Spoiled for Choice during Cold Season? Habitat Use and Potential Impacts of the Invasive Silurus glanis L. in a Deep, Large, and Oligotrophic Lake (Lake Maggiore, North Italy)
Round 1
Reviewer 1 Report
The paper investigated the diet composition of an invasive alien fish species European catfish (Silurus glanis) in a deep, large and oligotrophic lake (L. Maggiore) in Italy. It represented the different trophic niches in littoral and pelagic habitats of the lake, and speculated the potential impacts of the invasive species on pelagic food web of the deep lake. It would enrich the fundamental information of trophic ecology for this invasive catfish and benefit the alien species control and fisheries management in the deep lake. I recommend the manuscript be published if the followed issues could be further addressed.
- In order to explore the trophic ecology of the invasive catfish in the deep lake, especially to understand the different trophic niches and its alteration with spatial and temporal changing, the sample collection should cover a whole year. While, only the seasons of later autumn and early winter have been considered for fishing in the present study. Although considering the relative stability of the water temperature during this period and excluding the effect of temperature could validate the influence of the different habitats on diet composition, which is the most important issue in this paper, however, there were less data to reveal the mechanism of the species invasion in the deep lake. Thus, I suggest tongue down some conclusions of the paper.
- The study site is appropriate to be incorporated into the part of Introduction, which is helpful to raise the study topic or hypothesis of this paper.
- During the fishing, the nets were set at dusk and withdrawn the following morning. It means the fish might have been caged in the nets more than 10 hours. During this period, some of the prey in the stomachs might have been digested when the fish were eviscerated and the diet composition finally got may be bias. At the same time, the prey that were not possible to recognize were discarded, which would result in bias as well. In fact, the unrecognized prey may be further identified through some other methods, such as DNA markers. The paper should admit these problems about samples and prey recognition, which should be mentioned in the part of Discussion.
- It is necessary to supplement why the seasons of late autumn and early winter were chosen for fishing and trophic ecology study for the species, especially need to narrate its context with the topic of this study.
- It is better to provide some details of the division of size classes. Was it related to the different development stages, diet transition, or some other trophic characters of this catfish? I suggest to replace “Class II >=101 cm” by “Class II >100 cm”.
- I am not sure if the definition of vacuity index is accurate. In my opinion, this index should be the proportion of empty stomach in all stomach sampled. While the description of VI in the text is really ratio of empty stomach to stomachs with contents. Nevertheless, the VI values presented in the Results were number of empty divided by total number of all stomachs, such as on line 265.
- What’s purpose of the temperature -depth profile in the first paragraph of the Results. I think it is more appropriate as a context of the season selection in the Material and methods incorporated with the topic issue of this study.
- The trends in L. Maggiore’s fishing harvest during the 20 years of catfish invasion seem have less relation to the exploring of trophic ecology of S. glanis during cold season. The assessment of potential role of catfish on the lake’s fishery is not the topic of this study.
- Supplement the legend meaning of Figure 2.
Author Response
The paper investigated the diet composition of an invasive alien fish species European catfish (Silurus glanis) in a deep, large and oligotrophic lake (L. Maggiore) in Italy. It represented the different trophic niches in littoral and pelagic habitats of the lake, and speculated the potential impacts of the invasive species on pelagic food web of the deep lake. It would enrich the fundamental information of trophic ecology for this invasive catfish and benefit the alien species control and fisheries management in the deep lake. I recommend the manuscript be published if the followed issues could be further addressed.
- In order to explore the trophic ecology of the invasive catfish in the deep lake, especially to understand the different trophic niches and its alteration with spatial and temporal changing, the sample collection should cover a whole year. While, only the seasons of later autumn and early winter have been considered for fishing in the present study. Although considering the relative stability of the water temperature during this period and excluding the effect of temperature could validate the influence of the different habitats on diet composition, which is the most important issue in this paper, however, there were less data to reveal the mechanism of the species invasion in the deep lake. Thus, I suggest tongue down some conclusions of the paper.
We thank the reviewer for this comment. The aim of the paper was to provide the first ever information on the diet and habitat use of the species in a deep, large and oligotrophic lake (i.e., Lake Maggiore), which so far has not yet been investigated. As pointed out by the reviewer, future works are needed to fully comprehend the invasion mechanism of S. glanis in oligotrophic and deep lakes, and this has been better highlighted in the discussion (Lines 490-494) and conclusion sections (Lines 549-551), toning down some of the conclusions, as suggested.
- The study site is appropriate to be incorporated into the part of Introduction, which is helpful to raise the study topic or hypothesis of this paper.
We moved the study site description in the introduction part, as per the reviewer’s comment. Lines 89-125
- During the fishing, the nets were set at dusk and withdrawn the following morning. It means the fish might have been caged in the nets more than 10 hours. During this period, some of the prey in the stomachs might have been digested when the fish were eviscerated and the diet composition finally got may be bias. At the same time, the prey that were not possible to recognize were discarded, which would result in bias as well. In fact, the unrecognized prey may be further identified through some other methods, such as DNA markers. The paper should admit these problems about samples and prey recognition, which should be mentioned in the part of Discussion.
We thank the reviewer for the suggestion. We specified that: “caution shuold be applied since some biases may have affected diet composition inferences. In particular, during the long permanence of catfish in the nets (from dusk to dawn) some prey items might have been already digested and thus missed. Similalry, the discard of highly digested material may have led to some underestimation of prey abundance and presence”. Lines 446-450.
- It is necessary to supplement why the seasons of late autumn and early winter were chosen for fishing and trophic ecology study for the species, especially need to narrate its context with the topic of this study.
The study was realized in the occasion of an exceptional experimental fishing period for which fishing authorities (the CISPP) granted commercial fishermen the permission to use large mesh gillnets during a fishing stop period. Moreover, this period is when there is, according to anglers, the higher number of catches of S. glanis in the pelagic habitat. We added this explanation in the material and methods section at Lines 152 – 157.
- It is better to provide some details of the division of size classes. Was it related to the different development stages, diet transition, or some other trophic characters of this catfish? I suggest to replace “Class II >=101 cm” by “Class II >100 cm”.
Division in size classes was done to detect possible diet transition demonstrated in other catfish populations (i.e., Ferreira et al. 2019). Size classes were selected based on the most recent work dealing with large size catfish diet (Ferreira et al. 2019). We improved this explanation as suggested at Lines 199 - 201 and we corrected to “Class > 100” all over the manuscript, as proposed.
- I am not sure if the definition of vacuity index is accurate. In my opinion, this index should be the proportion of empty stomach in all stomach sampled. While the description of VI in the text is really ratio of empty stomach to stomachs with contents. Nevertheless, the VI values presented in the Results were number of empty divided by total number of all stomachs, such as on line 265.
There was an error in the definition of vacuity index as the reviewer noted and we amended the text accordingly. Line 204.
- What’s purpose of the temperature -depth profile in the first paragraph of the Results. I think it is more appropriate as a context of the season selection in the Material and methods incorporated with the topic issue of this study.
Temperature did not have a role in the choice of the sampling season. But temperature-depth profile helped to interpretate some results and that’s why it was placed in the results. We followed the reviewer’s suggestion and we moved this part in the material and methods section at Lines 158 - 173.
- The trends in L. Maggiore’s fishing harvest during the 20 years of catfish invasion seem have less relation to the exploring of trophic ecology of S. glanis during cold season. The assessment of potential role of catfish on the lake’s fishery is not the topic of this study.
We understand that fisheries data are not strictly related to the trophic ecology of S. glanis in Lake Maggiore. However, our goal was not only to provide the first data on the trophic ecology of catfish in this lake, but also to discuss all the potential impacts (ecological but also economic; Lines 137 - 138) that may results from the presence of this species. Despite in scientific community the negative role of invasive species is widely accepted, this is not always true for other stakeholders (such as professional and recreational fishermen). As a result, invasive species are continuously released into new areas, and this is particularly true for freshwater fishes. Therefore, we think that it is important to highlight also the potential economic outcomes of invasive species and we think the harvest data presented in this study are useful for this purpose. Our data are not conclusive and, as highlighted in the discussion, a quantitative study is necessary but, still, we believe our data may serve as a starting point. For these reasons, we decided to keep this part, although marginal to the trophic ecology of the species.
- Supplement the legend meaning of Figure 2.
Legend of Figure 2 has been supplemented detailing what the points of different colours represent and adding reference to Figure 1 for samplings sites. Lines 258 - 259
Reviewer 2 Report
As the movement of people and goods has become more active across oceans, it is very important for the conservation of local ecosystems to understand how invasive alien species adapt to their new habitats and how the ecosystems change as a result. Especially when "plasticity", which is often used in this paper, is suspected, we need to be especially careful in the research. This paper reports on the distribution and feeding habits of the European catfish Silurus glanis, a non-native species in Italian lakes that seems to reign near the top of the ecosystem.
The results of the analysis presented in this paper are generally appropriate, but the following questions need to be explained.
・The meaning of "littoral" and "pelagic": the authors try to use these two terms to describe the habitat of S. glanis, but I don't think they are synonyms. If "littoral" means close to the shore, the synonym would be "off the coast", and if it means close to the bottom of the lake, "benthic" would be the synonym. Since the depth of the benthic gillnet and the pelagic gillnet is almost the same, "littoral" and "off the coast" may be appropriate expressions. If so, the way the sampling sites are shown in Fig. 1(a) would not be appropriate. The definition of "littoral" and "pelagic" in this paper needs to be clarified to determine whether these two habitats are simply different vertically, or whether they are different horizontally and vertically.
・The possibility of vertical migration of S. glanis: It is well known that flatfishes/flounders living on the seafloor ascend, search for food and prey on pelagic fish. It is possible that S. glanis living in the pelagic habitat lives near the bottom of the lake like the individuals living in the "littoral" habitat and occasionally ascends to feed, which needs to be explained. In the case of "littoral" samplings, gillnets were not set in the middle layer of the lake, so authors could not obtain data on individuals that ascended to feed.
・The effect of size selectivity of gillnets: The mesh size of pelagic gillnets was larger than that of benthic gillnets. This difference in mesh size may have led to the difference in the size of S. glanis caught. Explanation is needed.
・BPUE and NPUE: The mass or number of fish caught in the fishery is not the same as the biomass. These expression needs to be changed. It is not clear what the area of BPUE and NPUE in units of "/m^2" represents, since we do not know what range of fish the gillnet was trying to catch. In Fig. 1(b), the benthic gillnet appears to be fixed to the lake bottom, while the pelagic gillnet appears to be drifting without being fixed. It is important to explain the justification for comparing the quantity and number of fish collected by these different methods.
L.178-183: There are often differences in LWRs among seasons and regions, and it should be explained that they can be treated collectively.
That is all.
Author Response
As the movement of people and goods has become more active across oceans, it is very important for the conservation of local ecosystems to understand how invasive alien species adapt to their new habitats and how the ecosystems change as a result. Especially when "plasticity", which is often used in this paper, is suspected, we need to be especially careful in the research. This paper reports on the distribution and feeding habits of the European catfish Silurus glanis, a non-native species in Italian lakes that seems to reign near the top of the ecosystem.
The results of the analysis presented in this paper are generally appropriate, but the following questions need to be explained.
・The meaning of "littoral" and "pelagic": the authors try to use these two terms to describe the habitat of S. glanis, but I don't think they are synonyms. If "littoral" means close to the shore, the synonym would be "off the coast", and if it means close to the bottom of the lake, "benthic" would be the synonym. Since the depth of the benthic gillnet and the pelagic gillnet is almost the same, "littoral" and "off the coast" may be appropriate expressions. If so, the way the sampling sites are shown in Fig. 1(a) would not be appropriate. The definition of "littoral" and "pelagic" in this paper needs to be clarified to determine whether these two habitats are simply different vertically, or whether they are different horizontally and vertically.
We thank the reviewer to highlight this issue. We added a clarification of what we were referring to with the terms littoral and pelagic (Lines 114 - 116) that is, littoral stand for nearshore habitats in which light reaches the bottom (i.e., the depth of the water column is lower than the compensation depth) and pelagic stand for the surface (euphotic zone), open water (or off the coast) zone. Thus, the two habitats mainly differ horizontally. Figure 1b was also redone so now it is more clear the difference between the two habitats.
・The possibility of vertical migration of S. glanis: It is well known that flatfishes/flounders living on the seafloor ascend, search for food and prey on pelagic fish. It is possible that S. glanis living in the pelagic habitat lives near the bottom of the lake like the individuals living in the "littoral" habitat and occasionally ascends to feed, which needs to be explained. In the case of "littoral" samplings, gillnets were not set in the middle layer of the lake, so authors could not obtain data on individuals that ascended to feed.
We thank the reviewer for this suggestion. We added a comment on potential vertical migrations of catfish in the Discussion, as suggested. Lines 463 – 467.
・The effect of size selectivity of gillnets: The mesh size of pelagic gillnets was larger than that of benthic gillnets. This difference in mesh size may have led to the difference in the size of S. glanis caught. Explanation is needed.
We appreciate the concern of the reviewer, and we added a consideration about this in the discussion section at Lines 402 - 406. To our knowledge, no information is available in literature concerning the selectivity of gillnets for S. glanis and this has prevented us to provide any scientific support to our data. However, the shape of the fish is such that it is not caught because it is gilled or wedged but it is rather tangled in the nets by the spine/ray of the pectoral fins. Therefore, it is less likely that mesh size may have had a relevant influence.
・BPUE and NPUE: The mass or number of fish caught in the fishery is not the same as the biomass. These expression needs to be changed. It is not clear what the area of BPUE and NPUE in units of "/m^2" represents, since we do not know what range of fish the gillnet was trying to catch. In Fig. 1(b), the benthic gillnet appears to be fixed to the lake bottom, while the pelagic gillnet appears to be drifting without being fixed. It is important to explain the justification for comparing the quantity and number of fish collected by these different methods.
BPUE and NPUE are relative measure of abundance in terms of mass and number, and they are typically expressed like this and used as measures of catches per unit efforts. The units of “m-2” refers to the area of the nets used (length x height), and it is commonly used in lacustrine fish sampling to standardize measure according to fishing efforts (that can be calculated in various way (e.g., Olin et al.Journal of Fish Biology 60, 593–612; Emmrich et al. Freshwater Biology (2012) 57, 2436–2448) including per meter square of nets (e.g., Brucet et al. Freshwater Biology (2013) 58, 1779–1793). This relative measure allows to standardize and compare catches obtained with different methods. We improved the description of the calculation of BPUE and NPUE at Lines 194 - 195.
L.178-183: There are often differences in LWRs among seasons and regions, and it should be explained that they can be treated collectively.
We added that: “Even if LWRs can vary considerably among seasons and locations, this enabled to obtain a gross estimation of the biomass of catfish and their prey at each site and within each habitat”. Lines 191 – 193.
Reviewer 3 Report
Review
Paper title: Spoiled for choice during cold season? Habitat use and potential impacts of the invasive Silurus glanis L. in a deep, large and oligotrophic lake (Lake Maggiore, North Italy).
The authors conducted the first study to reveal stomach content and the role of the invasive catfish Silurus glanis in relation to habitat conditions in an oligotrophic lake. They found some differences in the diet of pelagic and littoral fishes. They discussed the contribution of this species in the catch composition and found an increase in landings. These results are important for fishery management and control of the invasive catfish in Lake Maggiore.
All these reasons explain the relevance of the paper by Vanessa De Santis and Pietro Volta submitted to "Water".
General scores.
The data presented by the authors are original and significant. The study is correctly designed and technically sounds. In general, the statistical analyses are performed with good technical standards. We authors conducted careful work which will attract the attention of a wide range of specialists focused on climate change, ecological modeling and freshwater ecosystems.
Specific comments.
L 9. Change “information” to “features”
L 12. Change “are available” to “is available”
L 14. NPUE and BPUE. These abbreviations should be defined in their first appearance.
L 27. Change “global” to “the global”
L 33. Change “habitat” to “habitats”
L 35. Change “population” to “populations”
L 39. Change “successful invader” to “a successful invader”
L 43. Change “have led” to “has led”
L 56. Change “(Reading et al., 2012; Rees, 2020)” to “[22, 23]”
L 58. Change “others” to “other”
L 62. Change “others” to “other”
L 69. Change “are particularly scarce for winter” to “is particularly scarce for the winter”
L 70. Change “Trophic ecology” to “The trophic ecology”
L 73. Change “known on” to “known about”
L 77. Change “It was in the second part of the 1970s that” to “In the second half of the 1970s,”
L 85. Change “degraded” to “the degraded”
L 89. Change “then there remain” to “there are”
L 92. Change “late” to “the late”
L 96. Change “reasons of” to “reasons for”
L 98. Change “habitat” to “habitats”
L 99. Change “preys” to “prey”
L 104. Change “demonstrate” to “demonstrating”
L 111. Change “south to the Alps and comprised into” to “south of the Alps and comprised of”
L 112. Change “others” to “other”
L 113. Change “the 80” to “80”
L 117. Change “re-stablished” to “re-established”
L 126. Change “has been” to “have been”
L 128. Change “hybrid” to “hybrids”
L 129. Change “here after” to “hereafter”
L 136. Change “of Lake” to “in Lake”
L 138. Change “pelagic compartment” to “the pelagic compartment”
L 141. Change “as biomass” to “in biomass”
L 152. Change “depths” to “depths of”
L 161. Change “his” to “their”
L 163. Change “they total length (1 cm). Prey” to “their total length (1 cm). Prey items”
L 179. Change “relations” to “relationships”
L 181. Change “literature” to “the literature”
L 186. Change “post doc test” to “post hoc test”
L 188. Change “in two” to “into two”
L 190. Change “class” to “classes”
L 191. Change “site and habitat” to “sites and habitats”
L 193. Change “percentual ratio” to “percent ratio”
L 213. Change “of different habitat was investigate” to “in different habitats was investigated”
L 216. Change “stomach” to “stomachs”
L 218. Change “composed by” to “composed of”
L 221. Change “significant” to “a significant”
L 230. Change “showed as” to “showed that”
L 232. Change “5 (June) to 20 m (October) depths” to “5 m (June) to 20 m (October)”
L 234. Change “10 meters depth” to “10 m”
Figure 2. Please, change "N, D, J" to "Nov, Dec, Jan" or "November, December, January".
L 248. Change “post doc test revealing” to “post hoc test revealing that”
L 259. Change “decrease of” to “decrease in”
L 262. Change “Numeric” to “Number”
L 269. Change “was of” to “was”
L 270. Change “month” to “months”
L 271. Change “variable” to “variables”
L 282. Change “indicating as” to “indicating that”
L 289. Change “belonged at” to “belonged to”
L 299. Change “exclusively” to “was exclusively”
L 304. Change “In term” to “In terms”
L 317. Change “have resulted” to “has resulted”
L 333. Change “observed as” to “observed that”
L 334. Change “suggest” to “suggests”
L 335. Change “appeared” to “appeared to be”
L 336. Change “specialised on” to “specialised in”
L 346. Change “at the start of the 1990s” to “In the beginning of the 1990s”
L 353. Change “In only five years” to “Over only five years”
L 354. Change “being of” to “being”
L 356. Change “the 3.2 % - 4.2 % in 2016 - 2018 to the 11.7 % in 2019 and the” to “3.2 % - 4.2 % in 2016 - 2018 to 11.7 % in 2019 and”
L 357. Change “mostly the same” to “almost the same”
L 358. Change “where,” to “when”
Figure 6. Change “ty-1” to “Annual catch, tons”
L 378. Change “was” to “were”
L 381. Change “a segregation” to “segregation”
L 383. Change “frequenting” to “occurring”
L 383. Change “a seasonality” to “seasonality”
L 395. Change “conspecific” to “conspecifics”
L 398. Change “once more as” to “that”
L 400. Change “were also” to “was also”
L 402. Change “variable” to “variables”
L 403. Change “most” to “best”
L 405. Change “high rate” to “a high rate”
L 406. Change “than” to “than in”
L 416. Change “joined with” to “coupled with”
L 433. Change “locally abundant population” to “a locally abundant population”
L 436. Change “composed by” to “composed of”
L 436. Change “then our” to “our”
L 437. Change “suggests” to “suggest”
L 438. Change “associated to the search of” to “associated with the search for”
L 442. Change “exclude” to “exclude that”
L 443. Change “of food” to “for food”
L 447. Change “reason of” to “reason for”
L 447. Change “answer of catfish to a higher” to “response of catfish to higher”
L 460. Change “suggests” to “suggest”
L 467. Change “effect” to “effects”
L 468. Change “is thus” to “, it is”
L 474. Change “showed as” to “showed that”
L 476. Change “has been” to “there was”
L 484. Change “then these results” to “our results”
L 488. Change “interpretated” to “interpreted”
L 492. Change “fishing ban” to “a fishing ban”
L 494. Change “has started” to “have started”
L 501. Change “a better” to “better”
L 520. Change “catfish is” to “catfish are”
L 525. Change “class can make a” to “classes can make”
L 531. Change “scientist” to “scientists”
L 533. Change “confirm once more as” to “confirms that”
L 536. Change “In future” to “In the future”
Figure S1. Change “S. glanis” to “Silurus glanis”
Table S1. Change “Linear regressions” to “Linear regression”
Table S3. Change “Perlagic” to “Pelagic”
Author Response
The authors conducted the first study to reveal stomach content and the role of the invasive catfish Silurus glanis in relation to habitat conditions in an oligotrophic lake. They found some differences in the diet of pelagic and littoral fishes. They discussed the contribution of this species in the catch composition and found an increase in landings. These results are important for fishery management and control of the invasive catfish in Lake Maggiore. All these reasons explain the relevance of the paper by Vanessa De Santis and Pietro Volta submitted to "Water".
General scores.
The data presented by the authors are original and significant. The study is correctly designed and technically sounds. In general, the statistical analyses are performed with good technical standards. We authors conducted careful work which will attract the attention of a wide range of specialists focused on climate change, ecological modeling and freshwater ecosystems.
We thank the reviewer for the positive feedback and we amended the manuscript according to the proposed specific comments as reported below.
Specific comments.
L 9. Change “information” to “features”
Done at Line 9
L 12. Change “are available” to “is available”
Done at Line 12
L 14. NPUE and BPUE. These abbreviations should be defined in their first appearance.
The definition of NPUE and BPUE abbreviations has been improved so it is now clearer. Line 15
L 27. Change “global” to “the global”
Done at Line 27
L 33. Change “habitat” to “habitats”
Done at Line 33
L 35. Change “population” to “populations”
Done at Line 35
L 39. Change “successful invader” to “a successful invader”
Done at Line 39
L 43. Change “have led” to “has led”
Done at Line 43
L 56. Change “(Reading et al., 2012; Rees, 2020)” to “[22, 23]”
Done at Line 56
L 58. Change “others” to “other”
Done at Line 58
L 62. Change “others” to “other”
Done at Line 62
L 69. Change “are particularly scarce for winter” to “is particularly scarce for the winter”
Done at Line 69
L 70. Change “Trophic ecology” to “The trophic ecology”
Done at Line 70
L 73. Change “known on” to “known about”
Done at Line 73
L 77. Change “It was in the second part of the 1970s that” to “In the second half of the 1970s,”
Done at Line 77
L 85. Change “degraded” to “the degraded”
Done at Line 85
L 89. Change “then there remain” to “there are”
Done at Line 127
L 92. Change “late” to “the late”
Done at Lin e129
L 96. Change “reasons of” to “reasons for”
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L 98. Change “habitat” to “habitats”
Done at Line 135
L 99. Change “preys” to “prey”
Done at Line 136
L 104. Change “demonstrate” to “demonstrating”
Done at Line 141
L 111. Change “south to the Alps and comprised into” to “south of the Alps and comprised of”
Done at Line 91
L 112. Change “others” to “other”
Done at Line 92
L 113. Change “the 80” to “80”
Done at Line 93
L 117. Change “re-stablished” to “re-established”
Done at Line 96
L 126. Change “has been” to “have been”
Done at Line 103
L 128. Change “hybrid” to “hybrids”
Done at Lines 104-105
L 129. Change “here after” to “hereafter”
Done at Line 106
L 136. Change “of Lake” to “in Lake”
This sentence has been deleted.
L 138. Change “pelagic compartment” to “the pelagic compartment”
Done at Line 116
L 141. Change “as biomass” to “in biomass”
This sentence has been deleted
L 152. Change “depths” to “depths of”
Done at Line 149
L 161. Change “his” to “their”
Done at Line 178
L 163. Change “they total length (1 cm). Prey” to “their total length (1 cm). Prey items”
Done at Line 180
L 179. Change “relations” to “relationships”
Done at Line 188
L 181. Change “literature” to “the literature”
Done at Line 190
L 186. Change “post doc test” to “post hoc test”
Done at Line 196
L 188. Change “in two” to “into two”
Done at Line 199
L 190. Change “class” to “classes”
Done at Line 202
L 191. Change “site and habitat” to “sites and habitats”
Done at Lines 202 - 203
L 193. Change “percentual ratio” to “percent ratio”
Done at Line 205
L 213. Change “of different habitat was investigate” to “in different habitats was investigated”
Done at Line 225
L 216. Change “stomach” to “stomachs”
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L 218. Change “composed by” to “composed of”
Done at Line 230
L 221. Change “significant” to “a significant”
Done at Line 233
L 230. Change “showed as” to “showed that”
Done at Line 166
L 232. Change “5 (June) to 20 m (October) depths” to “5 m (June) to 20 m (October)”
Done at Line 167
L 234. Change “10 meters depth” to “10 m”
Done at Line 170
Figure 2. Please, change "N, D, J" to "Nov, Dec, Jan" or "November, December, January".
Month label was changed as suggested (see new Figure 2)
L 248. Change “post doc test revealing” to “post hoc test revealing that”
Done at Line 251
L 259. Change “decrease of” to “decrease in”
Done at Line 263
L 262. Change “Numeric” to “Number”
Done at Line 267 (Figure 3 caption)
L 269. Change “was of” to “was”
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L 270. Change “month” to “months”
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L 271. Change “variable” to “variables”
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L 282. Change “indicating as” to “indicating that”
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L 289. Change “belonged at” to “belonged to”
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L 299. Change “exclusively” to “was exclusively”
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L 304. Change “In term” to “In terms”
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L 317. Change “have resulted” to “has resulted”
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L 333. Change “observed as” to “observed that”
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L 334. Change “suggest” to “suggests”
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L 335. Change “appeared” to “appeared to be”
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L 336. Change “specialised on” to “specialised in”
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L 346. Change “at the start of the 1990s” to “In the beginning of the 1990s”
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L 353. Change “In only five years” to “Over only five years”
Done at Line 358
L 354. Change “being of” to “being”
Done at Line 359
L 356. Change “the 3.2 % - 4.2 % in 2016 - 2018 to the 11.7 % in 2019 and the” to “3.2 % - 4.2 % in 2016 - 2018 to 11.7 % in 2019 and”
Done at Line 360 - 361
L 357. Change “mostly the same” to “almost the same”
Done at Line 362
L 358. Change “where,” to “when”
Done at Line 363
Figure 6. Change “ty-1” to “Annual catch, tons”
Axis label was changed to Annual catch (tons/year)
L 378. Change “was” to “were”
Done at Line 385
L 381. Change “a segregation” to “segregation”
Done at Line 387
L 383. Change “frequenting” to “occurring”
Done at Line 389
L 383. Change “a seasonality” to “seasonality”
Done at Line 389
L 395. Change “conspecific” to “conspecifics”
Done at Line 401
L 398. Change “once more as” to “that”
Done at Line 409
L 400. Change “were also” to “was also”
Done at Line 411
L 402. Change “variable” to “variables”
Done at Line 413
L 403. Change “most” to “best”
Done at Line 414
L 405. Change “high rate” to “a high rate”
Done at Line 416
L 406. Change “than” to “than in”
Done at Line 418
L 416. Change “joined with” to “coupled with”
Done at Line 428
L 433. Change “locally abundant population” to “a locally abundant population”
Done at Line 444
L 436. Change “composed by” to “composed of”
Done at Line 452
L 436. Change “then our” to “our”
Done a Line 452
L 437. Change “suggests” to “suggest”
Done a Line 452
L 438. Change “associated to the search of” to “associated with the search for”
Done at Line 454
L 442. Change “exclude” to “exclude that”
Done at Line 458
L 443. Change “of food” to “for food”
Done at Line 458
L 447. Change “reason of” to “reason for”
Done at Line 468
L 447. Change “answer of catfish to a higher” to “response of catfish to higher”
Done at Line 468 - 469
L 460. Change “suggests” to “suggest”
Done at Line 481
L 467. Change “effect” to “effects”
Done at Line 488
L 468. Change “is thus” to “, it is”
This sentence has been deleted
L 474. Change “showed as” to “showed that”
Done at Line 496
L 476. Change “has been” to “there was”
This sentence was rephrased
L 484. Change “then these results” to “our results”
Done at Line 506
L 488. Change “interpretated” to “interpreted”
Done at Line 510
L 492. Change “fishing ban” to “a fishing ban”
Done at Line 514
L 494. Change “has started” to “have started”
Done at Line 516
L 501. Change “a better” to “better”
Done at Lines 522 - 523
L 520. Change “catfish is” to “catfish are”
Done at Lines 542 - 543
L 525. Change “class can make a” to “classes can make”
Done at Line 548
L 531. Change “scientist” to “scientists”
Done at Line 553
L 533. Change “confirm once more as” to “confirms that”
Done at Line 555
L 536. Change “In future” to “In the future”
Done at Line 558
Figure S1. Change “S. glanis” to “Silurus glanis”
Done at Line 561 and in Figure S1
Table S1. Change “Linear regressions” to “Linear regression”
Done at Line 564 and Table S1
Table S3. Change “Perlagic” to “Pelagic”
Done in the revised Table S3.
Round 2
Reviewer 1 Report
The issues I cared have been carefully addressed and the manuscript has been further revised. I have no more comments now.
