Diversification of Aquaculture in the Sub-Saharan Region—The Obscure Snakehead

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article entitled “Diversification of aquaculture in the sub-Saharan region- the obscure snakehead” submitted by Sven Wuertz et al. for publication in Fishes is informative and will helpful for broadening the farming choices for aquaculture. However, some information is not very clear, and need restructured. I have several suggestions as follows:

1. The basic biological characters of the Parachanna obscura and comparisons to the Channa species should be given firstly, as most information were cited from Chnna species, C. striata, C. argus, C. maculata, etc. The geographical distribution of should be add too, perhaps a map would be better.

2. The annual output of the snakehead fish in major countries in Fig 1 should be noted in which year, because the output of 553196 tons of China is in 2022 (listed in the yearbook of 2023),but the cited yearbook is noted by 2024.  

3. In the article, the authors emphasized several times that not to introduce Channa or hybrids to avoid virus introduction. In fact, epidemic prevention could solve the problem.

4. In China, two hybrids, C. argus x C. maculata and C. maculata x C. argus, with different growth performance and cold torlerance are cultured. Hybrid in parachanna would be effective too.

Author Response

Response to Reviewer1

The article entitled “Diversification of aquaculture in the sub-Saharan region- the obscure snakehead” submitted by Sven Wuertz et al. for publication in Fishes is informative and will helpful for broadening the farming choices for aquaculture. However, some information is not very clear, and need restructured. I have several suggestions as follows:

1. The basic biological characters of the Parachanna obscura and comparisons to theChanna species should be given firstly, as most information were cited from Chnna species, C. striata, C. argus, C. maculata, etc. The geographical distribution of should be add too, perhaps a map would be better.

We attempted a map on the distribution of species (even on a selection of only 3 species). Due to the overlapping distribution, such a map is rather confusing.

2. The annual output of the snakehead fish in major countries in Fig 1 should be noted in which year, because the output of 553196 tons of China is in 2022 (listed in the yearbook of 2023),but the cited yearbook is noted by 2024.

As stated, the FAO database was assessed in 2024. We used the citation required by the FAO. To clarify that data reflect production in 2022, we have changed the legend accordingly:

 The overwhelming production of Channa, dominated by Chinese (553196 t) and Indonesian (39637 t) farmers and Parachanna obscura, focusing on Nigeria as main producer (2376 t) in 2022. Data accessed from FAO FishStatJ cited 3 November 2024

3. In the article, the authors emphasized several times that not to introduce Channa or hybrids to avoid virus introduction. In fact, epidemic prevention could solve the problem.

Indeed, epidemic prevention could solve the problem of virus introduction. Nevertheless, considering the level of biosecurity in Africa we strongly advocate to focus on farming Parachanna

4. In China, two hybrids, C. argus xC. maculata and C. maculata x C. argus, with different growth performance and cold torlerance are cultured. Hybrid in parachanna would be effective too.

Indeed we mention this in our article. Still, biosecurity in Africa is quite low and Asian snakehead may easily be introduced. Here, the invasive potential needs to be considered! Similarly, one has to consider escapees in discussion on Parachanna hybrids. For sure there will be an introgression nto endemic populations. In our point of view this can only be avoid if hybrids are excluded at the moment.

Reviewer 2 Report

Comments and Suggestions for Authors

Comments:
1.- The introduction provides a good foundation for the article, but it would be helpful to integrate global background information on Channa obscura farming.
2.- The language is generally clear, although some sections could benefit from linguistic revision to improve fluency and precision.
3.- Regarding practical implications, it would be interesting to include recommendations for policymakers and aquaculture companies interested in implementing the proposed diversification.

Comments for author File: Comments.pdf

Author Response

1. Main Question Addressed by the Research:

The research addresses the production and diversification of snakehead (Parachanna obscura) farming in sub-Saharan regions, emphasizing sustainable aquaculture production and the potential for diversification into modern systems such as RAS (Recirculating Aquaculture Systems) and aquaponics. It also focuses on analyzing the socioeconomic importance and market opportunities in producing countries, particularly Nigeria, highlighting the need to strengthen these production systems.

2. Originality and Relevance of the Topic:

The topic is relevant and original within the field of sustainable aquaculture in tropical regions. It addresses an existing gap in the documentation of Parachanna obscura production in sub-Saharan Africa, where information on aquaculture practices, water parameter management, and processing strategies is limited. This work provides key information that can be used by researchers, aquaculturists, and policymakers in the region.

However, I recommend the authors further justify the need for diversified systems (RAS and aquaponics) compared to traditional methods, specifying how they would contribute to improved production and sustainability.

We integrated further information:

Indeed, recirculation aquaculture systems including aquaponics support much higher production densities and, at the same time allow for a better control over the rearing conditions, reducing stress and disease susceptibility. Also, such closed systems provide a better control over pathogens. Aquaponics systems allow for a double use of water since water from the fish unit is directed to the plant crop thereby providing the nutrients needed for plant growth and reducing nutrient emissions to adjacent water bodies.

3. Contribution to the Thematic Area Compared to Other Published Material:

Compared to other studies on snakehead species in Asia, such as Channa argus, this work provides a specific perspective on West Africa, analyzing the production potential of Parachanna obscura. Additionally, it introduces relevant information on markets, processing, and technological diversification—topics less addressed in the existing literature. However, I suggest that the authors include a more comparative discussion with studies on snakehead in other regions to strengthen the global relevance of their findings.

We added a chapter on global perspective of snakehead farming

4. Consistency of Conclusions with the Evidence and Arguments Presented:

The conclusions are consistent with the results and data presented. The study demonstrates

the economic and productive potential of Parachanna obscura in Nigeria, as well as the

feasibility of expanding its production through the implementation of modern technological

systems.

Nevertheless, it would be useful for the authors to:

• More explicitly relate how adaptation to specific water parameters (temperature,

pH, and tolerance to ammonia/nitrites) favors its farming under sub-Saharan

conditions.

We added information in the respective chapter

• Reinforce the discussion on the concrete benefits of diversification (economic and

environmental) by presenting additional data or projections about its impact.

There is a long debate if diversification vs focus on few species is the way to go. This debate is beyond the scope of review. Still, it is generally accepted that for an expansion of aquaculture diversification is actually beneficial with regard to resilience of the sector (refer to [1-3]). Still, this is a wider debate and actually data in Parachanna is very limited.

5. References:

The references are mostly adequate and relevant. However, I suggest that the authors

incorporate more recent studies on:

• Successful experiences in implementing RAS or aquaponic systems in similar regions.
• Updated information on snakehead species processing and its impact on final

product quality.

Honestly, extending the discussion on RAS and aquaponics would mean to incorporate more literature on Channa. This would distract from Parachanna and disrubt the current balance. We did not intend to write a review on Channa

6. Comments on Figures:

• Figure 1: It is clear, but it would be helpful to visually highlight the differences in

production between Asia (China and Indonesia) and Africa (Nigeria). I recommend

including a legend that clearly explains the units used and the data source.

Done

• Figure 2: The figure is relevant and provides valuable information on diversification

into systems and products. However, I suggest adding more details in the legend to

describe how this diversification would impact production.

General Comments:

Overall, the manuscript presents a valuable and well-structured contribution to the field of

sustainable aquaculture, with emphasis on Parachanna obscura production in sub-Saharan

Africa. The study highlights its economic relevance, production potential, and the need to

implement modern technologies such as RAS and aquaponics.

I recommend that the authors:

1. Strengthen the comparison with other snakehead species farmed globally.
2. Clarify the specific benefits of the proposed diversification.
3. Review and update the bibliographic references.

These improvements will strengthen the clarity, relevance, and applicability of the findings

presented.

1. Cao L, Halpern BS, Troell M, Short R, Zeng C, Jiang ZY, Liu Y, Zou CX, Liu CY, Liu SR, Liu XW, Cheung WWL, Cottrell RS, DeClerck F, Gelcich S, Gephart JA, Godo-Solo D, Kaull JI, Micheli F, Naylor RL, Payne HJ, Selig ER, Sumaila UR, Tigchelaar M (2023): Vulnerability of blue foods to human-induced environmental change. Nat Sustain, 6(10): 1186-1198
2. Tigchelaar M, Cheung WWL, Mohammed EY, Phillips MJ, Payne HJ, Selig ER, Wabnitz CCC, Oyinlola MA, Frölicher TL, Gephart JA, Golden CD, Allison EH, Bennett A, Cao L, Fanzo J, Halpern BS, Lam VWY, Micheli F, Naylor RL, Sumaila UR, Tagliabue A, Troell M (2021): Compound climate risks threaten aquatic food system benefits. Nat Food, 2(9): 673-+
3. Metian M, Troell M, Christensen V, Steenbeek J, Pouil S (2020): Mapping diversity of species in global aquaculture. Rev Aquacult, 12(2): 1090-1100

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Please specifically address the observation regarding Figure 2.

Author Response

Response1: the legend has been extended:

Figure 2: Diversification envisioned with the increase in production of snakehead in the sub-Saharan region will furthermore support future diversification in systems that will help reducing nutrient emissions to adjacent water bodies (recirculation aquaculture systems (RAS), aquaponics). Also future poducts will include salted and chilled fillets, a trend that is currently also been observed in catfish and tilapia. Over all, this diversification diversifies the existing market for fish in sub-Saharan region and will thereby increase resilience of the aquaculture sector.

For further information refer to the text...