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    A Comparison of Ageing Techniques to Improve Precision of Age Estimation from Fish Scales
    (Ege Univ, Fac Fisheries, 2005) Gursoy, Cigdem; Tarkan, Ali Serhan; Gaygusuz, Ozcan; Acipinar, Hasan
    Scales of rudd, Scardinius erythrophthalmus (L, 1758), prussian carp, Carassius gibelio ( Bloch, 1782) and roach, Rutilus rutilus (L., 1758) were sampled from two different habitats. Two methods of determining age from scales of fish were applied for all fish species. There was disagreement between methods. The agreement between the determinations of different age readers was better with the impressing scale method than cleaning scale method. Impressing method produced the best results in terms of precision of the age estimates besides it had many advantages such as quick - apply, storing data and easy back-calculation.
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    Öğe
    Interannual variability of fecundity and egg size of an invasive cyprinid, Carassius gibelio
    (Taylor & Francis Inc, 2007) Tarkan, Ahmet Nuri; Gaygusuz, Ozcan; Tarkan, Ali Serhan; Gursoy, Cigdem; Acipinar, Hasan
    A population of the invasive Prussian carp (Carassius gibelio) was examined over a three-year period in a mesotrophic reservoir to find out interannual variations of fecundity and egg size and the influence of maternal condition (total length, TL, and age class) and environmental factors (water temperature and fish density) on these variables. Prussian carp reproduction was synchronous, with only a single batch, and fecundity ranged from 1,250 to 62,400 eggs per female. Relative fecundities and egg size showed no significant between-year differences. Fecundity increased with age, whereas egg diameter remained unchanged with age and TL. Fecundity was affected positively by TL and negatively by fish density, whereas temperature had no significant effect. Egg size was not affected by fish density or temperature.
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    Preference of zebra mussel, Dreissena polymorpha in the diet and effect on growth of gobiids
    (Foundation Environmental Protection & Research-Fepr, 2007) Gaygusuz, Oezcan; Gaygusuz, Cigdem Cuersoy; Tarkan, Ali Serhan; Acipinar, Hasan; Turer, Zeynep
    We investigated presence of zebra mussel, Dreissena polymorpha, which is considered as harmful for two freshwater ecosystems (Omerli 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 Omerli 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 (Omerli 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 (Omerli Reservoir). In generally, slopes of the relationships in fish species from Lake Sapanca were bigger than those of Omerli 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.
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    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, Zeynep
    We 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.
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    Öğe
    Use of bone and otolith measures for size-estimation of fish in predator-prey studies
    (Inst Vertebrate Biology As Cr, 2007) Tarkan, Ali Serhan; Gaygusuz, Cigdem Guersoy; Gaygusuz, Oezcan; Acipinar, Hasan
    To estimate the size of fish taken as prey by piscivorous predators, linear or non-linear relationships between bone measures (pharyngeal, opercula, cleithra, anal and dorsal spine bones, otoliths) and body length were elaborated for eleven Eurasian cyprinid fish species captured in three lakes of Turkey: rudd Scardinius erythrophthalmus, Baltic vimba Vimba vimba, Danube bleak Chalcalburnus chalcoides, gibel carp Carassius gibelio, roach Rutilus rutilus. silver bream Blicca bjoerkna, common carp Cyprinus carpio, chub Leuciscus cephalus, Dnieper chub Petroleuciscus borysthenicus, tench Tinca tinea and tarek Alburnus tarichi (endemic species for Lake Van). All calculated regressions were highly significant, with coefficients of determination >81 % in most of cases. The results suggest that the biometric relationships between fish length and some bones (pharyngeal, opercula, cleithra) are well suited for use in prey-predator studies of all the studied species, but otoliths and the dorsal and anal spines can be used for some fish species only (rudd, Baltic vimba, roach, silver bream, gibel carp).