Can We Turn Harmful Invasive Non-Native Fish Species into a Valuable Food Resource?

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents interesting findings; however, there are some important considerations that may limit the wider applicability and interpretation of the results.

This classification strictly limits the import, keeping, breeding, and sale of the species in the European Union. Breeding is not completely banned, but it is tightly regulated, and keeping or trading may require permission.

Source: https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A32022R1203

In terms of animal health and biosecurity, the use of fish collected from natural waters in closed aquaculture systems (RAS) can carry inherent risks. In Europe, mass mortality events have been documented in Ameiurus species, often linked to viral pathogens such as ranaviruses and herpesviruses. These examples highlight the importance of careful health monitoring and pathogen screening when working with wild-caught stocks, especially in controlled environments.

Articles in connection with it:
Abonyi F, Doszpoly A, Czeglédi I, Eszterbauer E. 2024. Molecular Detection of a Novel Poxvirus in Black Bullhead (Ameiurus melas): Emerging Pathogens in a Natural Freshwater in Hungary? J Fish Dis. doi: 10.1111/jfd.14076. 
Alborali, L., G. Bovo, A. Lavazza, H. Cappellaro, and P. F. Guadagnini. 1996. “Isolation of an Herpesvirus in Breeding Catfish (Ictalurus Mela).” Bulletin of the European Association of Fish Pathologists 16, no. 4: 134–137.
Bigarré, L., J. Cabon, M. Baud, F. Pozet, and J. Castric. 2008. “Ranaviruses Associated With High Mortalities in Catfish in France.” Bulletin of the European Association of Fish Pathologists 28, no. 4: 163–168.
Juhász, T., M. Woynárovichné Láng, G. L. Csaba, S. Farkas, and Á. Dán. 2013. “Isolation of a Ranavirus Causingmass Mortality in Brown Bullheads (Ameiurus nebulosus) in Hungary.” Magyar Állatorvosok Lapja 135: 763–768.
Pozet, F., M. Morand, A. Moussa, C. Torhy, and P. De Kinkelin. 1992. “Isolation and Preliminary Characterization of a Pathogenic Icosahedral Deoxyribovirus From the Catfish Ictalurus melas.” Diseases of Aquatic Organisms 14: 35–42. https://doi.org/10.3354/dao014035

Methodologically, the study appears to be well-structured and adequately replicated. However, the relatively low stocking densities applied (14 individuals per cage, corresponding to 1.23–2.26 kg/m³) are substantially below the levels typically used in commercial aquaculture (~10–50 kg/m³, and up to >200 kg/m³ in African catfish farming). This discrepancy may limit the direct applicability of the findings to real-world production systems, particularly in the context of economic assessments.

Overall, the study provides useful data and helps us to understand how the species performs in culture. However, if the above points were taken into account, the paper would be stronger and show better how it relates to current aquaculture and regulations.

Author Response

Sir/Madam,

I would like to sincerely thank you for the time and effort you have devoted to reviewing our manuscript. Your valuable comments and suggestions are greatly appreciated and will certainly contribute to improving the overall quality of the paper.

Together with my co-authors, I will do my best to provide detailed and thoughtful responses to all of your remarks and questions. Please find below our point-by-point replies.

We are submitting separate responses to each reviewer.

Kind regards,

Milica Jaćimović
On behalf of all co-authors

Comments and Suggestions for Authors

Comment: The manuscript presents interesting findings; however, there are some important considerations that may limit the wider applicability and interpretation of the results.

This classification strictly limits the import, keeping, breeding, and sale of the species in the European Union. Breeding is not completely banned, but it is tightly regulated, and keeping or trading may require permission.

Source: https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A32022R1203

In terms of animal health and biosecurity, the use of fish collected from natural waters in closed aquaculture systems (RAS) can carry inherent risks. In Europe, mass mortality events have been documented in Ameiurus species, often linked to viral pathogens such as ranaviruses and herpesviruses. These examples highlight the importance of careful health monitoring and pathogen screening when working with wild-caught stocks, especially in controlled environments.

Articles in connection with it:
Abonyi F, Doszpoly A, Czeglédi I, Eszterbauer E. 2024. Molecular Detection of a Novel Poxvirus in Black Bullhead (Ameiurus melas): Emerging Pathogens in a Natural Freshwater in Hungary? J Fish Dis. doi: 10.1111/jfd.14076. 
Alborali, L., G. Bovo, A. Lavazza, H. Cappellaro, and P. F. Guadagnini. 1996. “Isolation of an Herpesvirus in Breeding Catfish (Ictalurus Mela).” Bulletin of the European Association of Fish Pathologists 16, no. 4: 134–137.
Bigarré, L., J. Cabon, M. Baud, F. Pozet, and J. Castric. 2008. “Ranaviruses Associated With High Mortalities in Catfish in France.” Bulletin of the European Association of Fish Pathologists 28, no. 4: 163–168.
Juhász, T., M. Woynárovichné Láng, G. L. Csaba, S. Farkas, and Á. Dán. 2013. “Isolation of a Ranavirus Causingmass Mortality in Brown Bullheads (Ameiurus nebulosus) in Hungary.” Magyar Állatorvosok Lapja 135: 763–768.
Pozet, F., M. Morand, A. Moussa, C. Torhy, and P. De Kinkelin. 1992. “Isolation and Preliminary Characterization of a Pathogenic Icosahedral Deoxyribovirus From the Catfish Ictalurus melas.” Diseases of Aquatic Organisms 14: 35–42. https://doi.org/10.3354/dao014035

Answer: Thank you very much for your insightful comments and the valuable references provided.

We fully acknowledge the limitations regarding the breeding, keeping, and commercialization of Ameiurus melas within the European Union, as outlined in Commission Implementing Regulation (EU) 2022/1203. As you correctly stated, this species is listed as a Union concern under Regulation (EU) No 1143/2014, which indeed imposes strict restrictions. However, as also mentioned, breeding is not entirely banned but may be permitted under strictly controlled conditions, with authorization from competent authorities. Our intention in this manuscript was not to promote commercial aquaculture of A. melas in the EU, but rather to explore sustainable management options within Serbia, where national legislation currently allows controlled use of invasive species removed from natural ecosystems.

With regard to your concern about fish health and biosecurity risks associated with the use of wild-caught individuals in RAS, we completely agree that this is a crucial issue. The references you provided are highly relevant, and we thank you for pointing them out. In future research, we will place greater emphasis on pathogen screening and fish health monitoring. Although no mass mortality or symptoms of viral disease were observed during our experiment, we recognize that the absence of overt signs does not exclude the presence of pathogens such as ranaviruses or herpesviruses. We have now acknowledged these risks in the revised manuscript and emphasized the need for rigorous biosecurity protocols when considering the reuse of wild stocks for aquaculture purposes.

To address your remarks, we have revised the manuscript and included two additional explanatory passages:

1. At the end of the subsection 2.2. Experimental rearing and data analysis, we added a short paragraph emphasizing the need for pathogen screening and biosecurity in future applications.
2. At the end of the Discussion section, we added a comprehensive paragraph highlighting known disease risks and justifying the importance of health monitoring. In this part, we also cited all the references you kindly provided, including recent studies on ranaviruses, herpesviruses, and novel pathogens in Ameiurus species [70–74].

Methodologically, the study appears to be well-structured and adequately replicated. However, the relatively low stocking densities applied (14 individuals per cage, corresponding to 1.23–2.26 kg/m³) are substantially below the levels typically used in commercial aquaculture (~10–50 kg/m³, and up to >200 kg/m³ in African catfish farming). This discrepancy may limit the direct applicability of the findings to real-world production systems, particularly in the context of economic assessments.

 

Answer: Thank you very much for your constructive feedback.

We fully agree that the stocking densities applied in our experiment (14 individuals per cage, corresponding to 1.23–2.26 kg/m³) are lower than those typically used in commercial aquaculture (10–50 kg/m³ or more, depending on species and system). This discrepancy indeed limits the direct applicability of our findings to intensive production environments.

However, these densities were deliberately selected given the exploratory nature of the study and the use of wild-caught individuals, whose health status was unknown. Our primary aim was to assess the adaptability, growth potential, and survival of Ameiurus melas in controlled conditions with minimal stress, providing a sound baseline for future research.

In response to your comment, we have added a dedicated paragraph addressing this issue in the revised version of the manuscript. The paragraph was inserted immediately after the discussion of final body weights and condition of reared individuals, to preserve logical continuity. It emphasizes the rationale behind our choice of densities and clearly outlines the need for further research under commercial-scale conditions.

Overall, the study provides useful data and helps us to understand how the species performs in culture. However, if the above points were taken into account, the paper would be stronger and show better how it relates to current aquaculture and regulations.

Answer: Thank you very much for your overall positive evaluation of our work and for highlighting the importance of aligning our findings with current aquaculture practices and regulatory frameworks.

We have carefully addressed all of your comments and suggestions in the revised version of the manuscript. It is our sincere hope that the changes made have improved the clarity and scientific relevance of the study, and that the revised manuscript now better reflects its applicability within the context of sustainable aquaculture and existing regulations.

We truly appreciate your time, expertise, and constructive feedback, and we hope that the revised version meets your expectations.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The submitted manuscript is well-written and methodologically sound, although I am not an expert in all presented methodological approaches.

Nevertheless, I must make a significant criticism of the paper. A notable omission is the discussion of the potential consequences of initiating economic processes associated with the production of an invasive species. Juveniles for stocking aquaculture facilities are intended to be taken from the natural environment. This raises several questions, such as what motivation would there be to eradicate an invasive species from the natural environment if it also served as a resource? Would this not lead to the spread of such a species to other locations? Incorporating the view published in Nuez et al. 2012 https://doi.org/10.1111/j.1755-263X.2012.00250.x and others that address the same issue would be beneficial.
A discussion of the potential dangers of the presented approach is essential to the publication of the manuscript.
The manuscript would benefit from minor English improvement and the structuring of the sentences to give them an intended meaning e.g. revision of the use of the term fry in the MS. Some suggestions for improvement are given in the attached document.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The manuscript would benefit from minor English improvement and the structuring of the sentences to give them an intended meaning e.g. revision of the use of the term fry in the MS. Some suggestions for improvement are given in the attached document

Author Response

Sir/Madam,

I would like to sincerely thank you for the time and effort you have devoted to reviewing our manuscript. Your valuable comments and suggestions are greatly appreciated and will certainly contribute to improving the overall quality of the paper.

Together with my co-authors, I will do my best to provide detailed and thoughtful responses to all of your remarks and questions. Please find below our point-by-point replies.

We are submitting separate responses to each reviewer.

Kind regards,

Milica Jaćimović
On behalf of all co-authors

 

Comment: The submitted manuscript is well-written and methodologically sound, although I am not an expert in all presented methodological approaches.

Nevertheless, I must make a significant criticism of the paper. A notable omission is the discussion of the potential consequences of initiating economic processes associated with the production of an invasive species. Juveniles for stocking aquaculture facilities are intended to be taken from the natural environment. This raises several questions, such as what motivation would there be to eradicate an invasive species from the natural environment if it also served as a resource? Would this not lead to the spread of such a species to other locations? Incorporating the view published in Nuez et al. 2012 https://doi.org/10.1111/j.1755-263X.2012.00250.x and others that address the same issue would be beneficial.

A discussion of the potential dangers of the presented approach is essential to the publication of the manuscript.

Answer: Thank you very much for your critical and thoughtful comment, which we fully acknowledge as highly important.

You rightly point out that the economic utilization of an invasive alien species, such as Ameiurus melas, raises important ecological and ethical concerns. The potential contradiction between using the species as a resource and promoting its eradication indeed deserves careful consideration. We agree that such an approach may carry unintended risks, including reduced motivation for eradication, reinforcement of established populations, or even the risk of spreading the species to new habitats through economic incentives.

In response to your comment, we have added a dedicated paragraph at the end of the Introduction section that explicitly addresses these concerns. We have also cited and incorporated the perspective from Nuez et al. (2012) [https://doi.org/10.1111/j.1755-263X.2012.00250.x], which critically evaluates the risks of economically exploiting invasive species. In this paragraph, we discuss potential policy safeguards, such as strict control of movement, prohibition of artificial propagation, and the use of individuals exclusively removed from targeted ecosystems under supervision.

We fully agree that any implementation of such practices must be accompanied by a strong regulatory framework to prevent unintended consequences. By including this discussion, we hope to have clarified that our study does not promote the farming of Ameiurus melas in new areas or its propagation, but rather explores the possibility of valorizing individuals already targeted for removal — in line with the existing legal context in Serbia.

Comment: The manuscript would benefit from minor English improvement and the structuring of the sentences to give them an intended meaning e.g. revision of the use of the term fry in the MS. Some suggestions for improvement are given in the attached document.

Comments on the Quality of English Language

 

Answer: Thank you very much for your helpful remarks regarding the language and terminology used throughout the manuscript.

We have carefully reviewed the entire text and addressed all of your suggestions. In particular, we have revised the use of the term “fry”, which was not always appropriate, and replaced it with more accurate alternative terms “juvenile fish”, “stocking fish” and "broodstock". Furthermore, we have implemented several minor language improvements and restructured sentences to enhance clarity and ensure that each statement conveys the intended meaning.

We sincerely appreciate your attention to detail, which contributed to improving the overall quality and readability of our manuscript.

 

Below, we have listed the specific changes made in response to the comments, as indicated in the annotated PDF version provided.

 

Line 13: Change "fry" to "stocking fish"

 

We did as suggested.

 

Line 41: 23% of fish species? If yes add species, it is not clear from the sentence.

 

Thank you for your comment. We have revised the sentence to clarify that the 23% refers to fish species, as suggested. We have also retained the reference to the black bullhead as a representative example, without listing all non-native species.

 

Line 46: Add the names, it is hard to imagine what is behind the the numbers

 

We did as suggested.

 

Line 91: Change "fry" to "broodstock"

We did as suggested.

 

Line 338: do not start with the citation.

 

Thank you for the suggestion. We have revised the sentence to avoid starting with the citation, in accordance with standard writing conventions.

 

Line 454: Change "fry for stocking" to "stocking fish"

 

We did as suggested.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Interesting work on the utilisation of an invasive alien species for the purpose of food production through its fattening in aquaculture.

 

I have 2 main concerns that should be better explained:

1) Why not directly use the fish caught in the removal operations for direct human consumption. I think that some of the fish removed would already be large enough to be marketed directly or processed into food products. What are the advantages of doing an intermediate fattening, with the inherent costs, before using it for human consumption?

2) The methodology used to grow the fish needs to be better explained to ensure that it is repeatable for those who want to use it in the future.

 

More specific questions:

Line 22 - why use the term ‘particularly’ if these are the only two systems used;

Line 119 - what is the ‘consumable size’? Is it legally defined?

Line 125-130 - point out that the detailed composition of diets is defined in the supplementary material.

Line 135-149 (main concern 2)

What are the characteristics of the pond?

Size of the cages?

Characteristics of the RAS (total volume, filters)?

Were cages also used in the RAS? Were they the same as those used for cage culture in the ponds?

Line 173 - Why were only the fish from the 2021 experiment (experiment 2) used for chemical analysis, and not also those from experiment 1 (2018)?

Row 215-231 - Pay attention to the different sizes of the letters.

Why is the starting weight of experiment 1 so different from the starting weight of experiment 2, in which the fish are more than twice as heavy?  Couldn't this jeopardise the reasonableness of the comparisons made?

Line 253-255 - What is the measure of dispersion used? I think it's mean ± SD. Don't forget to include it.

Explain why the initial body length was not determined in experiment 1.

Line 257-275 - Try to explain better in the discussion the reasons for the large differences in mortality values between the RAS system and the cages and between experiment 1 and the experiment 2. How could these mortality figures be improved? Don't these values call into question the alternative use proposed in this work, especially in the cage system?

Line 318-319 - Legend to Figure 1 is incorrectly placed.

Line 331-332 (Table 4). The data presented is for which diet? 3 and 4? So, what does cage 1 and cage 2 and RAS 1 and RAS 2 mean?

From line 394 onwards, the acronyms PN and RC are used. What do they stand for?

Line 436 - ‘...control than the RAS...’ instead of ‘...control and the RAS...’

Author Response

Sir/Madam,

I would like to sincerely thank you for the time and effort you have devoted to reviewing our manuscript. Your valuable comments and suggestions are greatly appreciated and will certainly contribute to improving the overall quality of the paper.

Together with my co-authors, I will do my best to provide detailed and thoughtful responses to all of your remarks and questions. Please find below our point-by-point replies.

We are submitting separate responses to each reviewer.

Kind regards,

Milica Jaćimović
On behalf of all co-authors

 

Comment: Interesting work on the utilisation of an invasive alien species for the purpose of food production through its fattening in aquaculture.

I have 2 main concerns that should be better explained:

1) Why not directly use the fish caught in the removal operations for direct human consumption. I think that some of the fish removed would already be large enough to be marketed directly or processed into food products. What are the advantages of doing an intermediate fattening, with the inherent costs, before using it for human consumption?

Answer: Thank you for this insightful question. While it is true that a portion of the removed black bullhead individuals may already reach marketable size, immediate use for human consumption poses several challenges. Wild-caught fish, especially from potentially degraded habitats, carry uncertain health status and may harbor pathogens, parasites, or accumulated contaminants. Furthermore, variability in body condition and flesh quality often limits their direct market value. The proportion of individuals that reached consumption size was also very small, further reducing the feasibility of direct marketing.

In addition, we would like to emphasize that the percentage of such crayfish is extremely small, and that, among other goals, we aimed to explore whether smaller specimens—typically not suitable for direct human consumption—could be raised to marketable size through aquaculture. This approach not only adds potential economic value but also reflects our intention to apply a humane strategy for managing invasive species that must be removed from natural aquatic ecosystems due to their significant negative impact on native ichthyofauna.

The intermediate fattening phase under controlled conditions allows for health monitoring, pathogen mitigation, and improvement in flesh composition (e.g., lipid profile and n-3/n-6 PUFA ratio), thereby enhancing nutritional and sensory quality. Despite the associated costs, this step increases the final product’s value and supports both consumer safety and market acceptance. We have now added clarification in the revised manuscript.

 

2) The methodology used to grow the fish needs to be better explained to ensure that it is repeatable for those who want to use it in the future.

 Answer: Thank you for your valuable comment regarding the need for more detailed methodological information to ensure repeatability of the experiments. We fully agree that clarity in experimental setup is essential for reproducibility, and we have now revised the manuscript to provide additional technical details in Section 2.2.

More specific questions:

Line 22 - why use the term ‘particularly’ if these are the only two systems used;

Answer: Thank you for your observation. We agree that the use of the word “particularly” was unnecessary, as only two systems were used in the study. We have deleted the word in the revised manuscript accordingly.

Line 119 - what is the ‘consumable size’? Is it legally defined?

Answer: Thank you for your comment. We have clarified in the manuscript that, in the absence of an official legal definition in Serbia, the consumable size for black bullhead is considered to be individuals weighing between 250 and 300 grams, based on market practices and consumer preferences.

Line 125-130 - point out that the detailed composition of diets is defined in the supplementary material.

Answer: Thank you for your comment. We have revised the manuscript to indicate that the detailed composition of all four diets used in the experiments is provided in the Supplementary Material.

Line 135-149 (main concern 2) What are the characteristics of the pond? Size of the cages? Characteristics of the RAS (total volume, filters)?

Were cages also used in the RAS? Were they the same as those used for cage culture in the ponds?

Answer: We have clarified that the same cages were used in both the recirculating aquaculture system (RAS) and the pond environment to ensure standardized experimental conditions. Each cage had a volume of 216 liters, with dimensions 0.6 m × 0.6 m × 0.6 m.

The pond in which the cages were placed had a surface area of 30 × 20 m (600 m²), an average depth of 1.4 m, and an estimated volume of 840 m³. This pond was used exclusively for experimental purposes and did not contain any other fish species during the rearing trials.

The experimental RAS consisted of tanks with a volume of 1,000 liters each. Each tank operated as an independent unit and was equipped with a complete filtration and water treatment setup, including:

• a mechanical filter,
• a biological filter,
• an oxygenation system,
• a UV disinfection unit, and
• a water heating system to regulate temperature.

These additions ensure that the rearing environment in both systems is now clearly described and that the experiment can be replicated by other researchers or aquaculture practitioners. All these clarifications have been incorporated into the revised manuscript as requested.

Line 173 - Why were only the fish from the 2021 experiment (experiment 2) used for chemical analysis, and not also those from experiment 1 (2018)?

Answer: Thank you for your question. Chemical analysis was conducted only on samples from the 2021 experiment because, during the 2018 experiment, the analytical protocol for chemical and fatty acid composition had not yet been fully established, and the necessary laboratory capacity and equipment were not available at that time. By 2021, these limitations had been resolved, allowing for standardized sample processing, immediate freezing, and high-resolution analysis. Therefore, to ensure data consistency and reliability, only specimens from the second experiment were used for meat composition analysis.

Row 215-231 - Pay attention to the different sizes of the letters.

Answer: Thank you for pointing this out. We have reviewed the manuscript and corrected the formatting inconsistencies related to letter size. The text is now uniformly formatted.

Why is the starting weight of experiment 1 so different from the starting weight of experiment 2, in which the fish are more than twice as heavy?  Couldn't this jeopardise the reasonableness of the comparisons made?

Answer: Thank you for your comment. The difference in initial body weight between the two experiments reflects the intentional use of fish from different age classes, as individuals were collected during separate mass removal campaigns. This design allowed us to explore the growth potential and adaptability of black bullhead across a broader developmental range. Although the starting weights differed, each experiment was internally consistent and independently assessed, and no direct comparisons were made between them.

Line 253-255 - What is the measure of dispersion used? I think it's mean ± SD. Don't forget to include it.

Answer: Thank you for your observation. We confirm that the measure of dispersion used for the parameters presented in Table 2 is the standard deviation (mean ± SD). This has now been clearly stated in the manuscript caption to ensure clarity for readers.

Explain why the initial body length was not determined in experiment 1.

Answer: Thank you for your comment. Initial body length was not determined in the 2018 experiment due to logistical constraints and the primary focus at that time on assessing body mass gain and survival under different rearing conditions. Standardized protocols for comprehensive morphometric measurements, including length, were established and implemented in the 2021 experiment to enhance data quality and comparability. We acknowledge this limitation and have ensured more complete data collection in subsequent trials.

Line 257-275 - Try to explain better in the discussion the reasons for the large differences in mortality values between the RAS system and the cages and between experiment 1 and the experiment 2. How could these mortality figures be improved? Don't these values call into question the alternative use proposed in this work, especially in the cage system?

Answer: Thank you for this insightful comment. We agree that the high mortality rates, particularly in the cage system during the second experiment, deserve further elaboration and contextualization in the discussion. Several factors likely contributed to the observed differences:

1. Fish Size and Stocking Density: In experiment 1, smaller fry (average ~19 g) were stocked at a lower density (1.23 kg/m³), while in experiment 2, larger individuals (~49 g) were stocked at nearly double the density (2.26 kg/m³). The increased biomass likely caused greater metabolic waste accumulation, elevated stress levels, and heightened competition for oxygen and food, especially in the cage system, which is more vulnerable to external environmental fluctuations.
2. Environmental Exposure in Cage Systems: Cage systems are more directly affected by external factors such as water temperature fluctuations, dissolved oxygen variability, and potential predation or mechanical damage. Unlike RAS, which offers stable and controllable conditions, cages are exposed to environmental instability that may negatively affect fish health and increase mortality.
3. Fish Origin and Acclimation: The fish used in both experiments were sourced from natural habitats (mass removal), which could have impacted their adaptability to intensive aquaculture settings. This effect may have been more pronounced in older, larger individuals, who are less plastic in their physiological and behavioral responses to sudden environmental changes compared to younger fry.

To improve survival rates, several measures are recommended for future trials:

• Further lowering of stocking densities, especially in cages.
• Extended acclimation periods prior to stocking.
• Gradual size grading to avoid competition.
• Enhanced monitoring of water quality, particularly in open systems.
• Improved cage design and protection from mechanical stressors.

Despite the high mortality observed in some scenarios, especially in the second cage trial, the growth performance results and survival in RAS conditions suggest that black bullhead can be successfully cultivated under optimized conditions. The aim of this study was not to immediately establish a commercial protocol but to assess the feasibility of utilizing removed individuals as aquaculture stock. The findings highlight the potential for this approach, particularly in controlled systems, while also indicating clear areas for technological refinement in cage systems.

We have included a more detailed discussion of these factors in the revised manuscript to clarify the implications and future directions of the proposed alternative use.

Line 318-319 - Legend to Figure 1 is incorrectly placed.

Answer: Thank you for pointing this out. It appears that a formatting error occurred during manuscript preparation. We have corrected it by moving the legend to Figure 1 to its appropriate position beneath the figure.

Line 331-332 (Table 4). The data presented is for which diet? 3 and 4? So, what does cage 1 and cage 2 and RAS 1 and RAS 2 mean?

Answer: Thank you for your observation. There was a typographical error in the table labels. We have corrected this by replacing “1” with “3” and “2” with “4” to accurately reflect the corresponding feed types used in the experiment (Feed 3 and Feed 4). The updated labels now correctly indicate the diet applied in each treatment group.

From line 394 onwards, the acronyms PN and RC are used. What do they stand for?

Answer: Thank you for your careful reading. We have adopted your suggestion and clarified the meaning of the acronyms upon their first mention in the text. Specifically, we now state that PN refers to fish reared in three 1,000 m² ponds, while RC refers to fish reared in three 2 m³ indoor tanks operating under a closed recirculating system, as described in the original source. The abbreviations PN and RC are used subsequently for readability.

Line 436 - ‘...control than the RAS...’ instead of ‘...control and the RAS...’

Answer: Thank you for this suggestion. We agree that the sentence structure was unclear and have revised it accordingly to improve clarity and accuracy.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

.

Author Response

Dear Sir/Madam,

We would like to express our sincere gratitude for taking the time to read and evaluate our manuscript. Although no specific suggestions for improvement were provided, we are deeply appreciative of the attention and care devoted to reviewing our work. The absence of critical comments is interpreted as a sign that the manuscript was found to be methodologically sound and clearly presented; nevertheless, we remain fully committed to scientific rigor and transparency, and we value the opportunity that the review process has given us to reflect further on the implications of our findings. We are grateful for the constructive spirit in which this manuscript was received; your engagement, even in the absence of explicit requests for revision, has been an important part of the peer-review process, and we thank you once again for your professional contribution and the time you dedicated to our submission.

Sincerely,
Milica Jaćimović

(on behalf of all co-authors)

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made improvements to the manuscript. My main comments on the issue of commercial exploitation of invasive species have been included in the introduction. However, the issue is not further developed in the text. I strongly recommend adding a sentence to the conclusion referring to the application of strong measures to reduce the risk of further spread, given the potential misuse of invasive species for commercial purposes.

Author Response

Dear Sir/Madam,

Thank you very much for your insightful and constructive suggestion. We fully agree that the Conclusion should reiterate the importance of precautionary measures when considering the economic utilization of invasive species. While we have discussed these risks in detail in the Introduction, we have now added a sentence at the end of the Conclusion to emphasize the need for strict regulatory safeguards to prevent further spread and misuse.

The added sentence reads:

“However, to avoid unintended ecological consequences, any economic valorization of invasive species such as Ameiurus melas must be accompanied by stringent regulatory measures aimed at preventing their further spread, including restrictions on intentional breeding and mandatory traceability protocols for harvested individuals.”

This addition underscores our recognition that commercial utilization should not come at the expense of biodiversity protection and aligns with the broader ecological concerns outlined earlier in the manuscript.

Sincerely,
Milica Jaćimović

(on behalf of all co-authors)

Author Response File: Author Response.docx