Resource Use among Six Commercial Fish Species from the South-Eastern Gill Net Fisheries, Korea
, Myung-Joon Kim 2, Seok-Nam Kwak 3, In-Seong Han 4 and Joo-Myun Park 1,*
Round 1
Reviewer 1 Report
The paper is relevant and presents some important results concerning trophic ecology of six commercial fish species. It is well written and organized. Nevertheless, some methodological questions must be fixed and clarified, and some information must be added to the text. There are some specific comments that must be clarified to sustain the manuscript and make it more fluid and attractive for an international audience. I recommend the article below to improve some issues in your text:
Estevan Luiz da Silveira, Nabil Semmar, Joan E. Cartes, Victor M. Tuset, Antoni Lombarte, Eduardo Luis Cupertino Ballester & André Martins Vaz-dos-Santos (2020) Methods for Trophic Ecology Assessment in Fishes: A Critical Review of Stomach Analyses, Reviews in Fisheries Science & Aquaculture, 28:1, 71-106, DOI: 10.1080/23308249.2019.1678013
Specific comments:
Introduction Section
The most part of it was devoted to explaining and presenting methods, but your paper is not focused on methods: you are only using them! In this way, this section must present the relevance of resource use, and a background about these six commercial species, focusing on fishing aspects and previous knowledge about them. You must conduct hypotheses/goals clearly, avoiding the use of common phrases.
Third paragraph – It must be reviewed to properly address the problem.
Fourth paragraph – Please, verify the current taxonomic status of each species and present their authors in the first quote in the text. Use Eschmeyer’s Catalog of Fishes (CAS - Eschmeyer's Catalog of Fishes: (calacademy.org))
Material and Methods Section
2.1 Sampling
The first paragraph presents relevant information about sampling, whose aspects have a “result effect” that must be discussed and cannot be neglected.
The text informs that samples were obtained from bycatch. In this way, they were not focused on target species. In this way, what do these six species represent? An ecological assessment (trophic ecology) must be carefully done when based on fisheries samples, due to selectivity.
Although it is not possible to change samplings, these questions must be clearly discussed: species representativeness, some lacks, what this ecological approach means.
Another point that must be discussed is the sampling period. Dietary composition can present cyclic changes due to environmental conditions (e.g., water masses and associated fauna, plankton season blooms, etc.). Please, link your analysis with the incipient discussion about this that was presented.
2.2 Stomach content analysis
The first paragraph lacks enough references to subsidize the methods applied. I was wondering how the mass percentage was quantified, whether grouping or individually. Please, check Silveira et al. (2020) to verify this important question.
The use of Shannon index is not clear: what were the counting units used for it? It is a taxonomic index, and there are different taxonomic levels analyzed. In my opinion, it brings more noise than clearness. Nevertheless, if it will be maintained, values must be statistically compared.
2.3 Stable isotope analyses
The first paragraph lacks enough references to subsidize the methods applied.
Results Section
It is important to present a statistical description of body lengths. It is not possible to understand the trophic ecology unknowing the size structure of each species once dietary patterns present ontogenetic variation. This information must be presented and discussed.
3.1 Trend in dietary composition
Please, pay attention that you inform that “At least 17 taxa (functional prey groups)…” were identified. But your analyses comprised a taxonomic perspective, including the use of Shannon index. At Table 1, it is also important to highlight the number of stomachs with any content. For example, we are talking about a very low number for H. otakii (5) and S. schlegelii (8).
Still considering Table 1, I am concerned about the Shannon index (and other applications) due to the very different taxonomic levels: seaweed (a general classification), classes, orders. What is debris? Please, define and explain. Pisces is a term no more applied; it is an artificial classification of a set of some Chordata. What is in the caption “relative frequency of occurrence, and relative mass contribution”? There is only one piece of information in the table.
Table 2 and other captions: replicate the codes, once each figure/table must be independent.
The PERMANOVA must be detailed presented, or in the main text or in an appendix/supplementary material.
Break the long paragraph of results considering the different analyses performed.
3.2 Stable isotopes values
The ANOVA must be detailed presented, or in the main text or in an appendix/supplementary material.
Discussion Section
This section must be improved and explored, considering the changes requested. Species representativeness in light of environmental conditions, selectivity, and temporal effect must be clarified. This will allow for the readers to understand your universe.
Various aspects must be explained. For example, you say shallow/bottom, but it is not possibly known what you mean. The absence of an area description also makes some understandings not easy.
The last paragraph is not a conclusion. Your paper was not focused on methodological approaches and a knowledge contribution is not a conclusion. Please, rewrite the conclusion focusing on your goals, essentially resource use. In the Introduction section a sequence of hypotheses and objectives would help to build concluding remarks.
Author Response
The paper is relevant and presents some important results concerning trophic ecology of six commercial fish species. It is well written and organized. Nevertheless, some methodological questions must be fixed and clarified, and some information must be added to the text. There are some specific comments that must be clarified to sustain the manuscript and make it more fluid and attractive for an international audience. I recommend the article below to improve some issues in your text:
Estevan Luiz da Silveira, Nabil Semmar, Joan E. Cartes, Victor M. Tuset, Antoni Lombarte, Eduardo Luis Cupertino Ballester & André Martins Vaz-dos-Santos (2020) Methods for Trophic Ecology Assessment in Fishes: A Critical Review of Stomach Analyses, Reviews in Fisheries Science & Aquaculture, 28:1, 71-106, DOI: 10.1080/23308249.2019.1678013
Response: Thank you for your careful review and evaluation of the manuscript. We revised the manuscript, especially in the method section based on the reference suggested.
Specific comments:
Introduction Section
The most part of it was devoted to explaining and presenting methods, but your paper is not focused on methods: you are only using them! In this way, this section must present the relevance of resource use, and a background about these six commercial species, focusing on fishing aspects and previous knowledge about them. You must conduct hypotheses/goals clearly, avoiding the use of common phrases.
Response: Thank you for your suggestion. We added the explanation of relevance of resource use and a background about six commercial fish species in the introduction as you mentioned in the comment (line 65-74)
Third paragraph – It must be reviewed to properly address the problem.
Response: We have revised this as suggested (line 57-62)
Fourth paragraph – Please, verify the current taxonomic status of each species and present their authors in the first quote in the text. Use Eschmeyer’s Catalog of Fishes (CAS - Eschmeyer's Catalog of Fishes: (calacademy.org))
Response: We have added the information about the current taxonomic status of each species as well as their authors based on Eschmeyer’s Catalog of Fishes in the fourth paragraph of the introduction (line 68-71).
Material and Methods Section
2.1 Sampling
The first paragraph presents relevant information about sampling, whose aspects have a “result effect” that must be discussed and cannot be neglected.
Response: We have revised this as suggested, adding the relevant information about samples (line 87-93).
The text informs that samples were obtained from bycatch. In this way, they were not focused on target species. In this way, what do these six species represent? An ecological assessment (trophic ecology) must be carefully done when based on fisheries samples, due to selectivity.
Response: The six fish species were the most abundant fish species during our sampling and also listed as main fishes based on previous catch data. Therefore, our samples of fish species can be enough to provide resource uses among higher trophic level species in marine ecosystem of the southeastern Korean waters (line 72-74).
Although it is not possible to change samplings, these questions must be clearly discussed: species representativeness, some lacks, what this ecological approach means.
Response: The six target species were the common fish species in the study area usually caught by gill net, there they have ecological importance as top predators in the marine ecosystem. Such information added in the last paragraph of the introduction section (line 72-74)
Another point that must be discussed is the sampling period. Dietary composition can present cyclic changes due to environmental conditions (e.g., water masses and associated fauna, plankton season blooms, etc.). Please, link your analysis with the incipient discussion about this that was presented.
Response: Although our samplings have been conducted for over a year (except the winter season), the six fish species were caught mostly during the warm season. In addition, fishing activities in the study area also occurred mostly during the warm season. Therefore, we analyzed resource uses among the six fish species when their abundances were high (line 91-94).
2.2 Stomach content analysis
The first paragraph lacks enough references to subsidize the methods applied. I was wondering how the mass percentage was quantified, whether grouping or individually. Please, check Silveira et al. (2020) to verify this important question.
Response: The methods of stomach analysis subsidized as suggested by reviewing references of Hyslop (1980) and Silveira et al. (2020) (line 111-123)
The use of Shannon index is not clear: what were the counting units used for it? It is a taxonomic index, and there are different taxonomic levels analyzed. In my opinion, it brings more noise than clearness. Nevertheless, if it will be maintained, values must be statistically compared.
Response: We calculated the Shannon index based on the number of individuals by dividing the prey items into as possible as species-level. We provided numerical dietary data in supplementary table (Table S1).
2.3 Stable isotope analyses
The first paragraph lacks enough references to subsidize the methods applied.
Response: We have added more references to justify our methods for describing isotope trophic ecology.
Results Section
It is important to present a statistical description of body lengths. It is not possible to understand the trophic ecology unknowing the size structure of each species once dietary patterns present ontogenetic variation. This information must be presented and discussed.
Response: First, the ranges of body length were added in the result section (line 177-180). However, we could not analyze ontogenetic variations because of the lack of samples and narrower ranges of lengths. Because our study focus on population level of resource uses, we think intra-specific variations look not considerable for main research aim of the current study. Nonetheless, due to the lack of samples, we will conduct the further study on entire dietary habitat for the species including ontogenetic and temporal variations.
3.1 Trend in dietary composition
Please, pay attention that you inform that “At least 17 taxa (functional prey groups)…” were identified. But your analyses comprised a taxonomic perspective, including the use of Shannon index. At Table 1, it is also important to highlight the number of stomachs with any content. For example, we are talking about a very low number for H. otakii (5) and S. schlegelii (8).
Response: First, we added supplementary table included frequency, number and mass dietary data, and then re-calculated Shannon index using numerical dietary data. Low number of samples containing prey items for H. otakii and S. schlegelli are due to the low number of samples and high ratio of empty stomach. Such relatively low numbers of sample subsidized by comparing previous results. Consequently, S. schlegelli showed similar results with previous study despite of low number of sample number, but the results were slightly different for H. otakii. We discussed this point in the discussion section (line 330-338).
Still considering Table 1, I am concerned about the Shannon index (and other applications) due to the very different taxonomic levels: seaweed (a general classification), classes, orders. What is debris? Please, define and explain. Pisces is a term no more applied; it is an artificial classification of a set of some Chordata. What is in the caption “relative frequency of occurrence, and relative mass contribution”? There is only one piece of information in the table.
Response: Again. Shannon index was re-calculated based on numerical dietary data at a possible species levels of prey items. In addition, taxonomic classifications of prey items were re-arranged as suggested. The caption of Table 1 was also revised accordingly.
Table 2 and other captions: replicate the codes, once each figure/table must be independent.
Response: We have added the codes in all tables and figures independently.
The PERMANOVA must be detailed presented, or in the main text or in an appendix/supplementary material.
Response: We added more information of PERMANOVA result in the results section (line 195-201).
Break the long paragraph of results considering the different analyses performed.
Response: We separated the paragraph with PERMANOVA, Bray-Curtis sections and canonical analysis sections.
3.2 Stable isotopes values
The ANOVA must be detailed presented, or in the main text or in an appendix/supplementary material.
Response: We added the more information for ANOVA in the text (line 245-246).
Discussion Section
This section must be improved and explored, considering the changes requested. Species representativeness in light of environmental conditions, selectivity, and temporal effect must be clarified. This will allow for the readers to understand your universe.
Response: Thank you for your suggestion. We have added the explanation about species representativeness in the first paragraph of discussion section (line 287-296).
Various aspects must be explained. For example, you say shallow/bottom, but it is not possibly known what you mean. The absence of an area description also makes some understandings not easy.
Response: We revised the first paragraph of discussion section by adding more descriptions. The habitat descriptions of shallow/bottom were supplemented by including depth and substrate information (i.e., ~30 m of rocky bottom or sandy/muddy bottom) (line 285-288).
The last paragraph is not a conclusion. Your paper was not focused on methodological approaches and a knowledge contribution is not a conclusion. Please, rewrite the conclusion focusing on your goals, essentially resource use. In the Introduction section a sequence of hypotheses and objectives would help to build concluding remarks.
Response: We modified the last paragraph of the discussion section as suggested (line 388-399)
Reviewer 2 Report
This study investigated the resource use patterns of Chelidonichthys spinosus, Lophius litulon, Glyptocephalus stelleri, Cleisthenes pinetorum, Hexagrammos otakii, and Sebastes schlegelii using stomach content and stable isotope analyses. Results of this study contribute to the understanding of trophic relationships among fish species living in the East Sea, Korea.
For the introduction section, this study's background and rationale are unclear. Providing information on fishery resources in the East Sea can give a clear background for this study. In addition, The reasons for studying these six species are not clear. The habitats of these six species are also unclear.
The methods for stomach content analysis are insufficient. For example, the position of the fish stomach examined and the process of measuring dry mass are lacking.
The abstract describes the narrow and wide niches of fish. How are niche widths calculated in the method?
Figure 2, providing a circle for each species or group may be more meaningful.
Figure 3, what do dotted lines indicate?
The 1st paragraph of the discussion may be more appropriate for the introduction.
Author Response
This study investigated the resource use patterns of Chelidonichthys spinosus, Lophius litulon, Glyptocephalus stelleri, Cleisthenes pinetorum, Hexagrammos otakii, and Sebastes schlegelii using stomach content and stable isotope analyses. Results of this study contribute to the understanding of trophic relationships among fish species living in the East Sea, Korea.
Response: Your comment absolutely corresponds to the goal of our study. Thank you for your considerable review for the manuscript.
For the introduction section, this study's background and rationale are unclear. Providing information on fishery resources in the East Sea can give a clear background for this study. In addition, The reasons for studying these six species are not clear. The habitats of these six species are also unclear.
Response: We have added the reasons for studying the six fish species in the last paragraph of the introduction.
The methods for stomach content analysis are insufficient. For example, the position of the fish stomach examined and the process of measuring dry mass are lacking.
Response: We have revised the method of stomach content analysis more in detail including position of the fish stomach as suggested (line 92-94)
The abstract describes the narrow and wide niches of fish. How are niche widths calculated in the method?
Response: By using the variance represented by the stable isotope values, we obtain the convex hull total area (TA), standard ellipse area (SEA), and corrected standard ellipse area (SEAc) values (added in the method section). Trophic niche widths can be used to compare using above values, but we used a more robust SEAc values indicating the extents of niche widths of fish species. We have revised this as intended (line 144-148).
Figure 2, providing a circle for each species or group may be more meaningful.
Response: We have retained our visualization for Figure 2, because they are sufficiently distinguishable by both color and shape.
Figure 3, what do dotted lines indicate?
Response: We revised figure 3 caption as “Carbon (δ13C) and nitrogen (δ15N) stable isotope composition for six fish species. The solid and dotted lines indicate corrected standard ellipse areas (SEAc) and convex hull total areas (TA) based on their stable isotope values, respectively.”
The 1st paragraph of the discussion may be more appropriate for the introduction.
Response: We removed some information of the first paragraph of the discussion into the introduction as suggested (line 266-271)
Round 2
Reviewer 1 Report
Thank you for your attention with my comments. I guess that this is the correct way for the best science: I took some time to study your paper and contribute with it, and you also take some time to address and think about my comments.
Author Response
Thank you for your attention with my comments. I guess that this is the correct way for the best science: I took some time to study your paper and contribute with it, and you also take some time to address and think about my comments.
Response: Thank you for your generous evaluation of the manuscript. We deeply thank again your comments in more developing our manuscript in publication of JMSE.
Reviewer 2 Report
The only issue left is that the 1st paragraph of the discussion supports the validity of this study. It may be more appropriate in the introduction.
Author Response
The only issue left is that the 1st paragraph of the discussion supports the validity of this study. It may be more appropriate in the introduction.
Response: Thank you for your last comment for the manuscript. We moved the first of paragraph of discussion into the introduction section as suggested.
