abdol-azim fazel

The shore flies (Ephydridae) are a relatively large family of acalyptrate Diptera and are often prominent members of aquatic and semi-aquatic environments. Adult shore flies can be found in moist conditions, such as the borders of marshes, wetlands, lakes, pools, streams, and seashores. In the systematic and ontogenic studies of the Diptera order, the structure of the larval stages is of great importance. However, there is limited information about the body structure of shore fly larvae compared to that of adult insects. Despite their diverse morphological compatibility, the order Diptera provides many examples that contribute to our understanding of larval evolution. The aim of this study is to describe the morphology of the larval stage of the shore fly species belonging to the genus Ephydra sp. using light microscopy (Nikon Eclipse 50i, NY 11747-3064, USA with camera Digital Sight DS-L2, Nikon, NY 11747-3064, USA) and Binocular Stereo Microscope (SMZ171). The study will enhance our knowledge about the larval stages of the Ephydridae family in the Gomishan region (Golestan province), which is being reported for the first time. The importance of conducting specialist studies is emphasized in order to diagnose species using genetic and molecular methods in the future.

The excessive growth of the aquaculture industry, in addition to using more natural resources, causes a disturbance to the biological and non-biological balance through effluent releases, and water quality indicators provide the possibility of better management of pollution and direction for targeted biological monitoring. The purpose of this research was to evaluate the nitrogen load of the basin and rainbow trout breeding farm on the water quality of Zarin Gol River in Golestan province, Iran, based on a standard index (WQI) by measuring water quality parameters including: pH, total phosphate, temperature, nitrate, dissolved oxygen, turbidity, and total coliform. Sampling was done seasonally at five stations (before and after the first and second fish farm and 1000 meters downstream from the second fish farm) in 2018. The results showed that the concentration of nitrogen and phosphorus in the River during the six months of fish breeding on the second farm was estimated to be 16.5 tons of nitrogen and 2.9 tons of phosphorus. According to the WQI, the results showed that the water quality values in all the studied stations are 79.7 to 87.8, which indicates excellent water quality according to the descriptive table. It seems that under the current conditions, the Zarin Gol River has the ability to self-purification the effluent of two fish farms with the expected capacity.

The present study was conducted in order to monitor the water of the reservoir behind the Boostan Dam using the phytoplankton population and Palmer index for one and half years. The sampling was done seasonally in five stations from depths of 0.5 to 3 meters using One-liter Ruttner sampler. After identifying phytoplankton species; the Shannon-Wiener diversity index, Margalf richness index, Simpson index, Pillo's species uniformity index, and also Palmer's pollution index were determined. According to abundance, 5 phyllums were the dominant phytoplankton groups; Bacillariophyta (56%), Chlorophyta (23%), Cyanophyta (13%), Euglenophyta (4%), and Pyrophyta (4%). In this area, the Shannon-Wiener diversity index showed an average level of biodiversity. The highest value of the Pielou (0.88) and Simpson (0.95) indices were obtained in the summer. The lowest value of the Margalef index was calculated in the summer with a numerical value of 2.82. The results of Palmer's index showed that the water of reservoir behind the Bostan Dam is categorized at the level of very high organic matter pollution.

The aim of this study was to evaluate the environmental effects of growing rainbow trout Oncorhynchus mykiss (Walbaum, 1792) culture in cages. Data analysis was performed using information related to the storage of rainbow trout in floating cages located in the southern part of the Caspian Sea. The results showed that according to estimating the amount of nitrogen and phosphorus output of the studied cages and their concentration at a depth of 25 meters sea level, the maximum fish farming capacity in the cage is about 100 tons of biomass produced. In the study of the average effects by the Iranian Leopold method, breeding 100 tons of rainbow trout in sea cages has negligible and weak destructive effects. The results of this study confirm the maximum production capacity of about 100 tons in each breeding complex in the southern part of the Caspian Sea by maintaining a distance of at least 500 meters from other complexes.

In this study, the trophic status of the Bustan dam reservoir was investigated using Palmer and Carlson indices. Biological parameters including phytoplankton and environmental factors such as phosphate, nitrate and chlorophyll were sampled at the depth of 0.5 meter in five stations in three replicates seasonally in 2019, repetitions and Then the Palmer and Carlson indices were determined. The Palmer index in Bustan dam was estimated as 24, 31, 27.6, and 28.8in spring, summer, autumn, and winter, respectively.  According to the Palmer index classification, in all four seasons, Bustan dam water is in the category of water with high organic matter. The highest value of Palmer's index was obtained in summer (31) and its lowest value was obtained in spring (24). The highest nutritional status of Carlson's index was related to summer (60.46 eutrophication) and the lowest level was found inwinter (52.44 eutrophication), which indicates that the reservoir has moved to semi-nourishing condition in winter season. Also, the highest nutritionism status was observed in station 3 (54/23). According to Palmer's and Carlson's indices and the ratio of phosphate to total nitrogen, the main factor of nutritionism in the reservoir of Bustan dam was phosphorus compounds that enteres the reservoir from external sources of the dam and ultimately causes the decrease of water quality.

Dynamic energy Budget (DEB) theory describes the rate of energy absorb by living organisms and use it for body protection, growth, and reproduction. The present study was performed on Alburnoides eichwaldii in Zarrin-Gol and Kaboudwal rivers (Golestan province). The results showed that the DEB growth model in the two rivers and the allocation of energy fraction for body maintenance (κ) was more than 0.9, which indicates the high growth rate and short lifespan of this species. Maximum surface specific-area assimilation rate {pAm}  in Kabudwal river fish is about three times that of Zarringol River. Somatic maintenance based on body volume, pM  for Zarringol River is about 3 times and the maximum reserve density[Em]  is about 5 times less than Kabudwal. In Addition, maturity at birth EHb , In Zarringol river was less than Kabudwal and maturity at the time of reproduction EHp  in Zarringol river was more than Kabudwal but its size was bigger at maturity in Kabudwal river. On the other hand, the higher energy conductivity ϑ in A. eichwaldii in Zarringol River was due to its low energy density, and this fish in Zarringol River needs less energy to somatic maintenance. The DEB standard model is superior to other models in that it is able to provide quantitative and measurable descriptions for the aspects of individual and population metabolism of animals.

This study was conducted to investigate the possibility of breeding carp juveniles (Cyprinus carpio) in pen conditions in Gorgan Bay in two treatments with a density of 2 and 4 pieces per square meter in order to produce breeders for restocking centers. The first juveniles were raised in earthen ponds with concentrate feed. Then, with an average weight of 93.87± 32.66g, they were transferred to pens with an area of 50 m2each and 16 mm mesh size, in Gorgan Bay. 6 pens were considered for this research and for each treatment, 100 and 200 pieces of juveniles were considered in each pen. Feeding was done with concentrate feed and physical and chemical factors and biometry of fish were done regularly. The results showed 52% survival in first treatment and 49% for second treatment and the mean weight for two treatments were 410± 64.98 and 390±52.8. Results showed that there was no significant differences between weight and length in two treatments. The histological results showed that the male and female were mature in 4th stage. The eggs of the female fish were between 800 and 1200 microns in diameter.

Four streams with different sizes were selected for studying the effects of environmental factors on fish assemblages using indirect (Detrended Correspondence Analysis, DCA) and direct (Redundancy Analysis, RDA) gradient analysis in Golestan province. DCA of presence-absence and relative abundance data showed well gradient and linear model of species variability. In the within-site RDA, environmental factors explained 74.8 % variability for presence–absence data and 77.5% for the relative abundance data. Evaluation of two first axis of RDA showed that first axis has a high correlation with habitat characteristics and second axis correlated with channel morphology attributes. Based on RDA diagrams, Paracobitis malapterura and Capoeta capoeta gracilis presented in Zaringol and Tilabad Streams and had a high correlation with percent of in-stream vegetation and percent of cobble in first axis and low flow mean depth and low flow width in second axis. While Alburnoides bipunctatus and Neogobius fluviatilis had high correlation with percent of snag, pool and sand within streams. It should be stated that factors such as the size of the catchment, hydrographical and geomorphological characteristics, and land use change the morphology and stream habitats, and ultimately lead to the removal of some species in adjacent streams.

In order to evaluate water quality condition, biochemical oxygen demand (BOD), dissolved oxygen (DO), temperature, pH, turbidity, total suspended solid (TSS), phosphate (PO4 -), nitrate (NO3 -) and fecal coliform were measured seasonally from 9 sites from November 2009 to August 2010 in Zaringol Stream. Water quality condition was estimated using TOPSIS method. Comparison of TOPSIS values in different sampling stations showed the minimum (0.230) and maximum values (0.604) are in points 1 and 5, respectively. According this result, point 1 had the best water quality condition and point 5 had the lowest quality. Also, Seasonal results of TOPSIS values showed that the maximum value was found in spring. Discharge of effluents from land uses located along the stream specifically, trout farms and starting agricultural activity and production process in spring and summer are most important reasons for decreasing of water quality. TOPSIS estimates values ≤0.5 for almost stations and seasons. It shows Zaringol Stream has an average water quality.

In this study, 160 fishes were randomly collected from commercial catch by a cone net in Babolsar Port from January to October 2010. The biological features of specimens were measured. 2+ years old fishes made the dominant age group with 33.75% and 1+ and 5+ years old had the least frequency (8.75%). Relationship between length and weight indicated negative allometric growth pattern (b=2.581). The Von-Bertalanffy growth parameters were calculated as L=131.57 mm, k=0.26 and t0=-1.02. Growth performance index was 1.66 and the total mortality (Z), natural (M) and fishing (F) mortality coefficients were 0.9 year, 0.43 and 0.47, respectively. The exploitation ratio (E) was calculated as 0.52.

In this study, the distribution, abundance and some growth parameters of Spirlin, Alburnoides eichwaldii in the Tilabad stream in the Golestan province was studied over 2009-2010. A total of 535 samples of Spirlins were collected by catching with Electroshocker. A total number of 205 samples was analyzed and the rest of the specimens were released. Spirlin was found only in stations 1 and 2 (the Headstream and next station) while station 2 had the highest number of summer Sprilin (0.889 # m-2). Catched fish were in three age-groups: 0, 1+, and 2+ years old with the longitudinal range of 25.34-110.16 mm. The exponential relationship between length and weight in both sexes indicated negative allometric growth. Growth equation was Lt= 12.45(1-e-0.248(t+0.39)) and Lt= 11.66(1- e-0.281(t+0.39)) for females and males of Spirlin, respectively. Apparently, Spirlinin in the Tialabad stream has no biotic suitability and faces severe environmental stress.