High Loggerhead (Caretta caretta) Bycatch Rate along with Several Endangered Target Species: Two Reasons to Look for Alternative to Traditional Large-Mesh Bottom-Set Gillnets (Garrasia) for More Sustainable Fisheries in the Gulf of Gabès (Tunisia)

Round 1

Reviewer 1 Report

The reviewed article on turtle bycatch is recognized as a significant addition to the existing literature, offering valuable insights into this pressing environmental issue. It provides a comprehensive overview of the various factors contributing to turtle bycatch and underscores the importance of evidence-based management strategies for conservation efforts. The article's practical recommendations have the potential to inform policy decisions and guide conservation initiatives aimed at reducing turtle bycatch rates, making it a valuable resource for researchers, policymakers, and stakeholders in marine conservation.

Considering this, I have some doubts and comments:

Introduction: This article is an interesting addition to your introduction and even discussion which reveals much lower bycatch and mortality rates in midwater trawls, which emphasizes the need to focus on set nets as your results show much higher impacts: Pulcinella, J., Bonanomi, S., Colombelli, A., Fortuna, C. M., Moro, F., Lucchetti, A., & Sala, A. (2019). Bycatch of loggerhead turtle (Caretta caretta) in the Italian Adriatic midwater pair trawl fishery. Frontiers in Marine Science, 6, 365.

Figure 1: Very hard to read black on dark blue. Try to change to white, especially for relevant information such as scale. Also, it should be in the materials section, after first mentioning it.

Materials and methods: I recommend separating methods in the Study area; Data collection; Data analysis. I was very confused by your calculations, I can’t reproduce your estimates. Be very clear about how you calculated everything. More comments on this ahead.

Line 103: I would refrain from qualifying your methods in the methods section with statements like “thereby offering invaluable insights” unless you have references that tell you this method provides invaluable insights.

Line 107: “of each individual as(…)”

Line 108: No need for a paragraph in my opinion.

Line 114-115: I recommend deleting this sentence and abstaining from discussing or concluding about the methods in the methods section.

Line 120: Do you have any schematic representation or pictures of the Garrasia net operating?

145-146: All equations should be listed and numbered as equations to simplify for the reader.

Line 151-152: Isn’t this the same as what is explained in the paragraph before? If so, unnecessary paragraph.

Line 155: This formula makes no sense to me. You are multiplying BPUE2 by (total net length [km] × (soaking time[h]/24) which is already the denominator of BPUE2, which leaves you with the number of turtles captured alone. Was there a mistake in transcribing the formula?

Line 160: detect instead of detecte?

Line 164-167: References? What measure makes it a male or a female?

Line 1168-169: Makes it preferably a male and a female, according to the measurements?

Table 1: I recommend changing “total capture” for “estimated total capture”.

Line 198: Why are you estimating 95% CI here? Not needed in my opinion, you have 92.06% mortality rate in your sample. You only need it when estimating for the population and not your sample, or estimated number of deaths for the population derived from this method, which can be interesting information.

Line 205: References should not be in the results. If you wish to categorize your sample according to references, do it in the methods section. Then in the results you only need to say how many were subadults and adults.

Line 207-208: No need for CI in my opinion, unless you wish to extrapolate this info for the population.

Line 212-213: Same thing regarding CI. It is an observed value not an estimate, therefore no need for CI.

Line 214-215: did you test separately for the warm and cold periods? The difference between the ratios in the cold period is very notable.

Line 221-224: The discussion of your methods should be in the discussion section.

Line 225-229: Here you are talking about BPUE2 and not BPUE1 right?

Line 227-229: This information should be either in the introduction or methods (Study area).

240-241: Don’t discuss results here.

Figure 2: If you only have three seasons, this should be clear in the methods section.

Line 271: Why only use the BPUE2 in the discussion? You should discuss the different BPUE you calculated if you consider one better and only use one.

Line 296: I can’t find his information in the cited article. This is what I found in the cited article: "On the basis of these catch rates and on fishery statistics (Table 3) we estimate the annual total number of turtles caught along the Mediterranean coast of Egypt is 7,164 (these are captures, not necessarily individual turtles, because the same turtle can be caught more than once).” “(…)t is possible that the total annual number of turtles captured by the Egyptian Mediterranean fishing fleet is higher than our estimate of 7,164.” Where were the values retrieved from? Also, Are you sure “reported” is the right word? Maybe estimated would be a better fit.

Table A is very confusing because it seems like you are estimating Bycatch rate and Estimated number of by-catch only for one fishing “embarcation”. You estimated it for the sum of all right? Also, in the last line, “total fishing effort”, why not sum all columns? In this line you should have the sum of all number of embarcations (I suggest using a different word); number of fishing net pieces, total length of gill nets and number of sets. This all leaves the reader very confused about how bycatch rate and estimated number of bycatch were calculated.

Author Response

We appreciate the feedback provided on our manuscript, including the specific comments and suggestions . We have taken all the corrections into consideration and have made concerted efforts to enhance the quality of the the document.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors use onboard observations to assess the bycatch of loggerhead turtles when Garrasia gillnets are used to catch elasmobranchs in the Mediterranean Sea Gulf of Gabè along the coast of Tunisia. They determine a bycatch of 0.63 turtles per kilometer of net per 24 hours with a mortality rate of 92%, resulting in a projected annual total capture of 3756 turtles.  They call for immediate development of conservation strategies via collaboration among researchers, stakeholders and fisheries.

I have no knowledge of the Garrasia fishery so can only assess the quality of the manuscript itself. The title is misleading. The study reports data for loggerhead turtles, not guitarfish, which are never even mentioned. 

There is information in the Results (some of lines 234-240) that should be in the Discussion and there is information in the Discussion (most of the first two paragraphs) that should be in the Introduction or in the Results (the third paragraph). There is new information introduced in the first two paragraphs of the Conclusions that should be in the Discussion.

The number of references (60) seems reasonable, but I do not know if any are redundant so could be eliminated or if any relevant sources have been omitted.

I think that this information could be useful to researchers working in the Garrasia fishery and to conservationists and ecologists. Perhaps it could lead to collaborative conservation efforts as the authors hope. The paper is appropriate for publication in Sustainability, but revisions are needed.

Additional specific comments for authors:

Line 9 – what is meant by “co-last authors”? All three are co-authors.

Line 15 and others – sometimes you say “Garrasia gillnets” (lines 15, 228 -- capitalized in lines 38 & 185 but mostly not) or “Garrasia nets” (lines 128, 312) or just “Garrasia” (lines 231, 243, 289). Be consistent. Maybe “Garrasia gillnets” the first time and then just “Garrasia” thereafter.

Line 19 – Why is “Catch Per Unit Effort” abbreviated “BPUE”? Explain what the “B” stands for or use CPUE.

Line 30– “Bycatch” should not be capitalized

Line 33 & 34   – “fisheries worldwide” is repeated – rewrite to combine the sentences

Line 38 – you capitalize “Loggerhead” (and the other two turtle common names) here and in line 160 but not elsewhere – be consistent / also, no need to include the word “turtle” in each common name – you have already said they are sea turtles

Line 57– “Turtles” should not be capitalized

Lines 73-74 – this information is repeated in lines 120-122

Lines 82-84 – single sentence paragraph

Line 96 – What is meant by “key hub”?

Lines 114-115 – single sentence paragraph

Line 125 – change to 16 cm

Line 138 – “on the other hand”?  maybe “In addition”?

Line 141 – “This will allow” should be “This allowed” / use past tense – you are reported what WAS done, not what you are doing or will do

Line 144 – Identify what BPUE stands for (and again, why not CPUE?)

Lines 148-152 – use past tense (“was”, not “is”)

Lines 150 & 155 – what does * stand for?

Table 1 – delete “The” before “total”

Lines 206-207 – sentence reads poorly – reword

Lines 208 & 209 – “were exhibiting” should be “exhibited”

Line 212 – delete “of”

Figure 2 – the legend should not be the same as the y-axis label / the axis label should just be “number of turtles” / same comment for Figure 3 – y-axis label should be “CCL (cm)”

Lines 234-245 – some of this should be in Discussion / just report, don’t interpret results in Results section

Discussion – much of paragraphs 1 and 2 should be moved to the Introduction while part of paragraph 3 should be in the Results

Line 312 – “exhibited” is not the right word / how about “…the average soak time for Garrasia was 29.76 hours…”

Line 370 – no need to give Latin name – already done in line 39 (If you do want to repeat it, just use C. for the genus name).

Line 387 – maybe say “…the female dominated sex ratio…”

Conclusions – You should not introduce new information in the Conclusion / some of the info in the first two paragraphs should be in the Discussion (or Introduction)

Lines 412-414 – you never say anything about the effect on sharks until here and you never even mention guitarfish that is in the title / should at least be dealt with both in Introduction and Discussion if you are going to include in Conclusions but since you present no data you really should not include at all

Appendix A – why the blank columns? If there are no data, don’t include those columns

The paper is reasonably well-written but needs considerable editing to correct English grammar and to maintain consistency throughout (some examples listed in comments & suggestions). There are a few single-sentence paragraphs. Present verb tense is sometimes used when it should be past tense (some examples listed in comments & suggestions).

Author Response

We appreciate the feedback provided on our manuscript, including the specific comments and suggestions . We have taken all the corrections into consideration and have made concerted efforts to enhance the quality of the the document.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper includes very interesting and useful data, but they should be much more contestualised. Furthermore, the inter-annual variability should be showed and described. The target species of this problematic but traditional fishery shall be listed and better discussed in the conclusions. Even the bycatch should be better described. The comments are in details for helping in finding solutions and improve the paper.

Comments for author File: Comments.pdf

It should be useful to check the English in some parts.

Author Response

We appreciate the feedback provided on our manuscript, including the specific comments and suggestions . We have taken all the corrections into consideration and have made concerted efforts to enhance the quality of the the document.

Author Response File: Author Response.pdf

Reviewer 4 Report

The manuscript describe the bycatch rate of loggerhead turtles in the Gulf of Gabès. While the topic is generally important, the manuscript only examines part of the problem. According to the scope of the manuscript, it investigates the reasons while more sustainable fisheries should be employed. However, only the bycatch rate of loggerhead turtles is examined, while bycatch rates of other threatened animals and, particularly, catch rates of threatened targeted species (guitarfishes) and the impact of these catches on the populations are not examined. In my opinion, if the authors want to describe why more sustainable fisheries are needed (and I generally agree with their conclusion), data on bycatch and catch rates of other species need to be added as well to provide a more complete picture. When doing this, the title also needs to be revised, too, and should, e.g., include the full name of loggerheads (loggerhead turtles (Caretta caretta)), the other taxa examined (bycatch and direct catch) and needs to be reworded in general.

The language quality should be improved throughout for clarity, including the manuscript title.

Author Response

We appreciate the feedback provided on our manuscript, including the specific comments and suggestions . We have taken all the corrections into consideration and have made concerted efforts to enhance the quality of the the document.

Author Response File: Author Response.pdf

Reviewer 5 Report

Sustainability-2887833: High loggerhead bycatch rate and targeting vulnerable guitar-fish: two reasons to look for alternative to traditional large meshes dormant gillnets (Garrasia) for more sustainable fisheries in the Gulf of Gabès (Tunisia)

Dear editor and authors,

After reviewing the manuscript, I realized that this work presents an up-dated assessment of loggerhead turtles bycatch in the Gulf of Gabès, which is centered on the impact of the Garrasia gillnets. The main text is well organized and properly written.

All figures, tables and graphics have good quality, highlighting the locations of the sets deployed during the study (Fig. 1). The authors provided a good data regarding the length of gillnets, soak time, location, as well as biometric data of sea turtles and target species. They also provided valuable discussion of the impact of ray nets on sea turtle populations in the Gulf of Gabès.

Despite this, the authors should carry out some minor changes, mainly typos, all of them marked in the PDF file, and pay attention to the reference list, as I found some mistakes (see also the attached PDF).

All the best.

Comments for author File: Comments.pdf

The authors should carry out some minor changes regarding English, mainly typos, all of them marked in the PDF file.

Author Response

We appreciate the feedback provided on our manuscript, including the specific comments and suggestions . We have taken all the corrections into consideration and have made concerted efforts to enhance the quality of the the document.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The revised paper is certainly improved compared to the previous version, but there are still problems in some parts. The lack of annual data is challenging the understanding of the results and it is difficult to understand why the annual data are not provided. Having observers on board is a fantastic opportunity and therefore you should have the full data sets, allowing for a much more focused analysis. The full list of target species is necessary, while the list of by-catch species is certainly very useful 

There are just minor problems, all detailed in the comments.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding corrections in the re-submitted files.

Author Response File: Author Response.pdf