Search Results (5)

This study presents new records of three Critically Endangered angel shark species (Family: Squatinidae) occurring in the Eastern Mediterranean—Smoothback Angelshark S. oculata Bonaye, 1840, Sawback Angelshark S. aculeata Cuvier, 1829, and Angelshark S. squatina (Linnaeus, 1758). The supporting data serves to highlight three potential Critical Angel Shark Areas (CASAs) in Türkiye: Fethiye Bay, Çanakkale Strait (i.e., Dardanelles), and Antalya Bay. These data also demonstrate that female S. oculata may mature at a smaller size than prior published estimates of length at first maturity. This new dataset provides details of 23 S. squatina specimens, 52 S. oculata specimens, and 5 S. aculeata specimens, totalling 80 recent angel shark specimens found in Turkish waters mostly sent to us from small-scale fishers who had incidentally caught angel sharks. Also presented are four capture-induced parturition events in Turkish waters onboard fishing vessels, thus providing details on internal yolk sacs, reproductive habitats, and indications of spawning season. Our dataset presented here spans from 2018 to 2023 and suggests that mature adults of S. squatina and S. oculata still occur in Turkish waters, in Fethiye Bay and Çanakkale, respectively. Due to elevated chances of fishers encountering Critically Endangered angel sharks in Türkiye, we suggest that fishers are trained in handling and safe-release methods, to ensure reduced incidents of capture-induced parturition, and improved post-release survival. This study demonstrates that bottom set nets set by small-scale fishers pose less risk to mortality for angel sharks as they are almost always encountered alive after a usual 12 h soak time, suggesting that bottom trawling in critical habitats should be better regulated (or phased out) to help improve national angel shark conservation initiatives. Full article

This overview presents the different water masses present in the various primary and secondary marine regions of the Mediterranean Sea and Black Sea, providing information on their main physical characteristics (i.e., temperature, salinity, density), the water depths at which they have been observed and the processes involved in their formation. There is a characteristic difference in the overall hydrology of the Mediterranean Sea compared to the Black Sea, in terms of the number and characteristics of water masses and their formation processes, although they form a single (integrated) marine system. This difference is explained by the limited communication between the two seas through the Sea of Marmara and its straits (the Dardanelles and Bosporus) and by the fact that the Mediterranean Sea is a condensation basin while the Black Sea is a dilution basin; therefore, the deficit of water in the former is compensated by the inflow of Atlantic waters, while the surplus in the latter outflows to the Aegean Sea. In total, 21 different water masses have been identified in the Mediterranean Sea (excluding the Straits of Gibraltar and the Sea of Marmara) compared to the 5 water masses identified in the Black Sea (excluding the Sea of Azov). This large number of water masses is attributed to coastal morphology (i.e., presence of straits) and submarine relief (i.e., deep basin separated by shallow sills) and different formation processes. Full article

A new, high-resolution model for the northern part of the Aegean Sea, aimed primarily at climatological research (relaxation and data assimilation-free climate simulations), is hereby presented, along with the results of a 28-year-long simulation covering the period from 1986 to 2013. The model applied is the Regional Ocean Modelling System (ROMS). A significant improvement over previous models of the Aegean introduced in this work is the replacement of parameterizations of the Dardanelles exchange by a fully three-dimensional simulation of the flow in the Strait. The incorporation of part of the Marmara Sea in the model domain enables the interaction with other regional climate simulations, thus allowing climatic variability of the exchange of the Mediterranean and Black Seas. An extensive validation is carried out comparing the model output with all the available observations from several different platforms, i.e., satellite sea surface temperature and height, T/S profiles from R/V ships, and HF radar surface currents velocity. We focus on the model’s ability to reproduce, to some extent, the distinct thermohaline features and circulation patterns that characterize this specific area of the Mediterranean Sea. Our findings, after comparing simulation results with all the available observations, revealed the model’s sufficiency to simulate very adequately the complex hydrology of the North Aegean Sea, and the model’s ability to reproduce incidents of deep-water formation that took place in the region in previous decades during the Eastern Mediterranean Transient (EMT). Full article

The Turkish Strait System, which is the only connection between the Black Sea and the Mediterranean Sea, is a challenging region for ocean circulation models due to topographic constraints and water mass structure. We present a newly developed high resolution unstructured finite element grid model to simulate the Turkish Strait System using realistic atmospheric forcing and lateral open boundary conditions. We find that the jet flowing from the Bosphorus Strait into the Marmara creates an anticyclonic circulation. The eddy kinetic energy field is high around the jets exiting from the Bosphorus Strait, Dardanelles Strait, and also the leeward side of the islands in the Marmara Sea. The model successfully captures the two-layer structure of the Sea of Marmara. The volume transport at the Bosphorus is around 120 km${}^3$/year which is consistent with the recent observations. The largest bias in the model is at the interface depth due to the shallower mixed layer. Full article

This paper describes the 400 kV AC submarine link under the Dardanelles Strait composed of 12 submarine armoured single-core cross-linked polyethylene (XLPE)-insulated cables (plus a back-up power cable). The link consists of two parallel-operated double-circuit links named Lâpseki–Sütlüce I and Lâpseki–Sütlüce II. The transmissible power is 4000 MW (1000 MW per circuit) and the average length for a single-core cable is about 4.6 km: the submarine cables are part of overhead lines. This paper gives a wide account of the cable installations and, chiefly, of the cable protections on the seabed: different protection choices were extensively used (i.e., water jetting and mattressing). Full article