Yazar "Gaygusuz, Ozcan" seçeneğine göre listele
Listeleniyor 1 - 7 / 7
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe The Diel Changes in Feeding Activity, Microhabitat Preferences and Abundance of Two Freshwater Fish Species in Small Temperate Streams (Omerli, Istanbul)(Foundation Environmental Protection & Research-Fepr, 2010) Gaygusuz, Cigdem Gursoy; Tarkan, Ali Serhan; Gaygusuz, OzcanWe examined the abundance, food and microhabitat use of Proterorhinus marmoratus (Gobiidae) and Cobitis vardarensis (Cobitidae) during both day and night in two small temperate streams of the Black Sea region (North-West Turkey) between May and June 2005. Drift sampling catch per unit effort revealed significantly higher relative densities at night than during the day. Of the 110 fish captured during the seven sampling periods, 77 (88%) were C. vardarensis with the Bicki Stream having the most fish specimens both in frequency of occurrence and relative density. The main environmental variables that characterized the overall microhabitat use were velocity, light, depth, and proportions of cobbles. The fullness frequency of the gut contents was at their peak between 22:00 and 04:00 am and the most active feeding time was usually after midnight. Surf-lice insects composed mainly of chirinomid larvae were the dominant food item for both species in the streams during the sampling period. Further studies are needed at multiple spatial scales to assess how habitat use and feeding habits varies with fluctuating population densities.Öğe Fishes Encountered in the Turkish Thrace River Systems (NW Turkey)(Maik Nauka/Interperiodica/Springer, 2023) Ozulug, Muefit; Gaygusuz, Ozcan; Gaygusuz, Cigdem Gursoy; Kaya, Nilgun; Sac, GulsahIn the last 30 years, the natural life in the inland waters of the Turkish Thrace has been threatened by water pollution, deterioration of river continuity, the presence of non-native or invasive fish, and drought. The aim of the present study is to determine the recent status of fish fauna in the river systems lying at the Turkish Thrace, under these threats. The field surveys were conducted in a total of 164 sampling sites in both Marmara and Meric-Ergene water basins between July and August 2017. A total of 36 freshwater fish species representing 12 families (Acheilognathidae, Atherinidae, Centrarchidae, Cobitidae, Cyprinidae, Esocidae, Gobiidae, Gobionidae, Leuciscidae, Percidae, Poeciliidae, and Salmonidae) were determined. The most widespread species of the region was Cobitis strumicae and it was followed by Rhodeus amarus and Squalius orpheus. This study provides first detailed information on the distribution of the species of Barbus tauricus, Chondrostoma vardarense, Cobitis strumicae, Squalius orpheus, and Vimba melanops.Öğe The ichthyofaunal diversity of freshwater ecosystems in Gokceada Island (NW Turkey) under the pressure of nonnative species(Tubitak Scientific & Technological Research Council Turkey, 2021) Agdamar, Sevan; Sac, Gulsah; Gaygusuz, Ozcan; Dogac, Ersin; Acar, Umit; Gaygusuz, Cigdem Gursoy; Ozulug, MufitFreshwater ecosystems have a greater value for biodiversity per surface area than terrestrial and marine ecosystems. Streams and lakes are notably prone to biodiversity loss, being the greatest threats habitat destructions and nonnative species. The aim of the present study is to assess the fish composition of lotic and lentic water systems of an island ecosystem (Gokceada Island, Turkey), which is poorly studied, and to highlight the entry routes and possible impacts of translocated fish species in an island ecosystem. The field surveys were conducted in a total of 14 sampling sites (five reservoirs and nine streams) in the inland waters of Gokceada Island between September 2019 and January 2021. Fish samples were collected by electrofishing (SAMUS 1000; a backpack electro-shocker). A total of eight fish species belonging to six families (Anguillidae, Atherinidae, Cyprinidae, Leuciscidae, Mugilidae, and Poeciliidae) were determined. As a result fish community of the island was mostly composed by the introduced species Carassius gibelio, Gambusia holbrooki and Pseudorasbora parva. This study provides the first detailed information on the distribution of the fish species encountered in the inland waters of Gokceada Island. Results showed that the fish fauna of the island was predominantly shaped by fish stocking activities.Öğe Invasion of freshwater bodies in the Marmara region (northwestern Turkey) by nonnative gibel carp, Carassius gibelio (Bloch, 1782)(Tubitak Scientific & Technological Research Council Turkey, 2011) Aydin, Hamdi; Gaygusuz, Ozcan; Tarkan, Ali Serhan; Top, Nildeniz; Emiroglu, Ozgur; Gaygusuz, Cigdem GursoyThe aim of this study was to learn the invasion speed and sex ratio, which would be indicative of invasive character, of a nonnative fish species, gibel carp, by reporting its new localities in the Marmara region of northwestern Turkey. Whether the occurrence of gibel carp in freshwater bodies of the Marmara region was random (i.e. chance element) was tested. The question of population increase since first introduction was also examined. Among 14 new locations for gibel carp found during this study, the majority were in mostly lentic ecosystems. The invasion rate of gibel carp in the Marmara region, since its first introduction in the early 1980s, is approximately 1 new water body per year (1.17; number of sites invaded by gibel carp = 35). Females significantly outnumbered males in 10 out of the 12 populations studied, with the sex ratio deviating from unity (1:1) in all populations except 2. The regional extent of gibel carp occurrence increased with the number of years since first introduction (y = 1.34x - 2651.1, F = 47.41, P < 0.001, = 0.95). The implications for conservation of native fishes are discussed.Öğe Length-weight relationship of seven freshwater fish species from Turkish Thrace(Wiley, 2019) Sac, Gulsah; Gaygusuz, Ozcan; Gaygusuz, Cigdem Gursoy; Ozulug, MufitThe length-weight relationships (LWRs) of Alburnus istanbulensis Battalgil, 1941, Barbus tauricus Kessler, 1877, Cobitis pontica Vasil'eva & Vasil'ev, 2006, Cobitis strumicae Karaman, 1955, Gobio bulgaricus Drensky, 1926, Phoxinus strandjae Drensky, 1926 and Squalius orpheus Kottelat & Economidis, 2006 were analysed. Fish samples were collected by electroshocker (SAMUS 725 G and SAMUS 725 M portable electroshockers; frequency 50-55 Hz; 30-70 cm fishing depth) in some water bodies in Turkish Thrace from March 2012 to August 2017. The values of parameter b in the LWR equations varied from 2.916 (B. tauricus) to 3.336 (P. strandjae). This study also provides a new maximum length data for A. istanbulensis, G. bulgaricus, P. strandjae and S. orpheus.Öğe New Distribution Areas of Four Invasive Freshwater Fish Species from Turkish Thrace(Central Fisheries Research Inst, 2019) Ozulug, Mufit; Gaygusuz, Ozcan; Gaygusuz, Cigdem Gursoy; Sac, GulsahIn order to be able to assess the impact of invasive fish on native species and ecosystems, it is important to know their existing distribution areas. The Meric River, which is fed by some other rivers from Greece and Bulgaria, is the 'open door' where invasive species enter Turkish inland waters through European part of Turkey. Due to this need, it was aimed to determine the new distribution areas of invasive C. gibelio, L. gibbosus, P. parva and G. holbrooki in Turkish Thrace. The field surveys were conducted in a total of 135 stations in Marmara and Meric-Ergene basins. Carassiusgibelio and G. holbrooki were the species that expanded their distribution range the most; C. gibelio was captured from 24 stations and it was recorded as new to 15 localities while G. holbrookiwas captured from 17 stations and it was recorded as new to 15 localities. Lepomisgibbosuswas collected from Rezve and Sultanbahce streams in Marmara Basin and it was recorded as new to these localities. Pseudorasboraparvawas collected from 10 stations and it was recorded as new to 9 localities.Öğe A New Locality for the Freshwater Fish Chondrostoma angorense Elvira, 1987 (Osteichtyes: Cyprinidae) in the Marmara Region (Turkey)(Ege Univ, 2007) Tarkan, Ali Serhan; Ozulug, Mufit; Gaygusuz, Ozcan; Gaygusuz, Cigdem GursoyIn Lake Sapanca, C. nasus was reported in 1966. However, careful examination on this specimen in 1987 revealed that this species was Vimba vimba. In the present study, we report the finding of C. angorense from Lake Sapanca (Sakarya, Turkey) for the first time. The circumstances of identification and conservation status of the species are discussed.
