Age, Growth, and Reproductive Biology of Euchiloglanis davidi in the Middle and Lower Yalong River, China

Round 1

Reviewer 1 Report

Thank you for the opportunity to review Manuscript ID Fishes-2527914 entitled “Age, Growth, and Reproductive Biology of Euchiloglanis davidi in the Middle and Lower Yalong River, China”. I thought that the paper was generally well-written. It is of regional importance because it provides basic life-history information about an under-studied species that represents a local conservation concern. I thought most of the analyses were well justified and described in the methods section. I would like to see more of an effort to show model results (e.g. growth curves, regression fits, and coefficients) alongside plots of raw data in the results section to improve ability for the reader to evaluate the relative fit of models to data. I thought that the discussion, while well-written, could use some refocusing, especially as related to comparison of growth performance among systems or species using estimates in Table 4, and as related to comparing results of fecundity to other study systems using the information provided in Table 5. I have provided line-specific comments by manuscript section below.

 

 

Introduction

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Lines 81-83: Objective 3 could be made more direct as “3) describe reproductive characteristics of E. davidi including …“

 

Methods

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Line 88: Should “rap nets” be “trap nets”?

 

Line 89: Change “fish samples” to “fish”.

 

Table 1: I think “annual” should be “annulus” in the table and caption? Suggest just being consistent with the rest of the text that precedes the table.

 

Line 165: Should these be “excellent” and “good”? “Very good” was not one of the categories for assignment in Table 1.

 

Line 167: “Success rate” is not defined in the Table cited or in the methods section. How was this determined? Suggest moving reference to Table 2 to the previous sentence since those numbers are provided in Table 2.

 

Results

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Lines 183-184: Should read “indicating that growth of E. davidi in weight was negatively allometric”.

 

Figure 4: X-axis label should be “Standard length” instead of “Standrd length”

 

Line 190: I think this should read “…age was successfully identified for 141” since presumably all fish were identified.

 

Line 193-194: Left out ages 5 and 7 in these descriptions but all others have some description. Is the prose recounting of all necessary given the information in Figure 6 and Table 3?

 

Figure 7: Please add plotted von Bertalanffy growth function against raw data so the relative fit of the curve to the data can be assessed. The raw data are very informative, but it is impossible to evaluate the quality of the fitted model without plotting both together. The value of L-infinity and W-infinity are high compared to what one would expect based on the plot of the raw data, which suggests that the von Bertalanffy growth function does not actually asymptote and therefore may not be a great fit to the biology of the species.

 

Was any effort made to estimate natural mortality for this species from estimators reviewed in Then et al. (2015)? Either the maximum-age estimator or the modification to the Pauly (1980) method presented in Then et al. (2015) could be used to derive indirect mortality estimates for this species, which could be useful in management or conservation planning in addition to providing general life-history estimates.

 

Line 208: Decreased compared to what?

 

Figure 10: Please consider adding lines of best fit, regression coefficients and R-squared values for the regression fits. As with the von Bertalanffy growth function, it is impossible to evaluate the relative fit of each regression without this information. Likewise, as this provides potentially valuable information against which the research could be compared in the future, the coefficients for these relationships should be provided in the figure or a separate table if needed.

 

Discussion

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Line 278: Suggest changing to “indicates that species-specific values of b vary according to …”

 

Lines 283-295: Need to be cautious interpreting trends in k among species, especially if they have different mean asymptotic sizes (L-infinity or W-infinity). As the authors identify at the start of the paragraph, the Brody growth coefficient (k) is rate of approach to asymptote, and it is relative to the asymptote, so it should not be compared in isolation. Likewise, the high L-infinity (75 mm larger than the largest fish collected) actually suggests that the von Bertalanffy growth function may not adequately describe the life-history of this species so additional caution is warranted here. If the authors decide to continue comparison of k among species, then these should be presented alongside values of L-infinity for relative comparisons. Having said all of this, I do agree that a fish reaching 200 mm by age 8 or 9 is slow-growing, but may not be able to address this robustly through comparison of k in isolation. The authors present parameter values from other studies in Table 4, which is very helpful, but should make these connections clear for the reader in the text. It might also be helpful to provide the combined “growth parameter”, omega, of Galluci and Quinn (1979) for comparison as this accounts for relations between L-infinity and k and, in theory, allows for direct comparisons. But, maybe this is duplicative with the growth performance indicator, in which case the latter should be emphasized in the discussion over k in isolation.

 

Line 299: Suggest replacing “genetic” with “genetics” or “genetic factors”.

 

Lines 312-323: How does the relative fecundity (or individual fecundity) compare with the other species studied? These numbers are provided in Table 5 (which I really like!), but connections should be made clearer for reader.

I did not find major concerns with the quality of English language. Better than most papers I review in this regard.

Author Response

The authors gratefully appreciate the helpful comments of Reviewer #1 that greatly improved our manuscript. We have studied comments carefully and made correction which we hope meet with approval. All the modifications are highlighted in red. Please, kindly find below our reply to all the comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

The study has good potential in this area, but its presentation and some aspects need to be improved.

-The introduction is designed to give better information about age, growth and population characteristics of fish. (See attached file).

-Why were all fish samples evaluated together? Why were individuals in these tributaries not evaluated on a tributary basis? Perhaps there are one or more factors in the relevant living environment that affect the growth and life cycle of those individuals. Is there a possibility that this factor or factors found only in that habitat will affect all individuals?

-About age determination-

Statements about the method chosen for age determination and why the material was preferred should be added to the study. Thus, readers can better understand the subject. See following questions and attached file.

1- Have you determined reliable bony structure for age determinations of this species? The reason for this should be explained and the material should be added to the method section.
2- Why were lapiilus otoliths chosen for age determination of this species?
3-Was the otolith on only one side removed? Aren't the otoliths left and right for each individual removed? Why? The reason for this should be explained and the material should be added to the method section.

-In most catfish species, it is obvious that lapillus gives good results in age determination. The result is not surprising. Lapillus otolith is already quite thick in most fish species and is not preferred in many age determination studies.

However, at this point, I think that other otoliths should be examined if it is not suitable for determining the age for your species. There are very limited studies on otoliths of this species. Adding such an evaluation to the study will greatly increase the originality of the study.

-According to Figure 3, a lot of pollutants and residual material appear on the vertebrae. These materials may be given the cause of incorrect age readings. I would expect the figure to be given as an example of age readings to be more cleaner.

-Why is the growth type of this species not specified?
Is it isometric or negative or positive allometric?
It should be expressed more clearly and more appropriately for the readers.

-I think it would be more appropriate to give the relation equation and R2 value in the figure 5.

-The growth performance index of the species should be interpreted and compared with other studies in discussion section.

-The scientific names of species should be italicized.

-Other recommended corrections are in the attached file.

 

Comments for author File: Comments.pdf

Author Response

The authors gratefully appreciate the helpful comments of Reviewer #2 that greatly improved our manuscript. We have studied comments carefully and made correction which we hope meet with approval. All the modifications are highlighted in red. Please, kindly find below our reply to all the comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

I read the manuscript titled "Age, Growth, and Reproductive Biology of Euchiloglanis davidi in the Middle and Lower Yalong River, China" with interest. It is always important and interesting to know accurate data on the growth and reproduction characteristics of relatively recently known to science fish species. This allows us to increase the efficiency of its population management strategy and conservation, and also this is food for thought about the paths of evolution. This manuscript contains a lot of important information about such an interesting object as Euchiloglanis davidi.

At the same time, the possibility of commercial use (as indicated by the authors in line 39) of a fish species of such a small size seems surprising. I think that readers would be interested to know what is the catch volume of this species in China? 

Please indicate, females captured in May or December were used to study fecundity and oocyte diameter? When there is breeding season of E. davidi?

Have you found any differences in the growth characteristics of fish caught in different seasons?

In addition, I would recommend in the Figure 1 make an inset of a larger scale so that it is clear where in Asia (in China) the research area is located, and in the Figure 2 it would be useful to display a graphic scale.

As a whole, the manuscript is written clearly and well-structured.

I recommend this manuscript to be accepted for publication in FISHES.

Author Response

The authors gratefully appreciate the helpful comments of Reviewer #3 that greatly improved our manuscript. We have studied comments carefully and made correction which we hope meet with approval. All the modifications are highlighted in red. Please, kindly find below our reply to all the comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

After the examinations, it was determined that the questions were answered appropriately and the suggested corrections were made.