Age, Growth and Diet Composition of the Resident Brown Trout, Salmo trutta macrostigma Dumeril 1858, in Fırnız Stream of the River Ceyhan, Turkey


Abstract: It was aimed to describe some population charactersitics of Salmo trutta macrostigma from Fırnız Stream of the River Ceyhan. The age, growth, length-weight relationship and diet composition were investigated from May 2000 to February 2001. The ratio of male to female of 197 brown trout caught by electroshocker was 0.67:1.00 and their fork lengths varied from 8.0 to 48.5 cm and the majority of them were in the 11.0-17.0 cm length group. Total weights varied from 7.4 to 1441.0 g and age distribution ranged between 0 and 9. The length-weight relationships were estimated as W = 0.0149*FL^{3.009} (r = 0.994) for males and W = 0.0163*FL^{2.971} (r = 0.995) for females. The von Bertalanffy growth parameters were estimated as L_{\infity} = 51.00 cm, k = 0.131, t_{0}= - 1.220, W_{\infity} = 2034.96 g for males and L_{\infity} = 72.75 cm, k = 0.097, t_{0} = - 0.910, W_{\infity} = 5421.51 g for females. The condition factor of 197 brown trout ranged from 1.13 to 1.85 and the differences between females and males in the same age groups were not significant (P > 0.05). A total of 15 prey groups were identified in the diets of brown trout and most abundant were Coleoptera, Trichoptera, Ephemeroptera, Plecoptera, Malacostraca, Diptera, Acarii, Heteroptera, fish, fish eggs and plant seeds. According to the Index of Relative Importance (IRI%), five food items represented more than 99% of the total diet, with the most important being Gammarus sp. (43.96%), Nemoura sp. (18.85%), Hydropsychidae (13.44%), Isoperla sp. (12.83%) and an unidentified Diptera sp. (10.26%).

Keywords: Salmo trutta macrostigma, age, length, weight, condition, feeding

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