The Application of a Fish-Based Multi-Metric Index for the Assessment of Ecological Qualities of Estuaries in the Korean Peninsula

Round 1

Reviewer 1 Report

Comments :

1.     This manuscript provide us an alternative to do an bio-assesment of aquatic ecosystem, estuary, based on fish-multi-metric index in order to determine the quality of estuaries-in the Korean Peninsula. Results obtained from this manuscript could be used as a reference to asses the quality of estuary at other areas

2.     In this manuscript, the authors using fish community/fish index to determine ecological status and the health status of the two kind of estuaries : open and closed estuaries in the Korean Peninsula. The study was very comprehensive and integrative because covering almost whole 325 estuaries in the peninsula

3.     Fish community that is used for estuaries health status assessment was collected using four sampling gears depend on type of estuaries. These fish capturing strategies will provide representative fish sample for the health/ecological status assessment. In addition to fish community data, nine water physics-chemical parameters were also documented to support the health status assessment of the estuaries. 

4.     In general, this research was arrange accordingly : clear back ground, using standard method, clear data collection and analysis, and concise conclusion

5.     According to the results of this study, it could be summarized regarding the negative effect of development surrounding estuaries area by using obtained data in this manuscript especially for closed estuary. In this manuscript obtained  that the ratio of tolerant species is higher and KEFAI values were lower in closed estuaries than in open estuaries, indicating the negative effects of construction of transverse structures on fish assemblages. Therefore, an planning action related with increasing the number of open estuaries need to be taken as a serious consideration in the near future to improve the health status of the estuaries in the peninsula

Author Response

We appreciate your good comments on our manuscript. As you said, estuaries are important and valuable areas for biodiversity, and KEFAI is useful tool to assess current status of ecosystem health of estuaries. We also think this multi-metric assessment could apply not only to Korean peninsula, but also to different countries after adjustment of some metrics. Thank you.  

Reviewer 2 Report

The manuscript by Kim et al. explores the use of a fish-based metric (KEFAI) to assess the health of estuarine fish communities in the Korean peninsula. From my understanding, fish assessment metrics are often calculated based on number and diversity of fish as well as with environmental variables. Therefore, it is not clear to me why some of the analyses are conducted – specifically the correlations of fish assemblages and KEFAI values. I believe if KEFAI is set up more clearly in the introduction and Table 1, the methods, results, and conclusions will be much clearer for the reader. Please see my specific comments below.

 

Abstract

Set up the meaning of the ratios and significance of freshwater vs. saltwater fish and “tolerant” vs. not tolerant fish.

 

Line 43. This sentence is confusing as written. I would suggest use of “(e.g., estuary dikes, dams, and seawalls)”.

 

Line 49 – 59. This paragraph could benefit from more references to support these claims about the region.

 

Line 77. This is not true for all aquatic ecosystems. There can be predators higher in the food web. Please update to make it more specific to this system.

 

Line 102. “Health of the estuary aquatic ecosystems” is vague – can you please provide more detail as to what about it you will measure?

 

Line 106. Same comment as above – what is “differences in health”?

 

Line 112. Over what span of time have the estuaries formed? It sounds like they have formed from development of coastlines, making me believe that the systems have been shifting as of recently.

 

Line 134. Not clear whether the same estuaries were surveyed repeatedly year to year.

 

Line 141. What was the reason for the use of different sampling gear (i.e., gill nets) in the closed systems?

 

Line 159. Water collection methods could use more explanation – were samples filtered? Frozen? It is important to include these details in the methods.

 

Line 166. This should be explained earlier to alleviate the vagueness of the “health of the ecosystem”.

 

Line 166. Some of these categories need explanations. How would you define “tolerant species” in this case? What about “abnormal individuals”?

 

Table 1. Please provide more detail about the M values listed in the table. It is not clear to me how the Scores listed in the columns correspond with the M values in the rows.

 

Table 3. Please list all of these categories in the methods – there are a few here that were not listed. I would suggest adding a column here (or above) that defines each.

 

Table 3. It is good that relative abundance is used as the metric here – given that total number of individuals/species/families is influenced by sampling effort (number of systems sampled). However, it is not clear to me what the “number of estuaries” value is here that is listed before the RA.

 

Figure 2,3. I would suggest making the font size larger on these figures – including the titles, axes, and legends.

 

Line 284. Remove duplicate “88.05%”

 

Line 288. I would suggest either listen species in common names or scientific names.

 

Table 5. Please include what the asterisks denote.

 

Figure 4. I would suggest labeling the X axis as simply “open” and “closed” and then put the sites as titles in each sub-graph, similar to other figures.

 

Line 315. It is not clear to me why correlations between KEFAI and each variable would be compared. Aren’t the values (e.g., fish assemblage numbers, estuary fish, freshwater fish), used to calculate the KEFAI metric?

 

Line 334. Are there datasets or publications to support this claim?

 

Line 371. Could there be other ecological explanations for this beyond sampling methods?

Author Response

The manuscript by Kim et al. explores the use of a fish-based metric (KEFAI) to assess the health of estuarine fish communities in the Korean peninsula. From my understanding, fish assessment metrics are often calculated based on number and diversity of fish as well as with environmental variables. Therefore, it is not clear to me why some of the analyses are conducted – specifically the correlations of fish assemblages and KEFAI values. I believe if KEFAI is set up more clearly in the introduction and Table 1, the methods, results, and conclusions will be much clearer for the reader. Please see my specific comments below.

 

Abstract

Set up the meaning of the ratios and significance of freshwater vs. saltwater fish and “tolerant” vs. not tolerant fish.

• To clarify the meaning, we have changed ratio to relative abundance in revised MS.

 

Line 43. This sentence is confusing as written. I would suggest use of “(e.g., estuary dikes, dams, and seawalls)”.

• We appreciate your valuable comments. Following your comment, we have changed “for example, estuary dikes, dams, and seawalls” to “(e.g., estuary dikes, dams, and seawalls)” (Line 45)

 

Line 49 – 59. This paragraph could benefit from more references to support these claims about the region.

• Following your comment, we have added references to support our description

Rho, P.; Lee, C.H. Using GIS to estimate estuarine wetlands in three major estuaries and to quantify wetland changes over the last century. Journal of Wetlands Research 2007, 9, 21-31

Rho, P.; Lee, C.H. Spatial distribution and temporal variation of estuarine wetlands by estuary type. Journal of the Korean Geographical Society 2014, 49, 321-338

Kwak, S.N.; Huh, S.H. Changes in species composition of fishes in the Nakdong River Estuary. Korean Journal of Fisheries and Aquatic Sciences 2003, 36, 129-135.

Park, J.S.; Gwak, W.S. Effects of estuarine dam on fish assemblage in Danghang Bay of the South Sea. Korean Journal of Ichthyology 2019, 31, 83-89.

Park, S.H.; Lee, J.W.; Kim, J.H.; Baek, S.H.; Yoon, J.D.; Choi, K.R.; Jang, M.H. Fish distribution and salinity in the Saemangeum Reservoir. Korean Society of Environmental Biology 2013, 31, 411-418.

Line 77. This is not true for all aquatic ecosystems. There can be predators higher in the food web. Please update to make it more specific to this system.

• We appreciate your valuable comments. We have changed the sentence like below

Fish are one of the highest taxons of the food chain in an aquatic ecosystem except mammals and birds while having close relationships with other species, and can be regarded to represent the biodiversity of the relevant area (Line 81-83)

 

Line 102. “Health of the estuary aquatic ecosystems” is vague – can you please provide more detail as to what about it you will measure?

• Based on your comment, We have added the meaning of ecosystem health in Introduction (Line 61-64), and we have changed Line 102 like below.

“Therefore, in this study, 325 river estuary points throughout the country in individual sea areas (West Sea, South Sea, and East Sea) were divided into types of estuaries (open estuaries and closed estuaries) and fish communities were identified through the assessment of the health of the estuary aquatic ecosystems investigating the number of species and individuals. (Line 104-108)

 

Line 106. Same comment as above – what is “differences in health”?

• To avoid vagueness of the phrase “ecosystem health”, and transfer our intention more clearly, we have defined the meaning in Introduction (Line 61-64)

 

Line 112. Over what span of time have the estuaries formed? It sounds like they have formed from development of coastlines, making me believe that the systems have been shifting as of recently.

• As you commented, this sentence is not well written. So, we have changed the sentence like below

The Korean Peninsula, which was the study area, is surrounded by sea on three sides, and there are about 460 estuaries distributed (Line 116-117)

 

Line 134. Not clear whether the same estuaries were surveyed repeatedly year to year.

• We appreciate your valuable comment. We investigated different estuaries each year and a total of 325 estuaries were investigated during 2016-2018.

 

Line 141. What was the reason for the use of different sampling gear (i.e., gill nets) in the closed systems?

• Gill nets were used in Closed estuaries because there was no water flow compared to open estuaries and the width of the water was wider, and because it had to be used in Closed estuaries according to the guidelines for investigation of estuaries in Korea.

 

Line 159. Water collection methods could use more explanation – were samples filtered? Frozen? It is important to include these details in the methods

• Water sampling and analysis are very well known for most researchers, and the manuals is already well conducted. So, we presented titles of sampling manuals instead of specific explanation of sampling and analysis methods. Revised sentence is like below.

Chemical oxygen demand (COD), total nitrogen (T-N), and total phosphorus (T-P) were analysed in the laboratory according to the measurement method for general items under the “Test Standards for Water Pollution Process (MOE, 2017)” and Rice et al. [34]. (Line 160-163)

 

Line 166. This should be explained earlier to alleviate the vagueness of the “health of the ecosystem”.

• We have added the meaning of ecosystem health in Introduction.

Ecosystem health is a concept that has often been applied to the evaluation of ecosystems, and it integrates environmental conditions with the impacts of anthropogenic activities in order to give information for a sustainable use and management of natural resources (Line 61-64)

 

Line 166. Some of these categories need explanations. How would you define “tolerant species” in this case? What about “abnormal individuals”?

• Based on your comment, we have changed those sentences like below in revision.

“M6, Proportion of tolerant species, a species resistant to environmental changes.”, “M8, Proportion of abnormal individuals, individuals to appear deformity, Erosion of fin, lesions, tumors.” (Line 172-174) 

 

Table 1. Please provide more detail about the M values listed in the table. It is not clear to me how the Scores listed in the columns correspond with the M values in the rows.

• We appreciate your valuable comment. As you commented, we revised Table 1 so that M values is accurately distinguished.

 

Table 3. Please list all of these categories in the methods – there are a few here that were not listed. I would suggest adding a column here (or above) that defines each.

• As you commented, we added explanations of seven categories in M & M.

. Fish assemblages were categorized seven types, primary freshwater, estuary, marine, migratory, exotic, endemic, endangered and tolerant. Primary freshwater, estuary, and marine means the fishes could living in freshwater, estuary and sea area, respectively. Exotic and endemic means fishes introduced from different country and only distributed in Korean peninsula, respectively. Endangered fish are the listed species by law of Ministry of Environment (MOE), Korea. The tolerant fish indicate species can endure harsh environment and listed by MOE. (Line 184-190)

 

Table 3. It is good that relative abundance is used as the metric here – given that total number of individuals/species/families is influenced by sampling effort (number of systems sampled). However, it is not clear to me what the “number of estuaries” value is here that is listed before the RA.

• We appreciate your valuable comment. Following your comment, we have changed “number of estuaries” to “number of estuaries investigated”

 

Figure 2,3. I would suggest making the font size larger on these figures – including the titles, axes, and legends.

• We appreciate your valuable comment. Following your comment, we made font size larger.

 

 

Line 284. Remove duplicate “88.05%”

• We appreciate your valuable comment. As you commented, we removed that.

 

Line 288. I would suggest either listen species in common names or scientific names.

• We appreciate your valuable comment. Following your comment, we revised common names to scientific names
•  

Table 5. Please include what the asterisks denote.

• Based on your comment, we added an explanation like below in revision.

*P<0.05, **P<0.001

 

Figure 4. I would suggest labeling the X axis as simply “open” and “closed” and then put the sites as titles in each sub-graph, similar to other figures.

• We appreciate your valuable comment. As you commented, we revised the X axis of Figure 4

 

Line 315. It is not clear to me why correlations between KEFAI and each variable would be compared. Aren’t the values (e.g., fish assemblage numbers, estuary fish, freshwater fish), used to calculate the KEFAI metric?

• Thank you for your comment and we also think this content is not necessary to describe our results. So, we have deleted correlation result between KEFAI with fish data, and just remaining physico- chemical results.(Line 320-323)

 

Line 334. Are there datasets or publications to support this claim?

• We have added three references to support the claim, as follows.

30. Yoon, J.D.; Kim, J.H.; Park, S.H.; Jang, M.H. The distribution and diversity of freshwater fishes in Korean Peninsula. Korean Journal of Ecology and Environment 2018, 51, 71-85.
31. Jeon, S.R. Studies on freshwater fish fauna in the rivers flowing in the East Sea. Sangmyung University 1982, 10, 465-487.
32. Lee, W.O.; Ko, M.H.; Bak, J.M.; Kim D.H.; Jeon, H.J.; Kim K.H. Characteristics of fish fauna and community structure in Buk Stream of Goseong, Korea. Korean Journal of Ichthyology 2010, 22, 238-248.

 

 

Line 371. Could there be other ecological explanations for this beyond sampling methods?

• We think major factors are by sampling methods, and also high nutrient loading and chemical pollution at large sites from upper stream could impact, as you commented. So, we have changed the sentence like below:

These results can be majorly considered to be attributable to the collection tools used (cast nets, skimming nets, long bag set nets, and gill nets), which are more advantageous in small-scale estuaries than large-scale estuaries. However, high nutrients loading, chemical pollution and pesticides from upper stream could also impact to the fishes at some large sites which have larger watershed. (Line 367-372)

Round 2

Reviewer 2 Report

Thank you for your revisions. I have a few other minor changes that could be addressed:

Line 104-110. The edited sentences are still a bit confusing. Please edit to make clearer.

Line 116-117. Same comment as above. Please edit to make clearer.

Line 142-146. Thank you for clarifying in your response why gill nets were used in the closed system. I believe it would be helpful to include some of those details here.

Table 1. Please explain "M" in the table legend sentence.

Author Response

Line 104-110. The edited sentences are still a bit confusing. Please edit to make clearer.

• Thank you and we revised the sentences like below

Therefore, in this study, we investigated fish communities of 325 estuaries throughout the Korean peninsula to evaluate the health of estuaries using KEFAI, and also com-pared ecosystem health status by sea areas (West Sea, South Sea, and East Sea) and types of estuaries (open estuaries and closed estuaries).(Line 104-107)

 

Line 116-117. Same comment as above. Please edit to make clearer.

• Thank you. We have changed the sentence like below

The Korean Peninsula is surrounded by sea on three sides, and a lot of streams and rivers flow into the ocean, as a result, there are about 460 estuaries formed in South Korea.(Line 113-114)

 

Line 142-146. Thank you for clarifying in your response why gill nets were used in the closed system. I believe it would be helpful to include some of those details here.

• Thank you for your comment. We have added why we use gill net in closed estuaries.

and for the closed estuaries, gill nets (mesh size 12×12 mm; length 36 m; height 90 cm) was additionally installed because closed estuaries showed reservoir like characteristic, we have added a gear appropriate for lentic systems (Line 142-145)

 

Table 1. Please explain "M" in the table legend sentence

• We have added explanation of “M” in revised MS.

M1-M8 indicate eight different metrics used to estimate KEFAI.