ROCKFISHES (genus Sebastes) comprise a very diverse

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1 Copeia 2009, No. 3, Sounds of Captive Rockfishes Ana Širović 1,2 and David A. Demer 1 Sound production by many fish species has been studied extensively, but little is known about sound production by rockfishes (genus Sebastes), and only a few species have been reported to be soniferous. To determine if additional rockfish species produce sounds, passive acoustic recordings were made during 2007/08 at Hubbs-SeaWorld Research Institute and Southwest Fisheries Science Center in tanks containing Bocaccio (S. paucispinis), Cowcod (S. levis), Starry Rockfish (S. constellatus), and Sunset Rockfish (S. crocotulus). Data were collected using pre-amplified hydrophones (HTI- 94-SSQ) and digitized at sample rates of 44,100 or 8,000 Hz (using an Edirol R-09 recorder or Edirol UA-5 sound card and Ishmael software, respectively). Three distinct sounds were recorded in tanks containing only S. paucispinis and two of those sounds occurred at different rates during light and dark conditions. Their common characteristics were low frequency (below 800 Hz), short duration (,4 s), and low source levels ( db re: 1 mpa at 1 m). Also, there was evidence one or more other species produced sounds. These findings indicate that more rockfishes produce sounds, and suggest passive acoustics could be a useful tool for remotely monitoring their populations. ROCKFISHES (genus Sebastes) comprise a very diverse group consisting of just over 100 species, many of them living sympatrically in the northeast Pacific Ocean (Love et al., 2002). Many species, like Cowcod (S. levis), Bocaccio (S. paucispinis), and Vermilion Rockfish (S. miniatus), are slow growing, long lived, and late maturing (Love et al., 2002; Butler et al., 2003). They inhabit a variety of depths ranging from subtidal to over 1000 m, with some species found on the bottom (S. levis and Starry Rockfish, S. constellatus) and others schooling in the water column (S. miniatus and S. paucispinis). Most rockfishes are territorial with small home ranges (S. levis and S. paucispinis) and some show diurnal activity patterns (S. paucispinis, Starr et al., 2000). Many rockfish species have been heavily exploited by fisheries. Sebastes levis and S. paucispinis have been declared overfished by the National Marine Fisheries Service (Butler et al., 1999; Parker et al., 2000), while S. miniatus represents currently the top recreational fishery in southern California (MacCall, 2005). A new level of complexity to population estimation and management of S. miniatus has been added with a recent finding of a new cryptic species, called Sunset Rockfish (S. crocotulus; Hyde et al., 2008), generally found at depths greater than 100 m. Rockfish population estimation in southern California relied on fisheries data, and with the closing of a large part of the Southern California Bight (SCB) to fishing to protect S. levis, it has become imperative to develop non-lethal methods for population surveys (Yoklavich et al., 2007). Passive acoustic methods have been employed successfully for years to monitor marine animals (especially cetaceans, Clark and Ellison, 1989). Their application to fishes could provide a relatively inexpensive method to monitor population dynamics of soniferous fishes (Rountree et al., 2006; Gannon, 2008). The challenge in the past has often been linking the sounds from the wild to a particular fish species, particularly for the Pacific Ocean species (Fish, 1964; D Spain and Batchelor, 2006). This problem can be addressed with recordings of known species found in the Pacific Ocean in tanks which emulate natural conditions (e.g., light levels, bottom structure, school size, etc.) as closely as possible. These recordings should yield sounds similar to the sounds that can be expected from the fish in the wild. Sound production in fishes is relatively widespread (Fish and Mowbray, 1970; Hawkins, 1986; Kaatz, 2002; Rountree et al., 2006), yet most fish have a relatively limited acoustic repertoire (Amorim, 2006). Fish sounds are commonly comprised of low frequency pulses of variable duration, number, and repetition rate (Winn, 1964). Scorpaeniformes is one of the numerous orders of soniferous fish, and its sound-producing species include several from the genus Sebastes (e.g., S. atrovirens, S. carnatus, S. chrysomelas, S. melanops, S. nebulosus; Hallacher, 1974; Fletcher, 1981; Nichols, 2005). Behaviors associated with sound production documented thus far include agonistic encounters and territorial defense (Hallacher, 1974; Fletcher, 1981). It was hypothesized decades ago that gasbladder muscles in rockfishes may function in sound production (Hallacher, 1974); therefore, it seems plausible that more species in this diverse order produce sounds. We made passive acoustic recordings in the presence of four rockfish species (S. levis, S. paucispinis, S. crocotulus, and S. constellatus) held in tanks at Hubbs-Sea World Research Institute (HSWRI) and the Southwest Fisheries Science Center (SWFSC). Our goals were to investigate whether they produce sounds, if their sounds are species specific, and if they are more likely to occur at a particular time of the day. MATERIALS AND METHODS Recordings were made in the presence of four rockfish species including S. paucispinis, S. levis, S. crocotulus, and S. constellatus, in tanks at HSWRI in April and June 2007 and January 2008 (Table 1). One-half-hour and one-hour recordings in June and January, respectively, were collected while the tank pumps were turned off. Also, S. paucispinis and S. constellatus were recorded in single-species tanks at the SWFSC in March and April 2008 (Table 1). The fork and total lengths of five S. paucispinis held at SWFSC were measured as well. There were no other fishes or invertebrates in any of the tanks. 1 NOAA Fisheries, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, California Present address: Alaska Pacific University, Department of Environmental Science, 4101 University Drive, Anchorage, Alaska 99508; asirovic@alaskapacific.edu. Send reprint requests to this address. Submitted: 17 July Accepted: 26 February Associate Editor: E. Schultz. F 2009 by the American Society of Ichthyologists and Herpetologists DOI: /CP

2 Širović and Demer Sounds of captive rockfishes 503 Table 1. Tank Treatments: Number of Individuals of Each Species Present in Each Tank and the Total Number of Hours Recorded during Each Session. Tank name (type) Sebastes paucispinis Sebastes levis Species Sebastes crocotulus Sebastes constellatus Scorpaenichthys marmoratus Tank 1 (I) Tank 2 (I) Tank 3 (I) Tank 4 (II) Tank 5 (III) Tank 6 (III) Apr 07 Jun 07 Hours Jan 08 Mar/Apr 08 Sounds were recorded in six different tanks, with tank types I and II at HSWRI and tank type III at SWFSC. Type I tanks were round, with 2.44 m diameter and 1.52 m height, with an additional 0.56 m high cone cover, through which hydrophones were lowered into the tank. The tanks were filled 1.2 m with seawater at 14uC. Type II tank was oval with the maximum length of 6.4 m and rounded at the ends with 1.3 m radius. The tank was 2.5 m wide and 2.2 m tall. The hydrophones were lowered into the middle of the tank from the walkway on top of the tank. All type I and II tanks had various objects in them (artificial rocks in tank 4 and chairs and ladders tanks 1 3), and care was taken to lower the hydrophones in areas that provided the least amount of acoustic shadowing from these objects. Light levels in type I and II tanks emulated those expected at depths where the fish naturally reside. At night, to simulate oceanic conditions, the tanks were covered to eliminate light from the surroundings. Type III tanks were round with a 2 m diameter and 0.9 m depth. The water level was 0.6 m. The top of the tank was open, and one half was covered with a Styrofoam board to create a shaded section inside the tank. The hydrophone was suspended from the Styrofoam, in the middle of the tank, approximately 0.2 m off the bottom. The food that was provided for the fish was located on the bottom of the tank, underneath the hydrophone. The lights in the room with type III tanks were switched off automatically at 1830 hr and on at 0600 hr Pacific Standard Time. Recordings were obtained using one or two HTI-94-SSQ (High Tech, Inc., Gulfport, MS) pre-amplified hydrophones with a flat ( db re: 1 V/1 mpa) frequency response from about 20 Hz to 30 khz. The pre-amplifiers were powered by a 9 V battery (2008 recordings) or an AC-to- DC supply (2007 recordings). On most occasions, the hydrophones were connected to an Edirol R-09 handheld recorder (frequency response: 20 Hz to 22 khz). Data (16- bit) were recorded on two channels at 44.1 khz sample rate and stored as wav files on a 4GB SD card. On several occasions (13 18 June in tank 4, and both times in the SWFSC tanks), data were recorded directly onto a Dell Inspiron laptop using an external Edirol Audio capture UA-5 sound card. In those cases, data were sampled continuously on one channel at 8 khz using the software program Ishmael (Mellinger, 2002) and stored on a hard disk in 30- minute wav files. Data processing. The frequency and temporal characteristics of sounds of interest were measured using a program written in MATLAB (The Mathworks, Natick, MA). For short, frequency-modulated sounds, measurements were made in the frequency domain (with 1 Hz frequency and 0.1 s time resolutions) including duration (time between the beginning and the end of the sound) and minimum and maximum frequencies, and their means and standard deviations. For amplitude-modulated pulsing calls, pulse durations and rates were estimated in the time domain, the latter from the number of pulses and inter-pulse delays. The sounds were named based on their frequency and temporal characteristics for easier reference (Tables 2, 3). The names begin with a three-digit number which denotes the highest frequency of the sound. In one case with no dominant frequency, but with sidebands, the three-digit frequency number is replaced by SB. The following two letters describe the sound characteristics: IP individual pulse, RP repetitive pulse, and AM or FM amplitude or frequency modulated pulse, respectively. Recordings from the various tanks and sessions were compared to determine which sounds were produced by which rockfish species. Two types of automated sound detection were used to investigate diel patterns in the sound occurrence: spectral cross-correlation and energy sum (Mellinger and Clark, 1997, 2000). Frequency and temporal characteristics were used to develop kernels for spectral cross-correlation analyses using Ishmael. A kernel was developed for two common sounds (165-IP and 115-FM sounds), and crosscorrelations were performed for each kernel on all the data recorded at HSWRI. The kernel for 165-IP was set to detect sounds exceeding the detection thresholds for a period between 0.3 and 2 s, ranging in frequency from 160 to 130 Hz. The detection threshold was set low to allow a higher proportion of false positives and minimize missed calls. Spectrograms were generated with 32,876-point Fast Fourier Transforms (FFTs) with 90% overlap for R-09 recordings, and 8,192-point FFTs with 95% overlap for UA- 5 recordings. The frequency range was narrowed to avoid false triggering. The kernel for the 115-FM sound was set for frequencies between 110 and 90 Hz, with the same detection threshold settings and spectrogram characteristics as above. Two additional sounds (265-AM and SB-AM) were detected automatically using the energy sum detector in Ishmael. The detector was set to trigger on increases in energy in the frequency band between 170 and 200 Hz, which had relatively low noise in these recordings but was within the range of both call types. Again the detection threshold was set low to minimize missed calls, for duration between 0.3 and 3 s. When a detection event was triggered, a short wav file was automatically saved for subsequent inspection. All the saved files were verified for presence of

3 504 Copeia 2009, No. 3 Table 2. Frequency and Temporal Characteristics of Rockfish Sounds. Call type (tank number) Sample (n) Start freq. (Hz) End freq. (Hz) Mid freq. (Hz) Duration (s) Source level (db re: 1 mpa-1 m) 165-IP (1, 5) IP (4) NA 115-FM (2, 4, 5) FM (5) targeted sounds, and in the case of the energy detector, classified according to type. Diel patterns of four sounds that were detected more than 80 times were investigated (165-IP, 115-FM, SB-AM, and 265-FM). The significance in the difference in the number of detections during daylight and night conditions was tested with a goodness-of-fit test. The null hypothesis was that the number of detections was the same during light and dark conditions. Expected values were calculated based on the proportion of the recording effort that occurred in light and dark conditions (more recordings were collected during light than during dark conditions). Given the mostly diurnal activity of rockfishes (Starr et al., 2000), the alternative hypothesis was that rockfishes produce more sound during daylight. Source level estimation. The source level (SL) of a sound can be calculated from an estimate of the transmission loss (TL) and the measurement of the received level (RL), i.e., SL 5 RL + TL. To estimate transmission loss, one must know the range between the sound source and the recorder (r), assume a spreading loss function, and estimate the absorption loss characteristics of the medium (Fisher and Simmons, 1977). Knowing the dimensions of the tanks where recordings were collected, it was possible to constrain r as the maximum possible distance between the hydrophone to the farthest part of the tank. Also, as the depths of the tanks were comparable to their other dimensions, spherical spreading conditions were assumed (i.e., TL 5 20 log(r)) and absorption was considered negligible (Urick, 1996). Thus, an upper bound on the SL is estimated. The received levels were measured from the root-meansquare of the amplitude of the signal, averaged over a set time period (2 s for SB-AM, and 1 s for all other sounds). The hydrophones were calibrated by the manufacturer. The total system frequency response was measured for the UA-5 recording setup ( db from 20 to 8000 Hz) and applied to the measured received levels. No source level was reported for 125-IP and 800-RP sounds, as they occurred with high noise levels and it was not possible to reliably measure their received levels. RESULTS Three distinct sounds were recorded in tanks holding only S. paucispinis. No sounds were recorded in the tank holding a single S. constellatus. Three additional sounds were recorded in tanks holding multiple species, S. paucispinis, S. crocotulus, and S. levis. Common characteristics of all recorded rockfish sounds were low frequency (below 1000 Hz), short duration (,4 s), and relatively low source levels ( db re: 1 mpa at 1 m). Detailed characteristics of each sound are given in Tables 2 and 3. Sebastes paucispinis sound characteristics. The average fork length of the S. paucispinis held in tank 5 was mm. During the almost 80 h of recording in tanks containing only S. paucispinis, three distinct sounds were identified. One sound was a stereotyped solitary pulse, while the other two sounds showed more variation and often occurred with other sounds. The stereotyped pulsing sound occurred commonly in tanks 4 and 5, and the other two sounds occurred frequently only in tank 5. The most frequently occurring sound in tanks containing only S. paucispinis (tanks 1 and 5) was 165-IP (Fig. 1A). It is a stereotypical pulse: short, individual, quiet, low frequency, and often occurring with harmonics (Table 2). The 265-FM sound (Fig. 1B) was a moan that was recorded in tank 5. It was of relatively short duration, and it had more variation in the frequency range than there was in the 165- IP sound (Table 2). It occurred solo and with other more variable moans of comparable frequencies. This sound had the highest average source level. The SB-AM sound (Fig. 2) consisted of a series of quick repetitive pulses with amplitude modulation throughout its duration (Table 3). This sound was followed at times by a second, shorter, and more slowly pulsing variation of the same sound. In a modified version, this sound occurred either simultaneously with a moan similar to 265-AM, at the beginning or the middle of the pulsing, or consisted of a single, shorter duration pulsing sequence with a smaller number of pulses. The call characteristics of this sound were measured only when the longer version of the sound occurred without interference from other sounds. The modified, short version of the SB-AM sound was recorded only once in tank 1, but the longer sound was detected 88 times in tank 5. Other sound characteristics. The 115-FM type sound (Table 2) was recorded in the largest number of tanks (tanks 2, 4, Table 3. Characteristics of Pulsing Rockfish Sounds. Call type (tank no.) Sample (n) Number of pulses Total call duration (s) Pulse rate (pulses/s) Source level (db re: 1 mpa-1 m) SB-AM (5) RP (4) N/A

4 Širović and Demer Sounds of captive rockfishes 505 Fig. 1. Spectrograms of S. paucispinis pulse and moan sounds: (A) 165-IP recorded in tank 1 (44,100-point FFT, 90% overlap, Hanning window, band-pass filtered between 70 and 500 Hz) and (B) 265-FM recorded in tank 2 (8,000-point FFT, 90% overlap, Hanning window, band-pass filtered between 150 and 500 Hz). and 5), indicating it is produced by S. paucispinis, but also by at least one other rockfish species. This sound was frequency modulated, and it was recorded both solitarily (Fig. 3A) and as a part of a longer sequence of variable moans that lasted up to 6 s. It was the most common sound recorded in tank 4, and it was detected 135 times in tanks 2 and 4. The 125-IP sound (Table 2) was recorded during a quiet recording session (the pumps turned off) in tank 4 in January These were individual pulses, but occasionally they were repeated at an interval greater than 10 s (Fig. 3B). The 800-RP was a sequence of repetitive pulses (Fig. 3C) that was observed only once in tank 4, but as it has characteristics typical of fish sounds, it is reported here. Its pulsing rate was 2 pulses/s, and it was the longest recorded sound (Table 3). Diel patterns of sounds. All four sounds had significantly different numbers of detections during different light conditions (Table 4). Two S. paucispinis sounds, 265-FM and SB-AM, were more common in the dark (x ; df 5 1; P and x ; df 5 1; P , respectively), while one, 165-IP, was more common during light conditions (x ; df 5 1; P, 0.001). The 115-FM sound was detected more often during the dark hours (x ; df 5 1; P, 0.001). DISCUSSION Sebastes paucispinis produced a variety of sounds, including 165-IP, 265-FM, and SB-AM. Two additional sounds, 125-IP and 800-RP, were also produced by S. paucispinis, or they may have been produced by S. levis or S. crocotulus. The 115- FM sound was produced by more than one species. This sound was produced by S. paucispinis and either S. levis or S. crocotulus, or both. This could either be one sound, or a series of very similar sounds that were not distinguishable from each other using our characterization of sounds. Generally, sounds produced by S. paucispinis and other rockfishes had frequencies lower than 1000 Hz and were short duration pulses, although longer moans occurred as well. The maximum estimated SL of the recorded sounds did not exceed 113 db re: 1 mpa at 1 m, which is consistent with those previously reported for other fishes (Allen and Demer, 2003; Ladich and Myrberg, 2006; Wysocki, 2006). There were two sounds that currently cannot be positively linked to a single rockfish species: 125-IP and 800-RP. Both were recorded in a tank containing S. levis and S. crocotulus, as well as S. paucispinis. Given that these sounds were not recorded during the almost 80 h of data collected in tanks containing only S. paucispinis, it is probable that they are produced by either S. levis or S. crocotulus. Given their low rates of occurrence, S. paucispinis cannot be excluded. Alternatively, these sounds could be produced by more than one species, like the 115-FM sound. In these tank conditions, S. paucispinis appears to be the most soniferous of the four species held at HSWRI. They could be best suited for acoustic study in tanks, or it could be that their gasbladder muscle anatomy is the most favorable for sound production of the four species held in tanks. The similarity in some sounds recorded from multiple species (e.g., 115-FM) could be due to the fact that they are produced in similar ways. All the rockfishes that have been reported to produce sounds so far (Fletcher, 1981; Nichols, 2005), including S. paucispinis, have Type II gasbladder musculature, in which the extrinsic gasbladder muscle bypasses the pectoral girdle (Hallacher, 1974). Sebastes levis, S. crocotulus, and S. constellatus all have Type I musculature (the extrinsic muscle is attached to the pectoral girdle). While the species with Type I musculature produced some of the sounds in this study, their sounds were not as common as S. paucispinis sounds. To better address the full repertoire of sound production in S. levis, S.

5 506 Copeia 2009, No. 3 Fig. 2. Spectrogram (4,000-point FFT, 90% overlap, Hanning window, band-pass filtered between 130 and 600 Hz) and time series of S. paucispinis SB-AM sound recorded in tank 5. crocotulus, and S. constellatus, it would be useful to conduct recordings in single-species tanks for each of those species. It would be beneficial to have multiple individuals in each tank as well, since it is possible no sounds were recorded from the S. constellatus because it had no other fish for interaction. Fish produce sounds during a variety of social interactions, such as aggression, feeding, defense, or mating (Tavolga, 1971; Myrberg, 1981; Ladich and Myrberg, 2006; Myrberg and Lugli, 2006). In a review of the aggressive fish sounds, Ladich and Myrberg (2006) suggested that aggressive sounds tend to be broadband, while submission and courtship sounds have longer duration. Even though we do not know the behavioral context in which the sounds reported here were produced, we may be able to infer their possible function based on their characteristics. The 265-FM sound was the sound with the largest bandwidth and could be aggressive. Also, as it occurred with the SB-AM sound of longer duration, the two could be a part of an aggressive submissive interaction. More information on the function of the sounds may also be gleaned from the daily patterns of their production. Since S. paucispinis is a diurnal fish, it was unexpected that more of their sounds (265-FM and SB-AM) were detected at night. Sebastes paucispinis is known to move into the water column during the day (Starr et al., 2000). If they followed a similar behavioral pattern in the tanks, an increase in the production of these sounds at night could imply a possible function during aggressive interactions with other fish on the bottom, in the home territory. An interesting feature of the SB-AM sound is the large variation in the pulse rate among individual calls. In killer whales, calls with similar features can be used to identify individuals (Nousek et al., 2006). It is possible that pulse

6 S irovic and Demer Sounds of captive rockfishes 507 Fig. 3. Spectrograms of other rockfish sounds recorded in tank 4: (A) 115-FM, (B) 125-IP, band-pass filtered 60 to 200 Hz, and (C) 600-RP, bandpass filtered between 300 and 1,200 Hz. All spectrograms were generated with a 44,100-point FFT, 90% overlap, and Hanning window. Table 4. Number of Observed and Expected Detections of Each Call Type in Light and Dark Conditions. Call type Light-observed Light-expected Dark-observed Dark-expected 165-IP 265-FM SB-AM 115-FM

7 508 Copeia 2009, No. 3 rates may identify individual S. paucispinis as well. Or, if the pulse rate is dependent on the physiology of the gasbladder, the pulse rate could be related to anatomical characteristics of the fish, such as its length or maturity. We could not link individual sounds to individual S. paucispinis, but we observed variations both in pulse rate and fish length. Similar evidence of the links between features of animal sounds and their body sizes (particularly in males) has been found in Trichopsis vittata and Oreochromis mossambicus (Ladich, 1998; Amorim and Almada, 2005). In either case, this variation could be particularly valuable for monitoring S. paucispinis populations in the wild. The SB-AM S. paucispinis sound reported here is very similar to the motorboating sound reported by Thompson (1965) to have occurred in shallow water west of San Clemente Island in This is an indication that S. paucispinis produce this sound in their natural environment, and have been producing this sound for more than 40 years. Thompson (1965) also noted a strong diel occurrence of this sound, with higher rates during the night, which is consistent with our findings. Given these properties, this could be a useful tool for long-term monitoring of S. paucispinis populations in the SCB. There are a number of issues that arise from making recordings in tanks. Fishes in loud tanks could have damaged hearing (Amoser and Ladich, 2003; Smith et al., 2004) and therefore their sound production may be affected. Sounds recorded in small tanks are complicated by constrained sound propagation (Parvulescu, 1964, 1967). Waveform of fish sounds.1 ms, as the sounds reported here, would be distorted in our tanks (Akamatsu et al., 2002). On the other hand, the minimum resonant frequencies of the tanks (Akamatsu et al., 2002) were generally higher than the frequencies of the sounds of interest (the smallest was 469 Hz for the mode (1, 1, 1) in tank 4 at HSWRI). Therefore, there is probably no frequency-specific attenuation or SL bias in the reported values. Rockfishes produce sounds that can be both speciesspecific and shared among species. While the sounds are not loud, several species-specific sounds occur at high enough rates to be potentially useful for long-term monitoring of S. paucispinis populations. To use passive acoustics for abundance monitoring, the knowledge of the following information is required: sound produced by a species and the proportion of the population producing sounds, variation in calling during the day and the year, and relationship between call rate and metric of abundance (Gannon, 2008). This study starts to address the question of sound production by individual species, but a wider effort is needed for Sebastes and other Pacific Ocean species. Recordings should be collected in single-species tanks which emulate natural conditions (e.g., school size, light levels, noise levels, etc.) as closely as possible. Also, ability to localize individuals producing sounds would enable collection of information on the proportion of population producing sounds and the relationship between call rate and abundance metrics. A study to investigate the relationship between the variation in SB-AM sound and individual characteristics of fish, which would include localizing and tracking individuals, could provide enough information to make that sound useful for population monitoring. More recordings of other individual species in tanks are required before such monitoring can be applied to a greater variety of species. ACKNOWLEDGMENTS We thank J. Smiley and M. Drawbridge for giving us access to fish at Hubbs-SeaWorld Research Institute, L. Robertson for looking after the fish at the Southwest Fisheries Science Center, and J. Renfree for assistance with various parts of the project. LITERATURE CITED Akamatsu, T., T. Okumura, N. Novarini, and H. Y. Yan Empirical refinements applicable to the recording of fish sounds in small tanks. Journal of the Acoustical Society of America 112: Allen, S., and D. A. Demer Detection and characterization of yellowfin and bluefin tuna using passiveacoustical techniques. Fisheries Research 63: Amorim, M. C. P Diversity of sound production in fish, p In: Communication in Fishes. Vol. 1. F. Ladich, S. P. Collin, P. Moller, and B. G. Kapoor (eds.). Science Publishers, Enfield, New Hampshire. Amorim, M. C. P., and V. C. Almada The outcome of male male encounters affects subsequent sound production during courtship of cichlid fish Oreochromis mossambicus. Animal Behaviour 69: Amoser, S., and F. Ladich Diversity in noise-induced temporary hearing loss in otophysine fishes. Journal of the Acoustical Society of America 113: Butler, J. L., L. D. Jacobson, J. T. Barnes, and H. G. Moser Biology and population dynamics of cowcod (Sebastes levis) in the southern California Bight. Fishery Bulletin 101: Butler, J. L., L. D. Jacobson, J. T. Barnes, H. G. Moser, and R. Collins Stock assessment of cowcod. Pacific Fishery Management Council, Portland, Oregon. Clark, C. W., and W. T. 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