Characterization of Incremental Markings in the Sagittal Otolith of the Pacific Sardine (Sardinops sagax) Using Different Imaging Modalities

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is a very interesting manuscript (MS) on incremental marking characterization of sagittae for Pacific sardine integratedly revealed by BSE, laser scanning confocal microscope and synchrotron microCT imaging. I only have several minor comments for improvement of its quality.

(1)   It’s better to replace “saccular otolith” by “sagitta” or “sagittal otolith” throughout the MS, as the latter are more commonly used.

(2)   The in-text citation formats of all references in the MS are wrong and should be carefully revised throughout following the citation regulation of Minerals.  

(3)   The Fig. 1 is redundant for the MS and it could be deleted.

(4)   Current “Table 2. Biological data of Pacific sardine samples” is better to be present as a supplemental material for MS, as the authors actually did not measure all otolith for this study. Alternatively, a new Table 2 is necessary to assign for presenting the biological data of certain fishes and their otolith marked #4, #7, #13, #14, #83. Those fish were exactly measure for this MS.

(5)   I suggest the authors to revise the Fig. 2 and 3. It will be better to separate the map results of otolith # 4 and #13, respectively (e.g., Fig. 2 only for# 4, and Fig. 3 only for #13), for a more effective and comprehensive individual view.

(6)   A “Conclusion” chapter is necessary for the MS.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

It is a good paper. Does the daily growth increment become unclear after 2nd year of the fish or the first maturity.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Minerals-3018164

title ‘Characterization of incremental markings in the saccular otolith of the Pacific sardine (Sardinops sagax) using different imaging modalities’

 

Review report

 

Sorry to go right to the weak point, the manuscript does not meet the expectations to characterize incremental markings features in the otolith from the model, the guideline headed in the title and exhibit that incremental marking reflect different growth periodicity in the otolith.

 

Overall, except for micro-tomography method, the imaging modalities are not new and the paper does not offer clearly new insights. Despite in its present form, the manuscript lacks clarity and suffers from certain inconsistencies, in my opinion micro-CT and reconstruction would be the novelty to explore, provided the different orders of incremental markings are clearly exposed in the model. Insights from the Laser confocal scanning microscopy LSCM method and the 661 nm Laser used is not clear and lack definition in the methods presentation and in its use in the result section likewise. Same for fluorochrome labelling which processing was not found. Thorough revision is needed for methods clarification.

 

The sampling, albeit small, should be put of better comparison use :

It allows to assess comparison of the first order marks in the range of ‘0’ to ‘6’ years-old fish proposed with the available samples, which is set, in the manuscript, although presented in separate figures (figs.3 and 8) far from each other and without connector.

 

Since the authors did count several suites of thin increments and they have fish lengths, they could make ageing inferences of the fish in their study. Even though they do not have many data, it still might exhibit differences or similarities among the specimen studied.

 

The author did introduce the different orders of markings, a classification of which is given in table 1, but with unsorted growth rate annuli and daily increments. This confusing arrangement is reflected in the general organization in the result chapter and as a specific example in the unresolved description of sample #83 dark incremental marks (n=85)  vs #4 dark and light striation suite (n=9), same ‘age’ samples. Discuss n=40 increments counting for the presumed known period, depicted after labelling.

 

Table 3 report on microCT countings is also confusing. Width measurements of incremental zones and their frequency do not fit or I missed something.

 

Besides, the introduction section should be sharpened and focused. Large paragraphs far from the topic, and some with inconsistencies e.g. with reference to otoconia (seeding process) and bone (remodelled structure) should be removed. The diversity of otolith marks with different age estimation purpose, is suited with short sentence and few reference and should be developed instead.

 

Thus, in my opinion, this manuscript is not suitable for publication.

 

Minor remarks.

Footnotes : footnote 1 can be removed. Footnote 2, on the other hand, is essential and should be extended and inserted into the text.

 

Figures : Captions and some other parts are not those mentioned in the legend (e.g. fig.2b). Please revise all figures on this aspect.

Although the authors claimed they did so, some additional pictures should be flipped for easier reading.

 

References : remove the page number in reference cited in the text. Check uncomplete citation 

Author Response

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Author Response File: Author Response.pdf