivity and from 3 to 13 in the field. In captivity, the pulse period was 4 ± 1.2 ms (N = 249) and the pulse duration was 0.7 ± 0.2 ms (N = 310). These variables were similar in the field: 3.7 ± 0.7 ms (N = 105) and 0.8 ± 0.4 ms (N = 121), respectively. Spectral characteristics of female sounds strongly suggested that they were harmonic (Figure 7). The fundamental frequency was 246 ± 28 Hz (N = 50) in captivity and 249 ± 23 Hz (N = 18) in the field. There is a direct relationship between the fundamental frequency and the pulse period. Indeed pulse period is close to the inverse of fundamental frequency (Table 4). Moreover, in each case, these sounds presented at least a first and a second harmonic (Table 3 and Figure 7). Call duration, pulse number, pulse period, fundamental frequency, and 1st harmonic did not differ significantly between calls from the field and captivity but pulse duration and 2nd harmonic did (Table 5). These results tend to confirm the identification of female sounds on field recordings. The observed differences in pulse duration should be considered with caution because of the extremely short pulse duration in calls from both environments. Further, the differences between pulse duration are about 10-4 second (Table 3) and the methods employed to measure pulse duration have limited precision at this scale."

"Juveniles were found to emit spontaneous sounds which waveforms were similar to female calls (Figure 6). However, the signal to noise ratio was not high enough in most of the files to permit a quantitative comparison with calls from adults. For a few of the loudest sounds it was possible to perform an analysis. Call duration (27.3 ± 15.6 ms, N = 4), pulse number (5.5 ± 1.7 ms, N = 4), pulse period (5.9 ± 2 ms, N = 18), and pulse duration (0.9 ± 0.5 ms, N = 22) were measured. Juvenile calls were found to have longer pulse period durations than female calls recorded in captivity (Mann–Whitney U test, p < 0.05). No differences were observed for the other three variables (p > 0.05). The sounds contained harmonics and fundamental frequency was situated between 162 Hz and 352 Hz. Additional data are required for a precise description of spectral characteristics."

"A trend between pulse period and temperature is evident among existing datasets (14 to 21°C in captivity, 21.5°C in the field, and 23.5°C from Parmentier et al. [9]): shorter pulse periods were recorded at higher temperatures. Temperature-related variation in sound frequency spectra is less apparent because of the large variability observed in sounds recorded in captivity."

"However, 1st and 2nd main frequencies described by Parmentier et al. [9] in September 2008 were 226 ± 1 Hz and 410 ± 1 Hz, which is slightly higher than data from July 2010 (191 ± 7 Hz, N = 19 and 355 ± 59 Hz, N = 19)."

Observation Environment Quotes

"Twenty-four Fish, 67 to 217 mm TL (total length), were caught during May and July 2010 near the Cetina estuary in Dùlce-Glàva, Croatia (43°26 N, 16°40 E). They were trapped with a beach seine (22 m long, mesh size of 4 mm at the outer wing and 2 mm at the central part) in shallow water (<2 m depth) from 21:00 to 02:00. Then, they were held for one week in a 250 l tank at the Institute of Oceanography and Fisheries in Split (Croatia). Finally, they were transported to Liège (Belgium) and kept in a 1000 l tank with a 0.1 m high sandy bottom. In August 2010, an additional specimen was caught with a small hand net during a scuba dive at Banyuls-sur-mer, France (42°28 N, 3°08 E)"

"In July 2010, the DSG was used mainly during night time (21:30 to 04:30, UTC + 1) and recorded 10 min each 30 min. It was placed 70 m from the beach of Dùlce-Glàva at a depth of 2 m. These recordings were investigated for sounds produced by O. rochei."

"Four females (198, 200, 205, and 209 mm TL) were free to swim in a tank of 700 l. Sounds were recorded with the DSG from 21 September 2010 to 19 October 2010."

Behaviour Description Quotes

"Behaviors associated with sound production of this fish remain unknown."

Sound Name Quotes

"Males generally produced non harmonic, multiple-pulsed sounds that lasted for several seconds (3.5 ± 1.3 s) with a pulse period of ca. 100 ms. Juvenile and female sounds were recorded for the first time in ophidiids. Female sounds were harmonic, had shorter pulse period (±3.7 ms), and never exceeded a few dozen milliseconds (18 ± 11 ms). Moreover, unlike male sounds, female sounds did not have alternating long and short pulse periods. Juvenile sounds were weaker but appear to be similar to female sounds."