Herbivorous Grass Carp (Ctenopharyngodon idella) Exhibit Greater Olfactory Response to Amino Acids Than Filter-Feeding Bighead (Hypophthalmichthys nobilis) and Silver Carp (Hypophthalmichthys molitrix)

Round 1

Reviewer 1 Report

Abstract:

Some of the language in this abstract is a bit awkward or incomplete.  For example: How could olfactory stimuli be used to support management? It is not intuitive. Electro-olfactory responses to 6 amino acids, each at different concentrations were assessed in the three carp species. 

The final sentence in the abstract seems somewhat vacant given the earlier claim in the abstract that the research could be used for advancing management measures for these pest fish species. Are you saying that the EOG results need to be verified as a behavioural response that could be of use for attracting pest fish for improving their control?

Key contribution:

This statement does not adequately reflect the key findings from the research and needs to be revised to do so.

Introduction:

The introduction would benefit from a much clearer statement on the connection between EOG and behavioral responses that could result in a useful management outcome, i.e., currently there is the inference that an EOG response do a chemical odor would result in an attraction behavioral response in the fish, it would be good to be clear as to whether or not EOG is a reliable proxy assay for behavioral responses.

Materials and Methods:

Experimental fish were held in captivity for extended periods (or raised in captivity and naive to wild conditions) and exposed to food items that they  would never  encounter in a wild situation, including artificial diets which are frequently high in key amino acids to promote attraction and gustation. Many species tune their sensory physiology to their environment, especially predominant food cues.  I think the author's need to specifically address how using captive fish for their research adequately represents the olfactory response that would reliably represent the olfactory response of wild fish taken from invasive environments.

I am interested that unsterilized well water was mixed with amino acids and then held for up to a month at 8-10 degrees C, which would make them entirely vulnerable to bacterial degradation of the amino acids.

The data analysis section is quite confusing as it is not until later in the section that it starts to become clear as to what variables were analyzed in what way.  The re-use of the same data for multiple statistical models does not appeared to be controlled for, only when undertaking multiple t-tests.

The results are characterized by high levels of variability in the measures, making it difficult to discern any differences that may be present in the data. Some commentary on this aspect of the results could be helpful.

Discussion:

The discussion is well written and covers off some of the points I raised earlier. The narrative thread jumps around a bit, especially discussing the link between EOG and expression of behavior, then going onto signal response and amino acid concentration, then returning to the control of behavior for management of pest fish - would seem the behavioral sections might be better directly linked.

English is good overall.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The results have a great significance in invasive species control, but it lacks support for amino acid feeding preferences in fish. Indeed, the protein hydrolysis occurs in natural water, in another words, the amino acid is commonly found in natural water and tolerance may develop in fish. Will this have an impact on the experimental results?

1: L122 Although the three species of fish are selected forom juveniles, there are still great differences in length and weight. Will this difference in size affect the results of the experiment?

2: L149 Why Ala is used in relative response? According the rule of food additives in introduction, the relative response should be preference or avoiding of fish feeding, so that have reference value.

3: L469 The temperature has been varified that is crucial influence factor in fish sensor, such as cilia sensor. The temperature change is significant in fig.1, the temperature should be considered in sensor injury.

Please have someone competent in the English language and the subject matter of your paper go over the paper and correct it?

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

Thank you for submitting very interesting research for the potential management of these species in the US river systems.

I feel that the rationale for the project, the technique used and the overall approach are very valuable and provide new insights with potential direct applications down the track. 

My main comments are in relation to the clarity and the overall efficiency of the writing. The methods and the experimental design are sometimes unclear and would need to be re-written for better readability, in order for future research to replicate this work mainly.

The lack of true control is a shame. If this cannot be added at this stage, please make sure to at least include a clear diagram and description of the study design, replication levels and use it to clearly define the several 'models' referred to throughout the text. This would help in better understanding the approach and increase the natural flow of ideas between sections. 

Please see detailed comments and suggestions in the attachment.

Kind regards.

Comments for author File: Comments.pdf

The grammar will need to be checked further and the sentencing reviewed to increase the clarity and efficiency of ideas and arguments being presented. Please see detailed comments and suggestions in the attachment.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Please find my suggestions in the attached file.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Dear authors,

Thank you for the prompt corrections and all the tracked changes made, which very much increase the clarity and impact of the paper. It is much easier to read and flowing from paragraph/argument to the next now.

All the edits made thoroughly improve the readability of the reported work, hence its replicability. Important justifications / clarifications were added to the methods section, specifically to the data analyses sub-section, which was paramount for better understanding the work done but also ensuring that the research could be replicated / results tested again.

Apart some suggested corrections in the abstract, I could not suggest further changes in the text at his stage.

Best of luck for the final edits, One of the reviewers.

Comments for author File: Comments.pdf

Dear authors,

I appreciate all the changes made in this regard too. The text read much better throughout the manuscript, well done.

Kindly, R

Author Response

See attached.

Author Response File: Author Response.pdf