Full Description

"Field recordings of territorial, nest-guarding male midshipman during the breeding season identified a diverse vocal repertoire composed of three basic sound types that varied widely in duration, harmonic structure and degree of amplitude modulation (AM): ‘hum’, ‘grunt’ and ‘growl’. Hum duration varied nearly 1000-fold, lasting for minutes at a time, with stable harmonic stacks and little envelope modulation throughout the sound. By contrast, grunts were brief, ~30–140_ms, broadband signals produced both in isolation and repetitively as a train of up to 200 at intervals of ~0.5–1.0_s. Growls were also produced alone or repetitively, but at variable intervals of the order of seconds with durations between those of grunts and hums, ranging 60-fold from ~200_ms to 12_s. Growls exhibited prominent harmonics with sudden shifts in pulse repetition rate and highly variable AM patterns, unlike the nearly constant AM of grunt trains and flat envelope of hums. Behavioral and neurophysiological studies support the hypothesis that each sound type’s unique acoustic signature contributes to signal recognition mechanisms. Nocturnal production of these sounds against a background chorus dominated constantly for hours by a single sound type, the multiharmonic hum, reveals a novel underwater soundscape for fish."

"Our prior studies of the nesting and reproductive behavior of midshipman fish held in captivity show that type I males build and defend nests, acoustically court females with hums, and produce grunts and growls in agonistic contexts (Bass et al., 1999; Brantley and Bass, 1994; Genova et al., Novel underwater soundscape: acoustic repertoire of plainfin midshipman fish Eileen L. McIver1,*,†, Margaret A. Marchaterre1,†, Aaron N. Rice2,† and Andrew H. Bass1,3,†,§The Journal of Experimental Biology 2378 2012). Type II males follow a sneak and satellite spawning tactic and, like females, are only known to produce isolated grunts that have a very low amplitude compared with type I male sounds (Brantley and Bass, 1994)."

"Our prior study showed that grunts are produced in agonistic contexts (Bass et al., 1999; Brantley and Bass, 1994). Grunts were broadband with most energy concentrated below 500_Hz and produced either singly or serially at regular intervals as a grunt train (Fig. 3A,B). Individual grunts were a repetitive series of spike-like sound pulses (Fig._3C). Because of their brevity, selected grunts were analyzed manually at regular intervals for PRR by dividing the time difference between the first and final pulse by the number of pulses in the grunt (which ranged from four to 15 pulses). For 26 grunt trains from three nests that ranged from two to 209 grunts (median 33), individual grunt (N=194) PRR and duration ranged from 81.3 to 142.8_Hz (mean ± s.d. 112.7±14.0_Hz) and from 28 to 138_ms (mean 73.8±24_ms), respectively. To show trends in temporal characteristics within a grunt train, Figs 4 and 5 illustrate a range of measures for a representative sample of 10 of the longer grunt trains varying from 30 to 209 grunts per train. As trains progressed, there was an overall increase in the duration of individual grunts (Fig._4A). The interval between grunts, or inter-grunt interval (IGI), was fairly stable throughout most of a train, with longer intervals sometimes occurring near the beginning and towards the end (Fig._4B). Although patterns varied, the PRR was generally higher at the beginning of a train (Fig._4C). These trends in temporal characteristics were most pronounced in the longest trains (>150 grunts), and a comparison of the first and last 10% of measured grunts within these trains showed a significant decrease in PRR and increase in grunt duration (Mann–Whitney non-parametric t-test, P<0.05) The pulse period (PP), the inverse of PRR, within a given grunt became longer the later it occurred in a single grunt (Fig. 5). That is to say, each sound pulse in a grunt was generally more delayed than the previous pulse (see Fig._5, inset). Hence, as the duration of grunts increased later in the train (Fig._4A), there was a concomitant decrease in average PRR (Fig._4C). We investigated the dependence of grunt PRR on ambient temperature. Given the change in the PRR of individual grunts within a train (Fig._4C), we assessed the average PRR across grunts in each train and tested its Pearson correlation with water temperature. A train’s average PRR showed a significant positive relationship with temperature (N=26 trains, R2=0.1887, P=0.0266). Individual grunts observed within a train also showed this correlation (N=28 grunts, R2=0.1866, P=0.0217)."

"Observational and underwater playback studies show that female, type I male and type II male midshipman are attracted to hums (Brantley and Bass, 1994; McKibben and Bass, 1998; McKibben and Bass, 2001). Hums were the longest duration midshipman sound recorded, and exhibited a fairly flat envelope with a stable F0 and a prominent harmonic stack throughout the entire duration (Fig. 6). Hums can last for more than 1_h (Ibara et al., 1983). Hum duration in the sample studied here (N=91 hums, nine nests) ranged nearly 1000-fold from 0.488 to 451.44_s (mean 70.11±88.78_s)."

"For the entire sample size, hum F0 ranged from 84.0 to 104.1_Hz (mean 96.8±5.4_Hz; N=91 hums, nine nests). Temperature variance at recording sites throughout the night (14.24 to 16.32°C) could largely account for the F0 range (see below). For this same sample, hum F0 measured over the time course of this sample of individual hums was highly stable, only varying by 0–6.0_Hz (mean 1.7±0.95_Hz). Hum F0 varied with water temperature, such that an increase in 1°C corresponded with a 5_Hz increase in F0 (N=24 hums sampled from four nests)."

"Growls are the least studied in a behavioral context but appear to be made by type I males in an agonistic context (Bass et al., 1999). For example, growls were heard (by A.H.B. and M.A.M.) from the nest illustrated in Fig._1C just prior to overturning the rocky shelter. Growls, like grunts and hums, were also produced repetitively although at more variable and longer intervals (Fig. 7). Duration was intermediate between that of individual grunts and hums, varying nearly 60-fold from 0.197 to 11.62_s (mean 2.76±2.49_s) (e.g. Fig._7). The complexity of growls (Fig. 8A) became especially apparent in spectrograms that revealed a prominent harmonic structure with abrupt frequency modulation (Fig._8B). Closer inspection showed that growls could often be separated into initial sections of variable though higher PRR ranging from 74 to 117.1_Hz (mean 106.5±6.37_Hz) (Fig. 9A,B) and a section towards the end of distinctly more variable amplitude and lower PRR ranging from 46.4 to 96.9_Hz (mean 70.9±9.31_Hz) (Fig._9C, right panel). The majority (67%) of growls analyzed exhibited this high-to-low PRR shift. The others began with a low PRR section, and many alternated back and forth between the two modes, yielding a vast range of sound variability (Figs_7–9). Background hums were always apparent in the spectrograms of growls (Figs_8, 9), as they were for grunts (Fig._3A) and hums (Fig._6A); similarly, background growls and grunts were also apparent in focal recordings of other sound types (Fig._3A, Fig._6A, Fig._8)."

"When accounting for the nest from which the sound was recorded, grunts had a significantly larger bandwidth than either growls or hums, but growls and hums were not significantly different from each other (ANOVA, F2,89=19.669, P<0.0001) (Fig. 11A). Hums had a significantly lower dominant frequency than grunts or growls, but grunts and growls were not significantly different from each other (ANOVA, F2,85=9.573, P<0.0002) (Fig._11B)."

"Cohen and Winn first illustrated midshipman sounds, identifying grunts and buzzes that likely correspond to the growls described in the current report (Cohen and Winn, 1967)."

"While the long duration hum of midshipman that can last for more than 1_h (Ibara et al., 1983) may be a rare acoustic character among fishes [but see Hawkins and Amorim for a 20_min hum-like signal in haddock (Hawkins and Amorim, 2000)], it draws attention to the significance of sound duration as a salient acoustic feature during social interactions."

"During the nocturnal breeding season, midshipman fish are faced with the essential listening task of distinguishing hums that advertise a male’s readiness to spawn from grunts and growls that indicate ongoing agonistic encounters (Bass et al., 1999; Brantley and Bass, 1994)."

Observation Environment Quotes

"The physical attributes of each sound type were quantified on the basis of ~60_h of recordings by one of us (M.A.M.) from 14 nests in their natural habitat in Washington State over the course of 7_days during the 1997 breeding season (5, 6, 7, 20, 22, 23 and 24 June). The study site was one of prior investigations of nesting habitat and spawning success of midshipman fish (DeMartini, 1988; DeMartini, 1991). Figs 1 and 2 show photographs of the site. DeMartini established nests with roofs of varying size that were made of cement. These same nest covers were still present when we conducted our studies and along with natural rocky coverings were chosen as focal nests with resident type I males for hydrophone recordings (Fig._1). "

"To obtain a robust sample size for assessing the relationship of hum F0 to body size and temperature, we (M.A.M. and A.H.B.) recorded the hums of type I males collected from nest sites in northern California and held at the Bodega Marine Laboratory under semi-natural conditions (see Genova et al., 2012)."

Behaviour Description Quotes

"Our prior studies of the nesting and reproductive behavior of midshipman fish held in captivity show that type I males build and defend nests, acoustically court females with hums, and produce grunts and growls in agonistic contexts (Bass et al., 1999; Brantley and Bass, 1994; Genova et al., Novel underwater soundscape: acoustic repertoire of plainfin midshipman fish Eileen L. McIver1,*,†, Margaret A. Marchaterre1,†, Aaron N. Rice2,† and Andrew H. Bass1,3,†,§The Journal of Experimental Biology 2378 2012). Type II males follow a sneak and satellite spawning tactic and, like females, are only known to produce isolated grunts that have a very low amplitude compared with type I male sounds (Brantley and Bass, 1994). "

"During the nocturnal breeding season, midshipman fish are faced with the essential listening task of distinguishing hums that advertise a male’s readiness to spawn from grunts and growls that indicate ongoing agonistic encounters (Bass et al., 1999; Brantley and Bass, 1994)."

Sound Name Quotes

"Field recordings of territorial, nest-guarding male midshipman during the breeding season identified a diverse vocal repertoire composed of three basic sound types that varied widely in duration, harmonic structure and degree of amplitude modulation (AM): ‘hum’, ‘grunt’ and ‘growl’. Hum duration varied nearly 1000-fold, lasting for minutes at a time, with stable harmonic stacks and little envelope modulation throughout the sound. By contrast, grunts were brief, ~30–140_ms, broadband signals produced both in isolation and repetitively as a train of up to 200 at intervals of ~0.5–1.0_s. Growls were also produced alone or repetitively, but at variable intervals of the order of seconds with durations between those of grunts and hums, ranging 60-fold from ~200_ms to 12_s. Growls exhibited prominent harmonics with sudden shifts in pulse repetition rate and highly variable AM patterns, unlike the nearly constant AM of grunt trains and flat envelope of hums. Behavioral and neurophysiological studies support the hypothesis that each sound type’s unique acoustic signature contributes to signal recognition mechanisms. Nocturnal production of these sounds against a background chorus dominated constantly for hours by a single sound type, the multiharmonic hum, reveals a novel underwater soundscape for fish."

"Cohen and Winn first illustrated midshipman sounds, identifying grunts and buzzes that likely correspond to the growls described in the current report (Cohen and Winn, 1967)."