First Record of the European Hake Merluccius merluccius (Linnaeus, 1758) in Bulgarian Black Sea Waters

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is a first cite of European hake in the NW Black Sea and a careful analysis of the single specimen detected. The capture area is close to the straits conecting to the Mediterranean, so it can have migrated. In figure 1 please mark the other places were European hake has been caught in the Black Sea. It would help visualize the localizations, also this figure can be improved.

Unfortunately the whole otolith is broken in the tip and the section micrograph can be improved. I agree that the fish is around 3 yr old.

Did you observe parasitism? in the Mediterranean they have a high load of anisakis. 

In summary, an interesting first cite and a complete examination of the fish. It is important that it could thrieve at such low salinity.

Author Response

Comment 1: This is the first cite of European hake in the NW Black Sea and a careful analysis of the single specimen detected. The capture area is close to the straits connecting to the Mediterranean, so it can have migrated. In figure 1 please mark the other places was European hake has been caught in the Black Sea. It would help visualize the localizations, also this figure can be improved.

Response1: Fig.1 has been redrawn and other places  European hake has been detected were added.

Comment 2: Unfortunately the whole otolith is broken in the tip and the section micrograph can be improved. I agree that the fish is around 3 yr old.

Response 2: Yes, unfortunately the otolith taken was broken in the tip. A slight downward sawing section is applied to break the otolith into two sections trough the nucleus and the dorsoventral axis. We tried to make an incision right trough the nucleus to have a clearer view of the anulli.

Comment 3: Did you observe parasitism? in the Mediterranean they have a high load of anisakis. 

Response 3: No, we did not observed any.

Comment 4: In summary, an interesting first cite and a complete examination of the fish. It is important that it could thrieve at such low salinity.

Response 4: Yes, we will continue the monitoring.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript reports the first record of the European hake (Merluccius merluccius) along the Bulgarian Black Sea coast, combining morphological and molecular methods for a detailed study. The research design is reasonable, and the data collection and analysis methods are scientific, with results of certain scientific value. The  specific comments provided below.

 

Introduction Section:

Enhance Research Background: Further describe the potential ecological impact of this species in the Black Sea ecosystem, such as its role in the food chain and competition with local fish resources.

Methods Section:

Detail the specific conditions during freezing and preservation.

Evaluate robustness of phylogenetic analysis: Discuss whether other potential related species were considered and how the selected sequences’ representativeness and data quality were ensured.

Results and Discussion Section:

Deeply analyze the reasons for the species’ expansion in the Black Sea, such as climate change or human activities.

 

Author Response

Comment 1: Enhance Research Background: Further describe the potential ecological impact of this species in the Black Sea ecosystem, such as its role in the food chain and competition with local fish resources.

Response 1: The text was added into the Introduction section;

Commnent2 : Detail the specific conditions during freezing and preservation.

Response2:   A Description of specific conditions of preservation was added.

Commnent3 : Evaluate robustness of phylogenetic analysis: Discuss whether other potential related species were considered and how the selected sequences’ representativeness and data quality were ensured.

Response 3: The necessary information was added. 

Comment 4: Deeply analyze the reasons for the species’ expansion in the Black Sea, such as climate change or human activities.

Response 4: The informative text was added to section"Results and Discussion"

Author Response File: Author Response.docx