Effects of Biotic and Abiotic Factors on the Spatiotemporal Distribution of Round Scad (Decapterus maruadsi) in the Hainan Island Offshore Area
, Changping Yang 1,2, Yan Liu 1,2, Binbin Shan 1,2,3, Shengwei Ma 2,* and Dianrong Sun 1,2,*
Round 1
Reviewer 1 Report
Effects of biotic and abiotic factors on the spatiotemporal distribution of round scad (Decapterus maruadsi) in the Hainan Island offshore area
The authors have worked on the the biotic and abiotic factors on the seasonal and spatial distribution of round scad around Hainan Island. Generalized additive model (GAM) to analyze the relationship between the distribution of round scad abundance, in relation to biotic and abiotic factors.
Specific comments:
· When already authors (ref 9 and 10) have worked on the aspects what is the novelty of the work, the authors need to explain.
· Season wise number of surveys conducted may be mentioned. If the survey was done spatially in different places, which might have influenced the abundance. How many surveys conducted off the northern coast of Hainan Island in the spring.
· The survey sampling design is important for the abundance of the round scad, which needs to be explained in a detailed way with season-wise station information.
· As per the abundance (Fog. No. 2 ) the north-eastern part of the iceland is more abundant for round scad throughout the seasons. An explanation for the same may be made.
· It is quite obvious that, when two species occupy the same niche and compete for the same food a correlation exists between them, what is new in this.
Author Response
Dear Reviewer,
Thank you very much for your great efforts regarding our paper. We are grateful to you for the valuable and insightful comments, which have helped to improve our paper. We have made appropriate revision based on all the comments. The main points of the revision are summarized as follows. Point-by-point responses to the reviewers’ comments are listed below and all changes in the manuscript can be found using the tracking of MS Word.
Yours Sincerely
Dianrong Sun
On behalf of all co-authors
Detailed review report
Specific comments:
- When already authors (ref 9 and 10) have worked on the aspects what is the novelty of the work, the authors need to explain.
Response: Thank you for your suggestion. In the introduction, it was firstly explained that previous studies mainly focused on the significant correlation between the distribution of round scad and oceanographic factors, but the influence of biotic factors on their distribution was less mentioned, so in this study, several biotic factors were mainly introduced to investigate the distribution of round scad. Relevant modifications are mentioned in the Line 89-104.
- Season wise number of surveys conducted may be mentioned. If the survey was done spatially in different places, which might have influenced the abundance. How many surveys conducted off the northern coast of Hainan Island in the spring.
Response: The research survey was conducted for one cruise each in spring, summer, autumn and winter, and the station settings were the same for each cruise, with the 54 stations. The specific settings are mentioned in the manuscript (Line 127-133). The topography and hydrology of the Qiongzhou Strait in the northern coastal waters of Hainan Island are not suitable for trawl surveys, so no stations are set up. However, we set up four stations on each side of the east and west coastal waters of the Qiongzhou Strait (Fig. 1).
- The survey sampling design is important for the abundance of the round scad, which needs to be explained in a detailed way with season-wise station information.
Response: I agree with your comment about the station information. A specific explanation has been added to the text (Line 134-137).
- As per the abundance (Fog. No. 2 ) the north-eastern part of the iceland is more abundant for round scad throughout the seasons. An explanation for the same may be made.
Response: Thank you for your suggestion. The higher distribution of abundance in the northeastern part of Hainan Island may be closely related to the presence of upwelling in the region, and the related description has been added in the manuscript (Line 396-406).
- It is quite obvious that, when two species occupy the same niche and compete for the same food a correlation exists between them, what is new in this.
Response: Thank you for your insightful comments. When two important pelagic species have similar ecological niches, it will inevitably result in some competition for habitat, food, etc. This situation will probably have an impact on the early recruitment stage of the population, thus resulting in fluctuations in population dynamics. Referring to the “out-of phase” of Japanese sardine and Japanese anchovy in the northwest Pacific, if there are also differences in environmental suitability and competition for habitat between round scad and jack mackerel in the northern South China Sea in the context of climate change, it may also have an impact on the long-term population changes. Relevant sections have been added to the discussion in the Line 439-458.
Reviewer 2 Report
This article is relevant and presents new, unpublished information that is well-suited to the scope of the journal. The methodology used and the results are both consistent and relevant, and the authors have generated a plausible and well-supported hypothesis. Additionally, the maps, graphs, and tables provided in the article are clear and necessary for understanding the findings. However, Figure 2 could have one additional category of "kg/km2 abundance". The format presented by the authors is okay. However, the information conveyed in this figure may not be entirely clear to the reader and could generate some ambiguity regarding the author's explanation in the text. Nonetheless, I recommend publishing this manuscript without the need for changes.
Author Response
Dear Reviewer,
Thank you very much for your great efforts regarding our paper. We have made appropriate modification about Figure 2 in the manuscript to make it clearer.
Yours Sincerely
Dianrong Sun
On behalf of all co-authors
Reviewer 3 Report
Review of the manuscript: Diversity 2295356
Effects of biotic and abiotic factors on the spatiotemporal distribution of round scad (Decapterus maruadsi) in the Hainan Island offshore area
General comments
This study aims at analyzing the spatiotemporal variability in the distribution of round scad (Decapturus maruadsi) in the Hainan Island offshore area and quantifying the biotic and abiotic factors that affect this distribution. The authors use a dataset from 4 recent (March 2021- June 2022) oceanographic surveys around the Hainan Island, comprising 54 stations. Round scad abundance was obtained from bottom trawl sampling. Biotic factors were jack mackerel abundance (caught simultaneously to round scad), phyto and zooplankton abundance (sampled using a plankton net at the same time as trawl sampling). Abiotic factors were salinity and temperature (surface and bottom), water depth (measured using a CTD sensor) and Chla concentration. The distribution of round scad abundance in space and season is discussed and a Generalized Additive Model is used to evaluate the relationship between round scad abundance and biotic and abiotic factors, together with season and latitude/longitude. The final model shows a strong effect of temperature (surface and bottom), latitude and jack mackerel abundance and, to a lesser extent of longitude and Chla.
Considering the important sampling effort (4 oceanographic surveys with trawling, plankton sampling, Chla measurement and CTD probe use in 54 stations), I consider that the results are disappointing. As stated by the authors, many studies have already described the spatial distribution of the round scad in this area and the effect of several abiotic factors on its abundance. Consequently, the originality of the present paper should be the biotic factors such as phyto and zooplankton abundance and jack mackerel density. The model however doesn’t show any effect of phyto and zooplankton abundance.The only conclusion as regards biotic factors is a positive correlation between jack mackerel and round scad abundance. This seems of little interest, as it is already known that “their distribution areas strongly overlap and fish of both species are often caught together...” (l. 401 – 402). In the discussion section about biotic factors (l. 395 – 438), the authors only discuss this niche overlap between the two fish species but they don’t discuss the absence of effect of plankton, whereas this potential effect of plankton was one of their initial hypotheses. In these conditions, I wonder what is new in this study, compared to the considerable existing knowledge about the distribution and environmental effect on the round scad? A better review of the existing knowledge about round scad and focus on what is new in the present study would clearly improve the interest of this paper.
I would like to underline, however, that the use of GAMs for such statistical analyses is not a new methodological approach, as the method has been used for 3 decades in similar studies. The authors should not emphasize this approach as it is quite standard.
In a general way, in the introduction and the discussion section, the bibliographic reference are not enough related to the assertions of the authors: many sentences are not clearly associated to their references. This has to be improved.
Specific comments
l. 91: “round scad feed on zooplankton”: needs a reference ! In the discussion section (l. 477) the authors say: “Round scad predominantly feeds on small fish and crustanceans (ref 14)”. This is not consistent!
l. 99-108: This paragraph about the use of GAMs should not be here. It is a methodological consideration which should be in the Material and methods section.
l. 125: the months should be clearly associated to the seasons used in the results section (It is not trivial! Please think to readers from southern hemisphere!)
l. 136: 3 km/h instead of 3 kn/h?
l. 187-201: “In addition… jack mackerel” This has already been said above
l. 243: in which season? Spring?
l. 245: Please identify the Beibu Gulf on the maps in Figures 1 and 2
l. 262: Figure 2: use the same abundance scale for both 4 maps (maybe log scale)
l. 266: paragraph 3.2 should be called “Selection of variables”
l. 270 “SST and SSS were significantly correlated with other explanatory variables”: not clear on the graph. Please check
l. 272: what are “their residual factors”? Not clear
l. 292: SBS is not in the model. Please check.
In addition, the season has been included in the model, but nothing is said in the text about seasonal effect
l. 301: Table 3 is not useful. Only the final model should be shown
l. 307: Figure 4 is no use
l. 322-323 and 328-330: Maybe one could say that the relationship between abundance and latitude / longitude has an inversed dome-shape like with SBT?
l. 337: In what do Fig 3 and 5 show “significant seasonal and spatial differences”?
l. 349: Please link each reference to a specific assertion
l. 440: Fig 6 is of poor quality. Please enhance the readability
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Round 2
Reviewer 3 Report
Review of the manuscript: Diversity 2295356, revised version
Effects of biotic and abiotic factors on the spatiotemporal distribution of round scad (Decapterus maruadsi) in the Hainan Island offshore area
General comments
In this revised version (v2), the authors have made a considerable effort to address the reviewers' comments. Therefore I consider that this new version can be accepted after taking into account the minor changes listed below.
Specific comments
l. 71: “In addition, the distribution round scad” => “In addition, the distribution of round scad”
l 89-97: OK for the modification. Replace “feeding switching” by “a change in diet”. For the sentence “Meanwhile, jack mackerel fed on pelagic crustaceans and small fish, and there was also a feeding switch” => “Meanwhile, jack mackerel feed on pelagic crustaceans and small fish, and there is also a change in diet”. And the last sentence “Both round scad and jack mackerel…” also needs English checking.
l. 136-138: The new sentence “In addition to the Qiongzhou Strait in part of the sea is not suitable for trawling, all stations are evenly distributed…” is not clear. What did you mean?
l. 111-116: OK for removing this sentence about the use of GAMs. I also suggest to remove the next one “It is well established that… fisheries research” because this information is already given in paragraph 2.2.1, which is a better place for methodologic considerations.
l. 313: “Section of variables” => “Selection of variables”
l. 491: “crustanceans” => “crustaceans”
l. 547: Fig 6 is still of poor quality. Please clearly identify which species corresponds to left and right axes as the current label is the same for both. Use different colours for the 2 species, or different symbols that can be clearly distinguished (black dot and square cannot).
Author Response
Dear Reviewer,
Thank you very much for your great efforts regarding our paper. We are grateful to you for the valuable comments, which have helped to improve our paper. We have made appropriate revision based on all the comments. The main points of the revision are summarized as follows. Point-by-point responses to the reviewers’ comments are listed below and all changes in the manuscript can be found using the tracking of MS Word.
Yours Sincerely
Dianrong Sun
On behalf of all co-authors
Detailed review report
Specific comments
- 71: “In addition, the distribution round scad” => “In addition, the distribution of round scad”
Response: The mistake has been corrected.
l 89-97: OK for the modification. Replace “feeding switching” by “a change in diet”. For the sentence “Meanwhile, jack mackerel fed on pelagic crustaceans and small fish, and there was also a feeding switch” => “Meanwhile, jack mackerel feed on pelagic crustaceans and small fish, and there is also a change in diet”. And the last sentence “Both round scad and jack mackerel…” also needs English checking.
Response: Thank you for the revision. All modifications have been made in the manuscript.
- 136-138: The new sentence “In addition to the Qiongzhou Strait in part of the sea is not suitable for trawling, all stations are evenly distributed…” is not clear. What did you mean?
Response: This description is indeed inappropriate, we have made correct.
- 111-116: OK for removing this sentence about the use of GAMs. I also suggest to remove the next one “It is well established that… fisheries research” because this information is already given in paragraph 2.2.1, which is a better place for methodologic considerations.
Response: Thank you for your suggestion. It has been removed.
- 313: “Section of variables” => “Selection of variables”
Response: The mistake has been modified.
- 491: “crustanceans” => “crustaceans”
Response: The mistake has been modified.
- 547: Fig 6 is still of poor quality. Please clearly identify which species corresponds to left and right axes as the current label is the same for both. Use different colours for the 2 species, or different symbols that can be clearly distinguished (black dot and square cannot).
Response: Thank you for your comment. Fig. 6 has been modified to improve the quality.
