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    Distribution and composition of seafloor marine litter in the southeastern Black Sea
    (Turkish Marine Research Foundation-Tudav, 2020) Kasapoglu, Nazli; Dagtekin, Murat; Ilhan, Salih; Erik, Gokhan; Ozsandikci, Ugur; Buyukdeveci, Ferhat
    This study was conducted to investigate seafloor marine litter abundance between Samsun (Yakakent) and Hopa within the scope of Integrated Marine Pollution Monitoring Project (CSB/CEDIDGM-TUBITAK/MAM) in summer 2019. Totally, the trawl hauling operations were successfully performed in 30 stations. The works were done according to the MEDITS protocol: sampling was done at 3 different depths (0-20 m, 20-50 m and 50-100 m), marine litter was classified in 9 categories. At all sampling stations marine litter was assessed by weight and amount. The most common marine litter group was L2 tire/rubber by weight (53%) and amount (67%) when L1 plastic group - 25% by weight and L5 fabric and natural fibres - 12% by amount. Especially in the L2 group, the car and truck tires were dominated in weight of CB5 (Trabzon- Surmene) and CB3 (Trabzon) stations.
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    Length-weight relationships of 28 fish species caught from demersal trawl survey in the Middle Black Sea, Turkey
    (Tubitak Scientific & Technological Research Council Turkey, 2022) Dagtekin, Murat; Genc, Yasar; Kasapoglu, Nazli; Erik, Gokhan; Misir, Devrim Selim; Ilhan, Salih; Ok, Meltem
    This study provides updated the length-weight relationships and Fulton's condition factor of 28 fish species belonging to 23 families from the Black Sea. Samples were collected along the depths between 0-100 meters by demersal trawl surveys conducted seasonally from May 2017 to September 2019. A total of 83,885 specimens were collected. The length-weight relationships and Fulton's condition factor, minimum, maximum and mean lengths, total weights, descriptive statistics, and growth type were provided for all the species. The results indicate that LWR parameters of b varied from 2.2039 to 3.737 and Fulton's condition factor varied between 0.004 and 1.18. These findings could be useful for monitoring and management of sustainable fisheries and habitat health.
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    Population dynamics and ecology of the invasive veined rapa whelk, Rapana venosa in the southern Black Sea
    (Academic Press Ltd- Elsevier Science Ltd, 2022) Mutlu, Erhan; Kideys, Ahmet E.; Sahin, Fatih; Erik, Gokhan; Aksu, Hakan; Erdem, Ercan; Karayucel, Sedat
    Spatial and temporal changes in some ecological characteristics (i.e. biomass, abundance, morphometrics, sex composition, growth parameters and population dynamics) of the invasive veined rapa whelk (Rapana venosa) were studied off Sinop Bay, in the southern Black Sea. The whelk specimens were sampled from three depths (15 m, 25 m and 35 m) at monthly intervals between November 2005 and October 2007. Custom-made pots were deployed for the capture of R. venosa individuals. Monthly distributions in whelk biomass and abundance peaked in summer (June/July) and mid-autumn (October) and displayed no differences between 2006 and 2007. With the exception of gut weight, all morphometric variables produced three peak periods (January, June and September, respectively) over one year. Densities, morphometrics and sex composition were dictated significantly by bottom depth and monthly variation. Two stages were defined in the ovary and testis index maxima denoting longer spawning and recruitments periods starting as early as in March which is a different finding compared to previous studies from the Black Sea. For the estimation of population growth parameters, of the five morphometric variables analysed, siphon width was the best variable to produce clear size cohorts. Whelk growth in terms of shell length and width oscillated seasonally and ceased during February-March. Maximum age of the veined rapa whelk in the southern Black Sea was determined as 3.5 years corresponding to 7 cohorts. Among the environmental parameters, dissolved oxygen, temperature and salinity appeared to affect whelk densities. Results obtained here are important for better management of the whelk fishery in the Black Sea.