PONE-D-23-02344Assessment of treatment-specific tethering survival bias for the juvenile blue crab Callinectes sapidus in a simulated salt marshPLOS ONE

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PLOS ONE

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   "The authors thank Michael Seebo for mesocosm setup and advice on capturing, acclimating, and maintaining experimental animals. Authors also acknowledge the Virginia Institute of Marine Science’s NSF Research Experience for Undergraduates program. Finally, authors acknowledge the University of Maryland Center for Environmental Science Integration and Application Network media library for vector images used to create the conceptual diagram for Figure 1. 

Preparation of this manuscript was funded by a Willard A. Van Engel Fellowship of the Virginia Institute of Marine Science, William & Mary, the NMFS-Sea Grant Joint Fellowship 2021 Program in Population and Ecosystem Dynamics, and the National Science Foundation (grant number NSF OCE 1659656 to R.D. Seitz)."

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Additional Editor Comments:

Both reviewers find your study of potential interest for the community and are quite supportive in their overall evaluations but they also both point out the need for clarifications regarding the definition of the different hypothesis tested with your experiments and how they are connected to one another and to the experiments themselves. I believe that improving the description of the overall logical framework of this study will be beneficial to the manuscript and should be achieved by addressing the remarks of the reviewers.  

Also, I agree with reviewer #2 that the discussion currently remains a bit superficial and deserves to be expended a bit so I encourage the authors to follow some of the suggestions provided.

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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: Partly

Reviewer #2: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

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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

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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

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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 paper describes a set of experiments testing for interactions between tethering artifacts and treatments (artificial stem density) in mesocosm experiments. This is useful and important work, and it is refreshing to see papers properly grasping the implications of Peterson & Black 1994; such studies are often lacking, and such artifacts can invalidate the findings of tethering studies. The work seems sound, and the paper makes a useful contribution.

My main issues relate to:

1. the description of the experiments – more detail is needed and some work on the organization and flow is critically required to link the methods to the hypotheses and explain the experiments more clearly – see detailed comments below; and

2. some consideration of how well rigid wooden dowels at high density actually mimic Spartina stems in the field. My concern here is how reliable is the finding of lower mortality at higher stem density if the high density artificial dowels more effectively exclude large crabs than more flexible Spartina stems. I know they are pretty rigid vertically, but I strongly suspect a large crab could push through Spartina much more easily than through wooden dowels. This latter concern does not invalidate the substantive finding of no interaction between artifacts and treatment, but it does question the translation of findings about stem density into field scenarios.

3. L69, H5: the wording of this seems awkward or incorrect. If survival is inversely related to predator size, this means survival declines as predator size increases, yet the following explanation implies the opposite, i.e. survival increasing with larger predators because of lower efficiency in predation. Please clarify.

4. L72: should this be H5 not H15 for consistency?

5. L83: what is the relevance of citing a preprint for methods when it appears all the methods are described here? If they are not all described here, I would request that they should be, with no need to reference a preprint.

6. Fig 1: a photograph of a mesocosm would be nice. The figure seems oddly arranged. Why is the order of treatments different for the upper and lower panels?

7. The description of the experiments needs revising for clarity, and to relate them to the large number of hypotheses listed. For example, it is unclear which hypotheses are being tested by the experiments described at L114-124? What are these trials for, and how are they different to the trials described in the next paragraph?

8. L125: this explanation is also unclear. Why 4 juvenile crabs? I think I have figured it out (each trial involved 4 tethered and 4 untethered as per my comment below), but as currently written, the experiment descriptions are difficult to follow and to relate to the hypotheses posed.

9. Please provide more information about the tethering arrangement. Where was the tethered crab placed in the mesocosm and within the artificial stems? How much space was there around each pegboard in each mesocosm? Images of the actual tanks with the different densities would help. How far apart were the dowels in the high density treatment? Would this completely physically exclude the blue crab predators from entering the stems? It is also important to understand if both tethered and untethered crabs had access to both artificial stems and to open-water parts of each mesocosm.

10. L132: here too the description is confusing. How about saying something like “each trial involved a single replicate for each tethering (tethered or untethered) x shoot density (4 levels) combination, resulting in 8 tanks per trial.”

11. L140-141: these are unnecessary sentences. I suggest removing them. Maybe ok to mention using R for all analyses at the end of this section, but to say that all data were recoded digitally is redundant.

12. L151: Table 2 is cited before Table 1.

13. L166: please provide the specifics of how many replicates you ended up with for each treatment combination, e.g. in a table or just add the final sample size to Fig 1.

14. Fig 2 is redundant given the data in Table 1.

15. L200: do you mean interaction terms as well as predator size and prey size etc? This is a statement that just hangs and needs further explanation.

16. L206: “In addition,” is this statement not simply repeating what you already stated above as point 2 on L 203?

17. I understand the use of dowels as artificial Spartina stems, but I wonder how the rigidity of the dowels might impact your findings of the strong shoot-density effect? I imagine a large blue crab can move through real Spartina more easily than it can move through rigid dowls at high density. As per my earlier comment, more information is needed on the mesocosms, along with images of each treatment, and some discussion about the possibility that dowels at high densities might not be a realistic mimic of Spartina in the field, and therefore the conclusion that the experiments support the idea that higher density equals better refuge need to be tempered.

Reviewer #2: This study describes a set of experiments designed to determine if tethering is a valid method to understand the relative mortality (or survival) rates of juvenile blue crabs within salt marsh habitat. This is a useful question because the emergent vegetation within salt marshes are a somewhat under-recognized nursery habitat for blue crabs, particularly in regions without seagrass. The authors find that tethering did not induce a treatment-specific bias in survival of crabs across levels of marsh vegetation density, and is thus a useful methodology for future studies of crab survival in marshes.

The authors should clarify certain aspects of the Logical framework/hypotheses, but the larger workload will be to revise the discussion.

I hope that the authors find the following comments useful when revising the manuscript.

General comments

At some point prior to where it is currently written out, the authors should confirm that these are predation experiments. I recommend including this both in the Abstract and in the Logical framing section. This is important because survival could be measured over longer time scales and be, for example, part of density-dependence experiments (among others), so clarifying that these are short-term predation experiments is important.

Hypotheses: It’s unclear how H3 & H4 work together. In H3 you say that survival will be an additive function, while in H4 you say it may result in non-additive effects, indicative of treatment-specific bias. I don’t think you need each of these as separate hypotheses. I see the logical flow moving from H1 down to H6, but H3 and H4 need some clarification.

Relatedly, H5 seems to have an error, at least based on my understanding of “inversely”. That suggests a negative relationship, whereby prey survival would be lower at larger predator sizes. That is the opposite of what you then go on to describe in the justification for H5. Please revise and clarify.

Almost all of the first Discussion paragraph is redundant and could be removed, with the exception of the final sentence which should be revised and expanded (see comment below).

Much of the Discussion could be revised and expanded. It is short and mainly rehashes the Results section as opposed to critically discussing the mechanisms that lead to the results you found. One suggestion for an additional topic to include, considering this is a methods validation paper: what are the next 2-3 critical research questions that could be tackled using this technique, or what information could ultimately be provided to managers based on improved understanding of juvenile survival in marsh vegetation?

Specific comments

L3: “fisheries” don’t exhibit population dynamics. The stock/species that supports a fishery is what we refer to regarding population dynamics. The fishery is the social/commercial activity that utilizes the stock.

L39: alterniflora

L40: please define recruitment or revise this sentence to be more specific about the life stage/size you mean when you say “post-recruitment”

L44: does this specifically refer to tethering experiments? If not, please revise to clarify what is important about the interactive term. If yes, please clarify that you’re only talking about tethering.

L72: This says H1(sub)5, but I think you mean H5(sub)a and H5(sub)b, right?

L132: “trial”

L132: there is some redundancy in this methods section. Please revise to streamline and remove sentences with information that has already been provided.

Table order should be flipped, currently Table 2 is referenced prior to Table 1.

L180-181: replace dashes with () because currently it reads “g4 minus g3”

Fig 3: “points depict aggregated data;”- why not show each replicate and why use a semi colon in the caption? Were these logistic models fit to the aggregated data or the raw data? In my opinion it would be informative to see the raw data as opposed to (or at a minimum in addition to) these shoot density means values because it would be good to see how variable the effects of shoot density are on crab survival. Last, the legend is redundant because you already have titles on each panel.

L200: “all variables were informative” This sentence must need some clarification because all variables were not informative to explain variation in juvenile survivorship. You discarded temperature, salinity and DO at the outset, then your AICc-based model selection approach suggested that neither predator size nor prey size were useful. This sentence should be revised and equally important, expanded: tethering and shoot density were important, but why were the other variables not informative?

L219: there’s a ? in the list of references

L229-231 : seems like a bit of selective reference choice considering Lefcheck’s 2018 paper suggesting a huge recovery of seagrass in Chesapeake Bay. I suggest revising this sentence and toning down the dire nature of the predicted seagrass decline.

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Reviewer #1: No

Reviewer #2: No

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Assessment of treatment-specific tethering survival bias for the juvenile blue crab Callinectes sapidus in a simulated salt marsh

PONE-D-23-02344R1

Dear Dr. Miller,

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.

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Goulven G Laruelle

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

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 #1: All comments have been addressed

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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 #1: Yes

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

Reviewer #1: Yes

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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 #1: Yes

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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 #1: Yes

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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 #1: The authors have done a good job responding to the reviewer comments, and I feel the paper is now much easier to follow. It is well laid out and makes some simple but important points, and makes an important contribution to the literature.

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Reviewer #1: No

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