Dear Authors,

The topic is indeed timely and of significant importance; however, I have several concerns regarding the content and structure of the piece. Below are the major issues I identified:

Thank you for all your comments, which will definitely be taken into account when revising the text.

Before proceeding to answer the individual questions, I would like to point out that the Ocean State Report has a special format, in which the authors must adhere to a limited number of figures and words, and is therefore different from a scientific paper.

Also, the Ocean State Report is divided into chapters, and the articles in it have to stick to the topic of the chapter, in our case implications and solutions for stakeholders.

Title Scope: The heading appears too broad, as the study primarily focuses on a limited number of coastal regions in Italy and only examines two species of bioinvaders. I recommend refining the title for better clarity and specificity regarding the study’s focus.

Thank you for your comment, we will change the title of the manuscript, focusing more on Italian waters

Data Correlation: There is a lack of direct correlated data between temperature and the abundances or catches of the two species (Callinectes crab and Hermodice worm). The data presented seem to originate from only one location, which limits the study's robustness.

In this paper, the trends in temperature and species abundance have been shown, avoiding direct correlations between the two variables to show only that the increase in the last year affected both the temperature and the abundance of these species.

I do not think the comment about a limited number of coastal regions applies. As for the blue crab, this is the first time that an increase of this species has been observed in the Venetian lagoon, which is an important economic source for the shellfish trade. These two recent studies (Azzurro et. al., 2024 [https://www.sciencedirect.com/science/article/abs/pii/S0308597X24002938] and Chiesa et al., 2024 [https://www.sciencedirect.com/science/article/abs/pii/S0272771424004256]) illustrate the damage and impact that this species has on the ecosystem and the economy.

As for the Hermodice, the Sicily region is the first region affected by the spread of the organism and where the questionnaire has been massively applied.

Moreover, the data for this study were collected in these regions. For these reasons, it was decided to focus the work on these areas.

Sampling Methodology: The manuscript does not provide sufficient information about the sampling effort for the Hermodice data. Details such as the number of participants involved in the study, their age range, and work status are necessary for transparency and to assess the reliability of the findings.

Two questionnaires on Hermodice sightings were selected in this work, specifically the questionnaire described in Righi et al. 2021 (https://doi.org/10.12681/mms.23117), from which all the necessary information can be obtained. However, as for the other questionnaire, you are absolutely right, it was an oversight. The number of observations will be added as well as the situation regarding the observations.

Consider that most of the answers refer to observations made during scuba diving and fishing activities

Clam Production Data: The study lacks information on clam production, including species names and potential interactions with the studied crab (e.g., predation). Supporting references should be included to strengthen this discussion.

We will give details on clams and add a bibliography on predators. C. sapidus has been observed to significantly affect the aquaculture of Ruditapes philippinarum (Manila clam). Predation by blue crabs resulted in clam losses of up to 100% in certain areas, with up to 56% of clam shells showing signs of predation and a complete absence of seeds in natural recruitment zones.

I would like to point out that the development of clam production in the past did not show any significant problems.  After the appearance of the blue crab, the clam population declined drastically until it completely disappeared in 2024.

Integration of Arguments: The discussion and conclusion sections lack a cohesive flow of arguments. It is crucial to integrate the data on the crab, worm, and temperature more effectively. Several assumptions made in these sections do not seem adequately supported by the data or existing literature.

Thank you for the comment, for the nature of the manuscript it was chosen to describe the effects separately. Regarding the blue crab, this is discussed in terms of degree days to justify why the crab's proliferation was observed, and in context it is explained that the bad habits of fishermen also contributed to the proliferation of the species. With regard to Hermodice c., on the other hand, it was shown that in the last 20 years the increase of this thermophilic species has been observed in parallel with the rise in temperature, but again it was emphasized that the habits of fishermen have contributed to the increase of this species.

In addition, literature references were provided to substantiate the observed trends between temperature and proliferation. Based on your comment, we will try to integrate the different arguments.

Conclusions Specificity: The final paragraph of the conclusions is overly generic. More details regarding the studied regions and proposed management strategies would enhance the relevance and applicability of the findings.

We appreciate your comment and agree with your observation. The Ocean State Report differs from a conventional research report in a number of ways. In this chapter, we focus on discussing problems and solutions for stakeholders while maintaining a specific perspective. Our approach is to first emphasize the established and serious nature of the problem and then describe best practices aimed at mitigating the problems associated with the proliferation of these species. We will revise the last paragraph to make it more specific by including details about the regions studied and the proposed management strategies. For example, we will highlight the environmental and economic challenges in the Veneto-Po Delta, such as the dependence on aquaculture of Ruditapes philippinarum and the impact of predation by Callinectes sapidus. In addition, the conclusions will include actionable recommendations, such as the development of structured monitoring plans that account for seasonal fluctuations in blue crab abundance, with particular attention to ovigerous females in summer. We will also propose to explore adaptive aquaculture practices, such as the implementation of protective measures for clam farms or the use of predator deterrents, and evaluate containment techniques, such as the targeted removal of blue crabs or habitat modification to reduce their recruitment and the impact of predation.

Dear Authors,

The topic is indeed timely and of significant importance; however, I have several concerns regarding the content and structure of the piece. Below are the major issues I identified:

Thank you for all your comments, which will definitely be taken into account when revising the text.

Before proceeding to answer the individual questions, I would like to point out that the Ocean State Report has a special format, in which the authors must adhere to a limited number of figures and words, and is therefore different from a scientific paper.

Also, the Ocean State Report is divided into chapters, and the articles in it have to stick to the topic of the chapter, in our case implications and solutions for stakeholders.

Title Scope: The heading appears too broad, as the study primarily focuses on a limited number of coastal regions in Italy and only examines two species of bioinvaders. I recommend refining the title for better clarity and specificity regarding the study’s focus.

Thank you for your comment, we will change the title of the manuscript, focusing more on Italian waters

Data Correlation: There is a lack of direct correlated data between temperature and the abundances or catches of the two species (Callinectes crab and Hermodice worm). The data presented seem to originate from only one location, which limits the study's robustness.

In this paper, the trends in temperature and species abundance have been shown, avoiding direct correlations between the two variables to show only that the increase in the last year affected both the temperature and the abundance of these species.

I do not think the comment about a limited number of coastal regions applies. As for the blue crab, this is the first time that an increase of this species has been observed in the Venetian lagoon, which is an important economic source for the shellfish trade. These two recent studies (Azzurro et. al., 2024 [https://www.sciencedirect.com/science/article/abs/pii/S0308597X24002938] and Chiesa et al., 2024 [https://www.sciencedirect.com/science/article/abs/pii/S0272771424004256]) illustrate the damage and impact that this species has on the ecosystem and the economy.

As for the Hermodice, the Sicily region is the first region affected by the spread of the organism and where the questionnaire has been massively applied.

Moreover, the data for this study were collected in these regions. For these reasons, it was decided to focus the work on these areas.

Sampling Methodology: The manuscript does not provide sufficient information about the sampling effort for the Hermodice data. Details such as the number of participants involved in the study, their age range, and work status are necessary for transparency and to assess the reliability of the findings.

Two questionnaires on Hermodice sightings were selected in this work, specifically the questionnaire described in Righi et al. 2021 (https://doi.org/10.12681/mms.23117), from which all the necessary information can be obtained. However, as for the other questionnaire, you are absolutely right, it was an oversight. The number of observations will be added as well as the situation regarding the observations.

Consider that most of the answers refer to observations made during scuba diving and fishing activities

Clam Production Data: The study lacks information on clam production, including species names and potential interactions with the studied crab (e.g., predation). Supporting references should be included to strengthen this discussion.

We will give details on clams and add a bibliography on predators. C. sapidus has been observed to significantly affect the aquaculture of Ruditapes philippinarum (Manila clam). Predation by blue crabs resulted in clam losses of up to 100% in certain areas, with up to 56% of clam shells showing signs of predation and a complete absence of seeds in natural recruitment zones.

I would like to point out that the development of clam production in the past did not show any significant problems.  After the appearance of the blue crab, the clam population declined drastically until it completely disappeared in 2024.

Integration of Arguments: The discussion and conclusion sections lack a cohesive flow of arguments. It is crucial to integrate the data on the crab, worm, and temperature more effectively. Several assumptions made in these sections do not seem adequately supported by the data or existing literature.

Thank you for the comment, for the nature of the manuscript it was chosen to describe the effects separately. Regarding the blue crab, this is discussed in terms of degree days to justify why the crab's proliferation was observed, and in context it is explained that the bad habits of fishermen also contributed to the proliferation of the species. With regard to Hermodice c., on the other hand, it was shown that in the last 20 years the increase of this thermophilic species has been observed in parallel with the rise in temperature, but again it was emphasized that the habits of fishermen have contributed to the increase of this species.

In addition, literature references were provided to substantiate the observed trends between temperature and proliferation. Based on your comment, we will try to integrate the different arguments.

Conclusions Specificity: The final paragraph of the conclusions is overly generic. More details regarding the studied regions and proposed management strategies would enhance the relevance and applicability of the findings.

We appreciate your comment and agree with your observation. The Ocean State Report differs from a conventional research report in a number of ways. In this chapter, we focus on discussing problems and solutions for stakeholders while maintaining a specific perspective. Our approach is to first emphasize the established and serious nature of the problem and then describe best practices aimed at mitigating the problems associated with the proliferation of these species. We will revise the last paragraph to make it more specific by including details about the regions studied and the proposed management strategies. For example, we will highlight the environmental and economic challenges in the Veneto-Po Delta, such as the dependence on aquaculture of Ruditapes philippinarum and the impact of predation by Callinectes sapidus. In addition, the conclusions will include actionable recommendations, such as the development of structured monitoring plans that account for seasonal fluctuations in blue crab abundance, with particular attention to ovigerous females in summer. We will also propose to explore adaptive aquaculture practices, such as the implementation of protective measures for clam farms or the use of predator deterrents, and evaluate containment techniques, such as the targeted removal of blue crabs or habitat modification to reduce their recruitment and the impact of predation.

In view of an exceptional warm year (2023) in the Mediterranean, the work focuses on two invasive species (an alien crab and a thermophilic polychaete) and explores their expansion and increase in abundance in two distinct Italian areas. The work also discusses Impacts and mitigation strategies to control their population. My main concern is that impacts are not clearly demonstrated, but are rather based on literature.

Thank you for the comment and for your valuable work.

As for the blue crab, Figure 2 shows the drastic decline in clam production, which also occurs in conjunction with severe MHW. Similarly, an increase in the thermophilic species Hermodice c. has been observed over time. Of course, bibliographic references are essential to understand the behavior of these species and the relationship with temperature. I would like to point out that this work is part of the chapter of the Ocean State Report focused on stakeholder problems and solutions, and the objective of this work is to identify the problem and solutions that can be adopted to limit the problem, again referring to stakeholders. The paper does not aim to show the impacts, which will be discussed in a separate paper, but to shed light on the issue by trying to understand the relationship between temperature rise and proliferation. Given the limited number of figures and text, the literature plays a key role in explaining the issue, overcoming the limitations imposed by the number of words and figures.

Title: Record-breaking 2023 temperatures in the Mediterranean Sea, proliferation of bioinvaders, and impacts on fisheries: a chain reaction?

The second part: “ impacts on fisheries: a chain reaction?”is discussed extensively in the discussion. However, it is only marginally part of the results (questionnaire), and as such the title is misleading.

Thank you for your comment, we will change the title to meet the requests of both reviewers.

Abstract

Lines 30-36 discuss potential management measures to control the population of the two invaders, but these are based on literature only, not results of this study. I suggest removing the last paragraph from the abstract.

We thank you for the comment and will remove the sentence from the abstract. In the study we propose solutions that should be adopted by stakeholders to prevent further problems, so the sentence in the summary seems correct, also because the study did not focus on specific solutions that have already been undertaken, as no solution has currently been undertaken to prevent the problem

Introduction

Line 46 typo warming not worming

Thank you for the suggestion, we will change it.

Line 57: Bardelli et al., 2023. This source refers to the crab only, not the worm,

Sorry for this we will include a reference for this.

Line 70-71: This event had far-reaching effects on marine life and coastal communities.Please give reference(s) to it

Thanks for your suggestion, we will add a reference on it.

Thank you we will include the comments in the text

Methods

Lines 80-81: The study was conducted in two different regions within Italian waters: two adjacent lagoons in the Northern Adriatic 80 Sea (Canarin and Scardovari) and two coastal areas of Sicily.

Please move the sentence under Study areas (line 78)

Thanks for this we will move the first sentence under the paragraph 2.1

Figure 1. The images of C. sapidus and H. carunculata are redundant and rather misleading. C corresponds to the area not to the H. carunculata image.

I apologize for this, b and c were intended to represent both species and area, we will remove the species images leaving only the one related to the study area.

Line 124:   Streftaris and Zenetos, 2006 is an old source. I recomment using Tsirintanis et al. 2022.

Tsirintanis K, Azzurro E, Crocetta F, Dimiza M, Froglia C, Gerovasileiou V, Langeneck J, Mancinelli G, Rosso A, Stern N, Triantaphyllou M, Tsiamis K, Turon X, Verlaque M, Zenetos A, Katsanevakis S (2022) Bioinvasion impacts on biodiversity, ecosystem services, and human health in the Mediterranean Sea. Aquatic Invasions 17(3): 308–352, https://doi.org/10.3391/ai. 2022.17.3.01

Thanks for this, we will change the reference with the newest ones.

Line 134: Hermodice carunculata

Thanks for this we will fixed it

The way the lines 135-138 are written it appears that H. carunculata is an alien species. In fact. it is considered a Mediterranean species, not an introduced one. After all, all Mediterranean Sea biota are either of Atlantic or Indo-Pacific origin. It is invasive but not alien.

Absolutely agree with your comment, and thank you for the clarification, the authors are aware that this is not an alien species and the text will be corrected to avoid this issue.

Lines 190-191 While some Italian citizen scientists projects are listed, I am missing the inaturalist which includes many records from Sicily.

Thank you for the information, I was not aware of the existence of this portal, which is extremely useful for collecting information on the variability of these species. For this work it was chosen to use The two questionnaires produced by the authors.

Line 201: in addition to real-time data collected from maritime users. Who are the maritime users? Please explain

Thanks for the comment, maritime users will be integrated into the text. For knowledge, most of the comments were made mainly by fishermen and scuba divers.

Results

Figure 3. A very heterogeneous figure. Better split the productions and oceanographic data from those of the questionnaire.

Thank you for the comment, which is absolutely agreed with, however regarding the standard of the journal there is a limited number of figures and therefore it is necessary to keep the figure with the oceanographic part and the questionnaire.

It is not clear in the methodology how the number of observations has been calculated. Have you consulted other sources than the ones you refer to in methodology? Inaturalist?

Thank you for your comment, we will make the questionnaire methods part clearer.

For clarification, sightings related to the questionnaire of Righi et al., 2019, exclusively for the Sicily region, and those obtained from the worms out questionnaire developed taking into account that of Righi et al., 2019, were used. 

No other data sources were considered at this time, as I was not aware of Inaturalist. I will definitely try to consider incorporating Inaturalist's observations into this paper if possible. Thanks again for the suggestion.

Discussion

If discards is taken as a proxy for damage on fisheries it should be stated clearly. As it stands, in the discussion elaborates on issues that are not visible in the results.

E.g. Line 311: The proliferation of the blue crab in the  Po river delta has significantly disrupted the clams production (Figure S4). Figure S4 should be presented and commended in the results section.

Thanks for the suggestion we will include in in the result section.

Lines 373-374: Preliminary results show  that H. carunculata consumes mussel meat at high rates, leaving the shells almost completely clean. Results of this study? If not please cite the source of info.

This is a preliminary result of a specific study performed in Simonini et al 2024, we will move the reference in a better position.

References

Please check the format. Some journals are written in full, others abbreviated.

Sorry for this, we will correct all the wrong references.

Line 424. Çinar et al. The correct citation is as follows

Katsanevakis S, Wallentinus I, Zenetos A, Leppäkoski E, Çinar ME, Oztürk B, Grabowski M, Golani D, Cardoso AC (2014a) Impacts of invasive alien marine species on ecosystem services and biodiversity: a pan-European review. Aquatic Invasions 9: 391–423, https://doi.org/10.3391/ai.2014.9.4.01

Sorry for this and thanks, we will change it.