عنوان مقاله [English]
Salmo trutta fario is vulnerable population belong to Caspian brown trout and the fish exists in upstream areas of most Iranian rivers at southern Caspian sea basin and it has a relatively suitable density in Shafarud River. The fish was caught with electro-shocker, Cast-net and lines from winter 2009 to autumn 2010 and the aim was more information on the fish, biology. Body weight was measured in studied fish specimens 7.54-78.4 (26.54±14.7) g, total length 89-192 (128.43±21.8) mm and age was 0+ - 4+ (2.15±0.8) years old, too. The relative length average of gut was measured 0.85±0.10, gastero-somatic index 6.08±3.5, intensity of food, 195.45±157.4 and coefficient of vacuity was 0 (Zero), too. The fish has fed on 31 families belong to 14 invertebrate orders in Shafarud River consist of Oligochaet vorms (Lumbricidae and Lumbriculidae), Isopoda (Asellidae), Hydroacrina (Hygrobatidae), Myriapoda, Coleoptera (Dytiscidae and Elmidae), Diptera (Blephariceridae, Chironomidae, Empididae, Simuliidae, Stratiomyidae, Tabanidae and Tipulidae), Ephemeroptera (Baetidae, Ephemeridae and Heptagenidae), Hymenoptera (Formicidae), Megaloptera (Sialidae), Odonata (Agrionidae), Plecoptera (Leucteridae, Nemouridae, Taeniopterygidae and Perlidae), Trichoptera (Hydropsychidae, Lepidostomatidae, Limnephilidae, Philopotamidae and Rhyacophilidae) and Hemiptera and thus the fish is a euryphagous and carnivore species in studied area. Study on food preference or frequency of observance of food items in alimentary tract of studied fish showed Diptera and Ephemeroptera orders are main food items in winter, Diptera, Ephemeroptera and Trichoptera orders in spring, Diptera, Ephemeroptera, Trichoptera, Plecoptera and Hymenoptera orders in summer and Diptera and Ephemeroptera orders in autumn, too. These changes took place in different fish ages, too. In general, Diptera (97.9%), Ephemeroptera (83.3%), Plecoptera (52.1%) and Trichoptera (52.1%) were main food for the studied fish in Shafarud River and other orders were secondary or accidental food.
Keywords: Salmo trutta fario, Diet, Shafarud River, Guilan, Iran.