PONE-D-22-02571Isotopic signatures induced by upwelling reveal regional fish populations in Lake TanganyikaPLOS ONE

Dear Dr. Ehrenfels,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

I have now received three reviews of your manuscript. Because I first received two very different reviews I decided to send your manuscript to a third reviewer. Two of the reviews give rather coherent judgements which are in line with my own assessment of your manuscript. These reviewers, as do I, point to the problem that the manuscript lacks a necessary synthesis analyses of the results to be able to see whether or not they support your conclusions. You present very many results on which your final rather few conclusions rest which is challenging regarding use of statistical approaches. One of the reviewers suggests more synthetic analyses using multistatistical approaches (PCA, NMDS) to be able to demonstrate the relative strength of different driving variables.  The other reviewer suggests to give your results a better structure and focus using tables and/supplement to store details. I agree with both suggestions. Your result section, as it currently stands, is not convincing in supporting your discussion and conclusions. This is symptomatic from that the whole study lacks an overall appropriate statistical approach for analyzing basin-scale dynamics of food webs. Thus, you need to supply better statistical arguments to convince the reviewers and me that there is good support for your conclusions

The language is not up to standards as pointed out by one of the reviewers, for example in the abstract. This also includes many errors regarding references to statements e.g. lines 113-115, 119-120 and proper descriptions of statistical analyses (degrees of freedom, R2-values of regressions etc.). Also, I did not find numbers of sample sizes and there are often statements on differences without any analyses given. (e.g. lines 371-373, 382-383, 391-393, the whole paragraph starting with line 412). You need to thoroughly go through the whole manuscript to correct these types of errors. The success of your manuscript clearly depends on how you handle the reviewers’ and my comments. Therefore, in your response letter you need to supply detailed point by point comments to how you have dealt with the reviewers' and my comments

Please submit your revised manuscript by May 14 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Peter Eklöv

Academic Editor

PLOS ONE

Journal Requirements:

1. When submitting your revision, we need you to address these additional requirements.

Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at 

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and 

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. Thank you for stating the following in the Acknowledgments Section of your manuscript: 

(We are grateful for the support from our research collaborators at the Tanzania Fisheries Research Institute, particularly the Directors Rashid Tamatamah and Semvua Mzighani as well as Mary Kishe. Special thanks go to Mupape Mukuli as well as the captain and crew of the M/V Maman Benita for their steady toil in organizing and conducting the cruise work with us. We also thank Andreas Brand, Kathrin B.L. Baumann, and Tumaini M. Kamulali for their help during field work, Serge Robert and Fabian Kuhn for assistance in the lab, and Eliane Scharmin for administrative support. Special thanks go to Jessica A. Rick for providing help in the field, the data of the Lates genetic clusters, and comments on the manuscript. Thanks to Blake Matthews for insightful discussions. This work was funded by the Swiss National Science Foundation (grant CR23I2-166589). Thanks to the Tanzania Commission for Science and Technology (COSTECH) for granting the research  permits.)

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form. 

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: 

(This work was funded by the Swiss National Science Foundation. The grant CR23I2-166589 for the project titled “From biogeochemistry to the ecological genomics of pelagic fish stocks - a study across 4 trophic levels” was awarded to Bernhard Wehrli and Ole Seehausen (https://data.snf.ch/grants/grant/166589).

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.)

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

3. Please include your full ethics statement in the ‘Methods’ section of your manuscript file. In your statement, please include the full name of the IRB or ethics committee who approved or waived your study, as well as whether or not you obtained informed written or verbal consent. If consent was waived for your study, please include this information in your statement as well. 

4. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information. 

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This manuscript concerns measurements of stable carbon and nitrogen isotopes in fish tissues from Lake Tanganyika. Seasonally varying hydrology, with respect to patterns of upwelling and nutrient availability are hypothesized to affect changes to fish trophic structure – and thus community ecological function. A suite of limnological and biogeochemical parameters were measured to contextualize isotope measurements. The statistical analysis was sound, however sample sizes for some ellipses were quite small. This value wasn’t interpreted heavily though. Overall, interpretation is sound.

Reviewer #2: This paper study patterns of stable isotopes across the food web in Lake Tanganyika when the whole lake is stratified and when water is circulating resulting in differences in stratification and upwelling between the north and south parts of the Lake. The results suggest that differences in isotopic signal traverse the food web when there is water circulation but not when the lake is stratified. One conclusion of this pattern is that pelagic fish use “regional grounds” for foraging that should be accounted for in management.

Although there are no direct flaws in the paper it is very hard to read. Mainly the result section is very long and difficult to grasp the important information and I suggest to put detailed numbers and differences into a Table or Supplement. The result section could almost be summerised in: at the end of the rainy season no differences and at the end of dry season there was differences in the isotoic signal that was tracked through the food web.

I also have some concern regarding the title and the conclusion about “regional fish population”. The fish populations pick up the dC signal of their food but that does not mean they are “regional” (this is a bit problematic in itself as it is not defined what is meant, maybe causing a confusion). As far as I understand the isotopic signal does not reveal anything about where they spawn or how they move in the lake. Of course they don’t swim back and forth on a weekly basis but I don’t see any evidence against that a fish is in one part of the lake in one period and 7 month later in the other part, it will just pick up the current regional isotope signal. It would be informative to know how, when and where these fish species spawn, pelagic, demersal, littoral spwners, buoyant eggs? Although I can find it likely with some kind of regional population structure of these fish species I cannot see the evidence against it.

Specific comments

Abstract

Poorly written with many odd sentences, e.g. l. 26 (global warmin related), l. 31 (differences in habitat), l. 36-38 (regional forage grounds and record…gradients), l. 39-40 (regional population on a seasonal…), l 41 those?, l. 42-43 Not part of this study at all, l. 45-46 you don’t show these at all, l. 48 how does basin relate to regional?

Methods:

Reference or motivation to statement on l. 258.

l. 295. Fish was sampled from landing sites, not the sampling stations.

l. 303. In general are mixing models used to infer the diet of consumers from stable isotopes, but that has not been applied here, or? If not, why? Wouldn’t this show if they differ in diet between northern and southern area just not isotope signal?

Results

Far too long and detailed, see above.

l. 435 Compare with l. 415-418. Don’t seem to match to me.

Discussion:

l. 569-571: Why were these fractions not analyzed, sampling issues?

l. 580-581, Can’t there be competiotion from the nano- and picc phytoplankton also?

l. 607-620 Feels reduntant in this context.

l. 702, “phenotypic changes” is a bit odd in this context. From this study there is no indication (not studied) fish make any phenotypic changes (as number of gill rakers or gut length) or behavior (vertical migration, diet changes), all changes may just be an effect of the change in isotope signal of prey.

Reviewer #3: The authors provide seasonal isotopic data of two sites of Lake Tanganyika to study the regionality of the fish population. Authors have carried out massive sampling and provide detailed analysis based on the carbon and nitrogen isotopes. My main suggestion to the authors is to provide a picture of the whole food web in Lake Tanganyika based on the literature (add this as figure 1). Moreover, authors compare dry and rainy season and it would be interesting to know how phytoplankton communities are assumed to differ based on the literature. The introduction would greatly benefit if the introduction could describe whole food web starting from the phytoplankton – zooplankton -fish including a description of the main species. One could assume that upwelling is an important occasion for diatoms and diatom-based food web.

In the result section authors could also provide picture(s) of carbon and nitrogen values of all studied food web components of both sites and seasons. This could help readers understand seasonality and site impact at the whole food web level and to understand if the regionality is only related to the specific fish species or can we see systematical differences at the different trophic levels between north and south and seasonal effect. Or could you put whole of your data (isotopes, biotic and abiotic measurements) to the multistatistical analysis (PCA, NMDS) and show what is actually happening on these two seasons and sites.

Regarding on the nitrogen isotopes I wonder if the authors are aware of how upwelling influence on the nitrogen cycle and the uptake of nitrogen by primary producers (ammonium or nitrate, Bartrons 2009: DOI: 10.5194/bgd-6-11479-2009). This could explain differences in nitrogen values.

I recommend authors to add water temperature to picture 1 at least assumed range.

In the methods you describe that you have used the Folch method for lipid extraction, however, the Folch method uses chloroform, methanol, and water in the proportions 8:4: 3, please check your reference. Secondly, you do not have supernatant in the lipid analysis, but lower phase which includes lipids, and this phase is usually transferred to the new tube.

In figure 3 you could provide letter on which site station is located e.g. station 1 (N) or station 8 (S).

In line 541 you say that lipid content reduced by 43 to 45%, however, I would keep it more informative if you could provide real values, e.g. lipid content reduced from x to y.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PONE-D-22-02571R1Isotopic signatures induced by upwelling reveal regional fish populations in Lake TanganyikaPLOS ONE

Dear Dr. Ehrenfels,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. I have now received comments on your manuscript from two of the former reviewers. Although both found that the manuscript had improved in the line of their comments they also found that the message still needs to be clarified (see especially the result section). Most importantly, you need to convince the reviewers and me that your conclusions regarding regional fish populations and your suggestions of regional fisheries management hold according to data. As this is a major point of the manuscript on which you base your conclusions this also needs to be supported with a clear definition and hypothesis of what is expected from a "regional" population vs. lack of regionality (see especially comments of reviewer 2). You also need to respond to reviewer 3's comment on using multivariate statistics and merging single isotope pictures into one figure to show how different sites and season influence isotope value and food web structure.  Please submit your revised manuscript by Oct 14 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Peter Eklöv

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: (No Response)

Reviewer #3: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Partly

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: No

Reviewer #3: No

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

Reviewer #3: No

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: No

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: Although there have been several improvements of the manuscript I still find some weaknesses. In general, I still find especially the result section rather long and inconclusively written with a lot of detailed numbers that I think could be referred to figures (or Tables) instead. There is also a mix of presenting significant and non-significant results (compare l. 376, 391). I think for example you could remove or substantially shorten l. 342-353, 355-363, 384-386, 391-403, 433-448, 462-474, 482-486.

Maybe I was a bit unclear in my previous review or I misunderstand the interpretations of the result, but I cannot see that one of the main conclusions; “regional fish populations” hold based on this data. To expand my thoughts on this a bit. In the introduction it is referred to a study by Logan et al that “…isotopic study of fish and their surrounding food web along a geographical gradient can reveal regional population isolation if environmental differences among sites translate into divergent isotopic signatures of regional or local fish populations”. This is true but the cited study consider a global study comparing three different tuna-species over 16 years, which your study is not even close to. Importantly, they study GRADIENTS in isotopic signals whereas your paper focus on north and south samples, not a gradient, compare with Fig. 8 & 9 in Logan et al. In your study, if you assume all fish move completely random (i.e. no regional/spatial structure) fish will pick up signal of the food-web where it feeds, i.e. the differences in Fig. 4 are reflected in the fish in Fig. 5, or? Maybe I miss something important as I find it hard to pick out the important information in the result section, but I just don’t get how random movements will differ from movements with some “center of gravity”, unless you think fish traverse ~450 km (4°?) within a couple of weeks. Some clearly stated hypothesis of what is expected if there are “regional fish population” or not is necessary, especially as you don’t have extensive gradients as in Logan et al. Moreover, in the Conclusions it says “…regional fishery management strategies should consider including basin-scale quotas.” But what is basin-scale, from the profile in Fig. 2 there are no apparent “basins”? Based on your results, how many basins and where should the borders be according to you?

I find the study to be interesting also without any conclusions about fish population structure. However, I think the current focus on regional fish populations may be misleading.

Reviewer #3: Your revised version of the manuscript has improved especially illustration of figures 1-3 is now much better. You have added some correlation analysis, but you have skipped the main point for multivariate statistical analysis, which is to shorten and clarify the message of your manuscript. So, the point is to remove single isotope pictures (Fig. 4 c, d, g, h, I, j and Fig. 5) and have one stable isotope picture in PCA or NMDS plot which can clearly demonstrate how different site and season influence on the isotope value and food web structure. So, I still urge you to put all stable isotope data in PCA or NMDS and show your stable isotope data as one figure. See e.g. figure 4 in Ramos et al. 2009, who also published their paper in PlosOne doi:10.1371/journal.pone.0006236.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

Reviewer #3: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PONE-D-22-02571R2Pelagic fish in Lake Tanganyika are regionally sessile but lack local adaptationPLOS ONE

Dear Dr. Ehrenfels,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

 I have received comments from one of the reviewers and both this reviewer and I are quite happy about how you have dealt with the reviewers' comments and we both think that the manuscript is much clearer now. Nevertheless, there are still some minor clarifications needed, pointed out by reviewer 2, that you might want to consider, but these should be relatively easy to address.

Please submit your revised manuscript by Feb 04 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Peter Eklöv

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: Overall I think the authors have improved the writing, terminology and structure of the manuscript. I have some smaller issues but I think they can easlily be addressed by the authors.

1. I don't think the change of title was very successfull, don't really know what motivated this but think the former title is more informative.

2. I'm skeptic to 'regional sessile' as it imply they are some how fixed to some substrate. Maybe something along regional forage grounds that you use on l. 39 or so is better. As I understand actual spawning araes are not identidied?

3. To that respect, could region and basins be defined? it seems like the southern basin is >7 degree south, or? but what is northern basin/stock? On the map there is a central basin, but there were no fish samples from this basin if I got it right. So should this be a basin/region on its own or part of souty/north stock?

4. On l. 40-41 you write "...fish reside in a region for a season or longer." You should clarify that you have studied seasonal variation, what happens in a longer run you don't know. To me it seems fully possible that they aggregate in the south during the productive upwelling but then disperse over the lake for the rest of the year. There are many examples of fish where different stocks (spawning units) mix in a productive area for foraging and then return to more "native" areas for spawning (salmon maybe being the most extreme example). So you don't know what the long term distribution look like.

5. l. 127, exchange effects for barriers

6. l. 754-756: It may be the other way around, as the environment may be rather homogenous with, similar prey (and predators?) there are only very weak barriers to gene flow.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Isotopic signatures induced by upwelling reveal regional fish stocks in Lake Tanganyika

PONE-D-22-02571R3

Dear Dr. Ehrenfels,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Peter Eklöv

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments: