One of the major global concerns about the environment is the pollution of aquatic ecosystems by heavy metals. These elements contaminate aquatic environments and accumulate and concentrate at through bioaccumulation in the tissues of living organisms at higher levels of the food chain consumed by humans. The aim of this study was to investigate the concentrations of three heavy metals, lead, nickel and cadmium, in the muscle tissue of two species of fish Otolithes ruber and Sphyraena forsteri in the fishing ports of Konarak and Pozm were investigated. 36 fish samples were collected from Konarak and Pazm ports. After preparation of the samples, the concentrations of lead, nickel and cadmium were measured by acid digestion by Contr-AA-700 atomic absorption spectrometer. Based on the results of the study, the amount of hravy metal accumulation was different between the samples of the two regions. The amount of lead in the muscle of Otolithes ruber and Sphyraena forsteri was 0/59±0/12 and 0/55±0/2 respectively, and the cadmium concentration was 0/07±0/15 and 0/09±0/1 mg/kg, respectively. Also, the amount of lead and nickel in Sphyraena forsteri was less than Otolithes ruber. Concentrations of lead and cadmium in the muscle tissue of Otolithes ruber and Sphyraena forsteri less than the standards of the UK Department of Fisheries and Agriculture (MAFF), the US Food and Drug Administration (FDA), the Food and Agriculture Organization (FAO) and the US Environmental Protection Agency (USEPA). Except for the concentration of nickel, which was higher than the WHO standard.

Chlorophyll-a indicates the biomass of phytoplankton as the primary production. Chlorophyll-a changes indicate the situation of the ecosystem. The present study was conducted for monitoring it in the northern part of the Persian Gulf and ​​Oman Gulf. For this purpose, CTD and NASA site information was used. Samplings were done from January-March 2018-2021. Mean southern waters chlorophyll-a in 2018 was (0.97±0.84 mg/m3) mean southern water’s surface chlorophyll-a was (1.98±1.48 mg/m3) in 2019. The mean su rface chlorophyll-a of Oman Gulf in 2020 was (0.92±0.334 mg/m3). The mean of chlorophyll-a in the Persian Gulf in 2021 was (0.23±0.13mg/m3). The data result of NMDS showed significant differences between the two groups: (Bushehr, Hormozgan, Sistan & Blochestan, 2019) in comparison (Bushehr and Khuzestan, 2021). Mean surface chlorophyll-a in the first and second groups were (1.09±1.5 mg/m3) and (0.13±0.16 mg/m3), respectively. This significant difference and the greater biomass amount of the first group were due to floods and discharge of nutrients in March-April of 2019, and Nutrients will provide suitable conditions for phytoplankton’s growth.

According to the importance and position of fish for human protein supply, studying pathogens and more familiarity with their parasitic diseases can be a step towards improving the knowledge of parasitology in the country. The aim of this study was to identify the metazoan parasites of the Indian mackerel (Rastrelliger kanagurta) caught from the coasts of the Oman Sea in the Chabahar region. In the present study, 61 pieces of R. kanagurta were caught in summer 2019. The fish were transported to the laboratory and their length and weight were measured. Different organs of the fish such as gills, eyes, stomach, pyloric caeca, gonads, and intestines were examined for isolated parasites were stabilized in alcohol 70% and/or formalin 10%. The identified parasites were from the digene category and including Lecithocladium angustiovum and prodistomum orientale with frequency of 100% and 26.4%, respectively, from the category of monogenic parasites, Indomazocraes sp. And another example of the family Mazocraeidae, both with prevalence of 1.9% and from the nematode genus, the larvae of the parasite Anisakis sp. were identified with a prevalence of 1.9%.The results showed that the digenean parasite Lecithocladium angustiovum had the highest severity of infection in the stomach (16.1±17.3). In this study, according to the results, the identified parasites included two digens at the genus and species levels, a monogenean at the genus level and another in the family of flatworm branches, a nematode at the genus level in roundworm branch. This is the first report of the Indian mackerel parasites from the Oman Sea coast. Also, the parasites of Prodistomum orientale, Indomazocraes sp. and a specimen belonging to the family Mazocraeidae are reported for the first time of this fish from the coasts of Iran.

Nesarud and Kheyrud rivers are important rivers in Mazandaran province that are important in terms of having special populations of fish, spawning of migratory species and feeding of estuarine fish. The aim of this study was to evaluate the microbial quality of water in Nesarud (shilling) and Kheyroud (natural reproduction) rivers from April to August 2018 and microbial factors including total bacteria, total coliform, fecal coliform and fecal streptococcus were evaluated. For this purpose, 4 stations along the route of Nesarud and Kheyrud rivers were selected and monthly for sampling of river water was performed for 4 months (April, May, July and August). Based on the obtained results, the maximum changes in the average total bacterial count of Nesarud (20250 CFU/ml) and Kheyrud (21250 CFU/ml) were achieved in May and the maximum changes in the average total coliform of Nesarud (45 CFU/ml) per month. May and Kheyrud (50 CFU/ml) were reported in April and the range of mean changes in fecal coliforms in different months in Nesarud rivers (10 CFU/ml) in May and Kheyrud (8.5 CFU/ml) per month April was variable. According to studies, the water quality of the Nesarud and Kheyrud rivers is suitable for shill formation and natural reproduction in terms of bacterial indices and the number of bacteria was in the standard range.

Changes in river ecosystem conditions, including dam construction, provide new ecological conditions for the inhabitants of these ecosystems that must adapt to survive. This study was conducted to investigate the effect of Taleghan Dam on the suitability indices of Barbus cyri based on the Kernel smoothing method during 2018-2019. The environmental factors, including water depth, velocity, river width, pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), slope, elevation, bedrock diameter, and the number of rocks larger than 15 cm are measured and recorded. The Root-mean-square deviation related to bandwidth from 1 to 1000 was examined for each environmental factor. The results showed that increasing elevation, river width, velocity, EC, and TDS decrease the suitability of the studied species, and the suitability increased by increasing depth, slope, temperature, and pH. Some factors, including depth, river width and water temperature had many changes. In conclusion, the downstream conditions of the dam were better in the habitat suitability of Barbus cyri than the upstream region.

In this study, in the first phase, the optimum extraction conditions of the extract (temperatures of 50, 70 and 90°C, duration of 20, 70 and 120 min and the ratio of dry matter to solvent of 10, 20 and 30 mL/g) algae Nannochloropsis oculata was examined. The antioxidant activity of the algal extracts in the first phase was calculated by measuring the radical inhibitory power of DPPH (2, 2-diphenyl-1-picrylhydrazyl). In the second phase, the effect of adding the hydroalcoholic extract of N.oculata at 0, 350, 550 and 1000 mg/L in reducing the antioxidant activity of tuna oil was investigated. Treatment time of 120 minutes, temperature of 70°C, and dry matter to solvent ratio of 30 ml/g had the highest efficiency of the extract in terms of free radical scavenging.. The storage time was 56 days and the parameters of peroxide, TBA, and p-anisidine was measured in the tuna oil on 0, 7, 14, 21, 28, 35, 42, 49 and 56 days. The highest antioxidant power was measured at 1000 mg/L (85.45±0.55%). The index values ​​of peroxide, TBA, and p-anisidine of the tuna oil had an increasing trend with increasing in the storage time and reached its highest levels on day 56. The control group had the highest and the fish oil treatment 1000 mg/L hydrochloric extract of N. oculata had the lowest levels of oxidative indices. According to the results of treatments receiving hydroalcoholic extract of algae Nanochloropsis protective factor and antioxidant power compared to BHT, which shows that algal extract in all three concentrations of 350, 550 and 1000 mg/L can be well replaced with synthetic compounds.

This study aims to investigate the profile of sterols and fatty acids of four species of molluscs (rock oyster bivalve; Saccostrea cuculate, clam bivalve; Callista umbonella and cylindrical clam; Solen vagina) and one edible snail species. (Ampullaria cuprina) and determining the best mollusc species of Qeshm beach has been designed. Mollusc species (100 each) were kept in cold boxes with ice and transferred to the laboratory, and the content of fatty acids and mollusk sterols were analyzed with the help of gas chromatography. The highest amount of myristic acid (14:0), lauric acid (12:0), pentadecanoic acid (15:0), heptadecanoic acid (17:0), stearic acid (18:0) and total saturated fatty acids in snail Edible and lowest myristic acid (14:0), palmitoleic acid (16:1), pentadecanoic acid (15:0), heptadecanoic acid (17:0) and stearic acid (18:0) in rock oyster bivalves was observed. The lowest amount of cholesterol and the highest amount of 5 and 12 stigmadranol, campastonol, stigma sterol, delta 7 campestrol and delta 5 onasterol were also observed in edible snail. This study emphasized the difference in the profile of sterols and fatty acids of four selected mollusk species, and the best profile of sterols and fatty acids was observed in the edible snail, which can be suggested for the production of various health products in the pharmaceutical and food industries.

Considering the importance of using biosorbents to remove metal ions from wastewater and aquatic ecosystems, in this study the potential of using scales of two fish species (rainbow trout; Oncorhynchus mykiss and Caspian kutum; Rutilus kutum) to reduce the concentration of lead in aquatic environments were evaluated based on Box-Behnken design. The effects of some important parameters (biosorbent dose, biosorbent size, contact time, temperature, initial concentration, pH and salinity) on the adsorption capacity of the biosorbents were also evaluated. Among the seven studied factors, the effect of initial concentration, pH and adsorbent dose on the concentration of lead adsorbed by the two adsorbents was significant (P<0.05), while temperature and adsorbent size had no significant effect on the adsorption of lead by the sorbents. The initial concentration was the most effective independent variable (with a positive effect). The maximum adsorption capacities of lead by the two adsorbents are comparable to those of other adsorbents of aquatic origin, evaluated by other researchers. The maximum adsorption capacity of lead by scales of rainbow trout was higher than Caspian kutum. The characteristics of the adsorbents before and after adsorption were analyzed by SEM, EDX, XRF and FTIR. The lead ion concentrations were measured using AAS. The SEM-EDX and XRF analyses clearly revealed the presence of lead ions on the surfaces of both biosorbents after the adsorption experiments. The FTIR results showed that the two sorbents are composed of different functional groups, which could possibly play a significant role in their lead uptake capacity.

To evaluate the performance of small-scale fishery, biometric data and catch indicators of gillnets and longline from artisanal dhow in the coastal waters of Sistan and Baluchestan province, and pole and line fishing from the tuna tagging cruise in coastal waters of Oman was analyzed. The yellowfin tuna was the predominant species of the catch composition for gillnets and longline with 71% and 79% of fishing weight, respectively. Yellowfin tuna was the only species caught by pole and line. Catch per unit effort (CPUE) was obtained in accordance with the fishing method. On the same scale, the catch by weight of yellowfin tuna per fishing day from pole and line was almost 3 times more than the gillnets and almost 4 times more than the longline. On the other hand, the catch of yellowfin tuna by gillnets per each fishing day showed only 33% more than the longline. The yellowfin tuna catch index of longline and pole and line in the Oman Sea is comparable to the values obtained in the Indian Ocean region. The size of the fish in the longline was larger than the pole and line and gillnets, with the average length of 133±7.0, 105.0±3.7, and 94.4±4.4 cm for the respective fishing method, and the average weight corresponded to the length was calculated 40.8±2.2, 20.8±0.7 and 15.4±0.7 kg. It is recommended to use the pole and line fishing method as well as the development of longline for exploiting valuable resources of yellowfin tuna in the area.

Over the past years, eutrophication due to human activities has been recognized as a major ecological problem for the coastal areas, which in turn leads to significant changes in physicochemical and biological factors. The aim of the present study was to determine the eutrophication status of the Gorgan Bay, which was evaluated using the Carlson index as one of the efficient methods for assessing the eutrophication status of water bodies. The Gorgan Bay is located in the southeast of the Caspian Sea. The sampling was carried out in 23 stations with three replications seasonally from summer 2018 to spring 2019. Nitrate, phosphate, chlorophyll α, depth, and transparency were measured in each sample. Carlson's index in terms of chlorophyll α showed that the bay is in the eutrophic status in three seasons including summer, autumn, and winter (with the numbers 53.48, 53.69, and 53.67, respectively), and the mesotrophic status in spring (with the number 42.75). In terms of phosphate concentration, the bay was eutrophic in autumn and winter, and in summer (69.22 and 55.17) and oligotroph in spring (26.75 and 35.30), while in terms of transparency the bay was categorized as eutrophic in all seasons (63.33, 61.61, 69.93 and 61.58, respectively). In general, the results showed that the bay is in the range of mesotrophic to eutrophic status and therefore, more conservation management of this unique ecosystem is essential.