جستجوی مقالات مرتبط با کلیدواژه "caspian sea" در نشریات گروه "شیلات"

The aim of this study was to determine the optimal salinity for rearing the juveniles of Starry Sturgeon (Acipenser stellatus) in enclosed environments. Sturgeon with an average initial weight of 54.11 ± 1.54 g were raised in 500-liter fiberglass tanks (average temperature 22.58 ± 0.14 °C)in a control group (freshwater) and two treatment groups (6  and 12 ppt) in 3 replicates for 60 days. They were fed with commercial feed (Faradaneh) twice a day. At the end of the rearing period, specific growth rate (SGR), weight gain (WG), condition factor (CF) and hepatosomatic index (HIS) in experimental fish (12 ppt) were significantly elevated compared to control fish (p≤ 0.05). Food conversion ratio (FCR), on the other hand, was significantly reduced in the experimental fish (p≤ 0.05). The survival rate of fish was 100%. Intestinal villi length and internal space were significantly elevated and reduced in 12 ppt salinity, respectively (p≤ 0.05). The results suggest that the optimal salinity at this point of Starry Sturgeon life is the Caspian Sea water salinity (12 ppt) which provides the conditions for introducing this species as a suitable species for rearing in enclosed environments in natural water resources. Considering that A. stellatus lives in waters with diverse salinities at different stages of its life, it is important to know the appropriate weight and salinity for releasing in order to increase the percentage of survival and improve growth.

The stock status of most fisheries resources is not well-known, which is associated with limited data available for stock assessment. To overcome this gap, several data-limited stock assessment models, including the surplus production model, were applied to estimate stock status of these data-limited resources where no sufficient data is available to apply the conventional stock assessment models. To estimate MSY, catch and CPUE data for Cyprinus carpio caught from the southeastern Caspian Sea were applied. Twenty-two years data (1999-2022) were analysed by SPM to estimate MSY. Three parameters including population growth rate (r), population carrying capacity (K), and initial biomass for an exploited population (Binit) required for estimating MSY were guessed 0.075 (/yr), 6952 tones, and 3500 tones, respectively by the catch-MSY model. The estimated MSY using these guessed parameters by SPM was 130 tones. While, estimated MSY using the repeated (multiple) starting points was 1320 tones. Phase plot indicated that the current status was both below the limited and the target biomass reference points. These illustrated the stock of C. carpio in the southeatern Caspian Sea is unsustainable and overfished. Since, survival of C. carpio depends the releasing hatchery reared juveniles to the wild, specific fisheries management should be applied to prevent the undersize catch and illegal fishing.

The purpose of this research was to determine the concentration of poly aromatic hydrocarbons (PAHs) in the surface sediments during four seasons at different transects of the southern basin of the Caspian Sea and to investigate the causes of their temporal and spatial changes, to compare with the standard limits, and to find the origin of these compounds. The samples from the surface sediments were collected using a grab (van Veen grab) from depths of 10 and 30 m in the coasts of Guilan, Mazandaran, and Golestan provinces at eight transects (Astara, Anzali, Sefidroud, Ramsar, Nowshahr, Babolsar, Amirabad, and Torkaman) during the autumn and winter seasons of 2018, spring and summer of 2019. The sediment samples were prepared in order to investigate PAHs using a standard method (extraction with organic compounds by the Soxhlet apparatus). The results showed that the mean (±SE) annual concentration of PAHs in the four seasons of autumn, winter, spring, and summer was 29.6±11.5, 2125±611, 4.2±3.0, and 5.3±3.1 µg/kg dry weight, respectively, and the maximum concentration of PAHs was recorded in the Nowshahr transect in the winter season. The results of the current research showed that 2 and 6 rings compounds had a low percentage of abundance in the sediments and the mean concentrations of PAHs and BaP in most of the samples were lower than the international threshold standards. The origin of PAHs compound in the sediment was recorded in more pyrogenic sources based on the diagnostic ratio (LMW/HMW=0.3).

The quality of hatchery reared juvenile fish and their releasing quality to the wild would impact the rate of stock enhancement in the aquatic resource. This study examined the impact of size and density of the hatchery-reared juveniles on the biomass, catch and profit of fishing activities of common carp in the Caspian Sea. Data used in this study was extracted through literatures review, including the number and the size of hatchery reared juveniles of common carp at the releasing time to the wild, annual catch of common carp from 1999 to 2017 in the south-east of the Caspian Sea, and population parameters of common carp estimated using length frequency data in 2019 and 2020. The results indicated that economic rent and biomass decreased in the population without stocking. While, releasing hatchery-reared juveniles at the length of 7 cm (the length equal to the 10% of ) showed that catch profit and relative biomass declined by increasing fishing effort, which was associated with overfishing. Thus, releasing one-gram hatchery-reared, which the length of released juveniles is less than 10% of population asymptotic lengthy , may not increase common carp yield and biomass. In contrast, this may only increase the cost of stock enhancement. In addition, when the size or length of released juveniles increased to the 10% of population asymptotic length, the maximum economic rent (gross revenue) was obtained in the 30% of fishing effort unit.

This study used a dynamic model to predict the fishing status of the Persian Sturgeon (Acipenser persicus) along the coast of the Golestan province in the Caspian Sea. The findings indicated that based on the initial population in 2017 equal to 2500 samples of fish if harvested at the current rate, the stocks of this valuable sturgeon fish will be destroyed in the next 50 years. However, when considering the harvest rate of 0.2 per year (nearly half of the current catch), the amount of fish harvested will increase so that this stock will completely regain its ability to regenerate itself.

This study examines the characteristic of microplastics (MPs) in sediments collected from the coastal areas of the southern Caspian Sea, Mazandaran province (Babolsar and Sari cities). Twelve sites for sediment sampling selected during 2022. MPs identification detected primarily under stereomicroscope and then ascertains and discovers their polymer composition by ATR-FTIR. The results showed that Babolsar areas, with 5 meters far from the shoreline, had the most abundance (660±165.15items/Kg). On the other hand, Sari station with 500 meters far from the shoreline contained the least MPs (220±81.33). Average number of detected MPs in all samples was 406.66±161.33. Fibers (80.33%) were the most abundant MPs, whereas films (3.28%) detected the least. In the case of size, the range of 1000-3000µm showed the most abundant MPs (39.34%) and MPs less than 2 µm the least ones (4.10%). Gray and black (50.82%) was the dominant color and yellow (3.28%) was rarely detected color (3.28%). Polymer constituent of examined MPs includes: (PET: 30%); (PS: 20%); (PA: 20%); and (PP: 15%). The findings of this study revealed that MPs occurrence in coastal sediments distribute from several sources; including tourism as well as wastewaters and packaging. These activities cause entering plastic litters along the coastal areas and their degradation accelerated t MPs distribution.

The purpose of this research was to evaluate the consumer’s behavior of farmed carp in the north of Iran (Golestan, Mazandaran and Gilan province).

After defining the assumptions and designing the analytical-conceptual model based on the theory of planned behavior, a suitable questionnaire was developed and completed by the statistical community. In order to evaluate the intensity of the relationship between the research variables and the model elements, as well as to check the acceptance or non-acceptance of the assumptions, the structural equation modeling method (SEM) was used.

Per capita fish consumption of farmed carp consumers is 5.3 kg. Of this amount, 400 grams are canned, 600 grams are consumed in restaurants and outside the home, and 2.5 kg are consumed at home. Per capita consumption of their farmed carp is 1.4 kg, so half of their consumption is from other fish.In this research, all hypotheses were confirmed, In this way, the effect of perceived usefulness, perceived risk and quality on attitude, the effect of normative beliefs, moral obligation and household income on subjective norms, the effect of control power, control belief, experimental records, advertising and education on the perceived behavior control, the effect of attitude, subjective norms and perceived behavior control on the decision to buy farmed carp and the effect of the decision to buy and perceived behavior control on the final behavior were reported to be significant (p<0.05). The values of the effect coefficients showed that the most effective variable on the attitude, subjective norms and perceived behavior control, is quality (with an effect coefficient of 0.46), income (with an effect coefficient of 0.44) and experience records (with an effect coefficient of 0.37), respectively. Also, among the three main elements of the model, the attitude had the greatest effect on the decision to buy and consume farmed carp (with an effect coefficient of 0.48).

The purpose of this study was to determine the frequency of Vibrio parahaemolyticus and to identify pathogenic and non-pathogenic strains of this bacterium using a series of biochemical tests and polymerase chain reactions from the shores of the Caspian Sea (Gilan Province). The water and sediment samples of the Caspian Sea were collected from the depth of 30-50 and 10-20 cm respectively by aseptic method. Sampling date, sampling location, temperature, pH and salinity were measured. Isolation and identification of environmental isolates was done using standard methods in order to determine the genus and species using specific media such as thiosulfate citrate bile sucrose and Vibrio chrome agar. A total of 55 isolates were identified by biochemical, phenotypic and polymerase chain reaction tests. From the total of 55 cases of Vibrio parahemolyticus isolated, the frequency of tdh and trh genes was 1 case (1.8%) and 3 cases (5.4%) respectively. This study showed that Vibrio parahaemolyticus, which have pathogenic potential, should be continuously monitored as agents of contamination of coastal waters. The isolation of these species indicates a health warning for people who use raw seafood or are in direct contact with the waters of the Caspian Sea are in this area.

Breeding and production of fish in sea cages is one of the most common methods of commercial production of aquatic animals in the world. It is possible to develop aquaculture in the Caspian Sea by fully respecting the biotic, abiotic, social, and economic conditions, as well as the environment, with regard to sustainable development. Breeding fish in cages is very important from an economic point of view, and determining the challenges and obstacles before investment in order to reduce the investment risk plays a fundamental role in it. The purpose of this article is to investigate the economic challenges of cage culture development on the southern shores of the Caspian Sea using a combination of SWOT and FAHP analysis and then determine strategic priorities based on the Quantitative Strategy Planning Matrix (QSPM). In order to meet the challenges and also formulate strategies, the SWOT analytical model was used, and the opinions of 30 fisheries experts were obtained through face-to-face interviews and completing questionnaires in 2020-2021. According to the final score obtained, opportunity factors got 2.89 points, and threat factors got 3.54 points. As a result, the threat points prevail over the opportunities, and it shows that the current situation of this activity requires strategies in the field of adopting solutions to reduce threats. According to the total scores of the obtained matrix, the score of external factors indicates the need to formulate a defensive strategy in order to reduce the minimum risk of investment. According to the SWOT analysis, the strategies with the highest score are "development of standards and criteria and locating suitable areas for cage fish breeding sites," "allocating low interest loans and encouraging investors in order to facilitate investment," and "sustainable development in order to prevent Changing the use of valuable agricultural land" and "attention to export, introduction, and cultivation of species with global marketability" were presented in order to solve the existing challenges and suggestions to make the fish farming industry in the Iranian regions of the Caspian Sea.

This work aimed to compare hybrid and non-hybrid populations of Hircanian goby (Ponticola hircaniaensis) from two rivers, Kabudval and Shirabad, Golestan Province, respectively. For this purpose, 20 morphometric characteristics were measured. To reveal the morphological differences between the studied populations, the morphological characteristics after standardization were analyzed using Discriminant Function Analysis (DFA) and Non-parametric Multivariate Analysis of Variance (NPMNOVA) based on the P-value obtained from the permutation test with 1000 repetitions. The results of Kruskal-Wallis's test showed that out of 20 morphometric characteristics, 11 traits significantly differ between the two populations. Also, the results of DFA analysis based on the permutation test with 1000 repetitions showed a significant difference in morphology between the two populations of Kabudval and Shirabad rivers (P = 0.048). Since the habitat conditions of the two rivers, Kabudval and Shirabad, both forest streams, are almost identical, the morphological difference between these two populations of Hircanian goby can probably be due to the genetic difference due to hybridization.

This work aimed to investigate the morphological variations and patterns of morphological adaptation to their habitat in five populations of Iranian goby, Ponticola iranicus (Gobiidae). For this purpose, samples were collected from Siah Darvishan, Shafarood, Rostam-Abad, Masal, and Asalem rivers, Guilan province, and then 20 morphometric characteristics were measured. The morphometric characteristics after standardization were compared using PCA, Kruskal-Wallis and CVA analyses to investigate the morphological variation between studied populations of Iranian goby. Based on the results, all characters showed significant differences, and the Siah Darvishan differed completely from the others. Also, Rostam-Abad and Shafarud, and Masal and Asalem populations overlapped with each other. The most important discriminating traits include the body depth (0.3), predorsal length (0.4), preanal length (0.5), anal-fin base length (0.44), head width (32. 0), distance before dorsal fin (0.42), length of pectoral fin (0.34), maximum body depth (0.39), caudal-fin width in anal fin (0.33) and width of upper lip (0.34). The CVA results showed the distinction between populations. Based on the results, the members of this species adapt themselves to different habitats with traits related to body depth, dorsal and anal fins, and head size.

The ability of fish adaptation to different salinities depends on osmotic, ionic and biochemical regulation, on the other hand, transferring fish to salt water causes the development of their osmotic and ionic homeostasis mechanism. The adaptation of stellate sturgeon (Acipenser stellatus) in four weight treatments including 0.5-1, 1-3, 3-5 and 5-10 g in water with four salinity levels of 0.5, 4, 8 and 12 g/l during 8 phases and each experiment was performed in 4 predicted treatments. Each experiment was carried out in a period of about one month along with feeding with live foods, preferably gammarus, Nereis worms, and chironomidae larvae at the saturation level of 6 times a day, as well as daily siphoning and water changes. Osmolarity and factors of chloride, calcium, sodium and potassium were measured in fish blood serum. In the examination of the compatibility and adaptability of this fish with the conditions of changing salinity, the results showed that with increasing salinity, the levels of potassium, sodium, chloride and blood osmolarity increased. The stellate sturgeon are able to adjust the osmotic pressure and ionic composition of their blood serum when they migrate from hyperosmotic to hypoosmotic environment or vice versa. The blood osmolarity of fish with a weight of 5-10 g was higher than other weights, and the lowest osmolarity was observed in fresh water (0.5 g/l). The results of this study showed that the amount of potassium in the blood serum decreased with the passage of time and the increase in salinity, and increased the amount of sodium and calcium in the blood serum.

More than 50 fish species exist in Guilan coast waters and 20 species of them are economic, but there is few data about their fingerlings. This study has been done in Talesh, Anzali, Kiashahr and Chaboksar shores and fish seasonally caught by beach seine with 8 mm mesh size from winter to autumn 2021, and the main purpose was determining fish abundance in Guilan province coasts, too. Results showed 32 fish species belong to 13 families in studied are and Leuciscidae family was the most diversified with 8 species. The study of fish abundance showed dominancy of Chelon saliens, Alburnus chalcoides and Atherina caspia with 42.5%, 18.1% and 11.6% in Talesh shore, A. chalcoides, C. saliens, and A. caspia with 25.1%, 22.1% and 20.8% in Anzali shore, C. saliens, Rutilus frisii and A. chalcoides with 31.8%, 17.4% and 14.8% in Kiashahr shore and C. saliens, A. chalcoides, Neogobius pallasi and chelon auratus with 29.9%, 21.5%, 14.2% and 10.5% in Kiashahr shore, of total count (number), respectively and they were predominant. In general, were abundant fish, the fingerlings to non-adults of sharp-nosed grey mullet (Ch. saliens) and Shemaya (A. chalcoides) in all stations, Caspian silverside (A. caspia) in 2 stations and fingerlings of Golden grey mullet (Ch. auratus) and Kutum (R. frisii), and fingerlings to adults of Caspian sand goby (N. pallasi) in one station, that show a more adaptation of these species to environmental conditions in 4 studied stations. The continuous monitoring of density of small size individual of fish species in southern coasts of Caspian Sea is essential for conservation of their populations.

More than 70 millions of Kutum (Rutilus frisii) fingerlings are released in the rivers of Guilan province annually for restoring, but there is few data about biological chracteristics about the fish during staying in the rivers downstream, thus this study has been done on abundance, growth, condition factor and diet of released fingerlings of kutum fish (Rutilus frisii) in Khoshkrud River downstream, and for this propose, 3 stations selected in the river downstream and sampling has been done using electroshocker monthly from Oct. 2022 until March 2023. Results showed Alburnoides samii, Capoeta razii, Rutilus frisii, Ponticola gorlap and Cobitis with 249.2, 108.7, 85.2, 32.2 and 31.4 individuals in 100 m2 catch effort had the most abundant. The fingerlings of kutum fish present in all months in the river downstream and its density varied 20.0 to 212.5 individuals per 100 m2. Studied fingerlings (n=119) had a weight of 2.10-15.10 (5.77±2.54g, average±s.d), total length of 6.62-12.20 (8.61±1.13cm) and condition factor 0.71-0.97 (0.86±0.05) and there was significant statistical difference only in condition factor between autumn and winter. The length-weight parameters was calculated for b-value 3.09 and correlation coefficient (r2) 0.98 and indicated isometric growth patterns. It was determined vacuity index 40.9% and 59.6%, the mean relative length of intestine 0.78±0.08 and 0.75±0.08 and the mean fullness intensity 76.1±97.1 and 71.3±118 in kutum fingerlings in autumn and winter seasons, respectively. There was 6 macro-invertebrates and 14 genera of algae in gut of kutum fingerlings and in the fish intestine were abundant Chironomidae from benthos and genera Synedra, Navicula, Diatoma and Melosira from algae cells in both seasons. In general, fullness intensity, condition factor and water temperature were no suitable for staying fish fingerlings in the stuied duration, but was not distinguished the reason of settle of fish in rivers and no emigration to sea water.

This research was carried out in order to determine the length and age composition, calculate growth and mortality parameters and calculate the biomass of golden gray mullet in the Iranian waters of the Caspian Sea during the year of 2022-2023. The biometric data were collected from beach seine fishing cooperatives in the Guilan, Mazandaran, and Golestan provinces. The mean (± SD) fork length and total weight were measured at 29.9±4.8 cm and 305.7±143.0 g, respectively. The age range was 2 to 11 years, and more than 74.4% of the age group were 3 to 4 years with the mean (± SD) fork length of 26.3±5.1 and 31.3±5.6 cm, respectively. In the relationship between fork length and total weight, the values of a and b were calculated as 0.018 and 2.836, respectively, with a correlation coefficient of 0.97. Growth parameters, including the von Bertalanffy growth equation constants (K, L∞, and t0), were determined as 0.14 (/year), 64.0 cm, and -1.02, respectively. Mortality parameters, encompassing total mortality (Z), natural mortality (M), and fishing mortality (F), were calculated as 0.95, 0.30, and 0.65, respectively. The biomass of golden gray mullet was determined 12155.5 tons. This research provides valuable information in the direction of sustainable management and protection of golden gray mullet stocks in the Iranian waters of the Caspian Sea.

In order to evaluate the possibility of common carp culture, Cyprinus carpio, in cages located in the Caspian Sea, 700 common carp with an average weight of 50±10 gr were introduced in two floating cages (each cage contains 350 fish) in Anzali Free Zone. The fish were fed daily based on the fish biomass on two occasions using extruded pellet food. After 2 months of introduction of fry, the loss of 2-3 fish per day started. The biometrics also showed that the fish just reached to average weight 85.64±12.07 and do not grow properly. In order to identify the reasons for the lack of proper growth and gradual death of fish, sampling was done to investigate the bacterial pathogens and the pathological condition of the gill tissue. By bacterial tests Aeromonas hydrophila from internal organs including liver and spleen and Pseudomonas sp. was isolated from the gills of investigated fish. The pathological examination of gill tissue also showed extensive histopathological effects such as bleeding, hyperplasia of the epithelium, twisting and adhesion of the secondary blades, destruction of the pillar apparatus and gill chloride cells, etc. Probably, some of these injuries are the result of infection with bacteria and others are the result of environmental conditions, especially the relatively high salinity of seawater. At the end of four months of rearing, the fish survival rate was about 30% and the average final weight was 350 ± 150 gr. In general, the biological characteristics of common carp showed that although this fish is able to tolerate salinity to some extent and sometimes can be seen in the composition of sea catch, it is basically considered a freshwater fish and its cultivation in floating cages in the Caspian Sea where salinity varies between 7-13 ppt is not reasonable and economic and it is not recommended.

The development of aquaculture is inevitable with increasing population and to ensure food security. On the other hand, due to the limitation of fresh water, the development of aquaculture is expanding in the sea. In the last decade, the rearing of Rainbow trout (Oncorhynchus mykiss) in Caspian Sea cages was done to form a production chain with pond farms to produce big-sized fish for export. The purpose of this research was the economic evaluation of the production of big-sized (1.5< kg) Rainbow trout in sea cages using the Cost-Benefit Analysis (CBA) method. This research was done in 4 sea farms in the south of the Caspian Sea. Fish with an initial weight of 500 grams were introduced into the floating cage (volume of 2500 cubic meters). The fish reached a weight of 1517±71 grams to 1799±178 grams in 90 days of the rearing period. All production costs (variable and fixed costs) and profit from fish sales were calculated. For the economic evaluation, each marine farm was considered with four floating cages and the production rate of 5, 10, 15, 20, and 30 tons of fish for each cage. The results showed that the minimum reasonable profit margin for a farm with a production of 80 and 120 tons of fish and taking into account a loan with a bank interest of 23% and a 10-year equipment depreciation period has 30% and 70% net profit, respectively. On the other hand, raising rainbow trout in floating cages with a volume of 2500 cubic meters and producing less than 20 tons (less than 8 kg per cubic meter) for each cage is not recommended in marine farms in the southern Caspian Sea region.