Migration of Non-Native Predator Asp (Leuciscus aspius) from a Reservoir Poses a Potential Threat to Native Species in Tributaries

Round 1

Reviewer 1 Report

This manuscript reports on a radiotelemetry study that examines how a non-native fish moves within a reservoir-tributary system over time. The information might be of use if placed in an appropriate context for the reader. I have several suggestions to improve the manuscript.

 

line 20: delete “consequently”

 

line 32: Why is the acronym NIS for non-native species? Why not NNS?

 

line 36: I would add “some” before “native”

 

lines 40-41: What does this mean?

 

line 44: Introductions of what?

 

lines 50-62: Does this paragraph serve any purpose? I think it could be deleted without any loss.

 

lines 77-78: Needs a better transition.

 

line 78: Altered seasonal regimes of what?

 

lines 78-81: How are these things related?

 

line 79: what is “defragmentation”?

 

line 82: Should be “human-made” not “man-made”

 

line 91: this line is awkwardly written.

 

lines 93-94: Should probably make clear here that asp is non-native

 

Introduction: In general the Introduction needs to be better focused. It seems to bounce around and the reader has to work hard to really know what you are trying to get the reader to take away from the Introduction. I suggest you try to trim out all the unnecessary material and keep only the material that is most relevant to the “story” you are trying to tell.

 

line 117: What does “vastly diverse” mean?

 

lines 144-145: I would move this information earlier to when you first talk about the transmitters.

 

line 153: water temperature of what?

 

line 164: How did you determine the mean temperature?

 

line 168: How did you transform the data?

 

lines 171-176: These methods need to be more clearly described.

 

line 174: What classes?

 

line 177: Need to explain this occurrence more.

 

Figure 2: Why is the bar for 3 a different color?

 

line 211: I would move this information earlier when talking more generally about the radio tracking.

 

lines 211-213: But you don’t know where the males were so can you really draw such a conclusion.

 

lines 215-216: What evidence do you have for this statement?

 

lines 221-230: You don’t really have data to address this. I would delete this paragraph.

 

line 232: What evidence do you have for the foraging habitat? You didn’t actually observe the behavior of the fish only their location.

 

lines 239-241: Need a better transition here.

 

lines 245-246: What does this mean?

 

line 248: difference between what?

 

lines 248-251: This is not clear.

 

line 279: What evidence do you have for this?

 

lines 279-281: You only looked at one system (with a dam). You need to look/compare to river without a dame to be able to say this.

 

line 281 and throughout: “Positioning” is not a good word choice for this. Need to look at other literature to figure out a better word for this.

 

lines 286-287: What specific evidence do you have for this?

 

lines 293-297: Not sure you really were able to show this with your methodology.

 

The English needs work and polishing as does the overall organization and flow of ideas. The paper is somewhat hard to follow and determine the take-home message.

Author Response

Reviewer 1

This manuscript reports on a radiotelemetry study that examines how a non-native fish moves within a reservoir-tributary system over time. The information might be of use if placed in an appropriate context for the reader. I have several suggestions to improve the manuscript.

The introduction has been modified and shortened following the suggestions.  The Materials and Methods section has been clarified and clear description of statistical methods was provided. The MS was edited by American Journal Experts.

 

Line 20: delete “consequently”

Deleted.

Line 32: Why is the acronym NIS for non-native species? Why not NNS?

Corrected. The acronym “NIS” has been replaced by “NNS” throughout the manuscript.

Line 36: I would add “some” before “native”

The section was reduced in accordance with comments from other reviewer.

Lines 40-41: What does this mean?

Rephrased.

Line 44: Introductions of what?

Corrected.

Lines 50-62: Does this paragraph serve any purpose? I think it could be deleted without any loss.

Deleted.

Lines 77-78: Needs a better transition.

Corrected.

Line 78: Altered seasonal regimes of what?

Text clarified.

Lines 78-81: How are these things related?

Both, natural and anthropogenic changes, have an impact on home ranges.

Line 79: what is “defragmentation”?

Deleted.

Line 82: Should be “human-made” not “man-made”

Thank you, accepted.

Line 91: this line is awkwardly written.

Modified.

Lines 93-94: Should probably make clear here that asp is non-native

Thank for your suggestion. The paragraph is about asp in general. The next paragraph makes clear the asp is introduced to study area.

Introduction: In general the Introduction needs to be better focused. It seems to bounce around and the reader has to work hard to really know what you are trying to get the reader to take away from the Introduction. I suggest you try to trim out all the unnecessary material and keep only the material that is most relevant to the “story” you are trying to tell.

Introduction have been modified and shortened following the suggestions.

Line 117: What does “vastly diverse” mean?

Rephrased.  

Lines 144-145: I would move this information earlier to when you first talk about the transmitters.

Thank you for suggestion. According to maintaining the content composition of “2.2 Fish Origin and Tagging” and “2.3 Monitoring Procedures”, we decided to describe transmitters in 2.2 and receivers description remain in 2.3 part. We hope reviewer will understand our intention.

Line 153: water temperature of what?

Temperature data obtained from the sensor transmitters, i.e., the temperature in the area of fish occurrence.

Line 164: How did you determine the mean temperature?

The temperature used for determining temperature thresholds was calculated as daily average of the sampling day.

Line 168: How did you transform the data?

Clarified.

Lines 171-176: These methods need to be more clearly described.

The more detailed explanation provided.

Line 174: What classes?

Clarified.

 Line 177: Need to explain this occurrence more.

Information that this is a binary variable was added. A detailed description is in the first sentence of data analyses section.

Figure 2: Why is the bar for 3 a different color?

The color was modified.

Line 211: I would move this information earlier when talking more generally about the radio tracking.

Thank you for this suggestion. While we understand the intention to move information earlier, we decided to not separate the results focused on differences in sex.

Lines 211-213: But you don’t know where the males were so can you really draw such a conclusion.

We can draw such a conclusion, because we don’t know where they were exactly, but we know for sure that they were not in the river or in the shallow part of the reservoir. So, when they returned back to the river or shallow part of the reservoir, we can strongly suggest that they were previously in the deeper sections of the reservoir (maximum depth 25 m), because other possibility does not exist (the reservoir is not passable downstream).

Lines 215-216: What evidence do you have for this statement?

Evidence originates from temperature sensor transmitters data. As stated in the “habitat measurements” section, the water temperature (°C) was obtained from the sensor transmitters and was used to show the threshold when the asp entered and left the Vltava River.

Lines 221-230: You don’t really have data to address this. I would delete this paragraph.

Thank you for suggestion. The paragraph have been deleted.

Line 232: What evidence do you have for the foraging habitat? You didn’t actually observe the behavior of the fish only their location.

Thank you for your question. The asp remain in a river being spread within the longitudinal profile from spring to autumn, i.e., approx. 6 months. This is a period of time when asp utilize the river resources, i.e., utilize the river as a foraging habitat.

Lines 239-241: Need a better transition here.

Rephrased.

Lines 245-246: What does this mean?

Since there are no studies of the impact of asp as a trophic competitor or predator on species, e.g., salmonids, who inhabit the riverine system above Lipno Reservoir, we call for further studies focused on this topic.

Line 248: difference between what?

The difference in movement activity was demonstrated between months.

Lines 248-251: This is not clear.

Rephrased.

Line 279: What evidence do you have for this?

The evidence for differences between sexes is illustrated by Figure 4.

Lines 279-281: You only looked at one system (with a dam). You need to look/compare to river without a dame to be able to say this.

“The probability of occurrence of females was higher in the tributary, and females were positioned more often than males.”

We are afraid that we are not sure whether we fully understand this comment.

We agree, the study is focused only on dam – tributary system and that the comparison with other systems would be an interesting experiment and would provide additional information.

Line 281 and throughout: “Positioning” is not a good word choice for this. Need to look at other literature to figure out a better word for this.

We agree with the reviewers and have revised use of these words accordingly. Instead “positioning” term “detection was used.

Lines 286-287: What specific evidence do you have for this?

Thank you. The evidence is illustrated by Figure 4 based on related results.

Lines 293-297: Not sure you really were able to show this with your methodology.

We focused on the asp migratory behaviour and we demonstrated, the migration should not be understood as a spawning migration only. The migration and prolonged time spent in the river include also competition for resources (e.g., food, territory, space).

The English needs work and polishing as does the overall organization and flow of ideas. The paper is somewhat hard to follow and determine the take-home message.

Author Response File: Author Response.docx

Reviewer 2 Report

GENERAL COMMENTS

This is an interesting study about the migratory movements of a non-native species. My main concern with this manuscript is that it presents few novelties, as it seems (and is referred in the Discussion), there is already literature that focus on the migrations of the asp and detail these characteristics that are similar with the present study. The second point is that the authors refer to the effects of non-native species on native ones, but this was never addressed on the present study. The study is focused only on the asp, but do not explores if their occurrence, taking into account the specificities of their seasonal migration (already addressed on the literature), affects the native species. It would be very useful for readers, that the authors explore on how their findings – the specificities of fish movements they found- can affect native species, and then what implications can be drawn for other contexts, other than Vltava River on Czech Republic. This should be addressed on the last part of Abstract and Discussion. So basically, it seems to me your study is too local (does not point out how the findings can be applicable elsewhere, i.e. what implications for management) and has few novelty. Acceptance is therefore conditioned on how the authors improve their paper, taking into account these important aspects. Minor comments are detailed below.

 

SPECIFIC COMMENTS

Line 2-3, title – I think it has a low appeal. It should reflect possible implications for native species.

Line 17-18 – But why do you think this issue is important? This should be outlined here to capture increasing interest from the readers.

Line 32- Why “NIS” and not “NNS” (non-native species)? “I” may be confounded as “Invasive”. which is not the scope of the manuscript.

Line 36 – Could you be more specific on how non-native species facilitate native ones?

Line 103 – But why this is important?

Line 114 – A map of the study area would be useful here. Suggest move the one from Figure 1 and make this Figure 1.

Line 115 – Why did you only consider 15 km and not the whole reservoir, as it would make much more sense? How long is the reservoir?

Line 130 – Why using two types of transmitters?

Line 133- For how long?

Line 136 – Suggest Monitoring instead of Sampling.

Line 138 – This term “primary” should be removed. You only have one study area. The same on line 142.

Line 139, spawning migrations – provide the months and if possible, a reference to support it.

Line 139, “the fish movements were fast” – How do you know this? What evidence there is?

Line 143 – How deep?

Line 152 – Did you use a daily average?

Line 160 – Suggest something like “was used as a proxy of movement activity”.

Line 172 – Refer the names of exploratory variables.

Line 174- What classes?

Line 177- What was the purpose of this test?

Line 178 – Seasonal differences in what?

Line 187 – I don’t understand what you mean by “were positioned 13 times”. Please be clearer. Same on line 211, 281.

Figure 1 – This map should appear on the study area, not here. the fish silhouette should also be removed.

Figure 2 – Use the same color for all the bars (why the first one is different from the others?). X-axis: replace the numbers by the months acronyms (i.e. Mar, Apr, May, Jun,…).

Line 219 – not clear what you mean by number of individual positions.

Line 234-236 – According to what you say here from the existing literature, it seems the manuscript has very few novelties. After all, there is already evidence about spawning behaviour of asp.

Line 264 – Not understand the part of chain reaction. Please be clearer.

Line 293-294 – This is no novelty at all, i.e. that anthropogenically altered habitats favor the spread of non-native species. In addition, your study was only focused on the spawning migration of asp, and did not explore interactions with non-native species, particularly if these are affected by asp.

 

Author Response

Reviewer 2

This is an interesting study about the migratory movements of a non-native species. My main concern with this manuscript is that it presents few novelties, as it seems (and is referred in the Discussion), there is already literature that focus on the migrations of the asp and detail these characteristics that are similar with the present study. The second point is that the authors refer to the effects of non-native species on native ones, but this was never addressed on the present study. The study is focused only on the asp, but do not explores if their occurrence, taking into account the specificities of their seasonal migration (already addressed on the literature), affects the native species. It would be very useful for readers, that the authors explore on how their findings – the specificities of fish movements they found- can affect native species, and then what implications can be drawn for other contexts, other than Vltava River on Czech Republic. This should be addressed on the last part of Abstract and Discussion. So basically, it seems to me your study is too local (does not point out how the findings can be applicable elsewhere, i.e. what implications for management) and has few novelty. Acceptance is therefore conditioned on how the authors improve their paper, taking into account these important aspects. Minor comments are detailed below.

 

SPECIFIC COMMENTS

 

Line 2-3, title – I think it has a low appeal. It should reflect possible implications for native species.

Thank you for this suggestion. Title modified. „Migration of Non-native Predator Asp (Leicuscus aspius) from a Reservoir Poses a Potential Threat to Native Species in Tributaries“

Line 17-18 – But why do you think this issue is important? This should be outlined here to capture increasing interest from the readers.

Beside a river fragmentation caused by dam construction, an impact of non-native species migrating from the reservoirs on native assemblages in their tributaries should be considered from the long-term point of view. 

Line 32- Why “NIS” and not “NNS” (non-native species)? “I” may be confounded as “Invasive”. which is not the scope of the manuscript.

Corrected. The acronym “NIS” has been replaced by “NNS” throughout the manuscript.

 Line 36 – Could you be more specific on how non-native species facilitate native ones?

Deleted.

Line 103 – But why this is important?

We see the importance in possible impact on native species (e.g., grayling) since asp occupy river for longer period than expected according to previous studies.

Line 114 – A map of the study area would be useful here. Suggest move the one from Figure 1 and make this Figure 1.

Thank you. Figure 1 was divided into “Figure 1” the map of the study area and “Figure 2” showing the seasonality of asp occurrence in the river.

Line 115 – Why did you only consider 15 km and not the whole reservoir, as it would make much more sense? How long is the reservoir?

Information has been added.

Line 130 – Why using two types of transmitters?

Using various types of transmitters allowed us to tag fish of different size. Also, different operational life is of importance for data acquisition in such a long-term study.

Line 133- For how long?

Clarified.

Line 136 – Suggest Monitoring instead of Sampling.

Thank you for your suggestion. Rephrased.

Line 138 – This term “primary” should be removed. You only have one study area. The same on line 142.

The term “primary” was removed.

Line 139, spawning migrations – provide the months and if possible, a reference to support it.

Modified as requested.

Line 139, “the fish movements were fast” – How do you know this? What evidence there is?

Rephrased, the fish longitudinal movements were fast (i.e. over 1 km per day upstream).

Line 143 – How deep?

More detailed information is provided in first paragraph “2.1 Study Area”.

Line 152 – Did you use a daily average?

Yes, the daily average was used.

Line 160 – Suggest something like “was used as a proxy of movement activity”.

Thank you. Rephrased as suggested.

Line 172 – Refer the names of exploratory variables.

Corrected.

Line 174- What classes?

The paragraph was clarified.

Line 177- What was the purpose of this test?

This test is used in GENMOD procedure to estimate significance of tested variables.

Line 178 – Seasonal differences in what?

Differences in asp occurrence in the Vltava River versus occurrence in the Lipno Reservoir. The text was rephrased in order to improve its clarity.

Line 187 – I don’t understand what you mean by “were positioned 13 times”. Please be clearer. Same on line 211, 281.

Term was rephrased in order to assure better clarity. Improved definition of “number of detections” variable was also included in “data analyses” section.

Figure 1 – This map should appear on the study area, not here. the fish silhouette should also be removed.

Figure 1 was divided into “Figure 1” the map of the study area and “Figure 2” showing the seasonality of asp occurrence in the river.

Figure 2 – Use the same color for all the bars (why the first one is different from the others?). X-axis: replace the numbers by the months acronyms (i.e. Mar, Apr, May, Jun,…).

Thank you. The figure was modified as suggested.

Line 219 – not clear what you mean by number of individual positions.

Rephrased. It is a number of detections in the Vltava River (mean ± S.E.).

Line 234-236 – According to what you say here from the existing literature, it seems the manuscript has very few novelties. After all, there is already evidence about spawning behaviour of asp.

The asp stays in a river for approx. 6 months. Then they return to the reservoir for the winter period (minimize energy expenditures being protected from high flow conditions and predators), which significantly favor them compare to native species overwintering in the river (headwaters). The strategy is regularly repeated. We believe that such a finding is novel and can be expected in a riverine network affected by dam fragmentation.

Line 264 – Not understand the part of chain reaction. Please be clearer.

Since as a predator remain in the river for longer, it may affect native species, for example grayling, by predation or competition. Not only the jeopardized species, but the entire ecosystem can bear the consequences (e.g, Baxter et al., 2004).

BAXTER, Colden V., et al. Fish invasion restructures stream and forest food webs by interrupting reciprocal prey subsidies. Ecology, 2004, 85.10: 2656-2663.

Line 293-294 – This is no novelty at all, i.e. that anthropogenically altered habitats favor the spread of non-native species. In addition, your study was only focused on the spawning migration of asp, and did not explore interactions with non-native species, particularly if these are affected by asp.

With all due respect to the reviewer, we believe that this point is not correct. We focused on the asp migratory behaviour and we demonstrated, the migration should not be understood as a spawning migration only. We agree that specific impact of asp presence in the river on native species is an important area that requires further research.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for your thorough response to my previous comments. You have done a good job addressing my concerns and have significantly improved the manuscript.

Reviewer 2 Report

I'm overall satisfied with revisions and comments provided by the authors. It definitely has a broader scope now and details are clearer.

Just have a minor issue to deal before formal acceptance: Figure 1 needs a scale on the map. Also, an arrow indicating the flow direction would also be useful.