Caspian J. Env. Sci. 2011, Vol. 9 No.2 pp. 223~233 ©Copyright by The University of Guilan, Printed in I.R. Iran CJES [Research] Caspian Journal of Environmental Sciences Feeding behavior of brown trout, Salmo trutta fario, during spawning season in four rivers of Lar National Park, Iran 1 2 2 1 M. Salavatian* , Z. Gholiev , A. Aliev , K. Abassi 1- Inland Water Aquaculture Research Center, P.O.Box 66, Bandar Anzali, Iran. 2- National Academy of Sciences of Azerbaijan Republic (Faculty of Zoology, Azerbaijan Republic. * Corresponding Author’s E-mail: [email protected] ABSTRACT Brown trout, Salmo trutta fario, has a wide range of distribution in the north of Iran and in Karaj, Lighvanchai and Karun Rivers, but there is no report about its feeding behavior in some water resources including the Lar Natural Park. In order to study feeding behavior of this fish during spawning season, a survey was carried out in the rivers of Elarm, Aab-Sefid, Kamardasht and Delichayi in fall 2008. A total of 140 individuals of brown trout were caught by cast net and electro fishing. Mean weight and length of the samples were 130±79.5 g and 216.9±39 mm, respectively. The age of fish was 2 to 6 years and mean age was 3.02±1.3. The mean relative gut length (RLG) of samples was 0.86±1. It was found that brown trout fed on various preys (32 animal groups), that Chironomidae (88.6%), Simulidae (60%), Baetidae (51.4%) and Tipulidae (50%) have had the most frequency in the gut of brown trout. The proportion of food consumed by trout was Diptera 91.5% (Chironomidae pupa and larvae 85.8%), Coleoptera 6.4% and others 2.1%. Cannibalism was seen scarcely. In conclusion, brown trout consumes a wide range of food items in its spawning season. Therefore, it can be classified as euryphagous and carnivaorous. Keywords: Salmo trutta fario, Diet, Lar National Park, Iran. INTRODUCTION fishing (Emadi, 1988; Kiabi et al., 1999). Its Brown trout has a wide range of distribution maximum total length is 100 cm and its in the north of Iran and in Karaj, weight up to 20 kg (Froese and Pauly, 2011). Lighvanchai and Karun Rivers (Coad, 2011). Sport fishing is regulated by the It lives in the upstream region of rivers and Environmental Protection Organization of elevated lakes containing high ratios of Iran. For example, the proportion of catch dissolved oxygen. It is a native fish of rivers for each fisherman per day is limited to 3 which flow from the Alborz Mountains in fish specimens and authorized time of sport Northern Iran and probably was introduced catch is from 11 July until 10 September for to other Iranian water bodies. Its existence in two days in a week. some rivers of Tehran was reported firstly Nikolski (1954) stated that brown trout has by Derzhavin (1934). In addition, brown slower growth and less fecundity compared trout lives in most of the rivers flowing into to other Salmonids. The maturity age of the Caspian Sea (Armantrout, 1980; Saadati, male is 2 and of female is 3 years (Vosooghi 1977; Coad, 1979; Araghi, 1996; Abdoli, 1999; and Mostajir, 2005; Kazancheev, 1981), but Kiabi et al., 1999: Afrayi et al., 2000; Abbasi et Berg (1948) stated that the maturity age of al., 2004; Vatandoost et al., 2008; Ghane, 2008; brown trout is 3-4 years. Abdoli (1999) and Kheyrandish, 2010). Kazancheev (1981) Afrayi et al. (2000) reported that the stated that brown trout also inhabits in the spawning season of this species in Iranian Volga River, Caucasian rivers and the rivers rivers is between October and December. of the southern coast of the Caspian Sea. Feeding behavior of brown trout in Iran However, the stocks of brown trout in was investigated by Araghi (1996) in the Iranian rivers have extremely been damaged Noor River, by Moslemi (1997) and Afrayi and its catch has been limited to sport et al., 2000 in the Tonekabon River, by Online version is available on http://research.guilan.ac.ir/cjes 224 Feeding behavior of brown trout Abbasi et al., 2004 in Guilan Rivers, in its gut and to determine food indices for Fakharzadeh et al. (2008) in the Karaj River sustainable fisheries. and by Vatandoost et al. (2008) in the Ashkrood River, by Abdollahpoor et al. MATERIAL AND METHODS (2011 a,b) in Hevigh and Shafarud Rivers, The Lar National Park is located 55 km at all in the Caspian Sea basin. Although east of Tehran. Its elevation from open seas Elarm, Aab-sefid, Kamardasht and is 2531 m and its area is 276 km2 (Elmi, Delichayi Rivers of the Lar National Park 2003). The main rivers of the park are: are the main habitats of brown trout in Iran, Elarm, Aab-sefid, Kamardasht and no studies have been carried out on the Delichayi rivers. After constructing Lar feeding behavior of brown trout inhabiting dam in this area, water flow of these rivers form reservoir lake of the dam (Figure 1). in these rivers up to now. This fish is a Outlet of the dam is Lar River which after vulnerable species (Kiabi et al., 1999), and joining to Haraz River, flows into Caspian valuable for sport fishing, too, thus the Sea near Babol city (Jafari, 1995; Elmi, 2003). study has been done for obtaining food diversity, frequency and abundance of prey Fig 1. A view of the studied rivers in the Lar National Park (North Iran) Samples of brown trout were caught using and incidental foods were also determined cast nets and electro fishing in downstream following Biswas (1993). Sampling from areas of these rivers between October and benthic organisms was done on a monthly December 2008 (spawning season). Mesh basis using Surber sampler with a sectional size of cast net was (a=10 mm) and the area of 1600 cm2. Kruskal-Wallis non- voltage of Electro shocker (trade mark: Karl parametric analysis was used to determine Von Keitz) was 200-300 volts with flow differences in population after normality strength of 5 amperes. Total length of fish test and Mann-Whitney Test was used to was measured to the nearest 1 mm and separate groups (age, sex, month and river) weight of fish was taken to the nearest 1 g. (Zar,1984). Age of fish samples was determined by observing growth rings on otolith using Results stereoscopic microscope. Gut content of Studying on the sexual organs of 140 each fish was evacuated and fixed in 4% captured fish from four rivers (Elarm, Aab- formalin solution, and then identified in the sefid, Kamardasht and Delichay) of the Lar laboratory following Merritt et al. (2008) National Park showed that all fish were at and Kasimov (2000). In addition, gut length stage 4 or 5 of sexual maturity. The range of samples was measured and its ratio to and average weight of fish were 29-451 and fish total length was determined. Food 130.7±79.5 g respectively and its total preference, food relative importance, basic length was 142-328 (216.9±39) mm. Mean Salavatian et al., 225 weight and total length of males was families), Lepidopetra order, Hemiptera 148.8±89.1 g and 220.4±4 mm respectively, order (Corixidae family), Coleoptera order while that of females was 112.7±64.9 g and (Hydrophilidae, Dytiscidae, Elmidae and 200.9±3.6 mm. Captured fish were between Elateridae families), Odonata Order 2-6 years old with a mean age of 3.02±1.3 (Agronidae family), Homoptera order years.. The range of relative gut length (Fulgoridae and Aphilidae families), (RLG) was 0.55-1.08 and its average was Amphipoda order (Gammaridae family), 0.86±0.1. Average RLG for 2 and 3 years old Archnida order (Hygrobatidae family) and specimens was 0.84±0.1, and 0.9±0.06 for 4 - brown trout. 6 years old specimens. Food preference: Study of gut contents of captured samples In Aab-Sefid River; Diptera and Coleopetra showed that all of them were fed were the basic food, Ephemeropetra, (Coefficient of Vacuity=0). Index of gut Lepidoptera, Hemiptera and Homoptera fullness varied between 43.3 and 1336 with were secondary food and all other orders an average of 186.3±162.2. The average of were considered as incidental food. In this index for 2 years old fish was Delichayi River; Diptera, Ephemeroptera, 213.9±196.1 (n=86) and 142.4±71.4 (n=54) Trichoptera and Oligochaeta were basic food for 4-6 years old fish. ANOVA test shows items and Coleoptera was secondary food. that there is no significant difference In Elarm River; Diptera, Ephemeroptera, (P≥0.05) in gut fullness recorded in October Trichoptera and Amphipoda were primary and December. food items and Hemiptera and Coleoptera The results revealed that brown trout were the secondary ones. In Kamardasht inhabiting in Elarm, Aab-sefid, Kamardasht River, Dipetra, Hemiptera, Coleoptera and and Delichay Rivers feed mainly on 34 Gostropoda were primary food items and different food items consisting of Oligochaeta Oligochaeta, Ephemeroptera, Trichoptera, (Hirudinea order and Lumbricidae family), Homoptera and Prostigmata were known as Gastropoda (Physidae family), Diptera secondary ones. In all the studied rivers, (Chironomidae, Tipulidae, Simulidae, primary food items were Diptera (98.6%), Muscidae, Formidae, Ichneumonidae, Ephemeroptera (54.3%) and Coleoptera Colicoidae and Tabanidae families), Coelifera (51.4%) and secondary ones were Hemiptera sub-order, Ephemeropetra (Baetidae and (38.6%) Trichoptera (31.4%), Amphipoda Heptagenidae families), Trichoptera order (27.1%), Lepidopetra (17.1%), Prostigmata (Sericostomidae, Hydropsichidae, Limnephi- (15.7%), Homoptera (12.9%), Oligochaeta lidae, Psychomyiidae and Philopotamidae and Gastropoda (Figure 2).