Population Structure, Age and Growth of Sardine (Sardina pilchardus, Walbaum, 1792) in an Upwelling Environment

Round 1

Reviewer 1 Report

The article by Baldé et al. deals with the estimation of the growth of a commercial species of interest such as the sardine and of a stock that is poor in data such as in the Senegalese waters. Knowledge of growth allows the application of simple fishery management models that can be very useful for the sustainability of the resource. The authors present these data for the first time in Senegalese waters. They include an environmental analysis to explain the results obtained, especially in the comparison with sardine growth data from other adjacent areas. The paper is therefore perfectly in line with the editorial line of the Fishes journal.  The article is well written and structured, the methods are adequate for a data-poor stock and the discussion well developed. Tables and figures are also explanatory. Therefore, the article is publishable. However, the paper presents some gaps and considerations that the authors should be aware of and respond to in order for the manuscript to be published:

Final evaluation: publishable with moderate revision.

GENERAL CONSIDERATIONS:

A comparative study is made of the growth of the Senegal sardine with that of Morocco and with that of the Mediterranean Sea. The Mediterranean Sea is located between 30˚ N (Libya) and 45˚ N (Adriatic Sea) latitude and is not a sea characterized by upwelling phenomena. However, it seems more than appropriate that the comparison should also be made with the sardine found on the European Atlantic coast. An area that presents a certain geographical continuity with the Atlantic coast of Morocco. Therefore, if it is compared with the Mediterranean Sea, the comparison should also be made with the sardine of the Atlantic coast of the Iberian Peninsula and France, which is located between 34˚ N (Gulf of Cadiz) and 48˚ N (Bay of Biscay). In these waters, especially in Portugal and northwest Spain, upwelling phenomena also occur. The results of this comparison should be included accordingly in the different sections of the text as well as in Table 2 and Figure 5.

Size frequency analyses have been carried out considering class intervals of 1 cm. If we take into account that the common size of the sardine is less than 30 cm and that the large sizes, such as the samples in this work, correspond to the flat part of the von Bertalanffy curve, it seems appropriate that the class intervals should be 0.5 cm. In this way, we can obtain more precise estimates.

In material and methods there are some deficiencies in the application of ANOVA (check the assumptions) and in the precise description of the hypotheses to be tested. Also missing are the estimates of the standard errors of the parameters in the growth equation.

Finally, if possible, the fishery data should be updated. 2014 is far from the present time.

 

 

 

SPECIFIC COMMENTS:

ABSTRACT:

Lines 17-18: It is indicated that the maximum size found was 26 cm but however on line 177 it is indicated that it was 31 cm. Please check this data.

Line 18: before the performance index include the K and L_∞ values.

Line 19: Include the estimated maximum age in northern Senegal.

 

KEYWORDS:

Line 26: Add: " Fish Growth" and "Sardina pilchardus".

 

INTRODUCTION

Line 39. It is suggested to include in this distribution of sardine also the Atlantic coast of the Iberian Peninsula and the Bay of Biscay.

Line 44. Add: "... the dominant fish species in commercial fisheries, constituting..."

Line 45. Is there not a more current reference?  The year 2014 is far off. I think a much more current reference can be found in FAO catch statistics.

Lines 46-47. If possible please include more recent data. Check in FAO catch statistics books.

Line 54. Following the recommendation included in the general comment, the authors should add here the sardine studies in the northeast Atlantic (Bay of Biscay and Iberian Peninsula).

Lines 72-73. Include in this comparative the studies of the northeast Atlantic.

 

MATERIAL AND METHODS:

Line 94: Include the number of specimens sampled in 2015 in artisanal fisheries.

Line 96: Indicate the number of specimens sampled in the Fridtjof Nansen.

Line 96: Briefly explain the method of capture used in the Fridtjof Nansen.

Line 100: Italicize S. pilchardus.

Lines 106-109. Considering that measurements were collected to the lower mm, why were the sizes not grouped to the half centimeter as a class interval? The specimens sampled were adults of considerable size, over 21 cm, where growth is theoretically slower (Figure 4). In these cases a finer class interval may provide more accurate information on growth by analyzing size frequencies. If possible, I would urge the authors to perform this analysis considering the class interval at 0.5 cm. Also, as stated in the FAO fisheries science manuals: "Choice of the class interval for recording length measurements is a matter of judgement but it is usually made in 1 cm units for species which grow larger than 30 cm and in 0.5 cm units for species which do not reach 30 cm".

Line 124: italicize the parameter "f".

Lines 136-137: Are there estimates of standard errors? Please include

Line 144: Add: "...; L_∞ is the mean asymptotic length; K is ...".

Line 158. Add: "... against an estimate of its mean asymptotic length (L_∞)..."

Lines 163-164. Explain further which distributions were compared with ANOVA. What was the hypothesis to be tested, etc.

Here you should also include the previous analysis of whether the data meet the assumptions for applying an ANOVA: normality, homogeneity of variances, independence, etc.

 

RESULTS:

Line 177: Does not match this value = 31 cm with what is stated in the abstract, lines 17-18 which says 26 cm.

Lines 177-178. Specify which size distributions were compared.

Line 181. Check the value of L_∞ = 23.1. In Table 2 L_∞ appears as 30.5, which is close to Lmax.

In general, add here the comparative results with the Atlantic coast of the Iberian Peninsula and Bay of Biscay.

 

DISCUSSION

Check the value of L_∞ cited here = 23.1 cm, with the value in Table 2 = 30.5 cm.

Lines 228 - 231. Indicate that these distinctions into different "races" were based on meristic studies.

Lines 256-257. The last sentence is too blunt. The sardine has been in the Mediterranean Sea for thousands of years, in certain years with great abundance. Better to delete the sentence.

Line 282. "growth" not "growths".

Line 287. delete "and" after S. pilchardus.

 

FIGURES:

Figure 7: Update data as far as possible

Author Response

General Comments from Reviewer  1

The article by Baldé et al. deals with the estimation of the growth of a commercial species of interest such as the sardine and of a stock that is poor in data such as in the Senegalese waters. Knowledge of growth allows the application of simple fishery management models that can be very useful for the sustainability of the resource. The authors present these data for the first time in Senegalese waters. They include an environmental analysis to explain the results obtained, especially in the comparison with sardine growth data from other adjacent areas. The paper is therefore perfectly in line with the editorial line of the Fishes journal.  The article is well written and structured, the methods are adequate for a data-poor stock and the discussion well developed. Tables and figures are also explanatory. Therefore, the article is publishable. However, the paper presents some gaps and considerations that the authors should be aware of and respond to in order for the manuscript to be published:

Final evaluation: publishable with moderate revision.

A comparative study is made of the growth of the Senegal sardine with that of Morocco and with that of the Mediterranean Sea. The Mediterranean Sea is located between 30˚ N (Libya) and 45˚ N (Adriatic Sea) latitude and is not a sea characterized by upwelling phenomena. However, it seems more than appropriate that the comparison should also be made with the sardine found on the European Atlantic coast. An area that presents a certain geographical continuity with the Atlantic coast of Morocco. Therefore, if it is compared with the Mediterranean Sea, the comparison should also be made with the sardine of the Atlantic coast of the Iberian Peninsula and France, which is located between 34˚ N (Gulf of Cadiz) and 48˚ N (Bay of Biscay). In these waters, especially in Portugal and northwest Spain, upwelling phenomena also occur. The results of this comparison should be included accordingly in the different sections of the text as well as in Table 2 and Figure 5.

Response (Baldé et al.): Thank you for the comments that improved the results and the discussion. The other regions were added to the study (see Table 2 and Figure 5).

Reviewer  1

Size frequency analyses have been carried out considering class intervals of 1 cm. If we take into account that the common size of the sardine is less than 30 cm and that the large sizes, such as the samples in this work, correspond to the flat part of the von Bertalanffy curve, it seems appropriate that the class intervals should be 0.5 cm. In this way, we can obtain more precise estimates.

Response (Baldé et al.): Thank you very much for the comment, the corrections have been made. The max size was 31 cm. Therefore, according to the FAO, the class intervals are 1cm.

Reviewer  1

In material and methods there are some deficiencies in the application of ANOVA (check the assumptions) and in the precise description of the hypotheses to be tested. Also missing are the estimates of the standard errors of the parameters in the growth equation.

Response (Baldé et al.): Thank you for the comments that helped improve the methodology. We have clarified the use of the ANOVA test. Indeed, the ANOVA test allowed us to test the variability of the sizes as well as the differences between the growth parameters between the different regions.

Reviewer  1

Finally, if possible, the fishery data should be updated. 2014 is far from the present time.

Response (Baldé et al.): it is done.

- Reviewer  1

Lines 17-18: It is indicated that the maximum size found was 26 cm but however on line 177 it is indicated that it was 31 cm. Please check this data.

Response (Baldé et al.): Thank you very much for the comment, the corrections have been made. The max size was 31 cm.

- Reviewer 1

Line 18: before the performance index include the K and L∞ values.

Response (Baldé et al.): Thanks for the comment. The parameters have been added. “A growth performance index (φ’) and a growth rate coefficient (K) (2.65 and 0.85 respectively) were determined were determined, with this being the first record for this region.”

- Reviewer  1

Line 19: Include the estimated maximum age in northern Senegal.

Response (Baldé et al.): Thanks, The maximum age has been added.

- Reviewer  1

Line 26: Add: " Fish Growth" and "Sardina pilchardus".

Response (Baldé et al.): Thanks. The keywords have been added.

- Reviewer  1

It is suggested to include in this distribution of sardine also the Atlantic coast of the Iberian Peninsula and the Bay of Biscay.

Response (Baldé et al.): Thanks. We include in our distributions Atlantic coast of the Iberian Peninsula and the Bay of Biscay as suggested.

- Reviewer  1

Line 44. Add: "... the dominant fish species in commercial fisheries, constituting..."

Response (Baldé et al.): This part has also been added to the document. Thanks you.

- Reviewer  1

Line 45. Is there not a more current reference?  The year 2014 is far off. I think a much more current reference can be found in FAO catch statistics.

Response (Baldé et al.): Thanks for the comment, we have updated the data and the references.

- Reviewer  1

Lines 46-47. If possible please include more recent data. Check in FAO catch statistics books.

Response (Baldé et al.): Thanks for the comment, we have updated the data and the references.

- Reviewer  1

Line 54. Following the recommendation included in the general comment, the authors should add here the sardine studies in the northeast Atlantic (Bay of Biscay and Iberian Peninsula).

Response (Baldé et al.): Thank you for the comments. Northeast Atlantic data has been added to the analyses and discussion.

- Reviewer  1

Lines 72-73. Include in this comparative the studies of the northeast Atlantic.

 

Response (Baldé et al.): Northeast Atlantic data has been added to the analyses and discussion.

- Reviewer  1

Line 94: Include the number of specimens sampled in 2015 in artisanal fisheries.

Response (Baldé et al.): The number of specimens has been added for each year collected.

- Reviewer  1

Line 96: Indicate the number of specimens sampled in the Fridtjof Nansen.

Response (Baldé et al.): The number of specimens has been added.

- Reviewer  1

Line 96: Briefly explain the method of capture used in the Fridtjof Nansen.

Response (Baldé et al.): The method of capture in the Fridtjof Nansen and the sampling was described.

- Reviewer  1

Line 100: Italicize S. pilchardus.

Response (Baldé et al.): The name of the species has been italicized.

- Reviewer  1

Lines 106-109. Considering that measurements were collected to the lower mm, why were the sizes not grouped to the half centimeter as a class interval? The specimens sampled were adults of considerable size, over 21 cm, where growth is theoretically slower (Figure 4). In these cases a finer class interval may provide more accurate information on growth by analyzing size frequencies. If possible, I would urge the authors to perform this analysis considering the class interval at 0.5 cm. Also, as stated in the FAO fisheries science manuals: "Choice of the class interval for recording length measurements is a matter of judgement but it is usually made in 1 cm units for species which grow larger than 30 cm and in 0.5 cm units for species which do not reach 30 cm".

Response (Baldé et al.): Thank you for the comments that helped us improve the quality of the results. Thus, it allowed us to modify the figure.

- Reviewer  1

Line 124: italicize the parameter "f".

Response (Baldé et al.): Thank you. The parameter "f" has been put in italics.

- Reviewer  1

Line 144: Add: "...; L∞ is the mean asymptotic length; K is ...".

Response (Baldé et al.):  Thank you. The corrections have been added.

- Reviewer  1

Line 158. Add: "... against an estimate of its mean asymptotic length (L∞)...".

Response (Baldé et al.):  Thank you. The corrections have been added.

- Reviewer  1

Lines 163-164. Explain further which distributions were compared with ANOVA. What was the hypothesis to be tested, etc.

Response (Baldé et al.): Thank you. The use of the ANOVA test allows to see if the distribution is normal or not. All analyses have been added.

- Reviewer  1

Ligne 177 : Line 177: Does not match this value = 31 cm with what is stated in the abstract, lines 17-18 which says 26 cm.

Response (Baldé et al.): Thanks for the comment, we have corrected and added the real value to the summary (31 cm).

- Reviewer  1

Lines 177-178. Specify which size distributions were compared.

Response (Baldé et al.): Thanks. It is the monthly variability of the size distribution.

- Reviewer  1

Line 181. Check the value of L∞ = 23.1. In Table 2 L∞ appears as 30.5, which is close to Lmax.

Response (Baldé et al.): Thanks for the comment, we have corrected and added the real value.

- Reviewer  1

In general, add here the comparative results with the Atlantic coast of the Iberian Peninsula and Bay of Biscay.

Response (Baldé et al.): Data from the Atlantic coast of the Iberian Peninsula and the Bay of Biscay were added to the study.

- Reviewer  1

Check the value of L∞ cited here = 23.1 cm, with the value in Table 2 = 30.5 cm.

Response (Baldé et al.): Thanks for the comment, we have corrected and added the real value.

- Reviewer  1

Lines 228 - 231. Indicate that these distinctions into different "races" were based on meristic studies.

Response (Baldé et al.): Thank you, we have also added this specification on the methodology used in race distinctions.

- Reviewer  1

Lines 256-257. The last sentence is too blunt. The sardine has been in the Mediterranean Sea for thousands of years, in certain years with great abundance. Better to delete the sentence.

Response (Baldé et al.): Thanks for the suggestion. We have deleted the sentence.

- Reviewer  1

Line 282. "growth" not "growths".

Response (Baldé et al.): The corrections have been taken into account.

- Reviewer  1

Line 287. delete "and" after S. pilchardus.

Response (Baldé et al.): Thanks for the correction. The word has been removed.

- Reviewer  1

Figure 7: Update data as far as possible.

Response (Baldé et al.): Thanks for the suggestion; we added data from 1964 to 2017 to the study.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript "Population structure, age and growth of sardine (Sardina 2 pilchardus, Walbaum, 1792) in an upwelling environment " present several merits since growth studies on important exploited resources are of outmost importance for stock assessment modelling and correct management. In the study area of course there is lack of this informations therefore this study add new information useful.

However two main concerns raised up to be addressed by authors before publication:

1) The limits of LFD in evaluating proper VBGF parameters without age readings have to be addressed in the ms. . So I suggest to address this aspect both in the introduction and in the discussion also to evaluate your results compared to literature studies with different methods. I agree that in case of limited data stocks this technique could help but it is hard to say that results are well representative of the stock analysed.

2) the limited size range analysed: how the absence of smaller individual may affect the estimation? also when comparing your results with literature, the differences may be attributed to such aspect?

However if the ms will be upgraded also following suggestion and comments in the pdf of the ms. attached, it would be suitable for publication.

The discussions need to be revised widening the literature coverage, better focalize to support the results and accounting for the limits of your study i.e size range of the sampling and the method used (LFD) 

More details are in the pdf file comments.

Comments for author File: Comments.pdf

Author Response

Dear Editor in-Chief,

 

I am pleased to enclose herewith a manuscript entitled “Population structure, age and growth of sardine (Sardina pilchardus, Walbaum, 1792) in an upwelling environment” for evaluation as Fishes. This manuscript is in response to the previous article I had submitted in your journal (Fishes-1707218).

Thanks for giving us the opportunity to revise this manuscript. It should be noted that taking into account the comments of the reviewers, the line numbers have changed. So, we took care to answer the questions by putting the new numbers so that the reviewers and the editor could find themselves in the document.

We hope that this new submission will meet the criteria of our journal. The publication of our work in your journal would be a nice reward for the team effort and a strong encouragement for West African research.

 

Yours sincerely

Bocar Sabaly Baldé on behalf of all co-authors

 

 

 

 

 

Reviewer  2 General Comments

The manuscript "Population structure, age and growth of sardine (Sardina 2 pilchardus, Walbaum, 1792) in an upwelling environment " present several merits since growth studies on important exploited resources are of outmost importance for stock assessment modelling and correct management. In the study area of course there is lack of this informations therefore this study add new information useful.

Response (Baldé et al.): Thank you very much for the feed back and review.

- Reviewer 2

The limits of LFD in evaluating proper VBGF parameters without age readings have to be addressed in the ms. So I suggest to address this aspect both in the introduction and in the discussion also to evaluate your results compared to literature studies with different methods. I agree that in case of limited data stocks this technique could help but it is hard to say that results are well representative of the stock analysed.

Response (Baldé et al.): The corrections have been taken into account. We add in the introduction §:

“Stock assessment is about providing fisheries managers with possible management choices and their consequences [29]. Indeed, commercial fish species typically have substantial data sets that can be incorporated by complex stock assessment models [30]. These data may include time series of total removals, catch-at-length or catch-at-age, relative or absolute abundance data, fishing effort, and information on life history parameters. These data sets are generally unavailable for most fisheries. Fisheries and stocks lacking these multiple types of data are referred to as data poor or "data limited" fisheries [31–33]. However, data-limited stock assessment is a broad field that includes several families of models [34]. These models have been developed to meet the demand for management of unassessed and data-limited fisheries, stocks, and species [32,35]. In such data-limited situations, two main quantitative approaches, based on data availability, can be used to assess the exploitation status of data-poor fisheries. Size frequency data, when available, can be used by researchers to inform policy [3]. Length is also an important index of biomass (size-weight relationship), biology (number of eggs produced as a function of species size), and trophic position for many fish species (e.g., [4,6]. Thus, organism length is a key parameter in species ecological processes. Due to the rapid availability of length data for many stocks, a number of length-based stock assessment methods have been developed and applied to estimate biological parameters and understand fish population dynamics [36–38]. For example, simple size-based assessments can be made for many stocks considered too data poor to assess [37]. Several size-based techniques have been developed to estimate fish growth and mortality rates (e.g., [39,40]). Other length-based techniques using population size structure to estimate stock status and assist managers have been implemented recently (e.g., [28,37,41]). ”

- Reviewer  2

the limited size range analysed: how the absence of smaller individual may affect the estimation? also when comparing your results with literature, the differences may be attributed to such aspect?

 

Response (Baldé et al.): While in FISAT II and in ‘‘ELEFAN in R’’ (which uses the original P–W plot), only the starting point of the regression line can be defined for the plot (with all data points above being automatically selected), in TropFishR (Mildenberger et al. 2017), there is also the option of unselecting the largest size classes, which is an apparent advancement, and may apparently solve the problem of the influence of large size classes, at first sight. Recently, these methods have been incorporated into R, within two new packages called ‘‘ELEFAN in R’’ (Pauly and Greenberg 2013) and ‘‘TropFishR’’ (Mildenberger et al. 2017). These new software packages contain many promising new features, but still include the P–W method as a central part of the proposed analyses (Mildenberger 2017). The perceptions that L_∞  can be easily estimated and that it is always close to L_max (i.e., the length of largest individual in a given sample) are steadfast paradigms of fisheries science, especially for the study of data-poor fisheries scenarios and tropical stocks (e.g. Mildenberger et al. 2017). Even more importantly, applying a completely unconstrained search for L_∞ and K avoids the serious systematic errors (e.g. overestimation of K) that can happen when artificially constraining L_∞ a priori (e.g., from the largest individuals or by non-reliable methods, such as the Wetherall plot (Schwamborn, 2018).

 

- Reviewer  2

Les discussions doivent être révisées en élargissant la couverture de la littérature, mieux focalisées pour étayer les résultats et en tenant compte des limites de votre étude, c'est-à-dire la plage de taille de l'échantillonnage et la méthode utilisée (LFD)

Response (Baldé et al.): Thanks for the comments.

The literature review have been extended with e.g. Atlantic coast of the Iberian Peninsula and the Bay of Biscay works.

Silva, A.V.; Meneses, I.; Silva, A. Predicting the Age of Sardine Juveniles (Sardina Pilchardus) from Otolith and Fish Morphometric Characteristics. Scientia Marina 2015, 79, 35–42.

Silva, A.; Carrera, P.; Massé, J.; Uriarte, A.; Santos, M.B.; Oliveira, P.B.; Soares, E.; Porteiro, C.; Stratoudakis, Y. Geographic Variability of Sardine Growth across the Northeastern Atlantic and the Mediterranean Sea. Fisheries Research 2008, 90, 56–69.

Erzini, K. A Compilation of Data on Variability in Length-Age in Marine Fishes; Collaborative Research Support Program; University of Rhode Island: Kingston, USA, 1991; p. 36;.

Pertierra, J.P.; Morales-Nin, B. Sardine Growth in the Catalan Sea (NW Mediterranean) Determined by Means of Otolith Interpretation and Length Frequency Data. Scientia Marina 1989, 53, 821–826.

Pauly, D. A Preliminary Compilation of Fish Length Growth Parameters; Ber. Inst. Meereskd; Christian-Albrechts-Univ: Kiel, 1978; p. 200;.

Froese, R. Estimating Somatic Growth of Fishes from Maximum Age or Maturity. Acta Ichthyologica et Piscatoria 2022, 52, 125–133.

Alemany, F.; Alvarez, F. Growth Differences among Sardine(Sardina Pilchardus Walb.) Populations in Western Mediterranean. Scientia Marina 1993, 57, 229–234.

 

The limits of the study have been added in the discussion, corresponding to the transboundary aspect of the species in the North West African region.

“In fact, the biological parameters of small pelagic fishes are expected to differ with habitat, environment factors, and overfishing [3,4,6]. The current study showed that the asymptotic length (L_∞) of S. pilchardus is 30.5 cm maximum at six years, and that this value differed significantly to other countries in northwest Africa (Table 2). In particular, L_∞ was much larger compared to previous results obtained in the same study area (northwest Africa, i.e. Morocco). However, interpretation of S. pilchardus growth is influenced by the season in which samples are obtained, with seasonal differences in growth existing [3,52]. In migratory species, such as S. pilchardus, the input data in growth studies is often biased (some elements may be missing because the entire cohort is not present in the area where the samples are taken). Furthermore, representative samples of all class sizes might not be obtained in other regions of northwest Africa regions, because marginal stocks might be absent or under-sampled [80]. This difference in L_∞ was also reflected in the maximum length of S. pilchardus observed in Senegal (31.1 cm in the present study), which was higher compared to Morocco (Table 2). This difference could be explained by differences in stock and genotypic composition. For instance, Fréon and Stéquert [13] recorded two subspecies of S. pilchardus. One subspecies, S. pilchardus pilchardus, was found on the Atlantic coast of Europe, whereas S. pilchardus sardina was found on the Atlantic coasts of North Africa and the Mediterranean Sea. Genetic differences exist for these two subspecies. These subspecies include the northern Atlantic race (between the North Sea and the Cantabrian coast), the Iberian race (from the Cantabrian coast to the Strait of Gibraltar), the Moroccan race (from Cape Spartel to Cape Juby), and the Saharan race (from Cape Juby to Levrier Bay) [81]. Based on meristic studies, Silva [82] also recently showed that sardines in the southern Iberian Peninsula and Morocco are distinct to sardines in the rest of the western Mediterranean. Genetic studies carried out by Atarhouch et al. [83] also showed differences between the population of Pasajes (Bay of Biscay in the northern Atlantic), the Mediterranean Sea, and the Moroccan coast (Atlantic Ocean), with a contact zone around the Strait of Gibraltar. “

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear authors, you provided a partial report of the several comments included in the pdf referee's comments first round. It seems only partially replied manuscript.

Please provide a complete detailed point by point with the number of lines where the text was modified accordingly in the rebuttal letter for my past comments (first round revision).

Moreover I again suggest to restructure  the discussion clarifying better the limits of the results obtained according to the used method.

Please take into account that also in poor data stock these LFD methods are used when a proper age structured assessment is not developed, it means that the LFD irrespective of the method used present great uncertainties compared to direct otolith readings which remain the only accepted official method to estimate age in small pelagic fishes specially for stock assessment purposes. 

Therefore, when supporting your LFD results also try  to highlight clearly such aspect in the discussion conclusion section.

My best

Comments for author File: Comments.pdf

Author Response

Reviewer 2

this is a simple procedure of data preparation so you may avoid these details and reprhase the sentence as : Outlier data were   excluded from the analyses.

You may also delete this information because not important.

Response (Baldé et al.): Thanks for the comment, we have removed that part.

Reviewer 2

also this part could be omitted (see the comment before).

Response (Baldé et al.): Thanks for the comment, we have removed that part.

Reviewer 2

It is better to explicitate how many fishes from the survey and how many from the landings were sampled.

Response (Baldé et al.): We added the number of individuals sampled for each year.

"The data used in our study were collected during artisanal fisheries surveys led in 2015 (987 specimens) over keys artisanal landing sites (Kayar, Saint-Louis, and Yoff) located on the north coast of Senegal (from 16 ° 04' N to 14 ° 36' N, Figure 1). Surveys carried out by the fishery research vessel (FRV) Dr Fridtjof Nansen [53] in 2007 (2153 specimens) and 2008 (811 specimens) were also included (Table 1). ".

- Reviewer 2

The weight was not recorded?

Response (Baldé et al.): Weight was also sampled. However, in this study, this parameter is not used.

- Reviewer 1

Please be more precise with the description of the analyses were conducter per years separately or mixing cohoort from the two year. I suggest to estimate parameters per year  avoiding mixing cohoorts.

You have at least try to analyse separately and after joining with adequate cautions and discussing problems of mixing different cohoorts for stock assessment purposes.

Response (Baldé et al.): Thanks for the suggestions. We have added more details for the data. Indeed, the data was processed separately (year by year) and then combined to allow for better results.

A unique procedure applied to the length-frequency data yields both the age composition of the stock and the growth parameters. More explicitly, the procedure uses the length-frequency data to determine the percentage of fish at each age, as well as the parameters that define the mean length and standard deviation of length at each age. For example, three von Bertalanffy parameters (such as Linf, K, to) can be determined that define a growth curve through the mean lengths. In addition to providing growth data in addition to the usual age composition analysis, the new procedure has at least one other advantage over those used previously. It eliminates any ambiguity.

- Reviewer 2

avoid bold caraters.

Response (Baldé et al.): Thank you, we have removed the bold.

- Reviewer 2

this is material and method informations.

Response (Baldé et al.): Thanks for the suggestion.

- Reviewer 2

did you made age readings?

therefore delete ageing.

Response (Baldé et al.): No. Thanks.

- Reviewer 2

differences between what?..

Response (Baldé et al.): By year. Thanks you.

- Reviewer 2

in table 2 there is another value

why?.

Response (Baldé et al.): Sorry it was a typo in the first draft, we corrected it. The real value is 30.5 cm. Thanks.

- Reviewer 2

Please clarify better in the next sentence  what is the main disadvantage .

The following sentence is not so clear in this sense so please try to explicitate better the meaning.

Response (Baldé et al.): Thanks for the suggestion. We have made corrections to make it easier for readers to understand.

 

This work has a major disadvantage to consider. Indeed, the study of the biological parameters of the sardine, which is a species shared with neighboring countries, cannot be isolated and any exploitation outside the maritime borders of Senegal.

- Reviewer 2

The whole manuscript suffer of a local perspective with little attention to other Mediterranean and Atlantic literature on the small pelagic growth and habitat conditions.

I suggest to integrate more bibliography

i.e:

Alemany & Alavrez 1993 Scientia Marina

Tsikliras &Koutrakis Cah. Biol. Mar. (2013) 54 : 365-374

Silva et al. 2008 Fishery research

Moreover the following works should be  helpful to widening the perspective of the present work, on the link between biology of small pelagic with their environment including river runoff or upwelling regions.

The reading of these papers may help to improve the discussions supporting the authors findings even if the papers are not strictly related with the same species but other pelagic small species like anchovy. However if you are able to find more specific references it is up to you.

i.e.:

Bonanno, A., Barra, M., Basilone, G., Genovese, S., Rumolo, P., Goncharov, S., Popov, S., Buongiorno Nardelli, B., Iudicone, D., Procaccini, G., Aronica, S., Patti, B., Giacalone, G., Ferreri, R., Fontana, I., Tranchida, G., Mangano, S., Pulizzi, M., Gargano, A., Di Maria, A., Mazzola, S.

Environmental processes driving anchovy and sardine distribution in a highly variable environment: the role of the coastal structure and riverine input

(2016) Fisheries Oceanography, 25 (5), pp. 471-490.

Hattab, T., Gucu, A., Ventero, A., De Felice, A., Machias, A., Saraux, C., Gašparević, D., Basilone, G., Costantini, I., Leonori, I., Bourdeix, J.-H., Iglesias, M., Barra, M., Giannoulaki, M., Ferreri, R., Ayoubi, S.E., Malavolti, S., Genovese, S., Somarakis, S., Juretic, T., Tičina, V., Certain, G.

Temperature strongly correlates with regional patterns of body size variation in Mediterranean small pelagic fish species

(2021) Mediterranean Marine Science, 22 (4), pp. 800-811.

Basilone, G., Ferreri, R., Barra, M., Bonanno, A., Pulizzi, M., Gargano, A., Fontana, I., Giacalone, G., Rumolo, P., Mazzola, S., Genovese, S., McBride, R., Aronica, S.

Spawning ecology of the European anchovy (Engraulis encrasicolus) in the Strait of Sicily: Linking variations of zooplankton prey, fish density, growth, and reproduction in an upwelling system

(2020) Progress in Oceanography, 184, art. no. 102330, .

Basilone, G., Ferreri, R., Mangano, S., Pulizzi, M., Gargano, A., Barra, M., Mazzola, S., Fontana, I., Giacalone, G., Genovese, S., Aronica, S., Bonanno, A.

Effects of habitat conditions at hatching time on growth history of offspring European anchovy, Engraulis encrasicolus, in the Central Mediterranean Sea

(2018) Hydrobiologia, 821 (1), pp. 99-111.

Bonanno, A., Barra, M., Mifsud, R., Basilone, G., Genovese, S., Di Bitetto, M., Aronica, S., Giacalone, G., Fontana, I., Mangano, S., Ferreri, R., Pulizzi, M., Rumolo, P., Gargano, A., Buscaino, G., Calandrino, P., Di Maria, A., Mazzola, S.

Space utilization by key species of the pelagic fish community in an upwelling ecosystem of the Mediterranean Sea

(2018) Hydrobiologia, 821 (1), pp. 173-190.

Basilone, G., Guisande, C., Patti, B., Mazzola, S., Cuttitta, A., Bonanno, A., Vergara, A.R., Maneiro, I.

Effect of habitat conditions on reproduction of the European anchovy (Engraulis encrasicolus) in the Strait of Sicily

(2006) Fisheries Oceanography, 15 (4), pp. 271-280.

Basilone, G., Guisande, C., Patti, B., Mazzola, S., Cuttitta, A., Bonanno, A., Kallianiotis, A.

Linking habitat conditions and growth in the European anchovy (Engraulis encrasicolus)

(2004) Fisheries Research, 68 (1-3), pp. 9-19.

Brosset, P., Fromentin, J.-M., Van Beveren, E., Lloret, J., Marques, V., Basilone, G., Bonanno, A., Carpi, P., Donato, F., Čikeš Keč, V., De Felice, A., Ferreri, R., Gašparević, D., Giráldez, A., Gücü, A., Iglesias, M., Leonori, I., Palomera, I., Somarakis, S., Tičina, V., Torres, P., Ventero, A., Zorica, B., Ménard, F., Saraux, C.

Spatio-temporal patterns and environmental controls of small pelagic fish body condition from contrasted Mediterranean areas

(2017) Progress in Oceanography, 151, pp. 149-162.

Basilone, G., Mangano, S., Pulizzi, M., Fontana, I., Giacalone, G., Ferreri, R., Gargano, A., Aronica, S., Barra, M., Genovese, S., Rumolo, P., Mazzola, S., Bonanno, A.

European anchovy (Engraulis encrasicolus) age structure and growth rate in two contrastedareas of the Mediterranean Sea: The paradox of faster growth in oligotrophic seas

(2017) Mediterranean Marine Science, 18 (3), pp. 504-516.

Response (Baldé et al.): Thank you for the references that improved the discussion.

"Indeed, the early life stages and spatial distribution of S. pilchardus in the Mediterranean are strongly linked to environmental changes. According to Hattab et al. [91] and Basilone et al. [92,93], environmental changes may have impacts on the size and fecundity of small pelagic species in the Mediterranean. These results were also confirmed by Baldé et al. [4,6] in West Africa. Indeed, growth is strongly influenced by environmental variations; which lead to a decrease or increase in fecundity of small pelagics in Senegal. ".

- Reviewer 2

Have you evaluated or discussed the possible effetc of a different method adopted in these studies (otholith readings)?.

 

Response (Baldé et al.): we added it

"However, this difference in growth parameters may also be related to the types of data used (length frequency, otolith, ...).  Analyses applied to length-frequency data provide both the age composition of the stock and the growth parameters (e.g. L∞, K, t0; [82]). They require representative length frequency data, covering the full length range of the species [83–85]. The use of a limited length range may lead to a bias in the estimation of growth parameters. However, this approach is more suitable for young, fast-growing fish where length patterns for each age group are easily distinguished. Thus, the suitability of the length frequency analysis depends on the structure of the available length frequency data. Whereas the results obtained from the otolith studies showed that it was difficult to identify uncertainties with respect to aging errors. Indeed, the growth medium can have a considerable impact on the formation of the false ring and thus on the results [86,87]. Environmental factors, such as water temperature, affect fish growth, cause seasonal changes in the density of layers deposited in the otoliths, and in some cases it is possible to determine the age of fish from the resulting bands. Hammers et al. [87] indicate that measurement errors may be related to difficulty in locating the exact center of the scale focus or core of the otolith and in identifying the margin of the annuli or the location where faster growth has resumed [87]. It occurs mostly in young individuals, as the measurements involved are small and the error is more influential [87]. ".

- Reviewer 2

what you mean with the interpretation of growth?

Response (Baldé et al.): Here, we try to explain that the results can be influenced by the lack of part of the stock during the sampling period. Indeed, these stocks are shared between the different countries.

- Reviewer 2

Unfortunately also your data suffer of an undersampling of small size classes since in table 1 the specimens start from 21 cm .

Please try to discuss this important issue  in view of your result differences with other studies.

Response (Baldé et al.): We added this part to show the difference.

- Reviewer 2

too speculative try to support it better or rephrase or delete it.

Response (Baldé et al.): Thanks for the suggestion. This part has been removed to avoid misinterpretation or misunderstanding.

- Reviewer 2

Too speculative please rephrase add adequate references or delete it.

Response (Baldé et al.): This part has been removed to avoid misinterpretation or misunderstanding..

- Reviewer 2

Again too speculative ...

Generally when the Linf increase the K that is not the growth rate of the population, decrease .. as it was observed in other studies

However any conclusion on your results have to be considered starting from the two main limit of the study:

the use of LFR to obtain VBGF parameters

and the limited size range of the samples.

It appear that you sampled only a portion of the population, the older one?

Please try to clyrify in the discussion at least these two important aspects.

Response (Baldé et al.): Thanks for the comment. The limitations of the study, notably the sample size, were mentioned at the beginning of the discussion. There was also a discussion about the different methodologies used (otolith, length frequency). Therefore, any conclusions in this study should take these aspects into account.

- Reviewer 2

I'm not properly convinced about this based on your results, The Morocco estimations are different.

Response (Baldé et al.): Thank you for the commentary that provided further clarification of the study's findings.

- Reviewer 2

Thisi sthe final value obtained?

Response (Baldé et al.):  Yes. 30.5 cm.

Author Response File: Author Response.pdf