Evaluation of Water Quality in the Production of Rainbow Trout (Oncorhynchus mykiss) in a Recirculating Aquaculture System (RAS) in the Precordilleran Region of Northern Chile
, Piera Pepe-Vargas 1,2, Anahà Pérez-Aravena 1, Héctor Aravena-Ambrosetti 1,3, Jordan I. Huanacuni 1,3,4,*, Felipe Méndez-Abarca 1,3, Germán Olivares-Cantillano 5, Olger Acosta-Angulo 6 and Luis Espinoza-Ramos 7Round 1
Reviewer 1 Report (New Reviewer)
Comments and Suggestions for AuthorsThe introduction is very well written. It is very helpful to know what the environmental importance of each of the physical/chemical parameters is and what are the significant concentrations of each. These include: temperature (°C), dissolved oxygen alkalinity (mg/L), arsenic (mg/L), chloride (mg/L), true color (Pt-Co), conductivity (µS/cm), hardness (mg/L), phosphorus (mg/L), pH, potassium (mg/L), total dissolved solids (mg/L), and salinity (PSU).
The analysis of the measured parameters is well done and concise.
Discussion
The discussion section is a little verbose. It should deal with each water quality parameter in a more concise fashion. The topics are adequately addressed, but less detail might make the discussion points more effective to the reader.
Author Response
Response to reviewer 1
The introduction is very well written. It is very helpful to know what the environmental importance of each of the physical/chemical parameters is and what are the significant concentrations of each. These include: temperature (°C), dissolved oxygen alkalinity (mg/L), arsenic (mg/L), chloride (mg/L), true color (Pt-Co), conductivity (µS/cm), hardness (mg/L), phosphorus (mg/L), pH, potassium (mg/L), total dissolved solids (mg/L), and salinity (PSU).
The analysis of the measured parameters is well done and concise.
Discussion
The discussion section is a little verbose. It should deal with each water quality parameter in a more concise fashion. The topics are adequately addressed, but less detail might make the discussion points more effective to the reader
Thank you for the valuable feedback. We revised the discussion section to present each water quality parameter more concisely, reducing unnecessary detail while maintaining clarity. This improved the effectiveness and readability of the discussion points for the reader.
Reviewer 2 Report (New Reviewer)
Comments and Suggestions for AuthorsThe article ‘Evaluation of Water Quality in the Production of Rainbow Trout (Oncorhynchus mykiss) in a Recirculating Aquaculture System (RAS) in the Precordilleran Region of Northern Chile’ investigates the water quality and its impact on rainbow trout growth in a RAS located in the Chilean Altiplano. The study monitors various water parameters, analyzes their variability, and assesses their effects on the growth and development of juvenile rainbow trout. In the article there are some weaknesses which could be improved.
Introduction
It is important to elaborate on the significance of Recirculating Aquaculture Systems (RAS) in promoting sustainable aquaculture, particularly in areas with limited water resources in high altitude. Additionally, more context should be provided on the Chilean Altiplano, including the specific challenges and opportunities it presents for high altitude aquaculture development.
Materials and methods
The experimental setup requires additional details, such as the stocking density of fish, the feeding regime, and any water exchange protocols used. Additionally, the rationale for using groundwater in the RAS for high-altitude aquaculture should be clarified.
Results
Page 7, Line 226: Figure 4 presents the data on ammonium and nitrate levels throughout the cultivation period. - This is kind of a redundant sentence, please remove this kind of sentence from the other parts of the text.
Page 9, Line 277: These sentences sound discussion points, please move them to the discussion section.
Discussion
It is necessary to relate the findings back to the existing literature on RAS and trout farming, especially in high-altitude environments. The implications of the observed water quality parameters for fish health and growth need to be discussed. It is also important to consider the economic feasibility of the RAS operation and potential improvements.
Line 393 page 13: Dissolved oxygen showed significant differences across all months, with critical levels observed at CT4 and DT between October and December … Why were there fluctuations despite the continuous operation of aeration systems?
Conclusion
The conclusion should concisely summarize the main findings of the study and highlight their significance in one or two well-structured paragraphs rather than using bullet points. It should also propose directions for future research, such as optimizing feeding strategies, enhancing biofilter performance, and addressing other key aspects of RAS operation in high-altitude aquaculture.
Considering these points, a major revision of the article is recommended for the authors.
Author Response
Response to reviewer 2
The article ‘Evaluation of Water Quality in the Production of Rainbow Trout (Oncorhynchus mykiss) in a Recirculating Aquaculture System (RAS) in the Precordilleran Region of Northern Chile’ investigates the evis quality and its evisión rainbow trout growth in a RAS located in the Chilean Altiplano. The study monitors various evis parameters, analyzes their variability, and assesses their effects on the growth and development of juvenile rainbow trout. In the article there are some weaknesses which could be improved.
Introduction
It is important to elaborate on the significance of Recirculating Aquaculture Systems (RAS) in promoting sustainable aquaculture, particularly in evis with limited evis resources in high altitude. Additionally, more context should be provided on the Chilean Altiplano, including the specific challenges and opportunities it presents for high altitude aquaculture development.
We appreciate this suggestion and have expanded the introduction to include the socioeconomic and environmental context of the Chilean Altiplano. Relevant references were added to support this section (lines 144–152).
Materials and methods
The experimental setup requires additional details, such as the stocking density evisió, the feeding regime, and any evis evisión protocols used. Additionally, the rationale for using groundwater in the RAS for high-altitude aquaculture should be clarified.
We thank the reviewer for this observation. The manuscript has been updated to clarify: (i) the stocking density (0.45 kg/m³) (lines 265 - 266); (ii) the feeding regime, including frequency, ration, and feed type (lines 257-262); (iii) the water exchange protocol, specifying that 40% exchanges were conducted via the decanter tanks when nitrate levels were high (lines 204-209); and (iv) the rationale for using groundwater, which is the only reliable water source in this high-altitude desert region (lines 166 - 170).
Results
Page 7, Line 226: Figure 4 presents the data on ammonium and nitrate levels throughout the cultivation period. – This is kind of a redundant sentence, please remove this kind of sentence from the other parts of the text.
Thank you for the observation. We have revised the manuscript to remove or rephrase redundant introductory sentences describing the figures (lines 296-299).
Page 9, Line 277: These sentences sound evisión points, please move them to the evisión section.
Thank you for your suggestion. As recommended, we have moved these sentences to the Discussion section (lines 526-529) to ensure they are presented as part of the interpretation of results rather than the Results section.
Discussion
It is necessary to relate the findings back to the existing evisiónn on RAS and trout farming, especially in high-altitude environments. The implications of the observed evis quality parameters for fish health and growth need to be discussed. It is also important to consider the economic feasibility of the RAS operation and potential improvements.
We have addressed both points by including relevant literature on high-altitude RAS and trout farming, discussing the impact of water quality on fish health and growth (lines 560-582), and covering the economic viability and possible improvements of the system (lines 597-617).
Line 393 page 13: Dissolved oxygen showed significant differences across all months, with critical levels observed at CT4 and DT between October and December … Why were there fluctuations despite the continuous operation of aeration systems?
Despite the continuous operation of the aeration system, fluctuations in dissolved oxygen levels—particularly at points CT3 and CT4 during November and December, where values dropped as low as 1.78 and 1.82 mg/L respectively—can be attributed to a combination of environmental, biological, and operational factors.
Firstly, these decreases coincide with the period of highest temperatures recorded in the system, which reduces oxygen solubility in water and thus the efficiency of aeration. Secondly, the increased biomass present during these months results in a higher biological oxygen demand (BOD), from both the fish and accumulated organic matter (excreta, uneaten feed, and biofilm). This effect may be more pronounced at points such as CT3 and CT4, where water circulation might be less efficient or aeration insufficient to meet the demand.
Furthermore, differences in the aeration system setup or water flow distribution may create microzones with suboptimal oxygen levels. The specific case of the decanter (DT), which showed a higher value (4.84 mg/L) in December, suggests that solids removal at that point may have temporarily reduced local BOD, unlike the active culture tanks.
Conclusion
The evisiónn should concisely summarize the main findings of the study and highlight their significance in one or two well-structured paragraphs rather ev using bullet points. It should also propose directions for future research, such as optimizing feeding strategies, enhancing biofilter performance, and addressing other key aspects of RAS operation in high-altitude aquaculture.
Considering these points, a major evisión of the article is recommended for the authors.
Thank you for your valuable comment. We have revised the Conclusions section and restructured it to present the main findings in concise paragraphs, avoiding the use of bullet points. Additionally, we included a clear proposal for future research directions.
Reviewer 3 Report (New Reviewer)
Comments and Suggestions for AuthorsReview for the paper “Evaluation of Water Quality in the Production of Rainbow Trout (Oncorhynchus mykiss) in a Recirculating Aquaculture System (RAS) in the Precordilleran Region of Northern Chile” by Renzo Pepe-Victoriano, Piera Pepe-Vargas, Anahí Pérez-Aravena, Héctor Aravena-Ambrosetti, Jordan I. Huanacuni, Felipe Méndez-Abarca, Germán Olivares-Cantillano, Luis Espinoza-Ramos submitted to “Water”.
The authors of this research paper conducted an analysis to evaluate the water quality and culture performance of juvenile rainbow trout in a recirculating aquaculture system (RAS) located in the Chilean Altiplano. They found that key water quality parameters, such as temperature, total ammonia nitrogen, nitrates, and dissolved oxygen, fell within acceptable limits, indicating a generally conducive environment for aquaculture. The fluctuations in pH and instances of low alkalinity, however, were identified as stressors for the fish, potentially impacting their growth.
The results of this study may have important implications for the future of aquaculture in extreme environments like the Altiplano.
Some revisions are needed to improve the clarity of the paper.
Recommendations.
Abstract.
L 22. The authors should report the period when this study was conducted.
Introduction.
L 41-55. The authors mention that RAS is efficient but doesn't explain explicitly how it compares to other methods in terms of efficiency (e.g., lower water usage, reduced energy consumption, higher production yields). Including quantitative comparisons or case studies could make the efficiency claim more concrete.
What is the typical water usage in RAS compared to open-flow systems? The authors should report specific data or percentages on water savings (e.g., RAS requires X% less water compared to traditional systems).
The authors briefly reference the cultivation of aquatic organisms and mentions rainbow trout later, but it could expand to clarify whether specific species (e.g., fish, crustaceans) are more commonly suited to RAS and why.
The introduction focuses on the benefits of RAS but does not discuss potential drawbacks or challenges such as high capital investment, energy requirements, or technical expertise for maintenance. Including these would provide a balanced perspective.
L 107. The authors mention studying rainbow trout juveniles but don’t explain why this species is the focus. Is this due to its economic importance, sensitivity to environmental parameters, or suitability to RAS at high altitudes like 3000 masl? A more detailed background regarding this species and its aquaculture is necessary.
Materials and methods.
L 121. The authors state that the RAS was supplied by local groundwater but do not provide information about its quality or treatment prior to use. Was it assessed for contaminants, nutrients, or other factors?
L 153-154. The authors should report how the accuracy of measurement tools (e.g., the oximeter, photometer) was assessed during the study
L 166. The author should explain why cultivation tanks 3 and 4 (CT3 and CT4) were chosen as sampling points?
L 187. The year should be reported.
L 188. The authors should report the cultivation conditions (light regime, feeding regime, feed used, etc) in detail. The origin of juvenile trout used in the study should be reported.
L 194. The authors mention efforts to minimize stress and prevent injuries, but they do not indicate how stress levels were assessed or confirmed.
Results.
L 215-240. It would be useful to test these time-series for trends using an appropriate method like the Mann-Kendall trend test.
L 255. Table 2, column “Normal value”. The authors should check the text and change ”a” to “–“.
L 266. The same concern as above.
L 267-281. Did the authors use combined data for PCA? It would be useful to compare different seasons.
L 297 and Fig. 6. There is inconsistency between the text that mentions “r2” and figure that mentions “r”.
Discussion.
L 376-379. The authors mention that O2 and NH3 were not optimal but no negative effects were observed. What mechanisms allowed the fish to survive in environments with ammonium concentrations far above recommended thresholds? Can the authors prove that negative effects do not exist in prolonged cultivation periods?
The authors should discuss the most notable benefits and disadvantages observed for using groundwater compared to surface water under high-altitude conditions.
L 483. The authors should discuss long-term filtration strategies that could be implemented to reduce arsenic levels below the threshold for trout aquaculture.
L 564. How might the stress-related factors mentioned contribute to phosphorus accumulation specifically, and what steps could mitigate this? What environmental conditions at high altitudes were identified as potentially impacting the specific growth rate (SGR), and how can these be effectively managed?
L 611. What specific water management strategies have been successfully implemented in other regions that could be adapted for use in Chile?
Author Response
Response to reviewer 3
Review for the paper “Evaluation of Water Quality in the Production of Rainbow Trout (Oncorhynchus mykiss) in a Recirculating Aquaculture System (RAS) in the Precordilleran Region of Northern Chile” by Renzo Pepe-Victoriano, Piera Pepe-Vargas, Anahí Pérez-Aravena, Héctor Aravena-Ambrosetti, Jordan I. Huanacuni, Felipe Méndez-Abarca, Germán Olivares-Cantillano, Luis Espinoza-Ramos submitted to “Water”.
The authors of this research paper conducted an analysis to evaluate the water quality and culture performance of juvenile rainbow trout in a recirculating aquaculture system (RAS) located in the Chilean Altiplano. They found that key water quality parameters, such as temperature, total ammonia nitrogen, nitrates, and dissolved oxygen, fell within acceptable limits, indicating a generally conducive environment for aquaculture. The fluctuations in pH and instances of low alkalinity, however, were identified as stressors for the fish, potentially impacting their growth.
The results of this study may have important implications for the future of aquaculture in extreme environments like the Altiplano.
Some revisions are needed to improve the clarity of the paper.
Recommendations.
Abstract.
L 22. The authors should report the period when this study was conducted.
The study period (October 2014 to June 2017) was added to the abstract to clarify the temporal scope of the research (line 25).
Introduction.
L 41-55. The authors mention that RAS is efficient but doesn't explain explicitly how it compares to other methods in terms of efficiency (e.g., lower water usage, reduced energy consumption, higher production yields). Including quantitative comparisons or case studies could make the efficiency claim more concrete.
What is the typical water usage in RAS compared to open-flow systems? The authors should report specific data or percentages on water savings (e.g., RAS requires X% less water compared to traditional systems).
We have expanded the manuscript to explicitly compare RAS efficiency with other aquaculture methods, including quantitative data on water usage. This addition clarifies the significant water savings and operational advantages of RAS, making the efficiency claim more concrete. (Lines 62-67)
The authors briefly reference the cultivation of aquatic organisms and mentions rainbow trout later, but it could expand to clarify whether specific species (e.g., fish, crustaceans) are more commonly suited to RAS and why.
We appreciate this suggestion. We have added a sentence clarifying which species are best suited to RAS and why, emphasizing the suitability of rainbow trout and other common species (Lines 70-82)
The introduction focuses on the benefits of RAS but does not discuss potential drawbacks or challenges such as high capital investment, energy requirements, or technical expertise for maintenance. Including these would provide a balanced perspective.
Thank you for your valuable comment. We have expanded the introduction to include a balanced discussion of the limitations and challenges associated with RAS (Lines 62-67 and lines 144-152). These additions provide a more comprehensive perspective on the practical considerations of implementing RAS, especially in rural or resource-limited areas.
L 107. The authors mention studying rainbow trout juveniles but don’t explain why this species is the focus. Is this due to its economic importance, sensitivity to environmental parameters, or suitability to RAS at high altitudes like 3000 masl? A more detailed background regarding this species and its aquaculture is necessary.
Thank you for your comment. We have added a concise explanation in the introduction regarding the choice of rainbow trout as the study species. This includes its economic relevance, sensitivity to water quality parameters, and proven adaptability to high-altitude RAS environments, supporting its suitability for evaluation at 3000 msnm. (Lines 71-79)
Materials and methods.
L 121. The authors state that the RAS was supplied by local groundwater but do not provide information about its quality or treatment prior to use. Was it assessed for contaminants, nutrients, or other factors?
We appreciate the comment. The RAS was supplied with groundwater from a local spring in the pre-Andean area of Copaquilla, used without prior treatment to realistically assess its direct influence on culture water quality. During the study, comprehensive water quality monitoring was conducted, including physicochemical analyses and screening for potential contaminants such as arsenic, ammonia, nitrates, nitrites, pH, alkalinity, hardness, conductivity, salinity, and phosphorus. These parameters were systematically evaluated over five months, revealing from the start elevated arsenic levels, low alkalinity, and oxygen deficiencies—typical characteristics of groundwater in high-altitude Andean zones. The decision not to apply pretreatment aligns with the study’s objective to evaluate culture feasibility under real conditions, considering that many rural mountain communities operate with limited resources and without complex purification systems. Nevertheless, the results highlight the need to implement corrective strategies, such as metal removal or adjustment of pH and alkalinity, in later stages of design or scale-up.
L 153-154. The authors should report how the accuracy of measurement tools (e.g., the oximeter, photometer) was assessed during the study
We appreciate the reviewer’s comment. The instruments used for measuring the physicochemical water parameters during the study were acquired from Hanna Instruments®, a globally recognized brand known for precision and reliability in environmental monitoring equipment.
Throughout the study, the accuracy of instruments such as the oximeter and photometer was ensured by regular calibrations following the manufacturer’s guidelines. The oximeter was calibrated daily using atmospheric air at 100% saturation. For the photometer, certified standard solutions were used to calibrate parameters such as ammonium, nitrates, and phosphorus, with calibrations performed weekly or whenever deviations were detected.
These procedures ensured the reliability of the data collected throughout the monitoring period and are part of the standard protocols adopted to guarantee traceability and validity of the measurements.
L 166. The author should explain why cultivation tanks 3 and 4 (CT3 and CT4) were chosen as sampling points?
We appreciate the comment. A detailed explanation regarding the selection of sampling points within the RAS has been added to the manuscript (Lines 218-222). Cultivation tanks 3 and 4 (CT3 and CT4) were selected because they are located at the end of the water supply line, receiving similar inflow conditions but connected to different hydraulic discharge lines. This configuration allows for the assessment of parameter variation resulting from differential water treatment within the system, as well as the evaluation of biofiltration efficiency, oxygenation, and the accumulation of nitrogenous compounds in distinct microenvironments. Additionally, as terminal points in the system, CT3 and CT4 serve as critical locations for detecting nutrient buildup and dissolved oxygen depletion—factors that may limit operational performance under real culture conditions. This additional information clarifies the rationale behind the selection of sampling locations and supports their representativeness for monitoring purposes throughout the study.
L 187. The year should be reported.
L 188. The authors should report the cultivation conditions (light regime, feeding regime, feed used, etc) in detail. The origin of juvenile trout used in the study should be reported.
We appreciate the reviewer’s observation. In response, we have revised Section 2.3 of the manuscript to include detailed information regarding the year of the study, the origin of the fish, and the specific culture conditions. The study was conducted between July 2014 and June 2017. The juvenile trout were sourced from the Río Blanco hatchery (Pontificia Universidad Católica de Valparaíso) and transported to the experimental site in Copaquilla, where they were gradually acclimated to the recirculating system and high-altitude conditions. We have also added details regarding the natural photoperiod, feeding schedule, feed type and composition, biomass estimation, and management strategies applied during the experiment. These additions provide a clearer context for the growth evaluation and ensure methodological transparency. The new information can be found in Section 2.3, (lines 248–271).
L 194. The authors mention efforts to minimize stress and prevent injuries, but they do not indicate how stress levels were assessed or confirmed.
We appreciate this valuable observation. As now clarified in the revised manuscript (Lines 271-279), although no physiological indicators of stress (such as plasma cortisol or ventilation rate) were measured during the study, the general condition of the fish was monitored daily through direct observation. Behavioral indicators of stress—such as hyperactivity, loss of balance, erratic movements, lethargy, or reduced feeding—were not observed at any point during the experimental period.
Furthermore, the handling protocol was specifically designed to minimize stress: fish were weighed using soft rubber nets, with exposure to air kept under 15 seconds, and placed in containers filled with system water. No anesthetic agents were used, in accordance with common practices in RAS operations to avoid disrupting the biofilter microbiota or altering physiological parameters. The absence of mortality linked to handling and the maintenance of a favorable condition factor throughout the study support the effectiveness of these practices.
While the study’s focus was on water quality and growth performance, we agree that including physiological stress markers would strengthen future research, and we consider this a valuable suggestion for future studies with a broader scope.
Results.
L 215-240. It would be useful to test these time-series for trends using an appropriate method like the Mann-Kendall trend test.
We appreciate the reviewer’s suggestion. As now indicated in the manuscript, trend analysis was incorporated using the non-parametric Mann-Kendall correlation test (Kendall Tau) to identify significant relationships between key system variables. Specifically, correlations between temperature and dissolved oxygen, as well as between ammonium and nitrate, were evaluated. The results were integrated into the Results section (Linea 298-290).
L 255. Table 2, column “Normal value”. The authors should check the text and change ”a” to “–“.
L 266. The same concern as above.
The requested changes have been made as suggested.
L 267-281. Did the authors use combined data for PCA? It would be useful to compare different seasons.
We appreciate the reviewer’s comment regarding the Principal Component Analysis (PCA). Indeed, the data used for the PCA correspond to a combined dataset covering the operational period of the system; however, it does not span a full year, which limits the ability to perform robust seasonal comparisons. While we acknowledge that a seasonal analysis could enhance the understanding of the dynamics of water quality parameters, the lack of continuous and homogeneous data for the 15 parameters analyzed across all seasons prevented us from adopting this approach without compromising the statistical validity of the analysis.
L 297 and Fig. 6. There is inconsistency between the text that mentions “r2” and figure that mentions “r”.
The modification was implemented accordingly.
Discussion.
L 376-379. The authors mention that O2 and NH3 were not optimal but no negative effects were observed. What mechanisms allowed the fish to survive in environments with ammonium concentrations far above recommended thresholds? Can the authors prove that negative effects do not exist in prolonged cultivation periods?
The authors should discuss the most notable benefits and disadvantages observed for using groundwater compared to surface water under high-altitude conditions.
We appreciate the comment. The discussion was expanded to include an analysis of the use of groundwater in recirculating aquaculture systems at high altitudes, incorporating both its advantages and main disadvantages. This information was included in (lines 420-430) to provide a more balanced perspective on the topic.
L 483. The authors should discuss long-term filtration strategies that could be implemented to reduce arsenic levels below the threshold for trout aquaculture.
We appreciate the suggestion. In the discussion, we expanded the analysis of mitigation strategies to reduce arsenic levels below the acceptable threshold for trout aquaculture. Sustainable and context-appropriate removal options were incorporated in lines 513–521.
L 564. How might the stress-related factors mentioned contribute to phosphorus accumulation specifically, and what steps could mitigate this? What environmental conditions at high altitudes were identified as potentially impacting the specific growth rate (SGR), and how can these be effectively managed?
Thank you for the comment. A brief discussion was added addressing the impact of stress on phosphorus accumulation and the high-altitude environmental factors that may affect SGR, along with relevant management strategies. This information was included in lines 560–583.
L 611. What specific water management strategies have been successfully implemented in other regions that could be adapted for use in Chile?
Thank you for your question. In response, we have added specific examples of water management strategies successfully implemented in other regions that could be adapted to the Chilean context. These include the use of moving bed biofilm reactors (MBBRs) for efficient nitrification, automated alkalinity control systems, the integration of photovoltaic energy to reduce reliance on conventional power sources, and remote monitoring technologies to improve water quality management in isolated areas. These strategies have been incorporated into the discussion section with appropriate references lines 597–617.
Round 2
Reviewer 2 Report (New Reviewer)
Comments and Suggestions for AuthorsThe following comment has been addressed by the author(s) with responses provided however, the corresponding points have not been incorporated into the text of manuscript. Please integrate these points into the Discussion section where appropriate.
“Line 393 page 13: Dissolved oxygen showed significant differences across all months, with critical levels observed at CT4 and DT between October and December … Why were there fluctuations despite the continuous operation of aeration systems?
Despite the continuous operation of the aeration system, fluctuations in dissolved oxygen levels—particularly at points CT3 and CT4 during November and December, where values dropped as low as 1.78 and 1.82 mg/L respectively—can be attributed to a combination of environmental, biological, and operational factors.
Firstly, these decreases coincide with the period of highest temperatures recorded in the system, which reduces oxygen solubility in water and thus the efficiency of aeration. Secondly, the increased biomass present during these months results in a higher biological oxygen demand (BOD), from both the fish and accumulated organic matter (excreta, uneaten feed, and biofilm). This effect may be more pronounced at points such as CT3 and CT4, where water circulation might be less efficient or aeration insufficient to meet the demand.
Furthermore, differences in the aeration system setup or water flow distribution may create microzones with suboptimal oxygen levels. The specific case of the decanter (DT), which showed a higher value (4.84 mg/L) in December, suggests that solids removal at that point may have temporarily reduced local BOD, unlike the active culture tanks.”
Author Response
Thank you for your comment
We have inserted the suggested paragraph on line 465 to 481.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript presents a study evaluating water quality parameters in a recirculating aquaculture system (RAS) used to cultivate rainbow trout (Oncorhynchus mykiss) at high altitudes in northern Chile. The study monitors various physical and chemical water quality parameters and assesses the growth performance of juvenile trout over three months.
A well-defined research hypothesis is a fundamental component of any scientific study. However, this manuscript lacks a clear and testable hypothesis.
A significant limitation of the manuscript is the failure to provide measures of statistical variability, particularly standard error (SE) values, for the reported data. Without these, it is impossible to assess the reliability and precision of the findings.
A well-designed experiment should include a control group to establish a baseline for comparison. This study lacks such a control, making it difficult to determine whether the observed changes in water quality and fish growth were due to the RAS conditions or other extraneous factors. The lack of a comparative baseline significantly weakens the study’s internal validity and limits the ability to draw meaningful conclusions.
Reviewer 2 Report
Comments and Suggestions for Authors- Novelty missing.
- Missing exponential growth function of fish.
- Abstract should be re-write with more results of water quality data.
- In introduction section, should be describing of each component of RASs and their valuable parameters ranges.
- Figure 2, why not used degasser for gas control in RASs. How to control the CO2 level in RASs.
- What do you mean by Special Water Quality Parameters.
- What is the initial growth and final growth rate of fish. Make a table.
- Statistical analysis is missing.
- Fig 4. How to control the ammonia levels.
- What are the advances techniques used in RASs Describe and justify why you not used the Advance techniques? Your study is a traditional way.
- In conclusion section, final recommendation is missing.
NA
