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Öğe A comparison of ageing techniques to improve precision of age estimation from fish scales(2005) Gaygusuz, Çiğdem Gürsoy; Tarkan, Ali Serhan; Gaygusuz, Özcan; Acıpınar, HasanKızılkanat, Scardinius erythrophthalmus (L, 1758), gümüşi havuz balığı Carassius gibelio (Bloch, 1782) ve kızılgöz, Rutilus rutilus (L, 1758) balıklarının pulları iki farklı habitattan elde edildi. Tüm balık türlerine iki yaş tayini yöntemi uygulandı. Bu yöntemler arasında uyuşmazlıklar bulundu. Farklı okuyucuların yaş tayinleri arasındaki uyum, pul basma yönteminde pul temizleme metodundakinden daha iyiydi. Pul basma metodu yaş hesaplamalarının doğruluğu bakımından en iyi sonuçları ortaya çıkardı. Bunun yanı sıra hızlı kullanım, verileri saklama, ve kolay geri-hesaplama gibi birçok avantajları görüldü.Öğe A warning note on frequent mistakes in the authority of scientific names of fish(2003) Tarkan, Ali Serhan; Gaygusuz, Özcan; Gaygusuz, Çiğdem Gürsoy; Acıpınar, Hasan; Bilge, GökçenMaking parentheses mistakes in the authority of scientific names of fish is quite frequent. To determine this kind of errors, titles in Cumhuriyet Dönemi Su Ürünleri Bibliyografisi book and abstracts in ASFA (Aquatic Sciences and Fisheries Abstracts) in year of 1998 were studied. Both datasets gave unexpectedly high percentages of authority errors. For some species, the error percentages were up to 96%. Logically, omitting parentheses was more common than adding them. These statistics should be taken into account in the authority of scientific names. To prevent these kinds of mistakes, some recent references and websites should be taken into consideration before using authority of fish.Öğe Changes in the fish community of the Ömerli Reservoir (Turkey) following the introduction of non-native gibel carp Carassius gibelio (Bloch, 1782) and other human impacts(Regional Euro-Asian Biological Invasions Centre, 2007) Gaygusuz, Özcan; Tarkan, Ali Serhan; Gaygusuz, Çi?dem GürsoyChanges in the relative density (catch per unit effort; CPUE) of introduced gibel carp Carassius gibelio (Bloch, 1782) and native fish species were monitored over four years in the Ömerli Reservoir, a temperate drinking-water reservoir in northwestern Turkey. Following the species' introduction, the CPUE of gibel carp increased significantly with the decrease in CPUE of large-bodied native fish species. © 2007 The Author(s).Öğe Characteristics of a eurasian cyprinid, shemaya, chalcalburnus chalcoides (güldenstädt, 1772), in a mesotrophic water reservoir(2005) Tarkan, Ali Serhan; Gaygusuz, Özcan; Acıpınar, Hasan; Gürsoy, ÇiğdemAge, growth and reproduction of the Shemaya, Chalcalburnus chalcoides, was studied in the Ömerli Reservoir, a large drinking water system located in Istanbul province (Turkey). The von Bertalanffy growth function displayed variation in growth rates between the sexes. Asymptotic lengths calculated for both sexes were high, probably due to the lack of large predatory fishes and lack of fishing in the reservoir. Females dominated all age classes with the exception of the second age, and this phenomenon is characteristic of species from unstable and variable environments. The condition factor and the gonadosomatic index indicated that reproduction occurred around May-June. The estimated mean lengths at first maturity (LT50) were 14.83 cm and 15.98 cm for males and females, which corresponded to 1 and 2 years of age for both sexes. Natural mortality was 0.47/year. Fishing mortality as well as exploitation rate was negligible since fishing activity is prohibited throughout the year. © 2005 Taylor & Francis Group, LLC.Öğe Condition, Length-Length and Length-Weight Relationships for Four Introduced Freshwater Fish Species from an Insular Ecosystem (Gökçeada, Turkey)(2021) Ağdamar, Sevan; Gaygusuz, ÖzcanThe present study aims to investigate the condition, length-weight (LWRs) and length-length relationships (LLRs) of four introduced freshwater fish species (Carassius gibelio, Cyprinus carpio, Gambusia holbrooki, and Pseudorasbora parva) inhabited in the inland waters of Gökçeada (Çanakkale, Turkey). Fish samples were collected using electrofishing from one lentic (Büyük Stream) and four lotic (Aydıncık, Dereköy, Gökçeada, and Uğurlu Reservoirs) ecosystems between April 2019 and September 2020. The calculated values of parameter b in the LWRs were 3.275 and 3.230 for G. holbrooki (Uğurlu and Büyük populations, respectively), 3.031 and 2.937 for C. carpio (Aydıncık and Dereköy populations, respectively), 3.129 for C. gibelio and 3.047 for P. parva. Values of Fulton's condition factor (K) varied between 1.72 ± 0.23 (P. parva, Gökçeada population) and 3.60 ± 0.33 (C. carpio, Dereköy population). The coefficients of correlation (r) for all the LLR equations were greater than 0.95 and significantly linear. The present study provides the first knowledge about the selected biological parameters for four introduced freshwater fish species in Gökçeada.Öğe Conversions of total, fork and standard length measurements based on 42 marine and freshwater fish species (from Turkish water)(2006) Gaygusuz, Özcan; Gaygusuz, Çiğdem Gürsoy; Özuluğ, Müfit; Tarkan, Ali Serhan; Acıpınar, Hasan; Bilge, Gökçen; Filiz, HalitRelationships between total (TL), fork (FL) and standard (SL) lengths belonging 19 families from Aegean and Marmara coast of Turkey were presented for 42 fish species. The relationships between TL, FL and SL were all linear and they were all highly significant (P<0.001) with all $r^2$ values being >0.90. There were significant differences in the slope of length – length relationships between some localities and type of length conversions for the fish species.Öğe Preference of zebra mussel, Dreissena polymorpha in the diet and effect on growth of gobiids: A comparative study between two different ecosystems(Ekoloji, 2007) Gaygusuz, Özcan; Gaygusuz, Çi?dem Gürsoy; Tarkan, Ali Serhan; Acipinar, Hasan; Türer, ZeynepWe investigated presence of zebra mussel, Dreissena polymorpha, which is considered as harmful for two freshwater ecosystems (Ömerli Reservoir and Lake Sapanca), in the food preferences of several gobiid species namely; Neogobius melanostomus, Neogobius gymnotrachelus, and Neogobius fluviatilis. In Lake Sapanca, zebra mussel was the dominant food component in the diet of gobiids. However, in Ömerli Reservoir, plant with macropyhtes and algea were the dominant food sources both studied gobiids. Intraspecific diet overlap indices showed that gobiid species from the same lake preferred similar food types (S ? 0.8). However, when we compared the lakes, the diet overlap index between N. fluviatilis (Lake Sapanca) and N. gymnotrachelus (Ömerli Reservoir) was not significant (S = 0.5) which indicates different food choices. The relationships between total length and weight, which had slope values >3 in all but one case, differed significantly between species. One exception was between N. fluviatilis (Lake Sapanca) and N. melanostomus (Ömerli Reservoir). In generally, slopes of the relationships in fish species from Lake Sapanca were bigger than those of Ömerli Reservoir. This result suggests that gobiids fed with mostly zebra mussel had better weight gain compared to gobiids fed with mostly plant-based food. This study showed that gobiid fishes are an important consumer of zebra mussel and their predation would affect the mussel populations, especially in the ecosystems where zebra mussel is abundant.Öğe Preference of zebra mussel,Dreissena polymorpha in the diet and effect on growth of gobiids: a comparative study between two different ecosystems(2007) Gaygusuz, Özcan; Gaygusuz, Çiğdem Gürsoy; Tarkan, Serhan Ali; Acıpınar, Hasan; Türer, ZeynepÖmerli Rezervuarı ve Sapanca Gölü için zararlı olarak kabul edilen zebra midyesi, Dreissena polymorpha'nm bazı kaya balığı türlerinin, (Neogobius melanostomus, Neogobius gymnotrachelus ve Neogobius fluviatilis) besin tercihlerindeki varlığını araştırdık. Sapanca Gölü'nde zebra midyesi kaya balıklarının baskın besin maddesi iken, Ömerli Rezervuarında makrofitler ve algler en çok rastlanan besindi. Türler arası beslenme indeksi aynı gölde yaşayan kayabalıklarının benzer besin tiplerini seçtiklerini (S > 0,8) gösterdi. Ancak, her iki gölü karşılaştırdığımızda, N. fluviatilis (Sapanca Gölü) ve N. gymnotrachelus (Ömerli Rezervuarı) arasındaki besin indeksi, farklı besinleri tercih ettiklerini gösterecek şekilde önemsiz olarak çıkmıştır (S= 0,5). Boy ile ağırlık arasındaki ilişkinin eğimi, bir istisna dışında bütün karşılaştırılan türler arasında önemli derecede farklı çıktı. Sadece, N. fluviatilis (Sapanca Gölü) ve N. melanostomus (Ömerli Rezervuarı)'ın boy ağırlık ilişkilerinin eğimleri arasındaki fark önemsiz çıkmıştır. Genel olarak Sapanca Gölü'ndeki balıkların boy ağırlık ilişkilerindeki eğim Ömerli Baraj Gölü'ndekilere göre daha yüksek çıkmıştır. Bu sonuç, çoğunlukla zebra midyesi ile beslenen kaya balıklarındaki ağırlık artışının, genelde bitkisel materyalle beslenen kaya balıklarına göre daha iyi olduğu hipotezini desteklemiştir. Bu çalışma, kaya balıklarının zebra midyesinin önemli bir tüketicisi olduğunu ve kaya balıklarının av baskılarının özellikle zebra midyesinin bol bulunduğu ekosistemlerde bu türün populasyonları üzerinde önemli bir etkisi olabileceğini göstermiştir.Öğe The ichthyofaunal diversity of freshwater ecosystems in Gokceada Island (NW Turkey) under the pressure of nonnative species(Turkiye Klinikleri, 2021) Ağdamar, Sevan; Saç, Gülşah; Gaygusuz, Özcan; Doğaç, Ersin; Acar, Ümit; Gürsoy Gaygusuz, Çiğdem; Özuluğ, MüfitFreshwater 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 (Gökçeada 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 Gökçeada 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 Gökçeada Island. Results showed that the fish fauna of the island was predominantly shaped by fish stocking activities.Öğe Two new records for the fish fauna of lake Sapanca Basın (Sakarya, Turkey)(2007) Özuluğ, Müfit; Tarkan, Ali Serhan; Gaygusuz, Özcan; Gaygusuz, Çiğdem GürsoyTwo freshwater fish species, Phoxinus phoxinus (Linnaeus, 1758) and Gambusia holbrooki Girard, 1859, were recorded for the first time from Lake Sapanca Basin. P. phoxinus were captured from Mahmudiye stream while G. holbrooki was captured from Maşukiye stream. The measural and meristic characters of the specimens were similar to those reported elsewhere for the species. P. phoxinus known as predator of trout’s eggs was caught in big numbers in same stream with Salmo trutta macrostigma. The inclusion of these species has increased the species list of fish fauna of Lake Sapanca.
