Yazar "Deval, Mehmet Cengiz" seçeneğine göre listele

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    Antalya Körfezi’nde Barbunya Balığı (Mullus Barbatus) için Rombik ve Kare Gözlü Torba Seçiciliğinin Karşılaştırılması
    (Çanakkale Onsekiz Mart Üniversitesi, 2021) Deval, Mehmet Cengiz
    In this study, the selectivities of commercial 44 mm nominal polyethylene (PE) diamond mesh (PE44DM) and square mesh (PE44SM) codends for red mullet Mullus barbatus fisheries in Antalya Bay, Eastern Mediterranean, were compared and modelled. For this purpose, a conventional bottom trawl of 600 meshes was operated onboard R/V “Akdeniz Su” during night time at 25-50 m depths for a total of 21 hauls. Data were collected using the covered codend technique, and analysed using a logistic equation with maximum likelihood by SELNET software. The PE44DM codend had a higher catch rate (89.6%) and 32.5% of M. barbatus were below the minimum landing size whereas catch rates decreased to 42.1% and 9.9%, respectively, in the PE44SM codend. Changing from the diamond mesh to square mesh codend increased the mean L50 and SA values from 8.2 to 13.2 cm and from 2.11 to 2.87 cm, respectively. Both L50 and SA values obtained in the present study show a statistically significant increase (no overlap in 95% confidence limits) with a change in the same mesh size codends from diamond to square for M. barbatus. The use of the PE44SM codend resulted in a significant improvement in the selectivity of M. barbatus compared to the currently used PE44DM codend with a very low escape ratio (10%).
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    Evaluation of Illegal, Unreported and Unregulated (IUU) Trawl Infringements Committed by Turkish Fishing Vessels
    (Çanakkale Onsekiz Mart Üniversitesi, 2023) Karabacak, Gürkan Salih; Deval, Mehmet Cengiz
    This study analyses a highly damaging and prevalent fishing practice of trawl infringements, which is one of the crucial components of IUU fishing in Turkish waters. The raw data gathered from the Turkish Coast Guard Command (TURCG), covered 2012 – 2014 period. Data covered a total of 1040 trawl infringements, with considerable differences in trawling violations among the seas surrounding Türkiye; the Black Sea, the Sea of Marmara, the Aegean Sea, and the Mediterranean Sea. With respect to trawling infringements, the Sea of Marmara (37%) and Istanbul Strait (15%) were the hot points. The most common infringement type was trawling in a closed area (43%) and when combined with the rate of infringements on trawling during the closed season (10%), these violations accounted for 53% of spatio-temporal infringements. Regarding illegal trawling by vessel type, trawl vessels had a 44% share and non-trawlers had a share of 56%, of which included infringements by other type of fishing vessels (46%) and non-fishing vessels (10%). It was also found that infringement by vessels smaller than 12 meters in length had a share of 46%. These vessels (known as "şebeke" in Turkish), trawl illegally using small types of nets and gears in coastal waters without giving any obvious indication of fishing activity. The results of this study will be useful to policy-makers, practitioners and scientists to successfully combat trawling infringements by providing information on distribution, intensity and methods of trawl violations.
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    Keystone Porgy Species (Sparidae) Overcome the Alien Randall's Threadfin Bream (Nemipterus randalli) for Catch Balance in Space on An Oligotrophic Levant Shelf or Vice Versa?
    (Çanakkale Onsekiz Mart Üniversitesi, 2022) Mutlu, Erhan; Meo, Ilaria de; Miglietta, Claudia; Deval, Mehmet Cengiz
    Since 2008 spatiotemporal and ecological distributions of porgies (sparid, all indigenous fish) were examined in the presence or absence of Randall's threadfin bream, Nemipterus randalli in the present study area. Seasonal fish and environmental parameters samplings were conducted at three transects of the fishing (nMPA) or non-fishing (MPA) regions on an oligotrophic shelf (Levantine Sea) in 2014-2015 for understanding management and ecology of the porgies’ catches. Of 13 sparid fish determined during the present study, five species are rarely found. There were no seasonal significant differences in densities of the sparid fish with or without the alien nemipterid fish. However, there were differences in the densities by the bottom depths, the regions, and soft and hard bottoms vegetated by Caulerpa spp and meadow, respectively. Ecologically, fish assemblages and faunistic characters of the sparid fish were highly variable when excluding the N. randalli as highlighted and follows; i) seasonal variation occurred and ii) the depthwise community assemblages became irregular. N. randalli seemed to balance the sparid catch attributed to the biomass-abundance ratio in the ecosystem or vice versa in this trophically sensitive gulf (ultra-oligotrophic) of the eastern Mediterranean Sea.
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    The Occurrence of Phronima sedentaria Forskål, 1775 (Crustacea: Amphipoda) in the Gulf of Antalya (Eastern Mediterranean, Türkiye)
    (Çanakkale Onsekiz Mart Üniversitesi, 2022) Olguner, Mustafa Tunca; Deval, Mehmet Cengiz
    This study reports the occurrence of Phronima sedentaria in the Eastern Mediterranean. The new pram shrimps were collected from the Gulf of Antalya, located on the Levantine coast of Turkey. Examination and definition of the sampled specimen in the area reported as the first occurrence.