Effects of Sound Intensity and Frequency on Negative Phonotaxis in Adult Bighead Carp
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsGeneral Evaluation
The manuscript (MS) investigates the ex situ sound harassment effects on Hypophthalmichthys nobilis (bighead carp), focusing on exposure duration under control and varying sound source level (SL) and frequency treatments. The experimental design is well structured and appropriate for the stated objectives. The study provides useful data on behavioral responses to acoustic stimuli, which could contribute to developing deterrent strategies for invasive carp management.
However, the manuscript requires substantial improvements in the Introduction and Discussion sections to strengthen its scientific context and interpretation of results. Below are detailed comments and suggestions.
Major Comments
Introduction
The Introduction is overly brief and lacks sufficient coverage of recent and relevant literature on acoustic deterrence and behavioral responses of invasive bigheaded carps. A more comprehensive review is necessary to define the study’s novelty and position it within existing research.
The following studies should be reviewed and cited, as they are directly relevant to the topic:
* “Evaluating COâ‚‚ and sound as an invasive bigheaded carp deterrent in a model lock and dam”
* “Acoustic and carbon dioxide deterrents for invasive bigheaded carps (*H. molitrix* and *H. nobilis*)”
* “A complex sound coupled with an air curtain blocks invasive carp passage without habituation in a laboratory flume”
* “Effect of Broadband Boat Motor Sound on the Schooling Behavior of Invasive Bigheaded Carp”
* “Acoustic deterrence of bighead carp (*H. nobilis*) to a broadband sound stimulus”
* “Acoustic and chemical conditioning and retention for behavioral deterrence in invasive bigheaded carps (*H. molitrix* and *H. nobilis*)”
Expanding this section will clarify the study’s novelty, highlight knowledge gaps, and better justify the research objectives.
Discussion
The Discussion is currently limited and should be **substantially revised** to provide deeper interpretation of findings.
The authors should compare their results with previous studies (as listed above) to identify consistencies or differences in carp behavioral responses to various sound frequencies and intensities.
The ecological and management implications of the findings should be addressed — for example, how effective specific frequency ranges might be in field deterrence applications.
The Discussion should also emphasize the limitations of the ex situ model and suggest how these results could inform in situ experiments.
Language and Clarity
While the Abstract and Methods are generally clear, the manuscript would benefit from language polishing to improve flow and clarity, particularly in the Discussion section.
Ensure consistent terminology for acoustic parameters (e.g., “sound source level” vs. “sound pressure level”) and biological responses (e.g., “avoidance behavior,” “harassment response”).
Recommendation
Major Revision: The experimental framework and data presentation are solid; however, the manuscript’s contextual depth and discussion must be expanded through a more comprehensive literature review and comparative analysis.
Author Response
General Evaluation
The manuscript (MS) investigates the ex situ sound harassment effects on Hypophthalmichthys nobilis (bighead carp), focusing on exposure duration under control and varying sound source level (SL) and frequency treatments. The experimental design is well structured and appropriate for the stated objectives. The study provides useful data on behavioral responses to acoustic stimuli, which could contribute to developing deterrent strategies for invasive carp management.
However, the manuscript requires substantial improvements in the Introduction and Discussion sections to strengthen its scientific context and interpretation of results. Below are detailed comments and suggestions.
RE: We really appreciate your comments and have revised the manuscript according to your comments, please see below.
Introduction
The Introduction is overly brief and lacks sufficient coverage of recent and relevant literature on acoustic deterrence and behavioral responses of invasive bigheaded carps. A more comprehensive review is necessary to define the study’s novelty and position it within existing research. The following studies should be reviewed and cited, as they are directly relevant to the topic: “Evaluating COâ‚‚ and sound as an invasive bigheaded carp deterrent in a model lock and dam”, “Acoustic and carbon dioxide deterrents for invasive bigheaded carps (H. molitrix and H. nobilis)”, “A complex sound coupled with an air curtain blocks invasive carp passage without habituation in a laboratory flume”, “Effect of Broadband Boat Motor Sound on the Schooling Behavior of Invasive Bigheaded Carp”, “Acoustic deterrence of bighead carp (H. nobilis) to a broadband sound stimulus”, “Acoustic and chemical conditioning and retention for behavioral deterrence in invasive bigheaded carps (H. molitrix and H. nobilis)”. Expanding this section will clarify the study’s novelty, highlight knowledge gaps, and better justify the research objectives.
RE: Thank you for the relevant literature. We have reviewed and cited them “Culotta et al. (2024), Kramer et al. (2024) and Frett et al. (2025) evaluated and boat motor sound and dissolved CO2 as a bigheaded carp deterrent [20-22]. Vetter et al. (2017) compared the differences in the effects of single-frequency sound and broadband sound on behavior in bighead carp [15]. Dennis et al. (2019) reported a complex sound coupled with an air curtain efficiently blocked bigheaded carp passage [23]. To support the development of effective sound barrier technology for bigheaded carp, effects of sound intensity and frequency on phonotaxis should be studied” (Line 72-77).
Discussion
The Discussion is currently limited and should be **substantially revised** to provide deeper interpretation of findings. The authors should compare their results with previous studies (as listed above) to identify consistencies or differences in carp behavioral responses to various sound frequencies and intensities.
RE: Following your good suggestion, we have added information “In this study, the sound intensity in the high-intensity area (single-frequency sound) is ~150 dB (Fig. 3), and the bighead carp showed negative phonotaxis (Fig. 4). Vetter et al. (2017), Dennis et al. (2019) and Frett et al. (2025) also performed experiments with a sound intensity of ~150 dB (complex sound) and obtained similar results” (Line 208-210).
The ecological and management implications of the findings should be addressed — for example, how effective specific frequency ranges might be in field deterrence applications.
RE: Thanks for your suggestion. We have added information “In this study, 300-1000 Hz were effective sound frequencies for deterring bighead carp (Fig. 5) and their effectiveness should be further confirmed in field deterrence applications in the future” (Line 226-228) and “In this study, the sound intensity in the high-intensity area (single-frequency sound) is ~150 dB (Fig. 3), and the bighead carp showed negative phonotaxis (Fig. 4). Vetter et al. (2017), Dennis et al. (2019) and Frett et al. (2025) also performed experiments with a sound intensity of ~150 dB (complex sound) and obtained similar results. Therefore, ~150 dB is an effective sound intensity for bighead carp. Its effectiveness should be further confirmed in field deterrence applications in the future” (Line 208-213).
The Discussion should also emphasize the limitations of the ex situ model and suggest how these results could inform in situ experiments.
RE: Thanks for your suggestion. We have added information “In this study, there were ex situ model tests which have certain limitations; therefore, we should further confirm these results in situ experiments” (Line 242-423) and “this study was conducted with static water. The effect of flowing water on negative phonotaxis needs to be explored” (Line 244-245).
Language and Clarity
While the Abstract and Methods are generally clear, the manuscript would benefit from language polishing to improve flow and clarity, particularly in the Discussion section. Ensure consistent terminology for acoustic parameters (e.g., “sound source level” vs. “sound pressure level”) and biological responses (e.g., “avoidance behavior,” “harassment response”).
RE: We appreciate your valuable advice and will pay attention to this in future experiments. We used the term “dB” (sound pressure level) in generally, but in Table 1 we used the term “mV” (sound source level). If dB were used to report and create Table 1, the paper would be more meaningful. However, we only tested the sound intensity under some speaker power conditions, making it difficult to express the entire Table 1 in dB form. Therefore, we chose to use speaker power to create Table 1. We fully agree with your suggestion and will pay attention to this issue in future research, using dB to present this data. Thank you again for your advice. On the other hand, when we discussed the behavior of fish in response to sound, we uniformly use the term "negative phonotaxis"; and when we discussed technology applications, we uniformly use the term "deterring fish".
Reviewer 2 Report
Comments and Suggestions for Authors
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Author Response
This interesting manuscript presents the effects of sound intensity and frequency on phonotaxis in adult bighead carp. The manuscript has quality to be published, however, I believe the manuscript could be further improved by addressing, in greater detail, several important aspects.
RE: We really appreciate your comments and have revised the manuscript according to your comments, please see below.
The use of fish originating from aquaculture may represent a limitation for the sound stimulus due to the potential habituation effect under their original rearing conditions. Therefore, the acoustic conditions of the aquaculture environment should be characterized and discussed if appropriate.
RE: The fish farming ponds were in rural areas, so the acoustic scene around the fish living environment was natural. Hence, before this study, the tested fish had never encountered the experimental single-frequency sound, which is good for the experimentation (Line 86-88).
What modification was made to the test tank to absorb sound? Which absorbing material was used?
RE: This experiment was performance in Fishery Machinery and Instrument Research Institute of Chinese Academy of Fishery Sciences (section of Acknowledgments). I am very sorry. Although we consulted them to obtain information about the silencing material, they said that the silencing material came from other companies and that the formula of the silencing material was a trade secret and could not be provided. But we know it is similar to porous sponge (Line 95-96). And we point out in the paper that the silencing pool experiment was carried out in this laboratory.
The sound should be characterized by its frequency (Hz) and intensity (dB). The text alternates between reporting intensity in dB and electrical signal intensity in mV — this should be standardized to dB. Table 1 switches the frequency and intensity values.
RE: We appreciate your valuable advice and will pay attention to this in future experiments. If dB were used to report and create Table 1, the paper would be more meaningful. However, we only tested the sound intensity under some speaker power conditions, making it difficult to express the entire Table 1 in dB form. Therefore, we chose to use speaker power to create Table 1. We fully agree with your suggestion and will pay attention to this issue in future research, using dB to present this data. Thank you again for your advice.
There appears to be a positional preference of the control fish in the medium-intensity area — this relative advantage should be considered and taken into account in the results and conclusions. In my opinion, the high-intensity area should be considered when assessing stimulus efficiency (Figure 5), whereas the medium- and low-intensity areas should be treated as complementary analyses (behavioural gradient).
RE: The proportions of the cumulative time that fish spent in the medium sound intensity area was significantly higher than either the low or high sound intensity areas (p<0.001) (Fig. 4). This is attributed to the shelter provided by the mobile platform (Fig. 1) (Fish may have a tendency to rest in sheltered places and this may help them avoid predators) and avoidance of the physical barrier at each end of the pool (Line 198-202).
It is possible to observe in Figure 5 that, in the high-intensity zone, the frequencies of 400 and 800 Hz show the strongest negative phonotaxis. This aspect should be further explored and compared with available audiometry data for the species/family. The auditory capabilities of the species used are not characterized, particularly regarding the presence or absence of a Weberian apparatus. References to available audiometry studies for the species used, as well as for species of the same family, should also be included in the discussion.
RE: Following your comment, we have added some information “Vetter et al. (2017) reports that while broadband sound was better for deterring bighead carp, single-frequency sounds 500 Hz and 1000 Hz can also deterring bighead carp” (Line 224-226), “Cyprinids are ostariophysans, a superorder characterized by the Weberian apparatus connecting the swim-bladder to the inner ear and amplifying sound waves [8]” (Line 45-46) and “the bighead carp has a Weberian apparatus [8]” (Line 68).
Finally, it should be noted that these results cannot be extrapolated to other species or families, as morphological traits and trophic behaviours may significantly alter the outcomes.
RE: Thanks for the reminder. We have put this prompt at the end of the paper to hint the reader (Line 239-245).
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript (MS) is now better understandable for a publication in the journal. The authors covered and responded to my comments adding related scientific aspects. The MS was well improved ready to be accepted I can recommend.
Reviewer 2 Report
Comments and Suggestions for AuthorsAccept in present form
