A Proposed Method for Assessing the Spatio-Temporal Distribution of Carcharhinus melanopterus (Quoy and Gaimard, 1824) in Shallow Waters Using a UAV: A Study Conducted in Koh Tao, Thailand

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Introduction

The study area section is too long I recommended resuming the information and maintaining only the information that is relevant to this study, like the habitat description and oceanographic characteristics, maybe something about the main activities but just mentioning that Tourism and Diving are the main activities there.

 

Materials and methods

Sampling was carried out only during 20 days? In that case I believe the title is so ambitious because you have only a few days of data, and this is a snapshot of what was happening in that particular moment but can´t describe the spatio-temporal distribution of a specie based only in less than one month.

Line 36-39 This information in not necessary here, all the permits information should go at the end of the manuscript in Acknowledges section or in a separate section.

 

The measures of environmental conditions are very imprecise, for example for wind why you don’t use the wind speed values, which is easy to know from the weather forecast, also for the sea conditions why you didn´t used the Beauford scale that is a scale that is commonly used to describe the sea conditions and is comparable around the world? Also for Cloudines why you don’t report for example as a percentage of the sky? Because what you are reporting is affected greatly by the perception of the individual and variate from one to other person is not something that is replicable in the future for other researchers.

 

Line 158-160 The transects always started in the same spot always? Or do you use different spots to cover the entire beach area?

 

Line 180. What do you mean with leg of the transect? labeled nA1, nR2, nA2, nR2 this terms are not clear.

Line 186. It is not clar how do you calculate abundance? Please define well how do you estimate it. nMax is the total number of individuals observed? How do you know you are not counting the same shark several times?

Line 189. Is not clear what do you consider as animal´s activity? Please explain what do you mean

Line 191-200 Kruskall Wallis is a well-known test in the literature so I consider this information presented here is not necessary.

 

Line 210- 214 How do you know is the same individual? How do you identify them to know it is the same always?

 

Line 244-247 Similar comment as the Kruskal Wallis before

Line 279. In the formula is not clear the variables used. Please instead of putting the numbers put the name of the variables involved and explain what mean each of the variable. Then you can replace the variables for the numbers if you want.

 

Line 280-282. Why you didn´t convert the pixels to cm instead of the contrary here? Is easy for the readers if you report the length of the individuals in cm. In pixels is hard to visualize the size of an animal.

 

Results

Line 299-301. This is part of  method no results.

Line 309-311. This is part of  methods no results.

Line 345-349. This is part of  methods no results.

 

Discussion

There is not discussion in this section, is only a description of the results again this section need to much work to explain and analyze the results. Why do you believe you found what you are reporting? What are the explanations for this? Why do you find only females? Why are the sharks using this area? What is the literature said about the ecology and behavior of this species that you can use to explain what you found?.

There are several published studies that used drones for ecological studies on sharks that the author could use to discuss the method and its limitations of it.

 

The author should consider that light affects the brightness of the video and this is a factor that influenced the detection of individuals with drones, so is expected to find more sharks on a cloudy day and early in the morning this is not new.

 

Conclusion

This section presented a resume of the results but not a conclusion.

 

I consider the information presented in this manuscript is very preliminary and it is not a completed research. I recommended using this information for a scientific note focused on the standardization of a method to study sharks with drones, and I think a little more work could be improved and submitted to a journal with other scopes related to this method like Drons.

Author Response

Title

We can consider renaming the article in A Proposed Method for Assessing the Spatio-Temporal Distribution of Carcharhinus melanopterus (Quoy & Gaimard, 1824) in Shallow Waters Using UAV: A Study Conducted in Koh Tao, Thailand

Introduction

The study area section is too long I recommended resuming the information and maintaining only the information that is relevant to this study, like the habitat description and oceanographic characteristics, maybe something about the main activities but just mentioning that Tourism and Diving are the main activities there.

• OK. We removed lines about coral bleaching and eutrophication and the figure related to the algal bloom observed during the study

Materials and methods

Sampling was carried out only during 20 days? In that case I believe the title is so ambitious because you have only a few days of data, and this is a snapshot of what was happening in that particular moment but can´t describe the spatio-temporal distribution of a specie based only in less than one month.

• There are studies carried out for 10 days: “Using unmanned aerial vehicles (UAVs) to investigate shark and ray densities in a shallow coral lagoon (Jeremy J. Kiszka1,*, Johann Mourier2,3, Kirk Gastrich1, Michael R. Heithaus)
• By the way, our intentions are to propose a method to study blacktip reef shark in shallow waters in a non-invasive way using a very limited budget affordable even by citizen scientists. Though blacktip reef sharks are well known in Thailand to the media and public, there are no currently published studies about their ecology. The only available studies mention landed individuals.

 

Line 36-39 This information in not necessary here, all the permits information should go at the end of the manuscript in Acknowledges section or in a separate section.

• We moved to the Acknowledgements section.

 

The measures of environmental conditions are very imprecise, for example for wind why you don’t use the wind speed values, which is easy to know from the weather forecast, also for the sea conditions why you didn´t used the Beauford scale that is a scale that is commonly used to describe the sea conditions and is comparable around the world? Also for Cloudines why you don’t report for example as a percentage of the sky? Because what you are reporting is affected greatly by the perception of the individual and variate from one to other person is not something that is replicable in the future for other researchers.

• We thank reviewer for this suggestion. In material and methods we added Oktas, Beaufort scale and wind speed.

 

Line 158-160 The transects always started in the same spot always? Or do you use different spots to cover the entire beach area?

• We tkept  a straight trajectory every time, with same starting/end point 

 

Line 180. What do you mean with leg of the transect? labeled nA1, nR1, nA2, nR2 this terms are not clear.

• The term “leg” is the correct way to address the single run of a path (transect). In our case we run the transect 4 times per time slot (go, return, go, return). 

 

Line 186. It is not clar how do you calculate abundance? Please define well how do you estimate it. nMax is the total number of individuals observed? How do you know you are not counting the same shark several times?

• As stated in the lines 186-187 the abundance is the highest number of individuals counted in one of the legs of the transect. In this case we are sure to count different individuals because the drone is moving forward following a line, so we manually counted all the individuals that enter the screen as soon as they are visible and then we proceed with the others. Sharks move continuously but the drone is moving faster than them so they never enter the screen again. 

 

Line 189. Is not clear what do you consider as animal´s activity? Please explain what do you mean

• Definition of Animal’s activity added in the paper
• Animal activity is generally defined as the amount of time an animal spends in motion. Most shark species spend their entire lives in motion. When measuring the spatial and temporal niche partitioning among a species, for example using camera trapping, ecologists consider every sighting as 'activity,' regardless of whether it is the same or a different individual. Therefore, in our case, nTot (Animals activity) may contain double counted individuals, since going back and forth with the drone following a line we may encounter the same individuals. We used this value to compare it with the abundance (that are the individuals counted in a single leg of the transect). https://doi.org/10.1126/science.185.4145.27
  https://doi.org/10.1111/2041-210X.12278
  https://doi.org/10.1016/B978-012497781-5/50013-X
  
  

Line 191-200 Kruskall Wallis is a well-known test in the literature so I consider this information presented here is not necessary.

• OK, we removed

 

Line 210- 214 How do you know is the same individual? How do you identify them to know it is the same always?

• As stated above, we are sure to count different individuals because the drone is moving forward following a line, so we manually counted all the individuals that enter the screen as soon as they are visible and then we proceed with the others. Sharks move continuously but the drone is moving faster than them so they never enter the screen again.

 

Line 244-247 Similar comment as the Kruskal Wallis before

• OK, we removed

 

Line 279. In the formula is not clear the variables used. Please instead of putting the numbers put the name of the variables involved and explain what mean each of the variable. Then you can replace the variables for the numbers if you want.

• We added the original equation from the cited paper and the transformation in order to obtain the PCL equation

 

Line 280-282. Why you didn´t convert the pixels to cm instead of the contrary here? Is easy for the readers if you report the length of the individuals in cm. In pixels is hard to visualize the size of an animal.

• We agree it could be beneficial if our purpose would be to highlight individuals length, however we used those values only for comparison between individuals measured in the same way. Our Python/AppleScript application stores the length of the tracked lines in pixels. We did not perform any conversion in the Application, neither we computed the GSD, it was used by the application only to generate the dataset from videos, to be further processed using R. Moreover it is worth noting that as stated in the line XX, our length values may be inaccurate for the reported reasons, therefore we used these values only for comparison between individuals.

Results

Line 299-301. This is part of  method no results.

• OK, we moved

 

Line 309-311. This is part of  methods no results.

• OK, we moved

 

Line 345-349. This is part of  methods no results.

• OK, we moved

Discussion

There is not discussion in this section, is only a description of the results again this section need to much work to explain and analyze the results. Why do you believe you found what you are reporting? What are the explanations for this? Why do you find only females? Why are the sharks using this area? What is the literature said about the ecology and behavior of this species that you can use to explain what you found?.

• OK, we rewrote the discussion according reviewer’s comments

 

There are several published studies that used drones for ecological studies on sharks that the author could use to discuss the method and its limitations of it.

• OK, done

 

The author should consider that light affects the brightness of the video and this is a factor that influenced the detection of individuals with drones, so is expected to find more sharks on a cloudy day and early in the morning this is not new.

• The water in the bay is clear and shallow that all the adult individuals are visible from the video. Even on challenging substrate (rocks/corals) they are easily seen due to their constant moving.

Conclusion

This section presented a resume of the results but not a conclusion.

• OK, also in this case we rewrote the paragraph

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

This study provides critical insights into the temporal and spatial distribution patterns of C. melanopterus, revealing how environmental factors and anthropogenic disturbances influence their behavior. By utilizing UAV technology for aerial surveys, the research offers a novel approach to monitor shark populations with high precision, which enhances our understanding of their habitat preferences and activity levels. This research supports the hypothesis of thermoregulation, suggesting the need for further research into how temperature variations impact shark behavior and habitat use. I have a few suggestions regarding the manuscript, which I will briefly outline below;

Conduct longitudinal studies to examine seasonal variations in the distribution and behavior of C. melanopterus to gain a comprehensive understanding of their yearly patterns.

Implement temperature monitoring with infrared sensors to validate the thermoregulation hypothesis and assess how temperature fluctuations affect shark movements and habitat preferences.

Explore the impact of different types and intensities of anthropogenic disturbances on shark populations to develop more effective mitigation strategies.

Expand the study to include other regions with similar environmental conditions to compare findings and improve the generalizability of the results for broader conservation efforts.

Also, other corrections in pdf files in the system.

Best Regards.

Comments for author File: Comments.pdf

Author Response

Title

add classification as Carcharhinus melanopterus (Quoy & Gaimard, 1824)

• We changed according to reviewer suggestion.

Authors

Remove “and” before Emilio Sperone

• Done

Introduction

Are there any studies conducted in the studied area or in similar regions that focus on this species or other species belonging to this genus? This aspect can be elaborated upon in this section. Additionally, in the last paragraph of the introduction, it would be beneficial to enrich the text by explaining the importance and objectives of the study, including what specific contributions this research will make to the understanding and management of the region's marine ecosystem.

• We made it clearer that our intentions are to propose a method to study blacktip reef shark in shallow waters in a non-invasive way using a very limited budget affordable even by citizen scientists. Though blacktip reef sharks are well known in Thailand to the media and public, there are no currently published studies about their ecology. The only available studies mention landed individuals.

 

"Figure 1a" not in text.

• Done

Materials and Methods

Change 1pm in 13:00 and 6pm in 18:00

• Done

 

Line 281 it should be 20.06px and not 20.6px

• Done

 

Starting from line 307, all figures must have a number +1 since 2 figures are labelled as Figure 5.

• Done

 

Line 369: It would be beneficial to include a literature review on nursery areas. How did you determine that these regions are nursery areas? This should be explained.

• Done

 

Line 383 (sex ratio sharks pictures) should be add Fig. 15 in text.

• Done

 

References

Multiple abbreviations suggested.

Scientific names should be always in italic, and the species always lowercase.

• Done