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    Assessment of The Annual European eel (Anguilla Anguilla Linnaeus, 1758) Catches In Three Suggested Major Monitoring areas To Support The development of eel fishery management system In Turkey
    (Wiley, 2020) Yalcin Ozdilek, Sukran; Ozdilek, Hasan G.
    Thirteen river basins draining into the Marmara, Aegean and Mediterranean Seas were selected for evaluation of European eel (Anguilla Anguilla L., 1758) catch in Turkey. These basins were grouped into three so-called eel monitoring area (EMA). The official province-based annual landing data between 1996 and 2018 were assessed for each of the monitoring areas. Statistically significant decreases over the years were observed in the landing data in all of the monitoring areas. The adequate protection of the European eel standing stocks, particularly in some critical eel habitats such as Koycegiz lagoon showed over time a small decrease in eel catches in EMA-2. However, a substantial decrease was detected in the province of Adana, which includes the Seyhan and Ceyhan basins, and these are located in the EMA-3. The catch data mainly based on the commercial fisheries and the restriction on export seems to be the main reason for the decline in catches in the three EMAs. Thus the suggested monitoring areas (EMAs) are needed to structure research programmes on basic knowledge on escapement ratio of migrating silver eels, arrival and upstream migration of glass eels in the rivers of each of the EMAs in order to build area specific management strategies. These monitoring areas may provide practical units that management can use in future fisheries regulations.
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    Biological parameters and current status of European eel (Anguilla anguilla Linnaeus, 1758) from Asi River, Northeastern Mediterranean region, Turkey
    (Wiley, 2020) Demirci, Sevil; Akar, Ozkan; Simsek, Emrah; Demirci, Aydin; Yalcin Ozdilek, Sukran
    The biological characteristics of eels from the Asi River, Turkey, were assessed between December 2017 and November 2018. Eels were sampled monthly using fyke nets (operated by professional fishermen), yielding a total of 509 specimens. Total length and weight were measured, sex, age and maturity stages (silver or yellow eel) were determined. Catch Per Unit Effort (CPUE) was calculated for both biomass per unit effort and numbers caught on a monthly and annual basis. The length-weight relationships (LWRs) of silver and yellow eel was W = 0.009*TL3.22 (n = 262) and W = 0.0106*L-3.09 (n = 247), respectively. The age of the sampled fish ranged from year class II to VI. Von Bertalanffy growth parameters were estimated as L-infinity=69.25 cm, K = 0.43 1/year, t(0)= -0.41 and phi prime index ()= 3.31 for all samples. The overall eel fishing mortality rate (F) was 0.31 year(-1), and the exploitation and survival rates of silver stage eels were estimated with 30% and 39%, respectively.
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    Seasonal and ontogenetic diet shift of two sympatric cyprinid fish species from the temperate Karamenderes River, Canakkale, Turkey
    (Tubitak Scientific & Technological Research Council Turkey, 2017) Yalcin Ozdilek, Sukran
    Diet composition and feeding relationships of two cyprinid species, Squalius cii and Barbus oligolepis, from the Karamenderes River, northwestern Turkey, were assessed over a 1-year period. Both species were omnivorous and fed mostly on benthic plant materials (particularly algae) and insects. The diet of B. oligolepis primarily comprised Bacillariophyceae, Diptera larvae, and other insects, while that of S. cii comprised filamentous algae (Cyanobacteria and Chlorophyceae), insect larvae, and adults. Ontogenetic shifts in diet were identified in both species. The ratio of Chlorophyceae in the diet of B. oligolepis showed a gradual increase with increase in its body size; moreover, the number of ingested taxa decreased but diet diversity increased with increasing fish size. There were seasonal variations in feeding intensities of both fish, which decreased in the colder months. Seasonal resource availability was higher for S. cii than B. oligolepis; moreover, diet overlap was significant in the spring and summer. Findings indicate that S. cii may exclude B. oligolepis during limited resource availability conditions. The cooccurrence of these species may be explained by their generalist feeding strategies; ontogenetic and seasonal resource partitioning played an important role in the coexistence of these species.
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    THE EUROPEAN EEL IN TURKEY
    (Turkish Marine Research Foundation-Tudav, 2016) Yalcin Ozdilek, Sukran
    [Anstract Not Available]
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    The orientation of earthworms is influenced by magnetic fields
    (Tubitak Scientific & Technological Research Council Turkey, 2020) Yalcin, Fehime Sevil; Yalcin Ozdilek, Sukran; Altas, Rukiye
    Earth has a natural magnetic field that many animals use for orientation and navigation. With the development of technology, these natural systems have been exposed to high levels of man-made electromagnetism from the heavy usage of electric devices. This study aims to understand the possible effects of artificial magnetic fields on the behavioral responses of the earthworm, which is used in this study as a model organism in laboratory conditions. The 3 experimental groups, each composed of 20 earthworms, were exposed to 190-520 mu T magnetic fields using a 1.5 V current for 1-h durations in a wire-wrapped vivarium. The experimental and control groups were kept in similar conditions. A camera recorded the positions of the earthworms every 5 min. The angles, in terms of the mean vector of each earthworm's position beginning in the center of the vivarium, were documented using the Adobe Photoshop CS6 program. The mean vectors and angles of different experimental designs and controls were compared using circular statistics. The orientations of the earthworms in the control (261.4 degrees +/- 101.6 degrees) and experimental (251.2 degrees +/- 94.1 degrees) groups were statistically different (P < 0.005), and a deviation of approximately 10 degrees to the east was observed for the experimental group in comparison to the control group.