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  • Küçük Resim
    Öğe
    Assessment of Food Supply of Small Pelagic Fish in the Black Sea Based on Their Lipid Content
    (Turkish Journal of Fisheries and Aquatic Sciences, 2012) Nikolsky, Victor; Shulman, Georgiy; Shchepkina, Alla; Yuneva, Tatjana; Bat, Levent; Kaya, Yalçın; Kıdeys, Ahmet Erkan; Seyhan, Kadir
    Total lipids in anchovy and sprat were measured and interpreted as indicators of their nutritional condition and food supply for the period 2005 to 2010. High lipid content in anchovies suggested that they were able to found sufficient food and favorable environmental condition supporting their stock biomass on a certain level which was strongly limited by heavy fishing. Wide inter - annual fluctuations in anchovy landings could be caused by variability in yearly recruitment and due to shifts in the spatial distribution patterns of the exploited stock. Unlike anchovy, lipid reserves in sprat declined remarkably to the lowest levels recorded during the 50 - year observations period. Such a significant worsening in sprat nutritional condition followed the evident warming of the Black Sea and coincided with a sharp decline in sprat catches off Crimea. Thus, the deterioration of food supply together with intensive fishing could have contributed to the reduction of that local sprat stock.
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    Modelling growth and population parameters of the invasive gastropod Rapana venosa (Muricidae) in the Black Sea using statolith-based ageing
    (Springer Japan Kk, 2025) Basusta, Nuri; Durrani, Omerhan; Bat, Levent; Basusta, Asiye; Dagtekin, Murat; Seyhan, Kadir
    The veined rapa whelk, Rapana venosa, is the first invasive non-indigenous species to attain significant commercial importance in the industrial fisheries of the Black Sea. In this study, statoliths of R. venosa were used for age determination. Samples were collected monthly from the eastern Black Sea using a standard commercial dredge at three major fishing areas: Sinop, Samsun, and Trabzon. Four growth models (logistic, Gompertz, asymptotic exponential, and von Bertalanffy) were fitted to describe the relationship between age and shell length, with the von Bertalanffy growth function providing the best fit. A one-way analysis of covariance (ANCOVA) revealed no significant sexual dimorphism in growth curves at any station; however, significant temporal and spatial variations were detected, with the highest estimated growth rates in autumn and the most pronounced spatial differences in winter and spring. Furthermore, the shell length-weight relationship exhibited significant sexual dimorphism, along with notable spatial variation. These findings underscore the importance of considering growth model selection, sex, spatial (fishing area), and temporal factors when estimating growth parameters. This study provides the first direct estimates of age and growth for R. venosa in the Turkish Black Sea using statoliths, thereby establishing reliable parameters for its monitoring and sustainable management.
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    Öğe
    Trace elements in edible tissues of the veined rapa whelk (Rapana venosa) in the southern Black Sea, Turkiye: sex, monthly, and age variations and human consumer health risk
    (Springer Heidelberg, 2023) Bat, Levent; Basusta, Nuri; Oztekin, Aysah; Sahin, Fatih; Arici, Elif; Seyhan, Kadir
    Coastal areas face significant pressures from a variety of human activities, owing primarily to population growth in these areas. Human activities produce a variety of contaminants, including trace metals, which are common forms of contamination that enter marine ecosystems. This study was carried out to provide information on trace element concentrations (Hg, Pb, Cd, Cu, and Zn) in the muscles of Rapana venosa (Valenciennes, 1846) available on Sinop coasts of the southern Black Sea and to evaluate the possible risk associated with their consumption. The minimum and maximum values (mg/kg wet weight) of trace elements in the edible tissue of R. venosa decreased in the following order: Zn (1.75-8.53) > Cu (0.41-4.6) > Cd (0.021-0.255) > Pb (0.013-0.037) > Hg (0.010-0.035). The measured levels of all the trace elements in the present study were lower than the limits permitted by the European Community Regulation (EU), Turkish guideline, and the UK Ministry of Agriculture, Fisheries and Food (MAFF). The hazard index value of Hg, Cd, Cu, and Zn for the veined rapa whelk is lower than standard 1, demonstrating that ingestion of this mollusk from the southern Black Sea does not result in overexposure to these contaminants. The risk index value for human cancer risk of Pb for all seasons was found to be insignificant. When comparing the levels of elements in males and females, significant differences were found in some months for all the metals. In general, the trace elements were detected in higher concentrations in females than in males. Both females and males have accumulated less trace elements with increasing age. This study was the first to show the distribution of trace elements as a function of age in R. venosa.