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Background: The Caspian Sea is surrounded by Kazakhstan, Azerbaijan, Iran, Turkmenistan, and Russia. Rutilus kutum is a highly steamed fish species caught from the South Caspian Sea, but little data available on Trace Element (TE) concentrations in its skin. Methods: We caught 51 R. kutum from three stations (i.e., Anzali, Astara, and Kiashahr) in the southern shoreline of the Caspian Sea from September 2017 to January 2018, and ICP-OES was used to assay TE concentrations in their skin. Results: The Trace Element Concentrations (TECs) measured in the skin (except for potassium) did not display significant differences between the stations and only the concentration of potassium was higher in Kiashahr than in other areas. Conclusion: TE levels in the R. kutum skin were lower than those in the previous reports from the Caspian Sea, which could not result in any risk to human health.

Elements are the shared result of the erosion of rocks in the catchment area and human activities. Nutritional habits, ecological needs, heavy metal concentrations in water and sediment, duration of fishing in the aquatic environment, fishing season, and physicochemical properties of water (salinity, pH, hardness, and temperature) are among the effective factors in the accumulation of heavy metals in various fish organs. In this study, 150 specimens of Rutilus kutum were collected from the southern shores of the Caspian Sea including Astara, Anzali, and Kiashahr in Guilan Province, Farahabad in Mazandaran Province, and Bandar Torkaman in Golestan Province from December 2018 through October 2019. It is possible to predict the metal concentrations using the variables such as fish tissue, sampling region, and season. Akaike information criterion (AIC) was used to select the best regression model. We used fish muscle tissue and Anzali sampling site which were considered reference variables in the regression model. For some elements, a better model is obtained by considering all variables (AIC criterion is its lowest value). The best model obtained for Cu, Mn, and Si was only with region (as a variable). The best model obtained for Sn and Sr only concerns the region and tissue variables. The best model obtained for Sb only related to tissue variable. Using these models, environmental monitoring becomes easier and cheaper. We suggest further studies to be carried out in the shortest possible time along with the least laboratory cost.

Benthic diatom assemblages on the natural substrata at Balikhli River (northwest Iran) were investigated monthly. A total of 96 samples were collected from epilithic and epipelic substrata. A total of 110 taxa from 49 genera were identified. The most abundant diatom species were Cyclotella meneghiniana, Diatoma moniliformis, Nitzschia inconspicua, Planothidium lanceolatum and Gomphonema olivaceum. Non-metric multidimensional scaling (nMDS) analyses revealed explicit differences between diatom communities of stony and sediment substrates. Although common diatom taxa were not restricted to single substrates, some taxa had higher tendencies to every substrate. The nMDS analysis also showed differences between summer and autumn samples. Canonical correspondence analysis (CCA) of groups resulted from cluster analysis, showed that the nutrient concentration gradient, pH were the most important factors affecting the composition of diatom assemblages and species distribution. In our study orthophosphates had greater effect than nitrates, and Gomphonem parvulum and Navicula recenswere found in phosphate rich samples. Anthropogenic input including agricultural and domestic wastes may be responsible for high levels of these parameters. Alkali volcanic rocks and limestone sediments underlying the watershed could explain the high pH in the Balikhli River. In total 67.5% of the identified species in the river are considered as alkaliphilous. The findings of this study denote that the main determinants of variation in benthic diatom communities of Balikhli River result from a combination of land use patterns caused by human activities, river hydrology and natural phenomena including geology.

Caspian kutum, Rutilus kutum Kamensky 1901, is a commercially important fish species in the southern basins of the Caspian Sea. In spite of the popularity and consumption of the gonads, muscles, and viscera of kutum as edible parts in the region, there is no report on concentrations of trace elements (TE) in its gonads. In this study, some 51 specimens of R. kutum caught from five different fishing regions (Astara, Anzali, Kiashahr, Sari, and Gorgan) in the southern shoreline of the Caspian Sea from September 2017 to January 2018. An inductively coupled plasma optical emission spectrometry (ICP-OES) was used to assay 36 element concentrations in fish gonads, but only 26 elements were detected and statistically analyzed. The concentration of elements in gonads (except for Ca, Sn, and Sr) did not exhibit significant differences between the eastern and western parts (p

This study investigates acute toxicity and histological effects of Lindane insecticide on intestinal tissues of immature grass carp (Ctenopharyngodon idella). For these purposes, 105 fish were exposed to different concentrations of Lindane for 96 h in 5 groups with 3 replications. Samples of intestinal tissues were prepared in both control and exposure groups during and after the toxicity test. Vaculation, necrosis, bleeding and epithelial degeneration were apparent in the intestine tissue of treated individuals. The LC50 96 h of Lindane was 0.788 ppm in the present study, also the results showed besides pesticide-induced lesions, symptoms of abnormal swimming, anxiety, tendency to swim near the surface, and death due to terminal toxicity with mouth widely open. The exposed fish were pale in color, showed oxygen deficit and severe respiratory problems. Overall, our results confirm the toxicity of different concentrations of Lindane insecticide affecting behavior, intestinal function and inducing tissue lesions of immature grass carp.

The aim of this study was to investigate the occurrence of microplastics (MPs) in the gastrointestinal (GI) tract, muscle and gonads of 193 individuals of nine commercially-important fish species from Anzali Wetland between May and July 2018. Tissues were removed, digested by 10% KOH for 24 h at 60 °C, filtered on cellulose nitrate filter and then dried. MPs were found in all tissues. There were significant differences between the numbers of isolated particles from GI tract and control groups (procedural blank containing Milli Q water without tissue), while their abundance in the muscle and gonads did not display significant differences with control groups. Higher abundances of MPs were recorded in omnivorous fish (2.26 ± 2.93 items/individual) than carnivorous species (1.10 ± 1.10 items/individual) (P 0.05). MPs were ranged from 20 to 4800 μm in size and were dominated by fiber-like in shape, polyethylene in polymer and black in color.

The present contribution gives a faunistic overview on the distribution of Caenidae in Iran. Four species have so far been reported, of which Caenis macrura Stephens, 1835 by far is the most abundant and most widely spread species. Caenis kopetdagi Kluge, 1985 was previously only known from three localities in the Kopet Dag Mountain range, which stretches along the border between Turkmenistan and Iran. We report this species from three further localities at the western border of the Zagros Mountains in southwest Iran, thus considerably expanding its distribution. The nymph of Caenis kopetdagi is re-described, its validity is confirmed, and modern diagnostic characters are added. Its CO1 sequence is provided and compared with sequences of other species of Caenis Stephens, 1835 occurring in the Middle East. The habitat of C. kopetdagi as well as the distribution of Caenidae in Iran and of Caenis in the Middle East is also discussed.

This study aimed to investigate the ecological risk assessment of Khamir, Tiyab, and Jagin estuaries and the impact of anthropogenic activities on these ecosystems during a one-year study period (April 2015 to March 2016) using trace metals as pollution indices. The sediment samples were collected from nine sampling stations, following a gradient of contamination from the industrial wastewater and shrimp farming effluents to the less impacted stations. Pollution indices (i.e. PERI and PLI) were applied to ascertain the sediment quality. Based on pollution indices, the overall pattern of environmental quality status demonstrated that industrial sewage and shrimp farming effluents are major sources of pollution in the Khamir and Tiyab estuaries, respectively. The sediments in the most stations in studied coastal ecosystems of Iran posed moderate or considerable ecological risk. Results from this study showed that Zn, Pb, Cu, and Cd were mostly derived from anthropogenic activities such as domestic sewage and industrial effluents. Also, the findings of this study revealed that the pollution indices are suitable for evaluating the environmental situation of coastal ecosystems and the separation of areas with less impacted by human activities from areas affected by these activities and could be used as a robust management tool for monitoring programs in coastal areas. Altogether, these findings could be useful in providing more effective and targeted strategies of development better management practices for coastal areas.

The occurrence, abundance and distribution of microplastics (MPs) were studied in sediments and surface waters of the Anzali coastal wetland, southwest of the Caspian Sea. Sediment and surface water samples were taken at 11 and 6 stations in June 2018 and January 2019 respectively. The abundances of MPs in sediment samples were 140–2820 and 113–3690 items/kg dry weight while in surface waters were 0.40–4.41 and 0.19–2.85 items/m3 in June and January respectively. Fiber was the most common shape, followed by fragment and film. Red, black and blue were the most frequent colors. Particles 1–2 mm were the dominant size. SEM/EDS and ATR-FTIR analyses were used to identify MPs. Polypropylene, polyethylene and polyester were the most frequently found polymers. Our results highlighted the widespread dispersion of MPs in Anzali Wetland which in turn might be a pathway of MPs pollution transporter to the adjacent and connected Caspian Sea.

An initial checklist of mayflies (Ephemeroptera) of Iran is compiled based on critical review of available literature data, complemented with new data from 38 localities of Gilan and Ardabil provinces. At present, altogether only 46 species and 25 genera are known from Iran, 18 species are reported as new to Iran in this study. Some previously published data are critically evaluated and doubtful taxa are excluded from the list. Basic analysis of the distribution and biogeography of recorded species is given. Procloeon (Pseudocentroptilum) caspicum Sroka, sp. n. is described based on mature larva and egg. Critical differential diagnostic characters distinguishing the species from related taxa are discussed in detail.

The pre sent study analyzed the relationships of two different biological assemblages (diatom and macroinvertebrate) when they are used to characterize a set of stations (from reference stations to impacted stations) within the Shahrood River. In particular, we examined the issue of concordance among these assemblages and the physicochemical parameters detected, using both multivariate and multimetric methods. In addition, the trophic diatom index and Hilsenhoff family-level biotic index for macroinvertebrate assemblages were used to evaluate the ecological status of the Shahrood River. Diatom and macroinvertebrate assemblages in the Shahrood River differed significantly between reference and impacted stations. ANOSIM showed a significant difference in the composition and abundance of diatoms and macroinvertebrates among reference, influence and impact stations, especially between reference and impact stations. Results of CCA ordination showed that benthic diatoms and macroinvertebrate assemblages were mainly affected by DO, TSS, NO3 −, PO4 3− concentrations and heavy metals such as Zn and Cd. Biotic indices for the Shahrood River suggested a water quality category of “fair” with fairly substantial organic pollution for the impacted stations. Finally, our results suggest that an appropriate management and restoration policy needs to be implemented for the Shahrood basin.

The size and number of chloride cells and serum ion concentrations in kutum, Rutillus frisii kutum Nordman, from brackish (Caspian Sea) and fresh water (Khoshkrood River) environments were studied to gain a better understanding of osmoregulation in this species. Twenty mature kutum specimens were collected from the Caspian Sea (Anzali coasts, 8.49 ppt salinity and 12.4°C temperature) and 20 specimens from Khoshkrood River (0.18 ppt salinity and 18°C temperature). Gill samples were analyzed histologically and concentrations of Na+, Cl- , K+, and Mg2+ ions were determined in the blood serum. Concentrations of Na+, Cl- , K+, and Mg2+ ions and osmotic pressure in mature kutum from brackish water were significantly higher than in specimens from fresh water. The average size and number of chloride cells in the fish from seawater were considerably larger than those from fresh water. The mean size of chloride cells was 6.89 ± 1.16 μm in brackish water samples and 5.1 ± 0.81 μm in river samples. The average number of chloride cells in brackish and river water samples were 16.92 and 6.57, respectively. The density and size of chloride cells increased with increases in salinity

Danube bleak Alburnus chalcoides (Guldenstadt, 1772) is a commercially important fish species in the southern part of the Caspian Sea. However, little is known about the concentrations of trace element (TE) in its muscles. To address the issue, we caught 77 A. chalcoides specimens at three different fishing regions (including Astara, Anzali, Kiashahr) of the southern shoreline of the Caspian Sea from September 2017 through June 2018. An inductively coupled plasma optical emission spectrometry (ICP-OES) was used to measure element concentrations in fish muscle and liver tissues. In the case of liver, 27 elements were detected. So that, 9 elements including Ag, Ba, Be, Ce, Co, Sc, U, V and Y which were not detected in liver. In the case of muscle tissue, 22 elements were detected and 14 elements including Ag, Ba, Be, Bi, Cd, Ce, Co, La, Li, Sc, U, V, W and Y. The element values in the muscle of A. chalcoides were significantly lower (p

This study evaluates the impact of anthropogenic activities on the Shahrood River using water physico-chemical variables and macroinvertebrates data sets obtained over a period of 12 months between February 2012 and February 2013 at 8 sampling sites. Biotic indices i.e. FBI and BMWP based on macroinvertebrates and physico-chemical indices (MPI, HPI and NSF-WQI) were employed to evaluate the water quality status in connection with natural- and human-induced pressures. Based on physico-chemical indices, water quality was categorized as low polluted level and it is suitable for drinking purposes. The water quality based on biotic indices was related to the anthropic activities; a clear deterioration of the water quality was observed from upstream to downstream sites. The water quality along the river changed from very good (class I; reference sites) to good (class II; midstream sites) and turned into moderate (class III) and poor (class IV) quality (downstream sites). These findings indicate that biotic indices are more powerful indicators in assessing water quality than physico-chemical indices. Allocapnia, Glossosoma and Hesperoperla were exclusively related to least disturbed sites, and Naididae, Orthocladiinae and Ecdyonurus were found in sites showing notable degradation. Our results recommended that the use of macroinvertebrates could be employed as a cost-effective tool for biomonitoring and controlling of polluted riverine ecosystems in the Middle East. Finally, the results from this study may be useful not only for developing countries, but also for any organization struggling to use macroinvertebrate based indices with restricted financial resources and knowledge.

The demographic variables of pike (Esox lucius ) were studied at the southern edge of the species' distribution in the Anzali Wetland, south-western Caspian Sea. The main aim was to provide data for the assessment of the stock and to explore possible fisheries management measures such as setting minimum landing size based on length-at-maturity. Pike collected from commercial landings ranged from 15.4 to 75.4 cm in fork length (FL), from 52.9 to 3462.5 g in weight and were between 0 and 8 years old. Von Bertalanffy growth function parameters were L∞ = 90.6 cm FL, k = 0.12 yr−1 and t 0 = −1.74 yr−1 . Male pike matured at 1–2 years with L 50 of 28.6 cm FL, whereas females matured at 2–3 years with a L 50 of 33.9 cm FL. Instantaneous total mortality (Z ) was estimated as 0.93 yr−1 , while fishing mortality (F ) was estimated to be 0.66 yr−1 . Yield-per-recruit analysis indicated that pike in the Anzali Wetland seems to be growth-overfished under the current fishing regime with no management measures, and substantial increases in yield could be achieved by increasing the length at first harvest. The results indicated that management actions such as enforced legislation are required to obtain a better stock status and higher yield. Management could be more effective if the number of fishers and their catch could be controlled, e.g., through the allocation of fishing licenses.