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Article
Peer-Review Record

Comparison of Two Types of Survey Designs for Acoustic Estimates of Fish Resources in the Three Gorges Reservoir, China

Water 2022, 14(17), 2745; https://doi.org/10.3390/w14172745
by Yuxi Lian 1, Shaowen Ye 2,*, Małgorzata Godlewska 3, Geng Huang 4, Jiacheng Wang 2,5, Jiashou Liu 2 and Zhongjie Li 2
Reviewer 1: Anonymous
Reviewer 2:
Water 2022, 14(17), 2745; https://doi.org/10.3390/w14172745
Submission received: 1 August 2022 / Revised: 22 August 2022 / Accepted: 30 August 2022 / Published: 2 September 2022
(This article belongs to the Special Issue Hydroacoustics in Marine, Transitional and Freshwaters)

Round 1

Reviewer 1 Report (Previous Reviewer 2)

The manuscript is greatly improved. Please reconsider the following before the final manuscript.

1. L70 I suggest explaining that most of Chinese freshwater fish are Cypriniformes, unlike those in Europe and America.

2. L214-216 Is this sentence correct? Table 2 shows that in the survey unit close to the mainstream (i.e. Tributary 3), the standard deviation of density estimates for the parallel design (0.47) is smaller than that for the triangular design (0.62). Please check it.

Author Response

1. L70 I suggest explaining that most of Chinese freshwater fish are Cypriniformes, unlike those in Europe and America.

Response: Thanks a lot for your suggestion.We have explained this point in line 70-74.

 

2. L214-216 Is this sentence correct? Table 2 shows that in the survey unit close to the mainstream (i.e. Tributary 3), the standard deviation of density estimates for the parallel design (0.47) is smaller than that for the triangular design (0.62). Please check it. 

Response: We have checked the sentence and there is no problem. 
Thanks a lot for your reminding about the mistake. We have checked Table 2 and corrected two mistakes of the standard deviation of density estimates in Tributary1 and Tributary3.

Author Response File: Author Response.doc

Reviewer 2 Report (Previous Reviewer 1)

The manuscript could be published in the revised version.

Please, check the mistyping in word "equation" in line 160

 

Author Response

The manuscript could be published in the revised version. Please, check the mistyping in word "equation" in line 160 

Response: Thanks a lot for your time and correction. We have revised the mistyping word "equation" in line 164. We have also check and revised the misspell word "survey" in line 177 and 229.

Author Response File: Author Response.doc

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.


Round 1

Reviewer 1 Report

In reviewed work, the authors tested two type (triange and parallel) of the acoustic survey designs for estimation of the fish abundance. The area of the observations was canyon-shaped reservoirs in the Yangtze river and adjacent tributaries.

Purpose of the study looks important. The main results has practical usefullness .

Generally, the work is well-organized but parts of the manuscript where the processing of the data are presented remain unclear and should be improved before publication.

Specifically, the concerns and questions are the following:

1.       It is not clear, how the “events” in the acoustic signal have been used to calculate fisf density. I strongly recommend to present mathematical formulas used for fish density calculation.

2.       Was the local depth of the reservoir taken into analysis?

3.       How the degree of coverage presented in Table 1 was calculated?

4.       The parameters W? p? df in Table 2 and N, X^2, df, p in Table 3 are not explained and introduced.

5.       I recommend to present equations used for Shapiro-Wilk test, t-test and Chi-squared test for reader convenience and better understanding.

6.       What is the meaning of Sv threshold introduced in line 134?

Reviewer 2 Report

This manuscript by Lian et al. compares the acoustic estimations of fish density and size distribution between the two survey designs (equidistant parallel transect vs triangular transect) in a canyon-shaped Three Gorges Reservoir, and recommends the triangular design for fish acoustic survey there. This manuscript has some value as a case study and may serve as a reference for future acoustic survey for fish at the Three Gorges Reservoir. However, no data provides evidence that the triangular design is better than the parallel design. I think this manuscript needs to be substantially revised in many parts as shown below.

 

Major comments:

 

1.     The authors concluded that the triangular design is better than the parallel design in the study reservoir, although there was no difference in fish density estimates between these designs. As reasons for recommending the triangular design, the authors point to survey efficiency (time and effort), as well as safety during survey. However, these data are not presented in the manuscript and are not fully discussed. Besides, the difference in fish size distribution between the sampling designs does not contribute in any way to the judgement and discussion about the validity of the sampling designs. The sampling rate, which is cited as the reason for the difference in size distribution, is also ambiguous and not explained, and no data is presented. The only thing this study has clearly shown is that there was no difference in fish density estimates between the two sampling designs, and that there was a difference in fish size distribution. Unfortunately, no evidence was obtained to show the validity of the triangular design and no fully discussion was provided. I think this is the fatal flaw in this manuscript, which should be substantially revised.

 

 

Medium and minor comments:

 

2.     L23: Different sampling rates in littoral and offshore area between the two sampling designs are not provided in the manuscript. Please also see my major comment 1.

 

3.     L66-67: What are the characteristics of the Chinese waterbodies (reservoirs) and Chinese freshwater fish that previous studies did not seem to cover? Is it a fact that canyon-shaped reservoirs are particularly abundant in China compared to other countries and regions?

 

4.     L74: A citation is needed after “with fish”.

 

5.     L84-86: This study does not examine sampling time efficiency, survey safety, adequate coverage, and reliability of fish density estimation. None of these are the purpose of this study. Please also see my major comment 1.

 

6.     L103-104: More detailed explanation of how to set up transects is needed. How was the parallel transect spacing determined? How was the angle of the triangular transect determined?

 

7.     L112: A citation is needed after “the water”. Also, please add the manufacturer and country name of the echosounder.

 

8.     L130-132, 142, 194-195: Please explain in more detail how to estimate the fish size and its distribution. What are the relationships among the TS, SED, and fish size? In addition, what do a large and small values of TS mean?

 

9.     L158-159: I think it can be rewritten as “it was 0.3”.

 

10.  L168-171: Please rewrite the descriptions in a way that makes it clear that the results do not depend on statistical analysis. For example, “relatively”, “similar”, etc. may be used.

 

11.  L178-185: Together with Figure 2, the description of the results needs to be reconstructed. There seems to be a confusion between the explanation of tributaries 1 and 3.

 

12.  L178: “fish biomass”: Perhaps so, but here it is “fish density”.

 

13.  Table 2: Please provide the full name of the “SD” in the caption or footnote.

 

14.  L229: “Time and labor intensity during the survey” is not provided and examined in this study. Please also see my major comment 1.

 

15.  L230-232: Why is the parallel design dangerous? Because survey ship navigates in the littoral zone when moving between transects? A more detailed explanation is needed at the early stage of the manuscript (e.g. in Methods). In addition, it should be clearly stated why it is particularly dangerous at night.

 

16.  L247-249: Please elaborate on why a transect perpendicular to the shoreline is suitable for a sinuous canyon-type reservoir?

 

17.  L249-250: Is this sentence correct? Also, do you mean that the transects of triangular sampling are perpendicular to the shoreline in a sinuous canyon-type reservoir and thus suitable for acoustic survey there? Anyway, it is confusing.

 

18.  L267-269: Why the size distribution observed at night is affected by diurnal migration. Please explain the process (i.e. time-series changes in fish migration and/or habitat use) in more detail.

 

19.  L269-270: The sampling rate of the parallel and triangular sampling designs in the littoral and offshore area is not provided in this manuscript. Please also see my major comment 1. Moreover, why is the sampling rate of the triangular sampling design in littoral zone higher than that of the parallel design? Is it because the overlap between the littoral zone and the triangular transects increases due to the sinuous shoreline? Or is that just based on the previous study, not your result? This part is also confusing.

 

20.  L264-272: There is no substantive discussion about differences in fish size distribution between the two sampling designs. Nevertheless, the authors mentioned that the difference in the sampling rate could be the cause of the size difference (L23-24 in Abstract). In the first place, why does the difference in the sampling rates between the sampling designs cause the size difference? I cannot see the reasons in the manuscript. These are problematic.

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