Environmental Variables Influencing the Distribution of Penaeus Shrimp (Decapoda: Dendrobranchiata: Penaeidae) in a Subtropical Estuary of the Gulf of Mexico

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

See attached file, I cannot copy here my comments,

Alternatively Is end them to edotors by e-mail

Comments for author File: Comments.pdf

Author Response

REVIEWER'S COMMENT

My comments/evaluation on the study “Environmental variables influencing the distribution of Penaeus shrimp (Decapoda: Dendrobranchiata: Penaeidae) in a subtropical estuary of the Gulf of Mexico” by Ayla M. Ayala-Cruz and coauthors.

This is a well-designed and well-executed study of a crucial time in the life history of littoral penaeid shrimp that deserves to be published. It is not common in marine biology studies to try to explain, based on environmental data, why species are distributed in certain areas and not in others, and this study is a good example. This is particularly the case in open waters (my area of work), but such approaches are also lacking in more accessible coastal studies.

RESPONSE FROM AUTHORS

We appreciate the reviewer's positive comments that our work was well designed and well executed.

 

REVIEWER'S COMMENT

My comments in the line I quoted above can't cover whether the references used by the authors are adequate, i.e. whether some important similar study is missing, because I work all my life (as I explained to the editors) in open deep waters. In general, however, the work would be improved by including some references from outside the study area to similar studies in the littoral, even in more open waters.

RESPONSE FROM AUTHORS

We confirm that the references used are appropriate since they include several previous studies evaluating the influence of different environmental factors on penaeid shrimps. These references are cited in the Discussion, mainly in sections 4.2 (Distribution of Penaeid Shrimps Along the Estuary) and 4.3 (Influence of Environmental Factors on Shrimp Abundance).

In addition, in the revised version of the manuscript we have included additional references comparing our results with those reported for other penaeids inhabiting other subtropical estuaries around the world. See new section 4.4. Utilization of Subtropical Estuaries by Penaeids in Other Regions of the World.

Therefore, we consider that the references reported in the revised manuscript are relevant and appropriate.

 

REVIEWER'S COMMENT

I have included some comments/suggestions to improve some aspects of the study.

1. The different biological stages used here (recruits, juveniles, etc.) should be defined in the methods, perhaps with data on the size of each category for each species (a histogram indicating each category, or a table with range size and morphological characteristics). This will help future researchers to repeat a similar study using the same criteria. Alternatively, if these stages are defined for the 4 species or genus, etc., the citation of an appropriate reference could cover this.

RESPONSE FROM AUTHORS

We appreciate the observation that the three biological stages used in our study (recruits, juveniles, and subadults) should be defined in methods. However, the description of these population groups according to their size is already included in the methods section (see section 2.2. Sampling and Laboratory Procedures). The manuscript states that, shrimp were categorized into three population groups according to their carapace length (CL) into recruits (CL < 8.0 mm), juveniles (CL ≥ 8.0 mm but < 15.0 mm), and subadults (CL ≥ 15.0 mm). The corresponding reference where this classification was first used is also already reported in the manuscript (i.e., Pérez-Castañeda and Defeo, 2001).

Regardless of the above, in the revised manuscript we have added the following information in the section 2.2 (page 3):

"This operational classification is based on the fact that 15 mm CL is the minimum size at which these species attain the subadult stage. The above means that this is the size at which thelycum (in females) and petasma (in males) assume adult form [28]. In addition, due to the lack of distinct species-level characteristics for shrimp smaller than 8 mm CL, that group of individuals was categorized as recruits".

Reference: Pérez-Castañeda, R.; Defeo, O. Population variability of four sympatric penaeid shrimps (Farfantepenaeus spp.) in a tropical coastal lagoon of Mexico. Estuarine Coastal Shelf Sci. 2001, 52, 631–641.

 

REVIEWER'S COMMENT

2. I think this species must be multivoltine in a tropical coastal environment (maybe I'm wrong). Anyway, the authors should justify a little why the study was done in November (only), e.g. if this is a good time for recruitment of this species in estuaries ?

RESPONSE FROM AUTHORS

According to monthly patterns of total abundance of shrimp and P. aztecus reported in a coastal lagoon adjacent to our study area (Laguna Madre), the greater abundance was observed in November (Blanco-Martínez et al., 2020). For this reason, November was considered an appropriate date to conduct the present study.

Therefore, in the revised version of the manuscript, we have added the following text to justify why the study was done in November:

"This is the time of year when peak shrimp abundance has been observed in seagrass beds near a tidal mouth (entry point for the postlarvae) in a nearby coastal lagoon [27]".

Reference: Blanco-Martínez, Z.; Pérez-Castañeda, R.; Sánchez-Martínez, J.G.; Benavides-González, F.; Rábago-Castro, J.L.; Váz-quez-Sauceda, M.L.; Garrido-Olvera, L. Density-dependent condition of juvenile penaeid shrimps in seagrass-dominated aquatic vegetation beds located at different distance from a tidal inlet. PeerJ 2020, 8, e10496.

 

REVIEWER'S COMMENT

3. This comment is completely optional, since the MLR models adopted here cover the statistical treatment of the data perfectly, but perhaps some "graphical" methods such as a CCA, although somewhat repetitive, could help to better show the tendencies found.

RESPONSE FROM AUTHORS

We appreciate the suggestion. However, we agree with the reviewer that the multiple linear regression models already cover the statistical treatment of the data to identify the main explanatory variables of shrimp abundance. Therefore, adding the analysis mentioned above (CCA) would be somewhat redundant.

Consequently, we decided not to include additional data analysis to those already performed.

 

REVIEWER'S COMMENT

Discussion.

L226-234. This part about sensitivity to changes in salinity is particularly interesting. I think the authors should indicate in each sentence whether the relationships with this variable found in other studies are for adult specimens or also (as in this case) for small (recruits, etc.) individuals in estuaries. Also, whether the salinity gradients in these studies are as wide as in this one, or whether shrimp are sensitive to narrower changes in salinity.

RESPONSE FROM AUTHORS

In the revised manuscript, we have specified that the sentences the reviewer mentioned refer to juvenile shrimps. We have also specified whether the salinity gradients in the other ecosystems mentioned are higher or lower than those in our study area.

This change was made in the first paragraph of section 4.3.

 

 

REVIEWER'S COMMENT

Also, some citations out from the Gulf of Mexico and/or from littoral systems (if available) might give more interest to this part of the discussion. In general, I think that salinity changes in decapods are more important than is often assumed, as the authors explain perfectly in the next paragraph for these 4 Penaeus species.

I hope to see this study published, although my comments may suggest a deep revision, I think they are all rather minor, and authors can assume them without problems.

RESPONSE FROM AUTHORS

In the revised version, we included several citations of studies on juvenile penaeid shrimp inhabiting subtropical estuarine ecosystems in Australia and South America. The above was added in a new section of the discussion entitled: 4.4. Utilization of Subtropical Estuaries by Penaeids in Other Regions of the World.

We appreciate the suggestion. However, since our interest is in juvenile shrimps, which are found in estuarine ecosystems, we did not include studies from littoral systems.

 

Reviewer 2 Report

Comments and Suggestions for Authors

·       write in the summary section the abiotic parameters studied

·       put this sentence (lines 75 and 76) in the section Materials and methods

·       corrects sites 1-3 by sites 2-3 line 137 because according to figure 2, it is 2 and 3 which present the high values​, not site 1

·       add this paragraph from line 270 to line 277 to the discussion, because it is not a conclusion it is a continuation of the discussion

 

·       and write a new conclusion in which you cite the main results and perspectives of your study

Comments on the Quality of English Language

 The English could be improved to express the research more clearly.

Author Response

REVIEWER'S COMMENT

write in the summary section the abiotic parameters studied

RESPONSE FROM AUTHORS     

In the revised version of the manuscript, we have added the names of the variables in the abstract.

 

REVIEWER'S COMMENT

put this sentence (lines 75 and 76) in the section Materials and methods

RESPONSE FROM AUTHORS     

The sentence was moved to section "2.2. Sampling and Laboratory Procedures" of the Materials and methods.

 

REVIEWER'S COMMENT

corrects sites 1-3 by sites 2-3 line 137 because according to figure 2, it is 2 and 3 which present the high values, not site 1

RESPONSE FROM AUTHORS     

We appreciate the comment. Correction made.

 

REVIEWER'S COMMENT                          

add this paragraph from line 270 to line 277 to the discussion, because it is not a conclusion it is a continuation of the discussion

and write a new conclusion in which you cite the main results and perspectives of your study

RESPONSE FROM AUTHORS     

We appreciate the comment. However, the text was not moved to the discussion but deleted to avoid redundancy. Following the reviewer's suggestion, a new conclusion was written.

Reviewer 3 Report

Comments and Suggestions for Authors

General comment

The article is interesting because it's the first study of its kind in the area.

What's more, this work is based on the fundamentals of ecology, since the authors study the interaction between species and their environment. In the context of climate change, this kind of scientific study is very important.

In the Materials and methods section on data analysis, the authors must justify why they used ANOVA instead of the Kruskal-Wallis test. In addition, to better appreciate the results, the authors should present the multiple regression formula.

In the results section, in Figure 4, all coefficients of determination are less than or equal to 50%. This means that the variables salinity and seagrass do not strongly explain variations in shrimp abundance. There are then other factors that play an important role in shrimp abundance variation.

It is imperative that the authors discuss these results and identify the factors that also explain variations in shrimp abundance in the study area. t's not just salinity and seagrass

Author Response

REVIEWER'S COMMENT

The article is interesting because it's the first study of its kind in the area.

What's more, this work is based on the fundamentals of ecology, since the authors study the interaction between species and their environment. In the context of climate change, this kind of scientific study is very important.

RESPONSE FROM AUTHORS     

We appreciate the reviewer's positive comments about our work.

 

REVIEWER'S COMMENT

In the Materials and methods section on data analysis, the authors must justify why they used ANOVA instead of the Kruskal-Wallis test. In addition, to better appreciate the results, the authors should present the multiple regression formula.

RESPONSE FROM AUTHORS

As already mentioned in the manuscript, using an ANOVA instead of a Kruskal-Wallis test is justified because the data met the required assumptions (normality and homogeneity of variances) for this analysis. The above was achieved by transforming the original data where necessary. For that reason, we were able to perform an ANOVA (parametric test) instead of the Kruskal-Wallis test (non-parametric test).

We do not consider it necessary to write further justification or explanation in Materials and Methods because these points are already mentioned in section 2.3 (Data Analysis). In addition, we also provide a citation for a book on biostatistics (Zar, 1999) that supports our procedure.

Regarding the multiple linear regression formula requested by the reviewer:

Seven formulas were obtained, which are already reported in Table 1. Therefore, the reader can construct each formula by taking the information from this Table. For example, four linear models with two independent variables and three linear models with one independent variable explaining shrimp abundance were obtained. These formulas explained the total abundance as well as the abundance of juveniles, subadults, P. aztecus, recruits, P. duorarum, and P. brasiliensis.

Since the formulas for the linear models are already described in Table 1, we decided not to include them in the text.

Reference: Zar, J.H. Biostatistical Analysis, 4th ed.; Prentice-Hall Press: Upper Saddle River, NJ, USA, 1999; pp. 1–663.

 

REVIEWER'S COMMENT

In the results section, in Figure 4, all coefficients of determination are less than or equal to 50%. This means that the variables salinity and seagrass do not strongly explain variations in shrimp abundance. There are then other factors that play an important role in shrimp abundance variation.

It is imperative that the authors discuss these results and identify the factors that also explain variations in shrimp abundance in the study area. t's not just salinity and seagrass.

RESPONSE FROM AUTHORS

We agree that additional factors influence the distribution and abundance of shrimp in the ecosystem. Unfortunately, we did not measure additional variables beyond those presented in the manuscript. Future studies evaluating the influence of other biotic and abiotic factors would be required to enhance our understanding of penaeid ecology in estuaries.

Despite the above, in the revised version (Discussion section), we have pointed out additional potential factors that could explain the abundance of shrimp in the estuary, as suggested by the reviewer.

The added text was placed at the end of section 4.3 (last paragraph).

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

No further comments. My concerns have been addressed.