Alien Rainbow Trout Oncorhynchus mykiss in the Balkhash Basin (Kazakhstan, Central Asia): 50 Years of Naturalization

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper is potentially interesting including recent distribution, diets and life history parameters, and therefore I recommend it for publication in “Animals” after revisions. However, some results are not tested statistically and not clear. My comments are as follows.

Materials and Methods:

L 112-113. I like to know your sampling effort because rainbow trout caught in your study are not numerous. How many hours did you investigate in one area?

L 170 “wase”?

L 194-195 You need to explain CCA for readers who don’t know this method. Why was this method used? What factors were analyzed in this method ?

Fig. 3. Show which group is i, ii, or iii in the figure. I did not understand what arrows mean.

L 233. Common names of fish are not shown in Suplement 4.

L241-243 If possible, indicate number of observations.

L277-278 Test statistically.

L282 smaller than ? It is not clear what you compared.

L283-284 Did you include all samples from all locations? If you tested for each water body, indicate it clearly. In method (L150), you mentioned “quantity of mesenteric fat and sexual maturity were assessed visually on a scale from 0 to 5”. However, their results are not shown. In L285, you described “most individuals” that is not clear. Show data in the text, or in a table or figure.

L 288-289, this result is not clear, maybe it should be explained by a scale from 0 to 5.

L 295-299. Similarly, your descriptions are not clear. Show exact figures or percentages when you used “some” (L295), “predominated”(L297, 298), “more numerous” (L299).

L 299 “that” should be replaced by “than”.

L302-305 It is not clear how you tested statistically. Did you compare for each age? If so, indicate age tested. If you analyzed including all ages, you should use a paired statistical test (other than U test). Figure 4. Letters in the figure are too small to read.

L 325. ”fish from” is not clear. It should be replaced by all fish or --% of fish.

L326. ”fish from” is not clear. It should be replaced by all fish or --% of fish.

Figure 6. Is each graph drawn using one individual data? Or does it show the average of several individuals ? Clarify this point in method or the figure legend.

L 424. I could not find Supplement 5. Is it Supplement 4 ? Supplements are confusing and I might receive incorrect supplements from the editorial office.

L 518- This part needs to be tested by DNA analysis in future studies.

L542-543 The habitat of the Masak population is not described in the result section, and therefore this part should be deleted. Or describe habitats of fish in the result section.

L549-550 If you have some data of fish fauna in the past, describe it here. Rainbow trout might have eliminated some indigenous fish in the past. Although the diets of indigenous fish are not shown in this study, there is a possibility that rainbow trout affected other fish through competition for food.

Comments on the Quality of English Language

There are some mistakes in English.

Author Response

All the authors are deeply grateful to you for your time, careful reading of the manuscript and valuable advice. Thanks to your help, we have significantly improved our professional skills and seen our shortcomings.

 

These have been improved according your recommendation:

L 112-113. I like to know your sampling effort because rainbow trout caught in your study are not numerous. How many hours did you investigate in one area?

L 170 “wase”?

L 194-195 You need to explain CCA for readers who don’t know this method. Why was this method used? What factors were analyzed in this method ?

Fig. 3.Show which group is i, ii, or iii in the figure. I did not understand what arrows mean.

L 233. Common names of fish are not shown in Suplement 4.

L282 smaller than ? It is not clear what you compared.

L 288-289, this result is not clear, maybe it should be explained by a scale from 0 to 5.

L 299 “that” should be replaced by “than”.

L302-305 It is not clear how you tested statistically. Did you compare for each age? If so, indicate age tested. If you analyzed including all ages, you should use a paired statistical test (other than U test). Figure 4. Letters in the figure are too small to read.

Figure 6. Is each graph drawn using one individual data? Or does it show the average of several individuals ? Clarify this point in method or the figure legend.

L 518- This part needs to be tested by DNA analysis in future studies.

 

These had been done:

L277-278 Test statistically. – U-test was applied

L283-284 Did you include all samples from all locations? If you tested for each water body, indicate it clearly. In method (L150), you mentioned “quantity of mesenteric fat and sexual maturity were assessed visually on a scale from 0 to 5”. However, their results are not shown. In L285, you described “most individuals” that is not clear. Show data in the text, or in a table or figure. – Proportions are presented

L 295-299. Similarly, your descriptions are not clear. Show exact figures or percentages when you used “some” (L295), “predominated”(L297, 298), “more numerous” (L299). - Proportions are presented

L 424. I could not find Supplement 5. Is it Supplement 4 ? Supplements are confusing and I might receive incorrect supplements from the editorial office. – Presented as Supplement 5 (picture)

 

These sentences are removed:

L241-243 If possible, indicate number of observations.

L542-543 The habitat of the Masak population is not described in the result section, and therefore this part should be deleted. Or describe habitats of fish in the result section.

 

Discussion

L549-550 If you have some data of fish fauna in the past, describe it here. Rainbow trout might have eliminated some indigenous fish in the past. Although the diets of indigenous fish are not shown in this study, there is a possibility that rainbow trout affected other fish through competition for food. – Our results revealed coexistence rainbow trout together with indigenous fish species during decades, except Lower Kolsy Lake

Author Response File: Author Response.doc

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors, 

I read your paper titled "Alien rainbow trout Oncorhynchus mykiss in the Balkhash basin (Kazakhstan, Central Asia): 50 years of naturalization" with great interest.  

I would like to suggest the following revision. 

1. I think the paper is very long and feel that you should focus on the most important question of whether rainbow trout has successfully established the wild populations in the area and how they have coexisted with native fishes historically.  

2. To improve the manuscript from the point above, I suggest that you omit the contents of phenotypic characteristics because the results you obtained are not quite scientifically relevant to the main point of the paper.  You can also omit or significantly reduce the trout diet (stomach contents) data because the diet of native fishes is not presented, therefore the potential niche overlap or evidence of interspecific competition over the prey resources cannot be discussed.  Maybe you can generate other short papers based on these.  

3. In revising the manuscript focused on the historical distribution patterns of rainbow trout, I suggest you present the data of the past stocking records as a table or figure instead of storing them in a supplemental file.  For example, can you show how many individuals of, or how much kilograms of, rainbow trout were stocked in the past at where and when site by site?  Then the readers can see more clearly the correlation between the past effort of stocking and the current presence/absence of the species.  Otherwise, we do not know whether the rainbow trout were established or not established due to the environmental factors or all other biotic factors but just because the trout were not introduced there.   

4. To show the impact of rainbow trout on native fish community assemblages, can you modify the Table 2 to show the list of the native fishes with their abundance in the density data (if not possible, catch-per-unit-effort data)?  Also, in the same table, can you organize it by presence and absence of rainbow trout?  It also would be helpful by organizing the native fishes by the scientific family names, so that those who are not familiar with the taxa in the region will understand the context better.

Thank you.    

Comments on the Quality of English Language

I am not a native speaker/writer in English and believe you did your best.  However, I was disturbed by the use of the word mykiss as the fish name, so I think you should just stick with rainbow trout.   

Author Response

All the authors are deeply grateful to you for your time, careful reading of the manuscript and valuable advice. Thanks to your help, we have significantly improved our professional skills and seen our shortcomings.

 

1. I think the paper is very long and feel that you should focus on the most important question of whether rainbow trout has successfully established the wild populations in the area and how they have coexisted with native fishes historically.   – We tried to do it.
2. To improve the manuscript from the point above, I suggest that you omit the contents of phenotypic characteristics because the results you obtained are not quite scientifically relevant to the main point of the paper.  You can also omit or significantly reduce the trout diet (stomach contents) data because the diet of native fishes is not presented, therefore the potential niche overlap or evidence of interspecific competition over the prey resources cannot be discussed.  Maybe you can generate other short papers based on these.  -  We have omitted the description of the spots but retained the description of the difference in skin tone, as this trait may reflect genetic variation in the population.
3. In revising the manuscript focused on the historical distribution patterns of rainbow trout, I suggest you present the data of the past stocking records as a table or figure instead of storing them in a supplemental file.  For example, can you show how many individuals of, or how much kilograms of, rainbow trout were stocked in the past at where and when site by site?  Then the readers can see more clearly the correlation between the past effort of stocking and the current presence/absence of the species.  Otherwise, we do not know whether the rainbow trout were established or not established due to the environmental factors or all other biotic factors but just because the trout were not introduced there.  – All reviewers recommended shortening the manuscript, but in different parts. Therefore, we decided to leave information about the number of fish universes in the appendix.
4. To show the impact of rainbow trout on native fish community assemblages, can you modify the Table 2 to show the list of the native fishes with their abundance in the density data (if not possible, catch-per-unit-effort data)?  Also, in the same table, can you organize it by presence and absence of rainbow trout?  It also would be helpful by organizing the native fishes by the scientific family names, so that those who are not familiar with the taxa in the region will understand the context better. – It is done.

Reviewer 3 Report

Comments and Suggestions for Authors

 

This paper seeks to provide a synoptic perspective of the exotic species Oncorhynchus mykiss in the area of the Balkhash basin in Kazakhstan. One of the main contributions is the combination of a trove of sources to examine this globally relevant fish species in an area that does not have a significant amount of information. One strength of this paper is that it adds to the review of information with some more recent data collected from the field. It also provides an interpretation of the regional context of O. mykiss.

 

General comments: Three main comments.

1.        There are grammatical issues throughout the paper. There are none that make the paper unreadable, but it should be proof-read for grammar and clarity before publication.

2.        The authors are presenting information about an area of the world that is not well known to most readers. There could be more information provided to the reader to explain the process of species introduction to these systems (not only O. mykiss, but also other species listed in Table 2). Also, the lack of familiarity of the area means that the authors should provide some more information about the geography in Figure 1. For example, the Lower Kolsay and Middle Kolsay Lakes are not indicated in Figure 1, even though they are referred to extensively. Also, in Table 2, there are many abbreviations of field locations. These could be included in Figure 1, as well.

3.     The Discussion section is not well structured. The authors tend to write starting with the conclusions and then working backward to the data. Each section should start with the findings of the study, then connect them with the available literature, and connecting them outward from there. For more information, see my individual comments, below.

 

Review.

I really liked the content of the article, since it highlights information about a globally important invasive species in an area that does not have a lot of information. The paper presents well-tested methods, which make the findings more easy to compare and contrast with studies done in other areas. If the authors address the issues with English and the presentation of their Discussion, I think that this would make a great addition to the literature.

 

Specific Comments about content

Lines 63 to 64: Style. It would be useful to put these in terms of relative frequency of use. Using simple online tools (Goole ngram and Google trends) confirms my own experience, that “rainbow trout” is by far the most common, followed by “steelhead trout.” The term “redband trout” is not very common. My suggestion, therefore, is to list them in descending order of use frequency: “rainbow trout, steelhead trout, and redband trout.”

Line 66: Comprehension. I would suggest being more precise and write, “…cold-water tributaries of the Pacific Ocean in Northeast Asia and Northwest North America.” This will stop the more “persnickety” readers from trying to read sideways into your statement. After all, under certain ways of interpreting “cold-water tributary” there are some that are NOT part of the range of O. mykiss. As an example of what I mean, the Mekong River flows into the Pacific Ocean, making it an Asian river flowing into the Pacific Ocean, and the Himalayan tributaries are definitely cold-water systems. HOWEVER, these cold-water tributaries of this Asian river that flows into the Pacific is NOT part of the native range of O. mykiss.

 

Line 89: Clarity. When were these introductions made? If prior to 1992, then these should be referred to as Soviet republics, and not countries. While it may be interesting to place all the prior paragraphs into the context of Soviet-era planning, that might be beyond the scope of this paper. If the authors don’t want to focus attention on the differences between the status of these areas as Soviet republics vs. independent, post-Soviet countries, then the authors can rewrite this part of the sentence as, “…water bodies of other areas in Central Asia, including in Uzbekistan and Kyrgyzstan.”

Lines 94-95: Clarity. When is “the past decade”? The use of relative time markers is not terribly useful, especially as time progresses. Being strict, the time frame should mean anything published from 2014-2024, but looking at the references, these were published in 2010 and 2012. I would just write, “There were also reports published in 2010 and 2012 on trout being found…”

Table 2 – It is unclear how the authors are structuring their table for “other alien species.” It may be useful to explicitly indicate the taxonomic Order (e.g., Perciformes) for each grouping of native and alien species. A quick visual evaluation of the species listed do show a lack of cold-water specialists among the exotic species, other than O. mykiss.

Figure 3– The presentation does not clearly show the native vs. exotic species. Instead of including another color, the authors could use different shapes to show native (O) and exotic (X) species?

Figure 4 – The text is too small to easily read. The authors should increase the text size. Also, it is not clear why this figure is split into A and B.

Table 6. How much of an ecological impact is there for the aquatic macroinvertebrates in this area in different seasons? In other words, how much of a difference would there be between sampling in March vs. May? In a similar manner, how much of a seasonal impact would be seen in a sample taken in June vs. August? In other words, how ecologically comparable is the March in Masak brooks to the May in Ulken Kokpak River – and the same with the August sample in Masak brooks to the June samples in the other two areas – when considering the abundances and diversity of macroinvetebrates in these systems?

Discussion. Section numbering. If the Discussion section is 4, then the first section should have the number 4.1.

Discussion. The structure of this section is haphazard, and it lacks the clear focus that was present in the other sections. Most important is that the authors tend to start with conclusions and work backwards to the data associated with their study, almost in a “post hoc ergo propter hoc” manner. I encourage the authors to start with their findings and then work forward to conclusions, with clear connection to the literature along the way. To take one example: Section 3.1 “Distribution, habitats and environment” – This paragraph contains a lot of inductive reasoning and inferential reasoning. The discussion about the study results do not show up until a few paragraphs down (Line 376 “Our results show….”). I contend that a Discussion section should begin with an interpretation of the study results through first deductive and then inductive reasoning. In other words, this paragraph should follow the interpretation of the data, not beforehand.

Line 422: Symbol. Use “≥”.

 

 

Comments on the Quality of English Language

Specific Comments about the Quality of English:

Line 35: Grammar. Change to “lowland rivers”

Line 44: Remove unneeded apostrophe in “land´”.

Line46-47: Change to “…in Lower Kolsay Lake.” There is no need for “the” in this case.

Line 61: Grammar. Change to either “novel environments” or “a novel environment”.

Line 70: Grammar. Change to “…alien fish species threatening indigenous aquatic fauna.”

Line 71: Grammar. Change to “…consists of 10-12 species…” Unless this is no longer the case, and the authors are going to talk about the recent extinction of some of these species, which would warrant the use of the past tense. Otherwise, this is a simple statement of how things are, which puts it in the present tense.

Lines 76-77: Syntax and clarity. Unless the readers are familiar with this area of Kazakhstan, it is not likely that they will be familiar with the names of the lakes (or what they are referred to in English). There are three Kolsay Lakes: “Lower Kolsay Lake,” “Middle Kolsay Lake,” and “Upper Kolsay Lake.” Whenever the authors refer to these lakes, they should be clear to use the full name portion of the lake. For example here, it should be “Lower Kolsay and Middle Kolsay Lakes.” If the authors refer to “Lower and Middle Kolsay Lakes” the mapping of the adjectives does not work clearly. Also the syntax overall syntax of this sentence needs some work, because there is a confusion between the adjective phrase “high mountain” and the adjective portions of the name “Lower Kolsay” and “Middle Kolsay.” My suggestion is to change the terms and rewrite it as, “…were introduced into the alpine lakes of Lower Kolsay and Middle Kolsay and the mountainous sector of the Chilik River…”

Line 78: Grammar. Almost always, landforms and rivers use “the” before the name. In contrast, lakes tend NOT to use “the.” For example, when referring to them in writing one uses “THE Kamchatka Peninsula,” “THE Chilik River” and “Upper Kolsay Lake”. Exceptions, of course, exist.

Lines 79 and 80: Capitalization. Change to “Tekes and Chilik Rivers” and “Tentek and Emel Rivers”.

Line 83: See comment for line 78.

Lines 84,86 & 87,: See comment for lines 76-77.

Line 100. Grammar. Change to “…resident (referred to as rainbow trout)…”

--- I will not make further comments about grammar beyond the Introduction section. I strongly recommend that the authors have a thorough review of the English grammar, syntax, and stylistic clarity of their writing prior to publication. ----

 

Author Response

All the authors are deeply grateful to you for your time, careful reading of the manuscript and valuable advice. Thanks to your help, we have significantly improved our professional skills and seen our shortcomings.

Table 6. How much of an ecological impact is there for the aquatic macroinvertebrates in this area in different seasons? In other words, how much of a difference would there be between sampling in March vs. May? In a similar manner, how much of a seasonal impact would be seen in a sample taken in June vs. August? In other words, how ecologically comparable is the March in Masak brooks to the May in Ulken Kokpak River – and the same with the August sample in Masak brooks to the June samples in the other two areas – when considering the abundances and diversity of macroinvetebrates in these systems?

Answer: It was not our intention to compare seasonal changes in aquatic macroinvertebrate communities in different rivers. This table shows the frequency of occurrence of different groups of aquatic invertebrates in the rainbow trout diet in each water body and, most importantly, the role of flying insects (imago) in the trout diet.

We have tried to follow all the other recommendations of Reviewer III. Then the text was revised and edited by the MDPI English editing services

General comments: Three main comments.

1. There are grammatical issues throughout the paper. There are none that make the paper unreadable, but it should be proof-read for grammar and clarity before publication.
2. The authors are presenting information about an area of the world that is not well known to most readers. There could be more information provided to the reader to explain the process of species introduction to these systems (not only O. mykiss, but also other species listed in Table 2). Also, the lack of familiarity of the area means that the authors should provide some more information about the geography in Figure 1. For example, the Lower Kolsay and Middle Kolsay Lakes are not indicated in Figure 1, even though they are referred to extensively. Also, in Table 2, there are many abbreviations of field locations. These could be included in Figure 1, as well.
3. The Discussion section is not well structured. The authors tend to write starting with the conclusions and then working backward to the data. Each section should start with the findings of the study, then connect them with the available literature, and connecting them outward from there. For more information, see my individual comments, below.

 Review.

I really liked the content of the article, since it highlights information about a globally important invasive species in an area that does not have a lot of information. The paper presents well-tested methods, which make the findings more easy to compare and contrast with studies done in other areas. If the authors address the issues with English and the presentation of their Discussion, I think that this would make a great addition to the literature.

 Specific Comments about content

Lines 63 to 64: Style. It would be useful to put these in terms of relative frequency of use. Using simple online tools (Goole ngram and Google trends) confirms my own experience, that “rainbow trout” is by far the most common, followed by “steelhead trout.” The term “redband trout” is not very common. My suggestion, therefore, is to list them in descending order of use frequency: “rainbow trout, steelhead trout, and redband trout.”

Line 66: Comprehension. I would suggest being more precise and write, “…cold-water tributaries of the Pacific Ocean in Northeast Asia and Northwest North America.” This will stop the more “persnickety” readers from trying to read sideways into your statement. After all, under certain ways of interpreting “cold-water tributary” there are some that are NOT part of the range of O. mykiss. As an example of what I mean, the Mekong River flows into the Pacific Ocean, making it an Asian river flowing into the Pacific Ocean, and the Himalayan tributaries are definitely cold-water systems. HOWEVER, these cold-water tributaries of this Asian river that flows into the Pacific is NOT part of the native range of O. mykiss.

 Line 89: Clarity. When were these introductions made? If prior to 1992, then these should be referred to as Soviet republics, and not countries. While it may be interesting to place all the prior paragraphs into the context of Soviet-era planning, that might be beyond the scope of this paper. If the authors don’t want to focus attention on the differences between the status of these areas as Soviet republics vs. independent, post-Soviet countries, then the authors can rewrite this part of the sentence as, “…water bodies of other areas in Central Asia, including in Uzbekistan and Kyrgyzstan.”

Lines 94-95: Clarity. When is “the past decade”? The use of relative time markers is not terribly useful, especially as time progresses. Being strict, the time frame should mean anything published from 2014-2024, but looking at the references, these were published in 2010 and 2012. I would just write, “There were also reports published in 2010 and 2012 on trout being found…”

Table 2 – It is unclear how the authors are structuring their table for “other alien species.” It may be useful to explicitly indicate the taxonomic Order (e.g., Perciformes) for each grouping of native and alien species. A quick visual evaluation of the species listed do show a lack of cold-water specialists among the exotic species, other than O. mykiss.

Figure 3– The presentation does not clearly show the native vs. exotic species. Instead of including another color, the authors could use different shapes to show native (O) and exotic (X) species?

Figure 4 – The text is too small to easily read. The authors should increase the text size. Also, it is not clear why this figure is split into A and B.

Discussion. Section numbering. If the Discussion section is 4, then the first section should have the number 4.1.

Discussion. The structure of this section is haphazard, and it lacks the clear focus that was present in the other sections. Most important is that the authors tend to start with conclusions and work backwards to the data associated with their study, almost in a “post hoc ergo propter hoc” manner. I encourage the authors to start with their findings and then work forward to conclusions, with clear connection to the literature along the way. To take one example: Section 3.1 “Distribution, habitats and environment” – This paragraph contains a lot of inductive reasoning and inferential reasoning. The discussion about the study results do not show up until a few paragraphs down (Line 376 “Our results show….”). I contend that a Discussion section should begin with an interpretation of the study results through first deductive and then inductive reasoning. In other words, this paragraph should follow the interpretation of the data, not beforehand.

Line 422: Symbol. Use “≥”.

 

Comments on the Quality of English Language

Specific Comments about the Quality of English:

Line 35: Grammar. Change to “lowland rivers”

Line 44: Remove unneeded apostrophe in “land´”.

Line46-47: Change to “…in Lower Kolsay Lake.” There is no need for “the” in this case.

Line 61: Grammar. Change to either “novel environments” or “a novel environment”.

Line 70: Grammar. Change to “…alien fish species threatening indigenous aquatic fauna.”

Line 71: Grammar. Change to “…consists of 10-12 species…” Unless this is no longer the case, and the authors are going to talk about the recent extinction of some of these species, which would warrant the use of the past tense. Otherwise, this is a simple statement of how things are, which puts it in the present tense.

Lines 76-77: Syntax and clarity. Unless the readers are familiar with this area of Kazakhstan, it is not likely that they will be familiar with the names of the lakes (or what they are referred to in English). There are three Kolsay Lakes: “Lower Kolsay Lake,” “Middle Kolsay Lake,” and “Upper Kolsay Lake.” Whenever the authors refer to these lakes, they should be clear to use the full name portion of the lake. For example here, it should be “Lower Kolsay and Middle Kolsay Lakes.” If the authors refer to “Lower and Middle Kolsay Lakes” the mapping of the adjectives does not work clearly. Also the syntax overall syntax of this sentence needs some work, because there is a confusion between the adjective phrase “high mountain” and the adjective portions of the name “Lower Kolsay” and “Middle Kolsay.” My suggestion is to change the terms and rewrite it as, “…were introduced into the alpine lakes of Lower Kolsay and Middle Kolsay and the mountainous sector of the Chilik River…”

Line 78: Grammar. Almost always, landforms and rivers use “the” before the name. In contrast, lakes tend NOT to use “the.” For example, when referring to them in writing one uses “THE Kamchatka Peninsula,” “THE Chilik River” and “Upper Kolsay Lake”. Exceptions, of course, exist.

Lines 79 and 80: Capitalization. Change to “Tekes and Chilik Rivers” and “Tentek and Emel Rivers”.

Line 83: See comment for line 78.

Lines 84,86 & 87,: See comment for lines 76-77.

Line 100. Grammar. Change to “…resident (referred to as rainbow trout)…”

 

Author Response File: Author Response.pdf