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    Biometric relationship between body size and bone lengths of Carassius gibelio and Rutilus frisii from Iznik lake
    (2008) Saç, Gülşah; Acıpınar, Hasan; Gaygusuz, Özcan; Tarkan, Ali Serhan; Gaygusuz, Çiğdem Gürsoy
    Biometric relationship between bone dimensions and body size are presented for non-native gibel carp and native black sea roach in Iznik Lake, Turkey. Regressions of the data were highly significant, with coefficients variation of the determination > 89% in most of cases. Non-linear and linear functions provided the best fit for black sea roach and gibel carp, respectively. The maximum values of relative errors of different structure’s measures for black sea roach were considerably higher than those of in gibel carp. Such information facilitates the assessment of the potential role of these fish species in the diet of piscivorous fauna.
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    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, Ozcan
    We 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.
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    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 Gursoy
    The 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.
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    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 Gursoy
    In 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.