Evaluation of Chlamydomonas reinhardtii Microalgae as a Sustainable Feed Supplement and Fishmeal Substitute in Aquaculture with a Positive Impact on Human Nutrition
, Iain Young 2 and David A. Gray 1,*Round 1
Reviewer 1 Report
1. The Latin name of zebrafish and other species should be italic. The authors should revise them all through the text.
2. The authors stated that fish meal can be replaced by C. reinhardtii as high as 50%. This is not true unless some essential amino acids such as argine and lysine are additionally supplemented. Thus, I suggest that the authors make some revisions on the conclusion.
3. In the abstract, the authors stated that this experiment was conducted in two strains of zebrafish (wild and mutant types). However, there was just one set of data presented in the manuscript.
4. Figure 1, the name of horizontal coordinate should be "Diet" rather than "SGR" or "FCR".
There are just some minor grammar mistakes in the text.
Author Response
Response to Reviewer 1 Comments
- The Latin name of zebrafish and other species should be italic. The authors should revise them all through the text.
The Latin name of zebrafish has been corrected in line (16, 104, 154,166)
The name C. reinhardtii has been made italic throughout the text.
- The authors stated that fish meal can be replaced by C. reinhardtii as high as 50%. This is not true unless some essential amino acids such as argine and lysine are additionally supplemented. Thus, I suggest that the authors make some revisions on the conclusion.
This point is considered in line 556,557.
Consequently, C. reinhardtii could potentially substitute up to 50% of the fishmeal in zebrafish diets with an extra individual addition of some essential amino acids such as Lysin and arginine.
- In the abstract, the authors stated that this experiment was conducted in two strains of zebrafish (wild and mutant types). However, there was just one set of data presented in the manuscript.
The data of the mutant strain is shown in Figure 3. This mutant was used as it is transparent which allowed an in vivo detection of the color changes in zebrafish body. It is mentioned in the caption that it is Casper strain. However, I added wild type in the caption of each data set where wild type was used.
- Figure 1, the name of horizontal coordinate should be "Diet" rather than "SGR" or "FCR".
Edited.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Overall is a well written manuscript and I can see the effort that the authors have put in. I have some minor suggestions that I would like the authors to consider.
Firstly, please check again the format of the scientific names in the text and change them to italics.
Secondly, in Lines 46-48 need to explain better how the increased FM/FO demand will threaten human food security when the wild caught fish are food grade. Please take into consideration that FAO suggests that the availability of FM/FO is expected to be stable until 2030 and at the same time the need for fish feed will be increased. Additionally, according to IFFO, the FIFO ratio for global aquaculture is 1:4.55 which means 1 Kg of fish can support the growth of 4.5 kg of farmed fish.
Thirdly, considering the zebrafish is an omnivorous fish you should explain the feed formulation and the high protein level (>46%) of the experimental diets (such high protein levels usually found in carnivorous species).
Based on my comments my suggestion is to accept after minor revision
Author Response
Response to Reviewer 2 Comments
Firstly, please check again the format of the scientific names in the text and change them to italics.
The Latin name of zebrafish has been corrected in line (16, 104, 154,166)
The name C. reinhardtii has been made italic throughout the text.
Secondly, in Lines 46-48 need to explain better how the increased FM/FO demand will threaten human food security when the wild caught fish are food grade. Please take into consideration that FAO suggests that the availability of FM/FO is expected to be stable until 2030 and at the same time the need for fish feed will be increased. Additionally, according to IFFO, the FIFO ratio for global aquaculture is 1:4.55 which means 1 Kg of fish can support the growth of 4.5 kg of farmed fish.
I explained this point in line 47 to line 61.
Currently the term fish-in-fish-out (FIFO) is used to express the efficiency with which the fishmeal and fish oil from wild fish are converted into farmed fish body [5]. This figure is continuously declining from (0.47) in 2000 to (0.19) in 2020, which means that each 1Kg of wild fish gives 5 kg of farmed fish [6]. Keeping this figure in mind, the use of wild fish in aquafeed is more efficient than using it in direct human consumption although 90% of wild-caught fish is food grade [3, 5]. However, there are many challenges caused by the use of FM and FO in aquafeed. In 2030, it is expected that global human consumption of fish is projected to increase by 1.3% while aquaculture production will provide 57% of the total human consumption compared to 53 % in 2020. However, the growth of wild fish capturing is believed to increase modestly of 3.6% by 2030, added to some fluctuation caused by climate changes such as in El Niño years (2022- 2027) [3, 6]. ThusThus, the availability of both commodities is expected to slow down compared to the growth in aquafeed sector and by 2030 the price of FM is expected to double and for FO to increase by over 70% with more competition with omega-3 production for supplement market.
Thirdly, considering the zebrafish is an omnivorous fish you should explain the feed formulation and the high protein level (>46%) of the experimental diets (such high protein levels usually found in carnivorous species).
This point is explained in line 136 to line 140.
The protein level in this study was guided by industry feeds at the time, research on optimal dietary requirements of zebrafish. Many researchers have suggested a range of protein requirements for Cyprinidea family with recommended levels of (30-53%) protein in their diet depending on protein quality.
Based on my comments my suggestion is to accept after minor revision
Author Response File: Author Response.pdf
