نشریه پژوهش های ماهی شناسی کاربردی
سال نهم شماره 2 (تابستان 1400)

According to the reports of the International Panel Climate Change (IPCC) there is no doubt about climate change occurring. All ecosystems on the earth have being concerned by the effects of climate change. Urmia lake basin and its rivers exposed to numerous anthropogenic stressors such as hydrological, morphological, connectivity and water quality pressures. The main objective of this study is to determine the effects of climate change on Acanthalburnus urmianus (Günther, 1899) distribution under optimistic and pessimistic scenarios in 2050 and 2080. For this purpose, Species Distribution Modelling (SDM) method was used. In the beginning, any data related to fish observation as well as environmental variables like elevation, slope, maximum air temperature, range temperature, precipitation and maximum width were collected. And then, with different models including GLM, GAM, GBM, RF, CTA, FDA, MARS, ANN and SRE as well as Ensemble model (in order to reduce the uncertainty), the potential distributions of A. urmianus at the scale of Lake Urmia basin and Iran with above mentioned climatic scenarios were predicted. The results indicated that climate change affects on the distribution of A. urmianus under all optimist and pessimistic scenarios and in contrast to  2050 in both scenarios, reduction in distribution in 2080 was observed.

251 specimens of kutum fish caught by bony fish persine on the southern shores of the Caspian Sea (Mazandaran) during the years 2017-2019 were studied to study the growth trend of this species. In this study, maximum estimated length (L∞) and annual growth coefficient (K) of kutum fish were estimated 71.79 cm and 0.13, respectively. The results of natural reproduction of this species in Kheirud river with a length of 2 km showed that in 2017-2018, more than 30,000 breeders (female) of anadromous fish migrated to Kheirud river for reproduction and more than 97% of it were kutum fish. As a result of this study, more than 525,000 kutum fish fry were produced and prepared to migrate to sea. (2017-2018). The results showed that the partnerships of fishermen and local rural communities can have a positive effect on the natural reproduction Influence coefficient of kutum fish (P <0.05). The results showed that the penetration coefficient (effectiveness) of fishermen (35%) and rural women (30%) ) were more than the students' effectiveness (16.7) (P <0.05). Thus, by protecting the natural reproduction of kutum fish, other species of anadromous fish have reproductive successes in the Kheirud river, which will establish the desired ecological balance and exploit the ecological carring capacity of the ecosystem.

The aim of this study was to investigate the effect of fish size and seasonality on the epidermis structure and protein profile of the skin mucus of Rainbow trout. Skin mucus samples were collected over three consecutive season periods including late winter, mid spring and early autumn. In each season, sampling was performed separately from three different weight groups including 2-20 gr fish (W1), 100-200 gr fish (W2) and 400-600 gr fish (W3). The results of histological analysis showed that goblet cell density and epidermal thickness increased with increasing temperature from winter to autumn in all weight groups. In juvenile (W1 fish), the size of goblet cells was not affected by the season, while in larger fishes (W2 and W3), the size decreased with increasing temperature in the autumn. There was a positive and significant relationship between fish size and density of goblet cells. Biochemical analysis of skin mucus showed that protein concentration increased simultaneously with an increase in goblet cell density. The protein profiles of rainbow trout mucus showed seasonal variations in all three weight groups. In autumn, the small proteins with molecular weights less than 35 kDa were more prominent, while these proteins were not observed in the winter. There were no significant differences in the mucus protein profile among different weight groups

Fish sardines play a key role in the primary chain of production in the sea, and unknowing harvesting of them causes irreparable damage to the marine ecosystem. Also, genetic studies can help preserve biodiversity and take steps to protect the reserves. In this research, the population dynamic of the Amblygaster sirm and it,s the maximum sustainable yield (MSY) were surveyed and calculated and finally, genetic markers were used to evaluate its genetic diversity. This study was conducted in the Persian Gulf and the Oman Sea (Hormozgan and Busher Provinces) in Bandar-e-Lengeh to the Jask ports. Sampling was carried out monthly during 2014-2015. The results showed that fish has negative almeteric growth pattern and infinity fork length was 11.29, and growth coefficient of 1.4/year, natural mortality was high (M=2.3 ind/year) and exploitation rate was 0.49, biomass and MSY were evaluated 43.3 and 41.3 tons. The genetic results showed that samples of A.sirm in the Delvar area (Bushehr) were completely isolated from other samples of other areas. Samples of the Bostane and Garze stations are more similar to each other, and samples of the Delvar station are far more than them.  In general, due to the high natural mortality of A.sirm, it seems that the fish catch ration is in suitable situation.

During 2019, the length-weight, length-length relationships and condition factor of Caspian kutum, Rutilus kutum  (Kamensky, 1901) were studied by catching a total of 339 specimens were collected from Chelvand, Khalehsara, Sefid, Khoshk and Shir rivers, Anzali Wetland and Turkmen Shores of the Caspian Sea basin. The equation W =aTLb was used to calculate the length-weight relationship, FL=a + bTL for the length-weight relationship, and K= (W / L3) × 100 to calculate condition factor. The b-value were estimated from 2.47 to 3.17 and condition factor from 0.85 to 1.01. Maximum and minimum parameter of b-value and condition factor were related to the Khoshk River, Torkman shore and Anzali wetland and Sefid River, respectively. In addition, the growth pattern was positive allometric for the Chelvand, Khoshk and Shir populations, isometric for the Khalesara population and negative allometric for others.

Microplastics are known to be emerging contaminants and there are widespread concerns about their potential toxic effects. Histopathological study is one of the appropriate methods in diagnosing the effects of environmental pollutants on aquatics. In this study, the accumulation and adsorption of polystyrene microplastics (PS-MPs) in the gills of Goldfish were identified and its toxic effects on gill histology were investigated. A total of 232 healthy, productive fish, with an average weight of 18.55±2.41 g, were selected. Microplastics were synthesized in two size ranges (0.25 and 8 μm) with two different functions (fluorescent and non-fluorescent). The experiments were performed in two stages. Initially, after the adaptation period, 64 fish were exposed to a constant concentration (PS-MPs) of 300 µg/L of both sizes (0.25 μm) and 8 (PS-MPs) fluorescent. Gill tissue was sampled at 24, 48 and 168 hours and samples were taken using a fluorescent microscope. Then, to determine the histopathological lesions, 168 fish were exposed to non-fluorescent microplastics at different concentrations (0,0.05, 0.5 and 5 ppm) for 28 days and were analyzed for histological lesions. After 168 hours of exposure at 300 µg/L of fluorescent particles, it was found that both dimensions (0.25 and 8 μm) were accumulated in gill tissue. The highest concentration of MP particles accumulated in gill tissue averaged in particles with dimensions of 8 (0.701±  0.098) μm and 0.25 (0.272 ±  0.046) μm, was determined as μg of gill dry weight per milligram. Examination of gill pathology revealed complications such as lamellar aneurysm, secondary blade epithelium protrusion, lamellar deviation, secondary blade connection, lamella shortening and paving in both size groups compared to the control group, but the severity of complications was different in each concentration. It can be concluded that although microplastics have accumulated in the gills of fish and have affected tissues, their potential toxic effects are largely unknown and further studies are needed.

This study was conducted to survey the feeding indices of Garra rufa in Gheshlagh River, Kurdistan Province. Seasonal sampling carried out during spring, summer, autumn and winter of 2018 using electrofishing and cast net with 20 mm mesh size. For diet analysis, 40 number of Garra rufa was used. The length and weight of sampled fishes was renged of 56 to 137 cm and 2.5 to 37 g, respectively. The average of RLG index was 8.22±2.25 that specified the herbivory or prephyton feeder. The mean of gastro- somatic index, condition factor (K) and vacuity index (CV) was 11.67±5.28, 1.35±0.23 and 10 respectively. Also, according to the percentage of food groups in the environment and gastrointestinal tract of fish, it was observed that this fish is more inclined to Nitzschia, Gomphonema, Amphora, Cocconeis, Rhabdoderma and Diatoma genera for feeding, respectively and They are the most preferred food items for this fish during the sampling seasons and the genus Ocillatoria with a value of -0.8 had the lowest priority. The genera Cocconeis, Cymbella, Diatoma, Gomphonema, Melosira, Nitzschia, Synedra and Navicula as the main food, The genera Cyclotella, Pediastrum, Stephanodiscus, Cymatopleura, Gyrosigma, Gloeotrichia and Spirulina as the supplementary food and the genera Amphora, Chlorella, Cosmarium, Ocillatoria, Rhabdoderma and Scenedesmus as the incidental food of Garra rufa

Temperature fluctuation is one of the most common stressors during fish transportation and aquaculture condition. Triploid rainbow trout (Oncorhynchus mykiss) get more attention because of its sterility. In this study, 24 rainbow trout belong to diploid and triploid group, average weight 13±0.23 g were subjected to temperature change from 13 to 20 ºC, and kept under tension for 10 min. Before applying the tension and 24 h after, blood samples were taken from 5 individuals from each ploidy groups and some haematological parameters were analysed. Temperature tension caused significant reduction in red blood cell (RBC) counts and haematocrits in both diploid and triploid fish, where the RBC were reduced from 1.25 × 106 cells to 1 and 0.9 × 106 cells in diploid and triploid groups, respectively (P<0.05). On the other hand, the haematocrits levels were reduced up to 25% in both groups after tension applied. While, there were no significant changes observed in white blood cell counts and hemoglobin levels in diploid, the significant changes were visible in triploid ones (P<0.05). The results showed that triploid rainbow trout affected more than diploid ones by thermal stress. Study on some other common stressors on triploid fish were highly recommended.