Seasonal and Spatial Variations in Fish Assemblage in the Yangtze Estuary and Adjacent Waters and Their Relationship with Environmental Factors

Round 1

Reviewer 1 Report

·      I strongly recommend to clearly establish the objective of the work. For instance, The aim of this work was to analyze the seasonality in fish abundance and biomass and its relation to environmental variables (conductivity, temperature, depth, salinity, dissolved, oxygen, total phosphorous, total nitrogen and chlorophyll a) between 28 stations in the Yangtze Estuary, in the East China Sea.

·      The abstract needs to include key finding beyond just mentioning that there were significant seasonal differences in fish abundance….Which fish species were the top ten, for instance? Which of the 28 sites showed the highest fish abundance and biomass and in which season? Were these sites near or far away from the coast? The sentence that reads “Differences in the distribution of fish assemblages in the Yangtze Estuary’s adjacent waters were caused by the selectivity of species to environmental conditions, and migration…? What do authors refer to with this? Why did authors do not mention specifically which fish species were more dominant despite differences in environmental conditions. The last sentence of the abstract is confusing: Why the Yangtze Estuary’s can provide a reference value? This is not clear.

·      I suggest an alternate title: Seasonal and spatial variation of fish assemblages in the Yang-Tze Estuary

·      In line 88, the manuscript reads “All catch was frozen and returned to the laboratory for identification; the number and weight of each species caught was recorded”. So, I suggest: Fish catch was frozen and delivered to laboratory for identification using the taxonomic keys and catalogue of…..¿? “The number and weight of each species caught was recorded”. Here, I suggest: Each specimen was measured in centimeters and weighed with an electronic scale to grams.

·      In lines 151 to 156, authors mentioned the FOUR more abundant species and also those with the high biomass, and also the most dominant species in the region (which family?) Please, mention this in the abstract too.

·      I find the figure 4 difficult to read because it is way too saturated. I recommend splitting it into two figures.

·      I find figure 5 very general since it is only showing variation of all species between seasons, but I do not understand why to compare biomass and abundance. It would be more relevant to identify changes in distance to the coast for instance or by depth if possible, rather than season only.

·      Table 2 must be a graph instead of a Table.

·      Figure 6 is not possible to discern because it is way too many images in one plate. I recommend authors to edit that and just leave in the Figure what it is really important.

·      I urge authors to consider keeping or removing figure 8.

·      What is the point of table 3? Is this information contained in a previous graph?

·      The beginning of Discussion is awkward. “Many fish species have been reported adjacent to the Yangtze Estuary in different years and seasons”. This is way too general. I strongly recommend authors to begin with a more convincing beginning of Discussion going straight to the dominant fish species first.

·      How many of the reported fish in this work are migraters? And which are commercially important?

·      I urge authors to shorten Discussion and go to the point in terms of comparisons of what they found and possible environmental influences and what is going on in other similar estuaries in the region and focus on the more abundant species and those of commercial importance.

·      The Conclusion is way too vague. Which were the key findings of the work? These would be the conclusions.

·      English requires to be improved.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Introduction,

The introduction reads disjointed, many topics come into play but without any path, just information about the Yangtze estuary. I would recommend introducing the lack of information and anthropogenic pressures affecting the Estuary, highlighting the relevance of fish assemblages and why their study is important to the site and conservation efforts.

methods,

Why not just take the full 12 sites?

Line 89-90 some parameters are capitalized and some are not (depth... turbidity... temperature etc...)

Lines 105-127, Statistical Methods reads choppy, try creating more flowing paragraphs.

Results,

Figure 2, a and b, needs better quality, the names are hard to read and the numbers are too small.

Some results are over-described, it would be better to simply point out the information that would be required in the discussion.

Some graphs/tables would work better as an appendix

Discussion

The global context should be thoroughly reviewed, since there are many results presented in the document, and the discussion tries to address them all, it would be just to focus on a few points and highlight how this study helps advance conservation efforts in the estuary o what are the environmental conditions that guide the assembly process, but not both.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

see attachment

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The manuscript reports a long and complex work in an estuary area. However, I find it very descriptive and not innovative. I suggest focusing the discussions and conclusions more on ecological implications.

Line 43 Coilia mystus must be written in italics, the reference (Linnaeus, 1758) must also be put. Refer to the FishBase website.

In Figure 1, please write the x and y bigger. It is not simple to read.

Please write in the 2.1 paragraph how far the stations are from each other, specify if those below the coast are closer and why this choice was made.

Lines 132 and 134, use the same style Figures 2a and 2B, or both 2a and 2b or 2A and 2B.

In figure 2a, there are some image problems. The 0 on the y is not completely visible.

The text in the colour image 2a is too small. Also, in the 2b legend.

Which identification keys were used? Specify.

The text in figure 4 is too small.

Please write “km2” km².

Figure 5, I recommend changing the figure colour. The black-on-black error bar is not seen.

Line 190 “Pampus argenteus” in italics.

Figure 6 is impossible to read. The text is too small, also in the legend. I also suggest splitting the images and taking a whole page if necessary.

The same problem of text dimension is in figure 8.

The first paragraph of the discussions appears to be part of the results. I recommend trying to write an excerpt of what you have found and going into the details later. It is one of the first parts that readers go to check after the abstract and must be vivid.

Respect the same space between paragraphs throughout the text. The one in line 354 is different.

I suggest rewriting the discussions and conclusions. As much as the ecological system you have studied may be of interest, it must become interesting for everyone from all over the world read your work. What makes this study innovative? What is the breakthrough in the knowledge of the ecology of similar systems?

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors covered almost all suggestion I done in the previous revision. However, I have a couple of suggestions still required to be considered:

·      The objective must be improved. I suggest this objective: “In this work, we identified seasonal and spatial variations in fish assemblages, and its relation to environmental variables, in the Yangtze Estuary”.

·      The very first sentence of Materials and methods must simply be “Surveys were conducted in February (winter), May (spring), August (summer), and November (autumn) of 2018”.

·      In Results, lines 300-301, it must be “Fish abundance and biomass were high in autumn….and low….”

·      Line 327, the sentence “Fish form two assemblages in spatial patterns.” Is awkward. I recommend improvement of the sentence.

·      In line 971, I strongly suggest removing any recommendation within the conclusions. If authors want to recommend something this has to be done in the last paragraph of Discussion.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Thank you for addressing my earlier comments. The paper has been much improved, but the newer version has made several potential issues in the new Figure 2a (Figure 5a from v1) more apparent. I missed this in the first review so providing these comments to you in the second round is my fault. However, the issues are serious enough that they need to be addressed.

First, what the bars in Figure 2a represent is not stated in the figure caption. Are the bars mean abundance and mean biomass, or medians? And what are the error bars? Are they standard error or standard deviation? And whatever they are, are they 1x, 1.96x, 2x, or something else?

Finally, you are estimating a negative abundance and negative biomass in some of these seasons. Since these are impossible results, a statistical approach more appropriate for these data (such as log transforming them (or something else which can contain zero), preparing the summary statistics, and back-transforming them (or not depending on your preferences)) will eliminate the negative estimates.

Author Response

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Author Response File: Author Response.docx