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The aim of this study is to provide necessary information on the biology of mosquitofish in Seyhan Dam Lake in Adana, which is located in southern part of Turkey. The population structure of eastern mosquitofish Gambusia holbrooki Girard, 1859 was studied in Seyhan Dam Lake. A total of 1582 specimens (772 males and 810 females) were collected monthly from January to December, 2007. The age composition of the sample range between 0+ and 2+in both sexes. The sex ratio was M:F= 1:1.04. The length-weight relationship calculated for all individuals, with W=0.0129 x L2.927. von Bertalanffy growth parameters were for males, L∞=3.31cm, K=0.6597 year-1, to =0.9483 year for females L∞=6.62cm, K=0.2369 year-1, to =0.9259 year for all samples, L∞=5.84cm, K=0.2369 year-1, to =-1.0740 year. A total of 102 stomachs were examined and total of organisms identified from alimentary canal. The diet mainly consist of Diptera (Chironomidae (pupa) 29.40% Diptera (adult) 24.50%), Egg (mosquito 14.70% different organisms 1.96%), Crustacea (Copepoda 9.80%, Cladocera 3.92%), Coleoptera 4.90%, Hemiptera 1.96%, Fishes (G. holbrooki 3.92%), Other Hymenoptera 1.96%, Tricoptera 0.98%, Plecoptera 0.98%, Formicidae 0.98%. These data were conducted to compare with the results of other studies to carry out for other geographic areas.

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Capoeta erhani is an endemic species to Southeast of Turkey. To date the information on biology of this species from inland waters of Turkey is very limited. The present study aims to provide the basic age and growth parameters of C. erhani from the middle basin of the Seyhan River. In total, 255 individuals were collected seasonally between October 2013 and September 2014. The overall sex ratio was 3.47:1 M : F.  The total length of the specimens ranged from 10.4 to 33.0 cm and the weight from 9.0 to 360.0 g. The ages of total examined fish ranged from 0 to 5 years. Maximum age was found to be 5 years for both sexes. Length-weight relationship was described as logW= -5.067 + 3.168 logTL (r²= 0.972). The von Bertalanffy growth parameters were: L_∞ = 32.51 cm; k = 0.400 year^-1; t₀ =-0.930 year for the entire population. Munro’s phi prime index in males, females and both sexes was calculated as 6.00, 6.12 and 6.04.

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The population structure of Aphanius mento in the Seyhan Reservoir was studied on the basis of 834 fish specimens (516 males and 318 females) caught on a monthly basisbetween September 2013 and August 2014. Fish were collected using dip nets of tulle with a 1mm mesh size. The maximum age of fish was found to be 4 years for both sexes combined, the 1 year old age group comprised 62.20% of male samples. The overall sex ratio of females to males was 1:1.62. Von Bertalanffy growth parameters were L_∞=54.33 mm, K=0.399 year^-1,  t₀ =-1.168 years for females, L_∞ =52.72 mm, K=0.397 year^-1, t₀=-1.137 years for males, and L_∞=56.50 mm, K=0.386 year^-1,                t₀=-1.257 years for both sexes. The length (TL) - weight (W) relationship was W= 0.00051xTL^2.635, (r= 0.965) for males, W=0.00088xTL^2.464, (r= 0.987) for females and W=0.00066xTL^2.554, (r = 0.974) for both sexes. Condition factor ranged from 1.696 for males and 1.613 for females to 1.664 for both sexes. The mean condition factor (CF) was not significantly different between the sexes among all fish during different months (p>0.05). The present study represents the first comprehensive information on the population structure of A. mento in the Seyhan Reservoir. The results of this study will contribute to the population management and conservation of this species and be useful in increasing knowledge on its ecology and biology.