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Rutilus firisii kutum is one of the important fish in Caspian Sea that has significant economical role to the region. The overall objective of the project is to compare the growth and survival of Rutilus frisii Kutum larvae under conventional conditions and conditions under use of organic fertilizer by anaerobic fermentation or slurry. This study was conducted in nine 1.7 hec pounds with 3 treatments with stocking densities of 1.7 million fish larva at Dr Yousefpoor Center at Siakal Village, 32km far from city of Rasht in North of Iran. The first treatment considered as control using concentrated food and grinded kilka fish. In the second treatment, the pound was supplied only by slurry for 13 days followed by concentrated fish food. The third treatment started with slurry for 13 days followed by slurry and concentrated food together. The physical and chemical parameters of water, plankton, biometry of fish, growth indices were monitored weekly. The result indicated that production was 1.7 to 2 times higher in slurry than traditional treatment also the survival rate was 1.7 times higher in slurry treatment. Slurry with several active substances is more effective and can promote the growth of zooplanktons that is the food for larval stage of Rutilus frisi kutum. Nutritional contents of phosphorous, nitrogen, calcium, magnesium, potassium, protein and lipid after anaerobic fermentation were higher in slurry treatment than control. The blue-green algae density in slurry pounds was less than control.

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A structure and growth pattern of Squalius cephalus (Linnaeus, 1758) in Tuji tributary of Talar River, Mazandaran Province, was studied during the period from August 2008 till August 2009. In total, 298 fish were caught by electrofishing and fixed in 10% formalin. The weight and length of fish were measured and the age was determinated by scallometric method. The age data showed that fishes were between 0+ to 4+ age groups. Pauli`s applied growth pattern showed a positive alometric for male and female and total fish and a negative isometric for unmature fishes. The average instantaneous growth rate of European Chub showed that the age groups 2+ and 3+ with 1.1 had the fastest growth compare to 3+ and 4+ age groups with 0.89. Condition factor of specimens showed that the highest one with 1.58 (r2 = 0.983) belong to females and the lowest with 1.17 (r2 = 0.901) belong to unmature fishes. The total sex ratio (123 males to 115 females) showed no significant differences between them.

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After the arrival of the invasive species (Mnemiopsis leidyi) in the Caspian Sea (in 1999) significant changes have been occurred in the ecosystem. In the present study, the data concerning the period 1996 to 2010 (extracted from the relevant research projects) were analyzed. The period was classified into two phases, before and after the species invasion (1996 and 2001-2010). In our study, the impact of the invasive species on the structure of southern Caspian zooplankton communities was assessed during the period 2001-2010, quantitatively.The combination of abundance and distribution range of the species (ADR) during the period 2001-2009 and the year 2010 were evaluated as E (occurrence in high numbers in all localities) and D (occurrence in moderate numbers in all localities), respectively. Considering the obtained results, the year 2001, in which the relative biomass was more than 90 percent, could be considered as the expansion phase and the following years (2002-2010) as the adjustment phase. With regards to the loss of the keystone and some other native species after the invasion of M. leidyi (2001 to 2010), the impact of the invasive species on the structure of southern Caspian zooplankton communities was assessed as massive (C4).

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This study was conducted to evaluate the effect of probiotic supplementation of Primalac on growth performance, some blood biochemical parameters, survival and salinity tolerance of the Caspian kutum fry. Fish (1.002±0.001 g) were classified to four groups fed on diets containing Primalac in different levels: 0 (control), 0.05, 0.10 and 0.15 % for 45 days. The results showed that there was a significant increase in final weight, weight gain and specific growth rate in those fish fed 0.10% Primalac diets (p<0.05). In addition, food conversion ratio of fish fed Primalac diets was significantly (p<0.05) lower than those fed the control group. However, there was no significant differences in condition factor, blood glucose and blood total protein content between fish fed different experimental diets (p>0.05). On the other hand, blood cholesterol of the Caspian kutum was significantly increased in control group in comparison with Primalac treatments (p<0.05). Survival and tolerance to salinity stress challenge remained unaffected by dietary supplementation of Primalac (p>0.05). The results of the present study indicate that the supplement of 0.10% Primalac have a positive effect on the growth performance and blood biochemical parameters of the Caspian kutum fry.

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Nowadays, herbal products as a new class of growth promoters that provide an alternative feeding strategy to
replace antibiotic growth promoters in aquaculture. This study was conducted to investigate the effects of
different levels of sangrovit (0, 0.05, 0.1 and 0.15 %) on growth, some of blood biochemical parameters,
survival and salinity tolerance capacity in Cyprinus carpio (2.62±0.117 gr). After 45 days of feeding, results
showed that growth performance including of weight gain and % specific growth rate improved which fish
fed whit sangrovit compared with to control group, but there was no significant differences in growth
parameters which fish fed with herbal supplement compared to control group (P>0.05). There were
significant differences in biochemical parameters in fish fed with sangrovit compared to the control group
(P<0.05). The lowest level of cholesterol was observed in 0.05 % group and the highest level of total protein
was observed in 0.15 % group. The highest levels of glucose observed in control treatment. In order to
determine the effect of the herbal supplement on resistance to salinity stress, salinity stress was carried out
after 45 days of feeding. Blood samples were obtained at 24, 72, 120 and 168 hours after stress. Hematocrit
had significant difference in each groups (P<0.05). On the third day after stress, hematocrit levels were
decreased in all treatments. Survival and tolerance to salinity stress challenge remained unaffected by dietary
supplementation of sangrovit. The results of this study showed that addition of sangrovit to fish diet can
improve growth performance and blood biochemical parameters of common carp fingerlings.

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This study was carried out at the southeast of the Caspian Sea on the shores of the Goharbaran region during 2013-2014. Sampling was repeated monthly in eight stations. A total of 157 species of phytoplankton, 10 species of zooplankton and 24 species from macro invertebrate were identified. There were significant differences based on abundance and biomass among different biological groups in various stations (p<0.05). Comparing the abundance and density of phytoplankton in different seasons showed that there was an increasing trend in phytoplankton from spring to winter, whereas the abundance and biomass of zooplankton showed a decreasing trend. The results of the multivariate statistical analysis, Pearson correlation coefficient and Principal Component Analysis (PCA) in different months showed that the biomass of phytoplankton and zooplankton had the highest correlation (0.943), whereas the abundance of zooplankton and jelly comb had the highest correlation which could be due to their physiological structure and ecobiological conditions. In conclusion, ecological relationships among biological groups can be due to the abundance and biomass changes, species diversity, environmental parameters, predator, seasonal changes, feeding habits and environmental pollutions.
 

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In this study the biotic and abiotic characteristics of Ardalan dam reservoir was studied from 2011 to 2012. Diatoms, Bacillariophyta, was the main phylum of phytoplankton in Ardalan dam reservoir that was dominant in the most seasons and green algae, Chlorophyta, was the second dominance groups. Survey of zooplanktons showed there were 25 genus from 6 phylum, and Rotatoria constitute 64% of the zooplanktons in. The average phytoplankton and zooplankton abundance during this study were about 19.15×106 and 1863 per liter of lake water respectively. Survey of benthic communities showed that Chironomidae and Tubificidae were the main benthic groups in Ardalan dam. Average of benthic biomass during this survey was 0.9 gr/m2 which is very poor. Sediments in Ardalan dam was mostly of silt and clay. Fish structure survey by gill nets in Ardalan dam showed that common carp and silver carp, by %53 and %45 respectively were the main economical species in the dam. Hydro chemical survey showed that total phosphorus and total nitrogen were 0.073 and 0.779 mg/L respectively. The amount of chlorophyll a was 6.03 mg/m3. The range `of dissolved oxygen was 6.4-10.5 mg/L. Average of EC was 576 µs/cm. Since the water temperature just in august month was more than 20ºC, the appropriate period for warm water fish culture in this reservoir is limited.

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This research was conducted to evaluate the effect of ecological factors on diversity and density of phytoplankton in Caspian Sea. Sampling was carried out from 5 stations included of Ramsar, Nowshar, Noor, Fereydunkenar and Miankaleh (Amirabad) regions (surface, 3 and 5 m depths) from 2016 to 2017. The totals of 56 species belong to 5 phyla of algae division were identified which maximum density and biomass were observed in Skletonema costatum, Thalassionema nitzschioides, Nitzschia acicularis, Pseudonitzschia seriata and Melosira moniliformis. Density and biomass of phytoplankton showed that the mean of biomass was 12.3±2.7×10⁶ cell/m³ and 35.6±7.7 mg/m³, respectively, with the highest average density in winter (19.1±4.4 ind.m^-3). The highest and lowest Shannon index was 1.97 and 1.84 in different seasons respectively. Silica, temperature and inorganic nitrogen play an important role in density of algae especially diatoma, cyanophyta and pyrrophyta. The recent study showed that a high N:P ratio in winter and characteristics along with a suitable strategy for Chlorophyta species are important and desirable reasons for increasing their populations.

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Primary production is an important component in the biological cycle in terms of carbon storage and a key indicator for evaluating of ecosystem function. In this study, net primary production and its components were investigated in the coastal zone of Iranian basin of Caspian Sea during four seasons from 2018 to 2019. In addition, the effective environmental factors on spatial-temporal distributions of net primary production have been studied. As a results, mean (±SD) of Chl-a, euphotic depth (Zeu), active photosynthetic radiation (PAR), maximum primary production per unit of Chl-a (P^B_opt) and daily net primary production (DNPP) were obtained 2.54±3.23 mg/m³, 28.9±6.8m, 40.42±16.84 Einstein/m².day, 5.05±1.11 mgC/mgChl-a.h and 2.04±0.73 gC/m².day. The value of DNPP in the central region was more than the western and eastern regions. It probably is due to effects of wind and waves turbulent on re-suspension of sediment and decrease of light penetration in water column in the western and eastern regions. The seasonal variation of net primary production was in order: autumn>summer>spring> winter. The significant higher NPP in autumn than other seasons (p< 0.05, ANOVA-test), primarily caused by Chl-a and P^B_optic. Based on regression and PCA tests, temporal-spatial changes of DNPP has been significantly affected by the two variables of Chl-a and PB_optic.  In general, the classification of trophic state based on net primary production showed that 52% of the data had trophic states in the range of oligo-mesotroph  and mesotroph (49%) to eutroph (3%) and 48% of the data were in the oligotroph group (mainly in the eastern region).
 

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This study was carried out in line with the Caspian Sea Central Plateau Water Transmission Program in the southern shores of the Caspian Sea and Goharbaran region in 2013-2014. Sampling was carried out monthly at 8 stations at depths of 5, 10 and 15 meters in 2 transects. The purpose of this study was to investigate the relationships between some physico-chemical parameters of water and TOM (total organic matter), distribution, abundance and biomass of different species of Amphipoda in half-lines, depths, stations and seasons. Overall, one species of Niphargoides caspius from the Gammaridae and four species of Stenogammarus similis, Stenogammaus macrorus, Stenogammarus carausuii and Stenogammarus compenus of Pontogammaridae were identified. A total of 15118 individuals of the benthic organisms were counted, in which, S. compresus and N. caspius with 68 and 2 percentages, respectively. Overall, the mean (± standard error) density and biomass of benthic organisms during the period were 128±14.08 ind.m^-2 and 0.15±0.01 g.m^-2, respectively. According to Spearman test, density of S. carausuii, S. macrorus and S. similis was significantly correlated with sedimentation (sand) (p<0.01). Multivariate cluster analysis based on Spearman's correlation coefficient on the relationship between density and biomass of different species of Amphipoda with some environmental parameters, grain size and total organic matter (TOM) of bed sediments showed that the members of this group belonged to a sand bed and dissolved oxygen are more strongly correlated in which could be due to ecological origin of Amphipoda groups.

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In the last two decades, the Caspian Sea has faced various ecological events, such as harmful algal blooms and increasing in the trophic level. It is necessary to conduct monitoring studies in this water body, because of applying the Caspian Sea for fisheries activities. The objectives of the present paper are the study of algal bloom potential and trophic level in the Iranian coastal of southern Caspian Sea up to 30m depth, during the year of 2018-2019 as well as the comparison of the obtained results to the condition in previous years. Boundary lines for the beginning of blooms (annual median+5%) based on the chlorophyll-a concentration, abundance, and biomass of phytoplankton were obtained 2.02 (mg/m³), 176 (million cells/m³), and 312 (mg/m³), respectively. The lowest percent frequency of bloom (13%) was recorded in spring and summer based on the chlorophyll-a, abundance, and biomass of phytoplankton, respectively. According to calculations based on the accumulation of the aforementioned parameters, water has excellent quality (oligotrophic state) in summer and moderate quality (mesotrophic state) in other seasons. An interannual study of trophic states showed oligotrophic, mesotrophic, oligo-mesotrophic, and mesotrophic level in 1996-97, 2009-10, 2013-2014, and 2018-2019, respectively. The highest seasonal abundance of species (187 cells/ml) was recorded in Pseudonitzschia seriata. This species is considering a serious ecologic problem and decreasing water quality in the winter season. The bloom potential of Pseudonitzschia seriata was obtained in the “medium density” group. It should be noted that the increasing trend of inter-annual trophic levels is the alarm of environmental health and show the ability of the ecosystem to thrive the harmful algal blooms. The environmental alarm is more emphasized in the central region (with a history of macroscopic toxic algal blooms) because the water quality in the central area (medium quality) was lower than in the eastern and western areas.