Age and Growth of European Sardine (Sardina pilchardus) in the Central Mediterranean Sea: Implication for Stock Assessment

Round 1

Reviewer 1 Report

Overall

The present study would provide useful knowledge about age-and-growth and stock assessment of European sardine, that is important fisheries target in the Mediterranean Sea. 

The authors obtained sufficient sample to satisfy reliability for estimation about age-and-growth parameters, mortality rates, and other related biological data for the species.

I have several concerns and suggestions to improve the manuscript as follows:

1. Title and abstract

Although I understand that main objective of the manuscript is to clarify the age-and-growth of the European sardine, the authors also showed various related data such as sardine total length by gear (Fig. 2), temporal trend in average size (Fig. 4), age-length key (Fig. 5), geographical difference in length-age relationship (Fig. 6) and mortality (Fig. 7). These results about biological aspects should be included in the title and abstract.

2) Methods (2.1. age estimation)

The authors should show the method how to analyze the edge state analysis (how to obtain the result of Fig. 3) in this section. 

3) L103 (Table 1)

This description should be shown in Results. In addition, this results should be shown as figure, not table, to visualize the data (this result is key of the present study). 

4) L115-L121

As L118, Figure 2 and Table 3 indicated that the data in 2018 was obtained by only purse seine net, this should be described in this section. 

5) Results of Table 4

This result should be shown as figure, not table, to visualize the data.

6) Figure 6

Useful data, but somewhat hard to compare the geographical difference in length-age relationship. Data point that obtained at same study region should be connected by line. 

7) Tabe 6 and Figure 7

These data is fundamentally same. Only Figure 7 is enough. If the authors want to show the numerical values about mortality and 95% confidence intervals, the numerical values should be entered in the Figure 7. 

Author Response

Dear Reviewer thank you for your valuable contribution.

We take into account all your comments and suggestion as detailed in the attached point by point response. (Review Report Form Referee 1.docx)

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript contains important information on the age and growth of European Sardine. The research design and methodology of the manuscript are adequate and the topic of the manuscript is of interest to a wide readership of Fishes. However, I felt that the manuscript can be improved by a more detailed discussion. The specific comments about my concerns regarding the importance of this study are as:

Specific comments:

1. Line 31: Please mention (Walbaum, 1792).

2. Line 45-47: Please include a reference. You can cite these papers, Nazir and Khan 2020 (https://doi.org/10.1071/MF19315) and Campana and Thorrold, 2001 (https://doi.org/10.1139/f00-177)

3. Line 71-80. The age estimation by counting annuli is subjective and ageing errors have a considerable effect on the understanding of population dynamics. Why did only one reader (or otherwise mention) counted annuli on otoliths to estimate age? (Please refer to Morales-Nin, 1992 and Campana, 2001). The underestimation of annuli or growth zones in older individuals by using the whole otolith method may be caused by the curvature of the otolith's edge, which results in crowded annuli that are difficult to distinguish from each other (Refer to Khan et al., 2016).

4. Line 96: The authors should state why they have considered that all individuals come from the hierarchically same population.

5.  Line 129: The authors should have tried other ageing structures as well.

6. Line 162-163: The maximum reported age for this species is 15 years. Why only a smaller age class was considered in this study?

7. In the text you have mentioned length in mm while in the Figures you reported in cm. Please keep the same scale.

Author Response

Thank you for your valuable review.

Author Response File: Author Response.pdf