An Assessment of Potential Beam Trawling Impact on North-Western Black Sea Benthic Habitats Aiming at a Sustainable Fisheries Management

Round 1

Reviewer 1 Report

General appraisal:

This work has interesting information deserving to be published. However, a better statistical link between fisheries/geophysical marks and biological parameters (see specific comments) is need to support the claims currently made in the manuscript. Also, the statistical procedures description and set of tests performed should be revised (see specific comments). Other minor corrections indicated in the specific comments should be conducted too.

 

Specific comments:

Abstract: If one of the main objectives of the work is to "propose effective spatial/temporal management measures for a sustainable zonation of the North-Western Black Sea shelf" (lines 19-20), the abstract should also have a summary of those proposes.

Lines 56-58: The second part of the sentence needs revision for clarity.

Line 89: A final period is missing here.

Lines 101-103: I think a "not" is missing here.

Line 106: A "Sea" is missing here.

Lines 119-125: The common name of this gastropod should be given the first time it is referred in rhe text.

Line 138: Few studies of?

Line 143: Remove the extra "the".

Lines 159-163. Hard to understand this sentence. Revise for clarity, preferably adding the correspondent formulae.

Lines 164-172: I think that this sentence should be placed before the previous one as it seems to be more about introductory information.

Line 216: Best to use "Macrozoobenthos and sediments sampling".

Lines 226-227: Some of these biological parameters (biomass and diversity) do not seem to be presented in the results section.

Lines 226-234: This subsection should be better described. Those additions should include, at least: the name and objective of each test referred; the data and design used in each case; the procedures used to relate the biological, geophysical/fishing data (the last two types of data are not referred here).

Figures: The numbers of figures after figure 1(i) should be revised because there are two figures 1 and two figures 3.

Line 255: Do not begin a sentence with numbers.

Figures 1(ii) and 3(i): The correlation tests referred in these figures should be indicated and explained in the methods section and more information about their results given in the results section (df and p, at least). 

Line 271: I think that current figure 2 should also be referred here together with figure 1(ii). In tact, it would be better to merge current figures 1(i) and 2 to allow a better analysis of the claim in this paragraph.

Subsection 3.2: This subsection should be totally revised and matched with the methods section. First of all, there are many statistical procedures used here not referred in the methods section and that should not happen. Secondly, the biological groups should be first statistically defined and only after that their significance tested and the taxa responsible for that determined. Finally, the redundancy of the analyes should be eliminated (as happens for the procedures represented in current figures 3(ii) and 4).

Lines 351-355: GES should be defined the first time it is referred in the text. The biological data should be statistically related with the trawling/geophysical data. That is crucial for the claims made in the manuscript.

Current figure 5: The caption should make separate reference to both diagrams (A and B) included.

Subsection 3.4: This subsection would be better placed before analysing biological data. The last sentence is more adequate to the methods section.

Line 404: Explain the meaning of HORECA the first time it is referred in the text.

Lines 458-460: Most of these data were not presented in the results and they need to be for use in the discussion here.

Lines 471-475: English needs revision.

Line 486: MBCG?

 

See specific comments.

Author Response

Dear Reviewer,

We appreciate the comments and have addressed in the attached documents all the concerns expressed by the reviewer. We also thank the reviewer for detailed suggestions, which improved the overall clarity of the MS.

Best regards,

Authors

Reviewer 2 Report

Fisheries for invasive species are interesting by their very nature but such fisheries are rare.  Even more interesting, however, are any unintended consequences of such fisheries to the environment that they should help protect.  Such unintended consequences are rarely examined.  In broad terms, the authors address questions associated with these issues.  Which is more beneficial – to accept harmful impacts of a fishery or allow increased effects of an invasive species that would occur as the density increases in the absence of fishing?  Or better said, how can the fishery be regulated to minimize harm to the ecosystem while reducing the impact of an invasive species?  I feel the authors have done a good job of providing clues to answer these questions.  The novelty of this research should ensure that it is of broad interest to scientists and environmental managers.

Overall, the study is well conceived and basically sound using some novel approaches.  However, although the results indicate that the extensive use of beam trawling harms the benthic community, I’m not convinced that the study directly links increased trawling with a greater impact on the benthos. 

I have some comments (some major and some minor) that I hope will improve the ms.

Major comments: 

The Introduction is overly long, providing too much information about some things and too little for other things.  For example, the paragraph starting on line 56 seems like methods section material to describe the study area.  The intro needs to be shortened and more focused.  Further, it seems the Danube Delta - 152 Marine Zone is a Marine Protected Area (MPA) but that information is not conveyed until a mention is made in the Discussion section.  What is the origin or purpose of this MPA and is trawling regulated there in any way?  Are all sampling sites within the MPA?  How could a reader unfamiliar with the area know that the study site is in an MPA or what the rules for its management are?

Two statements in the discussion section are not backed up adequately with analysis or by explanation.  They are: “The community-level indicators of species richness (S), Shannon diversity (H′), total abundance (A) and biomass declined significantly with increasing trawling disturbance in our study”, and “we observed a decrease in the values of the M-AMBI*(n) index with increasing trawling disturbance”.   Where are these relationships pointed out or discussed?  Trawling marks are shown in Figures 5 and 6 but no specific connection in the results section is made to the benthic community in these figures that could be considered a correlation in general let alone in a statistical sense.  Could an analysis of trawl marks and benthic communities be conducted (something with PRIMER or Permanova such RELATE or DISTM)?  There is some explanation provided in the conclusion section that justify the author’s contention of direct links between trawling and the benthic community, but these connections need to be pointed out where data are presented or provided as a plausible relationship in the discussion.  I do not feel that a statistical correlation analysis is a pre-requisite for publication but that if an analysis is not possible then the authors should be more circumspect/careful and reasoned in drawing conclusions.

The analysis of the benthic community is critical to this research but unless the reader is from Europe, it is not possible to evaluate their findings let alone the significance of their results.  AZTI, AMBI, M-AMBI and M-AMBI*(n) are unknown to me and the references given are not easy to access. GES seems an important quantity, but it is not defined making it impossible to evaluate the authors conclusions.  I feel the authors should at least explain what these terms represent and briefly how to interpret them. 

I don’t understand Figure 5, yet it could be considered the most important figure in the ms.  No explanation for the difference between the left and right sides is given.  Do the colors refer to density or the index mentioned (no legend is given for color intensity)?  There does not appear to be trawling marks on the right side – why not?

Minor comments:

The use of so many acronyms is annoying and distracting to an unfamiliar reader and detracts from the ms.  This is not a report to a granting agency in which those who read it will be familiar with the terms.  Many acronyms can be replaced with the words they describe.  For example, LEK and SS are used one time after they are defined, and use of acronyms in these instances is uncalled for.  Please comb through the ms. and use only acronyms that are used at least a handful of times.  In addition, the sentence starting on line 205 seems to use acronyms that are not defined.

Figures 1 and 2 seem to repeat information given in tables.  These figures do not appear to me to be needed.

 

Modest editing would improve the English.

Author Response

Dear Reviewer,

We appreciate the comments and have addressed in the attached documents all the concerns expressed by the reviewer. We also thank the reviewer for detailed suggestions, which improved the overall clarity of the MS.

Best regards,

Authors

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The comment about subsection 2.5 should still be better addressed. New additions should include, at least: the name and objective of each test referred; the data and design used in each case.  Even uf you did not used statistical procedures to relate the biological, geophysical/fishing data the way they were related should be indicated in the methodology.

Regarding the comment "The biological data should be statistically related with the trawling/geophysical data. That is crucial for the claims made in the manuscript"; if it could not be done, such constraint should be clearly stated and discussed in the manuscript.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

I have searched the document several times.  I cannot find a definition for GES.  Although the statistical methods are better described, this value stands out as most important but is not defined that I can see.

I cannot find and access supplemental material. 

Although the figure is complex, the legend for Figure 6 should do a better job of explaining the features.  A and B are not defined in the legend.  How do the black and red trawl marks differ?  The right Y axis should be labelled with units. 

English may need minor editing.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

I'm satisfied - I support accepting the ms in its current form.