Fish Diversity and Ichthyofauna of Areas Adjacent to the Demilitarized Zone in South Korea
Round 1
Reviewer 1 Report
Review of “Fish diversity and ichthyofauna of areas adjacent to the Demilitarized Zone in South Korea” by Hyeong Su Kim, Hyung Soo Seo, Su Hwan Kim, Hyun Mac Kim, and Myeong Hun Ko
The paper on fish diversity in the DMZ was well written and easy to read. The authors outline their three objectives clearly in the introduction. I feel, however, that the first objective to “investigate the current status of fish diversity and ichthyofauna in areas adjacent to the DMZ in Korea for the period 2015 to 2019” is broad, given what was actually done, and could be narrowed for the purposes of this paper.
I see two potential solutions: 1) As mentioned above, narrow the focus of the first objective and focus only on species richness instead of the broad term “diversity”, since diversity includes many components that are not addressed here. Or 2) conduct additional analyses that cover more aspects of species diversity (e.g., evenness, beta diversity, or community analyses using PCA or similar).
The analysis examining the relationship between elevation and species richness suffers from a fatal flaw. The richness values are not rarefied. Generally, as more individuals are captured, more species are encountered. Even though sampling methods were standardized, the area and volume of the sampled areas are not. If you imagine sampling in a large river versus a small stream, the same amount of effort will be less impactful in the large river. To account for this, rarefy your site level data to the minimum number of individuals captured.
The correlations are fine, but you should consider a more formal linear model for all species and endemic species. It is hard to predict the outcome given the lack of rarefaction, but the relationship might change.
Other minor points:
If you do not use any of the physical measurements in your analyses, why present them? With their presence, I expected more analytical work than was presented in the paper. A PCA or RDA could be used to relate the physical environment to the community of fish.
Section 2.2, paragraph 3, last sentence – How many of the sites were restricted? How do you account for the sampling effectiveness of visual observation and hand nets? Are they comparable to the other methods used in term of effort? Rarefaction would help.
Can the authors emphasize why the DMZ is an ecological axis? Is it because it is a band of relatively untouched wilderness?
On the point about banning wildfires? Is there a policy that they are not fought? How would they be banned? Do they not start naturally or are they intentionally set?
Lastly, the formatting of Appendix tables makes them difficult to read. Perhaps change the orientation of the page so they are wider. Or can these be submitted as excel sheets similar to the supplemental file?
Author Response
We thank you and the reviewers for your thoughtful suggestions and insights, which have enriched the manuscript and helped us produce a more balanced account of the research. The manuscript has been carefully rechecked and appropriate changes have been made in accordance with the reviewers’ suggestions. The responses to their comments have been prepared and attached herewith.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors have summarized a large, intensive fish survey and updated information about fish distribution from previous surveys. I offer the following comments regarding the manuscript.
Major concerns:
1. P 3. “The cast nets were cast 10 times, and scoop nets were used for 40 min at each site according to the Guidelines of the National Natural Environment Survey.” I am concerned that this amount of sampling effort was held constant even though the sites varied greatly in surface area. For example, Site 10 had maximum stream width of 3 m. If 100 m of stream length was sampled, the area of the site would be 300 sq. meters. The cast covered 4 sq. meters, and since 10 casts were made, the area sampled would be 40 sq. meters. This would equal 13.3% of the site’s area (40/300 = 0.133.) For sites that were 100 m wide and 100 m long, the 10 casts would have sampled only 0.4% of the site area (40/10,000 = .004). Thus, sampling effort was 33 times higher (13.3/0.4 = 33) at the narrow sites compared to the wide sites. The authors need to provide justification that their sampling methods were adequate for describing the fish assemblages at the study sites.
2. P 4. How can a cast net and scoop net be used to sample a reservoir site that is 10 m deep (Site 44)?
3. P 6. It’s not clear how “Human activities and disturbance” were measured other than by subjectively noting their presence. This information needs to be better related to the status of fish assemblages at the sites. Was species richness lower at affected sites? Do affected sites differ in species composition? An ordination of the sites based on species composition might help identify gradients of community change that then could be related to human activities and disturbance.
4. Appendix Table A2 is difficult to decipher. It would be better to create five tables, one for each of the biogeographic provinces. That would allow readers to make a more direct comparison as to which species appear to have added or lost for each of the five biogeographic provinces.
5. P 6. The authors note that 50 species were not collected in the current survey that had been collected in previous surveys. They attribute this to “to differences in estuary surveys and methods, including seawater species, the selection of different survey sites, the decrease in fish populations, and the appearance of ambiguous, misidentified, or diadromous species (27 species) in previous publications”. The authors should eliminate these species from the Appendix Table A2 so that a fairer comparison can be made between historical surveys and the current study.
6. P 7. The authors state: “The large decrease in the number of individuals is attributed to human activities related to flood damage restoration, river dredging, and water pollution [29,31,32]. There is little information in the current manuscript to support this broad conclusion. No data were presented on the extent of these anthropogenic activities or how they might have increased in intensity over time. This portion of the manuscript should be eliminated.
7. P 7: “Among the species that did not appear before the 1960s–70s in the Northeast Korea subdistricts, 11species, Pungtungia herzi, Pseudorasbora parva, Squalidus ultimaculatus, Misgurnus mizolepis, Silurus asotus, Odontobutis interrupta, Z. koreanus, Z. platypus, S. microdorsalis, Liobagrus andersoni, and Coreoperca herzi, were identified in this study and were presumed to have appeared since the 1980s–90s.” This is an example of good insight derived from the current study. The authors should present such information for each of the five biogeographic regions.
8. P 8: “Three exotic species (C. cuvieri, M. salmoides, and L. macrochirus) were identified at five sites, where four sites were reservoirs or streams just below the reservoir, and one site was the estuary of Imjingang. Site 44 of the Togyo reservoir was one of the areas where M. salmoides and L. macrochirus were introduced in the 1970s for aquaculture.” This is another example of a useful result of the present survey and serves as a warning about the role of reservoirs as invasion points for nonnative fishes.
Additional comments
9. Fig.1 – the area marked Yellow Sea appears to be terrestrial habitat.
10. P 2. “and appear the altitude at the survey site by an altimeter” It’s not clear what this sentence means.
11. P 4.”Pearson’s correlation analysis was used to test the relationships between the altitude and the total number of species, and total number of endemic species at each survey site.” I believe elevation is a better term than altitude. Altitude is the height of an object above a reference point that could be defined to be anything, such as mean sea level (MSL) or above ground level (AGL). The term “elevation” is used to refer to the height of a place above mean sea level.
12. P 4. I have not seen the term “puddle sites” used before. Please provide a description of what these sites were or else use a more standard term. Might the authors have meant, “impounded sites”?
13. P 4. “The river types in the mountainous zone were of Aa and Aa-Bb types, and they took the forms of Bb, Bb-Bc, and Bc types towards the Yellow Sea.” The authors need to define these river types somewhere in the text or in Appendix Table A1.
14. P 5. Please explain what “Natural monument” refers to.
15. P 7: “The Taebaeksanmaek is a barrier that separates the water systems in the east and west districts since the beginning of the Third Era …” What does the “Third Era” refer to?
16. Appendix Table A1: The column heading “Distircts” should be “Districts.” Why is river width presented as square meters for some sites, shouldn’t the units be meters? Why are data for water width missing for some sites (e.g. 75, 82) or given as a negative value for site 59?
17. Appendix Table A2. Why do some of the species entries have multiple rows of abundance values and sometimes two values separated by a comma (e.g. Zacco platypus)?
Author Response
We thank you and the reviewers for your thoughtful suggestions and insights, which have enriched the manuscript and helped us produce a more balanced account of the research. The manuscript has been carefully rechecked and appropriate changes have been made in accordance with the reviewers’ suggestions. The responses to their comments have been prepared and attached herewith.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments to the Author
The manuscript contains a lot of valuable scientific data obtained from difficult-to access areas, including interesting problem of endemism or record of exotic species. However, the submitted paper can be considered as an excellent technical report, but not exactly as a scientific manuscript of broad interest. This is because it has not research questions/hypothesis. It provides relevant available information in a simple manner without any in-depth systematic analysis.
The manuscript also lacks data analysis, other than performing some very basic and simple statistic. These data show a real fish diversity in the studied region.
1. Within each separated locations (5), the following biotic indices should be calculated for all sites:
- Simpson's index of domination: D = ∑pi2 ,where pi– probability of the individual presence from the i-species;
- Shannon-Wiener diversity index: H’ = -∑( piln pi) where: ln pi– natural logarithm of pi;
Similarity among sites should be presented on dendrograms (e.g. with UPMGA method)
2. The taxonomic part of manuscript needs some important corrections. The Nelson’s work cited in the text (2006) is not valid any more in many instances. More actual is Nelson’s work from 2016. However, the highest validity for taxonomists demonstrates FishBase 2022. As so, all scientific species names should be checked following this base.
Examples:
Zacco koreanus – valid name: Nipponocypris koreanus
Sarcocheilichthys nigripnnis czerskii: valid name Sarcocheilichthys czerskii
Also the belonging to the particular families should be verified. For example, the Cyprinidae family was divided into some families (FishBase 2022). And so, Nipponocypris koreanus belongs to Xenocyprinidae, whereas Sarcocheilichthys czerskii to Gobionidae. In addition, in my opinion, all scientific names should be written as whole Latin name, because there are a lot of species described and, therefore, it is difficult to recognized all abbreviations.
Author Response
We thank you and the reviewers for your thoughtful suggestions and insights, which have enriched the manuscript and helped us produce a more balanced account of the research. The manuscript has been carefully rechecked and appropriate changes have been made in accordance with the reviewers’ suggestions. The responses to their comments have been prepared and attached herewith.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Second review of “Fish diversity and ichthyofauna of areas adjacent to the Demilitarized Zone in South Korea” by Hyeong Su Kim, Hyung Soo Seo, Su Hwan Kim, Hyun Mac Kim, and Myeong Hun Ko
I appreciate the changes that have been made to the manuscript, including the addition of diversity metrics and the PCA. These are necessary to fully describe diversity and highlight the importance of the environmental controls on composition. But there are still several issues that need to be addressed, including the rarefaction of species richness and the linear models for elevation. See comments below for more detail.
Line 107: The sentence “Fish were collected using a cast net … and a scoop-net ... flowing the water width and depth”, is unclear. Is there a typo or is the context missing? Based on the following sentences I think a revision is needed, perhaps:
Fish were collected using a cast net (6 mm mesh; 12.5 m2 = 2 2 3.14 m) and a scoop-net (4 mm mesh; 1.35 m2 = 1.5 0.9 m). At river widths < 10m, the cast net was deployed 5 – 10 times and the scoop-net was deployed for 30 min. At river widths 10 – 30 m, the cast net was deployed 11 to 20 times and scoop-nets were used for 30 to 60 min; at river widths > 30m, greater than 20 casts and scoop-net deployments of over 60 min were used, following the Guidelines of the National Natural Environment Survey (IV) [24].
Line 119: This sentence is awkwardly worded. Perhaps, “In the reservoir and pond sites, representative locations were sampled for fish and habitat data collection.” Though more detail may need to be given on how this was sampled. Are you missing species because you did not sample all types of water (i.e., flowing and pelagic areas)?
Line 121: Revise to: “In two mine-hazard sites, we conducted at least one survey with permission from the military units.” How many sites, is two correct?
Line 142: I strongly advise the use of rarefaction for comparing richness. See
Gotelli N. J. and Colwell, R. K. (2001). Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness. Ecology Letters 4(4):379-391.
https://doi.org/10.1046/j.1461-0248.2001.00230.x
The differences in sampling effort and streams size (though proportional) are still likely biased by abundance. If they are not, you will need to at least show the species accumulation curves so the reader knows there is no effect of abundance on your richness estimates, but I strongly doubt that is the case.
Line 235: I see this remains the same as the previous draft. You included linear models in the plot, but did you consider a quadratic? If richness is lower at mid elevations, then a y = ax+b will not capture that.
Line 236: The r-squared values for these regressions is really low. They don’t appear to explain any of the variation. Further the p-values are not significant for the linear model, which indicates that there is no effect of elevation on richness. What was the alpha level and sample size? These should be reported.
Section 3.4, How was human activity included in the PCA? As a numeric code? As a percentage of area?
Author Response
Dear Reviewer
We would like to thank you for your helpful comments and suggestions which have improved the quality of our manuscript. We have also resubmitted the revised manuscript to accompany our responses, which reflects the additional analyses done based on your recommendations.
Author Response File: Author Response.docx
Reviewer 2 Report
I'm glad you used PCA to explore patterns in community composition. I suggest redoing the PCA after eliminating sites 83 and 80 since they are extreme outliers in terms of their fish species composition. These sites appear to be extremely wide and at low elevation, perhaps they are estuarine sites? After eliminating them, the authors should provide an interpretation of how the four quadrants differ in their fish assemblages. Right now there is virtually no information about what gradients of species changes are evident in the PCA.
Author Response
We would like to thank you for your helpful comments and suggestions which have improved the quality of our manuscript. We have also resubmitted the revised manuscript to accompany our responses, which reflects the additional analyses done based on your recommendations.
Author Response File: Author Response.docx
Reviewer 3 Report
I accept the manuscript in present form
Author Response
Dear Reviewers
We would like to thank you for your helpful comments and suggestions which have improved the quality of our manuscript. We have also resubmitted the revised manuscript to accompany our responses, which reflects the additional analyses done based on your recommendations.
