A survey on dite of SILURUS GLANIS of Amirkelayeh wetland was investigated seasonally during of 2001-2. Fishes were caught using different gears such as gillnet, common haul sciene, cast net , dipnet and electroshoker. Caught fishes were biometry, age was determinated and then necropsy. Results on diet survey of 132 SILURUS GLANIS showed that this fish was fed on 16 food types. Includings Tinca tinca and Amphipoda each with frequency of 36.3% and Blicca bjoerkna, SILURUS GLANIS, Pungitius Platygaster, Perca fluviatilis , Rat , Bird , Water buge, Pleochoptera each with frequency of 2.2% show the highest and lowest values respectively . Also Proterorhinus marmoratus , Odonata , Carassius auratus gibelio, Frog, Cobitis taenia and water beetle had meadium frequency. Amirkelayeh wetland SILURUS GLANIS were in age groups of 1+- 7+ (No any specieman was not at 6+ age group were catch), had average Total length of 50.6 cm (32.5 – 73 cm ), average weight of 944.2 gr ( 200 - 3000 gr) , average relative length gut of 0/71 (0/4 – 1/12 ), average Index of flulness of 292.5 (58.8 – 707.6) and average fullton’s condition factor of 670 (399.9 – 936.6 ). Meanwhile, vacuity index was zero. It is noteworthy that most of food types were in the stomach of SILURUS GLANIS and intestine had digested foods or food wastes, that express the palatability of these foods and ability of fish selection according to prey size and use of vision and olfactory. According to results of present study, SILURUS GLANIS is a carnivores, piscivores and shows cannibalistic deheviour. It’s diet change according to season , age and sex which is related to diversity of food types, but there is no significant differences between these values and relative length gut , Index of fullness and fullton’s condition factor.

Anzali lagoon located in south-west region of Caspian Sea and regarded as the most important lagoons in the Caspian Sea catchment. European catfish, SILURUS GLANIS constituted 3.78% of total catch during 1992-1996. At present study (1998-2001) 95 specimens of S. GLANIS have been checked to get data concerning total length, body weight and age of S. GLANIS is measurement as follows 19.8 - 186.5 cm, 47.7 - 30000 g and 1 - 9 years old respectively. Females constituted 68.5% of total specimens. Also, coefficient of vacuity, fullness Index and relative intestinal length averages were measured 41.15,322.0±273.8 and 0.83±0.17 respectively. According to this study, S. GLANIS feeds on 19 diversified food items including insects (4.13%), bivalve (0.5%), crustaceae (15.8%), amphibia (0.9%) and bony fishes (78.6%). Carassius auratus with 33.9%, Macrobrachium spp. with 14.22%, Neogobius kessleri with 4.59%, Insects with 4.13% and Proterorhinus marmoratus with 2.75% were dominant. On the other hand C. auratus in Spring and Autumn, Macrobrachium spp. in Summer and N. kessleri in Winter were the main food items consumed by S. GLANIS. Also, piscivorous behavior positively correlated to length growth, so that consumption of fish item from the length 20-55 cm (44.2%) increased to 94.5% when the fish reached to 91-125 cm. This fish foraged mainly on two fish families, Cyprinidae (78.7%) and Gobiidae (14.8%). In this study we didnot observe cannibalistic behavior in S. GLANIS. In general, European catfish has consumed only prey species and did not damage any commercial fish stocks in the ecosystem.

Gills of catfish SILURUS GLANIS (300g weight) of Mahabad Dam were examined for structural attributes in 2004. Immediately after catch, gills were removed and placed in Bouin and Glutaraldehyde for structural and microscopic examinations. For classical histological assessment, samples were stained with Hematoxylin and Eosin and examined under light microscope. For electron microscopy, cuts 90 nanometers each were prepared and stainted with Uranyl Acetate and Lead Citrate, covered with silver, examined and photographed. We found the gill cells being composed of ionocyte a,b, accessory, mucous, pillar and mosaiccells. The ionocytes were located at the base of the gill rakers and intra-raker spaces. Thesestructural attributes of ionocyte cells demonstrate their active role in osmotic regulation of catfish.

Amirkelayeh wetland is one of the most important international wetland in north Lahijan, Guilan province. This wetland area and average depth is more than 1230 hec and about 2 meters respectively. Wels (SILURUS GLANIS) is one of the 15 species of wetland fishes that its parasitical pollution was surveyed in 1380. For this reason in the middle of each season alive hunted fish by the usage of different hunting tools were carried to the laboratory. The fish different organs were studied. According to the performed researched in 80 fish, 7 species of parasites by the name of Diplostomum spathaceum, Gyrodactylus sp. , Lernaea cyprinacea, Dactylogytus sp., Raphidascaroides sp., Aphanurus stossichi and Triaenphorus Crassus was separated. Based on the results the highest Prevalence was related to Dactylogytus sp. (39/1 %) and the lowest prevalence was referred to D. spathaceum (2%), the highest mean intensity was related to the Dactylogyrus sp. (7/88) and the lowest mean intensity was referred to A.stosichi (1/5), the highest average abundance Dactylogyrus sp. (2/46) and the lowest average abundance was related to D. spatheceum (0/10), the highest number range was referred to Dactylogyrus sp. (1-49) and the lowest number range was related to A.stossichi (1-5). Also according to the parasite kind and their abundance was observed in seasonal, sexual and age groups.

The effect of aqueous solution of citric acid (CA) on the lipid stability of the European catfish (SILURUS GLANIS) fillets during frozen storage (up to 6 months) was investigated. Rancidity development was measured by several biochemical indices (free fatty acids, peroxides and TBA) and complemented by the measurement of expressible moisture and sensory evaluation (flesh odor, consistency and flesh appearance). The CA treatment led to some lower free fatty acids (6.43% oleic acid in total lipid at month 6), peroxides (7.98meq oxygen/kg lipids, at month 6) and secondary compounds formation (2.16mg malondialdehyde/kg fish sample). Lower peroxide, thiobarbituric acid-reactive substance (TBA), free fatty acids (during 0,3 and 6 months frozen storage), and expressible moisture (month 6) values were obtained from CA-treated fish fillets than the untreated (blank control) ones (P<0.05).

During storage and processing, result of some factors, fish quality will decrease .To determine of oxidative and hydrolytic rancidity of lipid in catfish (SILURUS GLANIS) during frozen storage, catfish were caught in Anzali lagoon in January of 2006. The prepared fillets, were freezed at freezing tunnel -40oc for 12 hours, and then were stored at -18oc for 6 months. Process of lipid quality changes of these fillets were measured by some factors related to lipid rancidity, included, Peroxide value (PV), Free Fatty Acid (FFA), Thiobarbituric acid (TBA) and value of Heme iron, lipid, moisture, ash were measured, too.  The experiments were performed at 0, 1, 3 and 6 months. The Peroxide value were increased and showed significant changes during different months (P<0.05). Peroxide value at the end of experiments was 8.22 times more than initial value. During the storage period, increasing of TBA was perceived that at last month’s was significant (P<0.05) and reached to 3.32 mg of malonaldehyde at kg of fish flesh. Amount of FFA increased due hydrolytic rancidity and at the last 2 months of measuring was significant. Heme iron decreased at 6 months and changed between 8.92 and 6.77 ppm (p<0.05). Correlation relations at most of indicators showed significant relations between them.  Oxidative and hydrolysis lipid indicators had positive and significant relation, together.

In this study, histological characterization of male gonad of wels, SILURUS GLANIS, were investigated over a period of one year in Anzali Wetland. The testes of 196 male specimens that were caught in different sizes by traps were fixed in Bouin’s solution. Then samples were prepared by classical methods of histology with Hematoxylin and Eosin (H & E) staining and studied by light microscope. Also, the gonadosomatic index (GSI %) were determined during the sampling period.  Six testicular maturation stages were observed including: immature (I), early developing (II), late developing (III), ripe testes (IV), running ripe testes (V) and spent (VI). Spermatogenesis was done during a relatively long period of one year. The stages IV and V and sperm production were occurred from late February to early June and stage VI was from June to early August. The maximum mean value of GSI% were due to late May and early June. This index decreased clearly in July. The results showed that spermiation was started in late June and resumed to late August.

In this article the population genetic structure of the European catfish(SILURUS GLANIS) in the Anzali wetland and Aras Lake was investigated based on the characterization of microsatellite markers. For this purpose, sixty fin clip samples of this species from the two regions were collected and for genetic analysis 8 microsatellite loci were used that 2 sets of them produced monomorphic and 6 polymorphic bands. Number of alleles, observed and expected heterozygosity values for each population, population genetic differentiation based on AMOVA test (Fst), genetic distance and Hardy-Weinberg equilibrium test (HWE) between samples of two areas were determined using Biocapt and GenAlex software packages. Totally 88 alleles were observed. The mean number of alleles in samples of Anzali wetland and Aras Lake were 9.3 and 5.3 respectively. There were significant differences based on average number of alleles per locus and heterozygosities between two populations (P<0.01). The value of Fst between populations was high (0.165) and genetic distance was 0.38 and both of computed parameters were significant (P<0.01). Excess or lacks of heterozygosity was seen but most of used microsatellite loci in two areas were at Hardy-Weinberg equilibrium. The result of this study showed the two population are genetically differentiated, so fisheries management for reproduction and breeding of these populations to export and exchange access is recommended.

To investigate and identify the helminthes parasites in the digestive tract of the catfish in Aras Dam in the spring of 2011, 50 catfish were caught measuring 0.5 to 4.5 kg and 50 to 120 cm from this dam. Their Gastrointestinal tracts were then removed and placed in plastic containers containing 10% formalin and transferred to Fisheries Laboratory, Faculty of Veterinary Medicine, Islamic Azad University of Tabriz. The helminthes parasites were isolated, stained and identified and their species were determined. During this survey of 50 catfish caught from Aras Dam, 145 Proteocephalus osculatus and 88 Siluritaenia SILURUS parasites was isolated and identified. The infection rate of these two parasites of catfish was 100%. This is the first report of these two parasites of catfish from Aras Dam.