Otolith Fingerprints and Tissue Stable Isotope Information Enable Allocation of Juvenile Fishes to Different Nursery Areas

Round 1

Reviewer 1 Report

Although this is a potentially useful contribution, the final evaluation is not possible until important information has been added to the manuscript. The methods description lacks a clear statement of numbers of individual fish used in the analysis - from the figures (Figs, 6-8) it appears that only 4-5 individuals from each species at each site have been analysed. At the same time, in Figs 3 & 4. there appear to be more individual data points where "Black dots present linear raster of Ba/Ca otolith ratios for each site and species". So, basic information on the number of data points (measurements from the otolith) used to represent each individual is required, as well and the number of individuals used to represent each species x site. Without this information it is impossible to evaluate the manuscript - not as a reviewer and not as a reader.

Taking this point further, there are two levels of concern with the data analysis and its presentation: 

1) the description of the data extraction from the otolith scans is insufficient. There is no indication of where on the otolith the "200um" section is located, nor how many of these sections per otolith are used. How was the 31pt moving average decided on, and how many of these are there per individual fish? In other words, the base data representing each individual needs to be detailed much more explicitly

2) If the black dots in Figs 3&4 represent 31pt average line rasters, then it appears that this is the combined data from multiple measures on multiple individuals. Surely the within-individual factor needs to be taken into account, and at the very least nested within fish for any further comparison of species and site differences.

3) With only 2 element ratios, and 2 isotope ratios it would be much more convincing to use parametric statistics such as MANOVA. Is it because of such low sample sizes, or non-normal distributions, or unequal variance that PERMANOVA is used? And is the data distribution a result of the low sample sizes?

Author Response

Dear reviewer,

thank you for your valuable comments. We considered all your suggestions and revised manuscript accordingally.

Please, find our responses.

Author Response File: Author Response.docx

Reviewer 2 Report

I consider the basic premise, method developed and questions asked by this study as valuable and interesting. The authors outlined an interesting method of evaluating the information on nursery habitat use from two Diplodus species. The strength of the study is the novelty and broad usefulness of this approach. Apart from certain minor comments laid within the text in the .pdf, i consider the ms worth of publication.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

thank you for your valuable comments. We considered all your suggestions and revised manuscript accordingally.

Please, find our responses.

Author Response File: Author Response.docx

Reviewer 3 Report

Abstract – I suggest this is rewritten; in its current form it is quite dry. Neither the abstract nor the title give the reader any idea where the study is taking place, what type of fish are being used and why they make good model species to test some hypothesis, assuming a hypothesis is being tested?

“Both species were allocated correctly to the estuarine waters based 27 on the chemistry and stable isotopes information and higher value of δ15N” – allocated correctly? This needs to be reworded. I am yet to see where these fish were caught from, or whether water samples were taken – insert otolith before chemistry

Keywords – remove words that appear in title; e.g. otoliths, stable isotopes, nurseries, allocation (whatever that is meant to mean in a keyword sections?)

Introduction:

First paragraph is a single sentence only – please combined with following paragraph.

Line 33- this is true of most animals, not just teleosts, also elasmobranchs

Line 47 – I can’t see where Caddy (reference 10) states that the Adriatic Sea, particularly its northern-most part (correct northern-most) is considered the most exploited.

Line 51 – “leaving to join adult populations during their ontogenetic development” – ontogenetic development also includes larval development – this sentence needs rewording

Line 53 – “how connectivity determines the spatial scale between fish populations” – I am unsure what this means

Line 55 – insert – is increasingly ‘being’ obtained

Line 58 – delete cycle

Line 61 – ‘fingerprints’ not “   “

Line 63 - asses’?

Line 78 – concluded ‘that the existence of a relationship…..(delete since) as primary producer groups exhibit….(or something similar)

Line 90 – authority for Diplodus puntazzo should be (Walbaum 1792)

Line 96-98 – if they occur at the same time in nurseries, how does this mean they partition habitats?

Line 100 – Delete ‘For this study’

Line 112 – say – one estuarine site, and once coast oceanic site, both of which are known nurseries for the species

Line 115 and Line 117 – need both places on the map – (also need to inset Europe onto the map)

125 – do you mean an especially constructed seine net? (place net after seine)

Line 127 – DELETE - The sampling was part of large nursery abundance assessment along eastern Adriatic coast

Line 129 - sampling was carried out in the shortest possible time – not sure this is needed (You already said June)

Line 131 – app. To ~ - perhaps you could even state the mean number caught (SE)

Line 132 – change to mm

Line 146 – does this mean for 2 minutes?

Line 148 - isotopic baseline in the coastal ecosystem – need a reference

Line 148 – I don’t understand the meaning of the last sentence.

Line 152 – how do you dry ‘until constant weight”? Reword

Line 154 – do you need to let the reader know what wasn’t performed? How come?

Line 162 – sectioned otolith?

Line 173 - cm2 to cm²

Line 179 - compare also [61-63]).? Explain this to your reader

Delete - The QCM results 179 are provided in Table 2

Line 181 - Details of the calculations are given in Mischel 181 et al. [65] – this will no doubt be different to your study – details are required – your paper should be repeatable without heading off to search for reference 65 and then trying to find the actual reference

Line 218 - samples exceeding 31-point (31-pt) running averages 218 by 5σ were considered outliers – what does this mean? Why is 31 the magic number?

Line 233 – define ‘settlement mark’ please (for other readers – it is interesting

Line 252 – italicise D. puntazzo

Line 255 – italics missing

Figure 6 – remove D.punc_C etc from bubbles (you repeat it in the caption)

Figure 7 – see above

Line 339 – delete - Finally, we related the isotope values directly to the otolith information. It reads, like Phew, we finally made it to the end of the results J

Line 344 – delete - In short,

Line 345 – this needs to be reworded (as well as in the abstract) – you new were the fish were from – the samples didn’t correctly allocate themselves, you did.

Figure 8 – see comment for Fig. 6

Figure 9 – see comment for Fig. 6

Line 363 - have been (previously)?

Line 365 - Di Franco 365 et al. [74] investigated within-otolith variability in chemical fingerprints and found that 366 individuals at the same site can show significant variability in elemental uptake. – what species did they use as a model species?

Line 372 – line 382 – this paragraph should be deleted – or moved to Introduction

General comment – can the stocks be assessed to see which accounts for better survival and input into the fishery? Are specific sites up and down the coast more successful as nurseries?

Author Response

Dear reviewer,

thank you for your valuable comments. We considered all your suggestions and revised manuscript accordingally.

Please, find our responses.

Author Response File: Author Response.docx