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Feeding of Shah – koolee which is one of the economical and popular fish in the northern part of Iran was studied in the area of the Sefidrood river. Carry out this research, 539fish were cought at selected stations from the scashore estuary to Kisum From April to August 2000 Intestinal content of sixty eight speciment in different sizes was collected and after primary biometry, their gastrointestinal system was removed and studied. Relative gut length (R.L.G) was 0.74 and the special charactristics showed that the main food of Shemaya is zooplankton. The vacuity index (C.V) was 23.5 percent Which proves that Shemaya is among greedy fishes. Instestinal examinations of Shan – koolee Shows that Three phytoplanktonal order including Crysophyta, Chlorophyta and Cyanophyta and two zooplankton order including Copepoda and Cladocera were the major food items consumed by this fish in Sefidrood river. In addition, some different organisms bigger than phytoplankton and zooplankton such as Chironmidae larvae and Gomphonaema were in its diet. Studies of Shah-koolee migration in Sefidrood river shows that spawning is more important than feeding.

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Sea surface temperature is considered as an important climatic index and Chlorophyll a concentration is regarded as an essential factor for sea phytoplankton biomass and productivity for marine ecosystem. Caspian Sea is known as one of the best marine ecosystem in the Earth. In order to assessment of problems and threats of Caspian Sea, it is necessary to monitor sea surface temperature and Chlorophyll a. This study attempted to investigate time series of sea surface temperature and Chlorophyll a in monthly and seasonal scales and analysis the temporal correlation of sea surface temperature with Chlorophyll a. Hence, MODIS images of Terra and Aqua satellite were gathered from January 2003 to December 2009 over Caspian Sea. After doing of image preprocessing, the algorithms of sea surface temperature and Chlorophyll a were performed on the images. And then, monthly time series of sea surface temperature and Chlorophyll a were done. The result of seasonal Man-Kendall showed that there is a rising trend in amount of Chlorophyll a concentration and a lack of trend in sea surface temperature. In addition, the monthly and the seasonal pattern of Chlorophyll a are based on sea surface temperature. This is a significant change in Chlorophyll a concentration based on Pettitt's test in mid-2006. The results of this study indicate that there is a positive correlation between Chlorophyll a and sea surface temperature in the period of study. So that, 65% of Chlorophyll a concentration is justified as a dependent variable with sea surface temperature by using linear regression model. Also, Fisher’s F test confirms this significance of relationship.

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The aim of the present study is estimation of the growth parameters of anchovy kilka (Clupeonella engrauliformis Svetovidov, 1941) in the southern Caspian Sea. In this study which was conducted during 2010, the samples were provided from Babolsar fishing harbor in Mazandaran province. In the laboratory, the measurements were done and samples were sorted into length and weight size bins. Age was determined using sagitta otoliths. The results were compared with the previous years. The mean length and weight of fish were 116.78±16.5 mm and 12.59±4.2 g, respectively, which has increased in comparison with the previous years. The growth parameters for females were (L∞=138.7mm, k=0.55 yr^-1, t₀=-0.42 yr) and for males were (L∞=160.5mm, k=0.25yr^-1, t₀=-0.92yr). Length-weight relationship in females was W=0/00008 FL^2/50 (R²=0.902) and in males was W=0/00007 FL^2/52 (R²=0.921) which have an allometric growth pattern. Age composition of females was constituted of 6 age groups, including 2-7 years. For males, this was constituted of 7 age groups, including 1-7 years. Mean age of females and males were 4.58±1.43 and 3.86±1.62 years, respectively. In this species population, 4 years old fish were dominant with relative abundance 26.55 percent. Results showed that in recent years, anchovy kilka population has been older and its length and weight has increased. These changes can be due to the weak stock reconstruction process which has affected by invader ctenophore and over-fishing.

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Although Coastal regions have occupied less than 15% of the earth surface, but (they invalue) 60% of the world population. These regions defined as eco-tone have more susceptibility than other terrestrial ecosystems. Pressure increase on these regions can decrease the quality of habitats and even ssensitive them. This study was done according to the national strategic plans of Irans fishery and environment to achieve general classification and encoding the coastal regions ecologically. It was conducted in 2010 based on coastal and marine ecological classification standard (CMECS) criteria as well as library and field studies, satellite photographs analysis, spatial coverage maps and two groups of data including surface geo-morphological components and bio-covering components. Eventually, the habitats were encoded. The results of the assessments determined the habitat adversity of the studied region (Mazandaran province) was bound to 4 types comprising coastal and sandy as the dominant types and estuary (seasonal and permanent rivers) and swamp ones. Environmental changes (season) could be identifiable and distinguishable for two fluctuation periods of spring-summer and fall winter.

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The Sharp nose mullet, Liza saliensRisso, 1810 is an economically important species of Caspian Sea. In this study mitochondrialDNA sequencing (mtDNA) of 16S rRNAwas used in order to clarify genetic structure and genetic diversity of Liza saliensin tworegionsof south part of Caspian Sea, i.e. Gilan (Anzali) and Golestan(Gomishan lagoon). According to results we obtained 552base pairsof16S rRNA sequence.A total of7 different haplotypes and 33 variable sites were identified.The averagehaplotype diversity(h) and nucleotide diversity(π) in samples of two regions was 0.44 and 0.007 respectively. The resultsof genetic distance determination showed low rate in the2 regions.Estimates of gen flow indicated there is no reproductive isolationbetween two regions and alsothere was not significant genetic difference betweenthe regions(p>0.05). Findings of the present study suggested that there is one population of Liza saliens in the studied regions.

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The marine survey for sturgeon stock assessment was conducted to estimate the abundance of each species, total abundance, biomass and their percentage composition. Trawling was carried out in 90 stations that were selected using a random stratified design. In each station trawling carried out up to 30 minute and with 2.5-3 knot speed. In Autumn 2001 totally 127 sturgeon specimens were caught including 90 A. persicus specimens, 34 A. stellatus, 2 A. nudiventrisand 2 Husohuso specimens. The catch composition comprised 70.3% A. persicus, 26.5% A. stellatus, 1.56% A. nudiventrisand 1.56% Husohuso. But in Autumn 2009 totally 62 sturgeon specimens were totally caught including 52 A. persicus specimens, 8 A. stellatus, and 2 A. gueldenstaedtii specimens. The catch composition comprised 83.9% A. persicus, 12.9% A. stellatus, and 3.2% A. gueldenstaedtii.Relative abundance of sturgeons caught in bottom trawls in autumn 2001 was 1.69 specimens per trawl, but in autumn 2009 were 0.69 specimens per trawl. The estimated total abundance of sturgeons in the autumn 2001 survey was 7930 thousand and in survey of autumn 2009 was 3463 thousand specimens. The estimated biomass of sturgeons in the Iranian waters of Caspian Sea in autumn 2001 was 5518.1 tons and in autumn 2009 3014.3 tons .the absolute abundance of commercial sturgeon in autumns 2001and2009were 281330 and 277677 respectively.The biomass of commercial sturgeon sturgeon was estimated 5518.1 tons in autumn2001, while it was 2193.5 tons in autumn 2009.

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In this study, investigation was conducted to determine the seasonal species composition and structure of zooplankton population of Caspian Sea at three commercial regions, Amirabad, Nowshar and Anzali harbors in 2010. According to the results a total of 24 species was found to build zooplankton populations. These zooplanktons were include of copepods (4 species), Cladocera (7 species), Rotatoria (9 species), protozoa (2 species) and 2 temporary plankton species (Meroplankton). Maximum species abundance of zooplankton species was recorded in autumn and Winter (21 species) and lowest in summer (15 species). The study showed that the average annual population density and biomass of zooplankton were 3848 ± 1114 /m3 and 35.1±9.6 mg/m3 respectively. Maximum average of annual zooplankton abundance and biomass were belonged to copepods with 3085±810/m3 and 23.9±5.7 mg/m3. Quarterly seasonal review (temporal distribution) of zooplankton abundance and biomass showed that was more in the summer with an average density of 4390 ± 1230 /m3 and 48.9±15.9 mg/m3 in winter, respectively. The aim of this study was to assess the zooplankton population in Anzali, Nowshar and Amirabad harbors which showed the highest density and biomass of zooplankton in Anzali region with 5789±1352 /m3 and 44.7 ± 11.1 mg/m3 respectively and the lowest was in Noshahr with 3142±658/m3 and 32.2±8.0 mg/m3 respectively.

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In this investigation effect of fish size on salinity tolerance of two size groups of Caspian sea Zander ,Sander lucioperca, fingerlings were investigated. The survival rate and plasma osmotic pressure changes in 0, 6, 24, 72 and 240 h after abrupt transfer to freshwater (0 ppt), 7 ppt and Caspian Sea salinity (12 ppt). Also, Hb, PCV, RBC and MCHC were measured at 240 h. The effect of body weight on plasma osmolarity was significant in both groups. There were not significant changes on plasma osmolarity of both size groups in fresh water. In size group 1, the highest plasma osmolarity value occurred at 72h after transfer to 7 and 12 ppt waters. The same situation was happened in 24 h for size group 2. The plasma osmotic pressure value of both groups reduced in both salinity of 7 and 12 ppt at 240 h and reached to new almost stable status. Hematological parameter values of size group 2 in salinity of 7 and 12 ppt were lower than fresh water at 240 h. Also there was a significant decrease in MCHC value of size group 2 fingerlings after transfer to salinity of 7 ppt at the 240 h. It seems that nevertheless the osmoregulatory mechanisms of size group 2 Zander fingerlings can act better than group 1, but the size group 1 zander fingerlings could tolerate salinity up to 12 ppt during 10 days acclimation period. Therefore we can conclude that zander fingerlings in 1 g body weight can tolerate up to 12 ppt water salinity (Caspian Sea salinity).

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The study investigated the relationship between some of biological parameters (phytoplankton, zooplankton and Mnemiopsisleidyiabundance) and some environmental parameters (temperature, salinity and water clearness) in the southern Caspian Sea during 2009 to 2010. Sampling was performed in four seasons (spring, summer, autumn and winter) and at eight transects perpendicular to the coast. Phytoplankton and environmental parameters samples were collected using Niskin. Zooplankton and Mnemiopsisleidyi samples provided by net. Total of 384 phytoplankton and water samples and 160 zooplankton andMnemiopsisleidyi samples were collected at the euphotic zone from depths of 5, 10, 20, 50 and 100 m. According to results, minimum and maximum values of phytoplankton biomass were observed in summer and winter, respectively. During spring and winter, the abundance of zooplankton was in highest level and conversely the minimum values observed during summer and autumn with obvious increasing inM. leidyi abundance. Maximum temperature and salinity were observed in summer and autumn, respectively. Result on PCA analysis in summer showed that decreasing of salinity had positive effect on M. leidyiandzooplankton abundance especially coppepoda and cirripedia groups. In this season, phytoplankton biomass was affected by temperature and salinity. However, with considering PCA analysis in autumn, phytoplankton biomass was correlated with PC1 which had a principal rule as compared to zooplankton. In this season, M. leidyiabundance was correlated with temperature and salinity of water. M. leidyiabundance was negatively correlated with water transparency during the two periods of time. It can be due to mucus excretion of M. leidyiwhich may decrease transparency of the water. In this study for the first time the dynamic population of M. leidyi is used as key factor in the Caspian seaecosystem events, however the interaction of different factors such as biotic and environmental parameters may also have effect on changes of dynamic of zooplankton abundance and its groupscomposition.

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This study was conducted to determine macronutrient concentrations of water and molar ratios of them at four transects (Tonekabon, Nowshahr, Babolsar and Amirabad) in the southern of Caspian Sea- Mazandaran Province in 2012-2013. Seventy two surface water samples were collected at 5, 15 and 30 meter depth and macronutrient concentrations were analyzed using standard methods. Results showed that minimum, maximum and mean (±SE) cocentration of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) and disoolved silicon (DSi) were registered 2.44-10.92 (5.89±0.21), 0.23-1.80 (0.58±0.04) and 5.30-15.12 (9.50±0.20) µM, respectively. In addition, annual mean (±SE) molar ratios of DIN/DIP, DSi/DIP and DSi/DIN were obtained 12.49±0.86, 18.82±0.78 and 1.75±0.07, respectively. Results of current study also showed that trend of the molar ratios of DIN/DIP and DSi/DIP were declined from May (2012) to March (2013) with increasing of DIP and DSi concentrations and decreasing of DIN concentration. In a conclusion, the molar ratios of macronutrients and the corresponding curves, the system was phosphorus limiting factor for phytoplankton during May and June but in December, January and February tend to be found towards nitrogen limitation and in September, system has experienced both limiting factor (P-limiting and N-limiting). There was no Si-limitation for phytoplankton growth at all regions and months in this area.

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Spring Viraemia of Carp (SVC) is a Rhabdovirus infection capable of inducing an acute hemorrhagic and contagious viraemia in common carp and other cyprinids. In this study, susceptibility of the Caspian Sea white fish to Spring Viraemia of Carp Virus (SVCV) was evaluated. Ninety fingerling fish were divided randomly into two groups with each group containing three replicates in separate aquaria (A1-3) and (B1-3). In order to conduct horizontal transmission model, in each related aquaria three fish were injected intraperitoneally with an inoculum containing virus. For oral virus exposure, fish were fed individually with food soaked in Eagle's minimal essential medium (EMEM) containing virus and then were transferred to their aquaria. Clinical signs and cumulative mortality of all fish were monitored daily for six weeks. Following observation of any clinical signs and mortalities, fish were sampled immediately for virological and molecular analysis (RT-PCR). In addition, the fish surviving at the end of experimental period were sampled. In order to isolate virus, fish tissues were homogenized and inoculated onto a monolayer of epithelium papulosumcyprini (EPC) cells. Identity of re-isolated virus was confirmed with Indirect Fluorescence Antibody Test (IFAT). According to the results horizontal transmission challenge model caused 57% of mortality while 10% of mortality observed in the fish of oral transmission challenge model. Inoculation of EPC cells using tissue homogenates prepared from dead fish induced CPE. IFAT analysis on CPE positive cells detected SVCV antigen as bright greenish dots inside EPC cells. In addition, RT-PCR analysis on tissue samples from fish that survived from virus exposure revealed presence of SVCV nucleic acid in the fish survived from horizontal transmission challenge model. According to the results, Caspian white fish is experimentally susceptible to SVCV infection and there may be variability in the degree of susceptibility to the virus depending on route of infection. It seems that SVCV, but also SVCV infection may result in no clinical signs and apparently healthy fish may serve as a reservoir of the virus, transmitting infection to healthy population of fish.

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For studying seasonal variations, density and biomass of macrobenthic fauna, samples were collected seasonally along three different depths (5, 10 and 15 m) in three transects (9 stations) using grab sampler in shallow water coasts of the Caspian Sea, and three stations in the estuary of Babolroud River at Baboolsar coast during 2007-2008. Crustaceans, bivalve and polychaetes were the dominant groups in different seasons in depths of shallow water coasts but in estuary stations, bivalve and crustaceans were dominant in different seasons. Density and biomass of macrobenthic animals increased with increase of depth to 15 m due to higher organic matter loads and decreasing of grain sediment ingredients. Grains sediment and water depth were the two main factors in distribution and biomass of macrobenthic groups in sea stations. However, in estuary stations, the salinity of water was the most important parameter affecting on the density and biomass of macrobenthos. Obtained results recommended that the estuaries region of Babolroud River has lower macrobenthic groups compared to shallow water coasts of the Caspian Sea, but the latter had higher density and biomass.

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To study the diversity and structure of zooplankton, samples were collected at two commercial regions, Nowshar and Anzali harbors at the depths of 5, 10, 15 and 20 meters in the southern Caspian Sea in 2011. A total of 10 species formed zooplankton populations included of copepods (2 species), cladocera (1 species), balanidae (1 species), rotatoria (2 species), protozoa (1 species) and 3 temporary plankton species (meroplankton). The study showed that the average annual population density and biomass of zooplankton were 3120±552 ind/m3 and 22.5±5.0 mg/m3, respectively. Maximum average of annual zooplankton abundance and biomass were belonged to copepods with 998±60 ind/m3 and 4.1±0.3 mg/m3. Quarterly seasonal review (temporal distribution)of zooplankton abundance and biomass showed that most with the spring season of an average density of 3767±770 ind/m3 and 32.9±7.4 mg/m3, respectively. Seasonal distribution of zooplankton showed that crustacea (included copepods, cladocerans and balanidae) consisted 70.5% of population and 36.4% of biomass.

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This paper presents distribution of phosphorus (P)(total P, organic and inorganic P) and parameters related to their releasing to the water column in the southern of the Caspian Sea. 36 samples of surface sediments(with triplicate) were collected from four sampling stations namely Anzali, Tonekabon, Noshahr andAmirabad at depths of 5, 10, 20 m during summer 2013. Several forms of the phosphorus in sediment were separated and extracted according to sequential extraction method. In the other hand, the concentration of Al, Fe and Ca and some parameters like Eh, EC and pH were measured for finding their relation with phosphorus releasing. Results showed that the most abundant forms of phosphorus were Ca-P(96.02%) and loosely-P(0.19%) has the lowest amount. Inabundances of different forms of phosphorus follow the order: Ca-P>Org-P>Fe-P>Al-P>Loosely-P. In conclusion, the high amount of pH in sediment and anaerobic condition(Eh<0) release the Fe bound P(2.7%) and loosely bound P to water column.

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The present paper aimed at evaluating nutritional value and fatty acid profile of muscle textures of the Caspian Sea wild carp, farmed wild carp and farmed carp. No significant differences were found between chemical composition indices (total lipid, crude protein, moisture) (p>0.05). However, ash contant was significantly higher in wild carp compared with farmed wild carp. There were not significantly differences of SFA, MUFA, PUFA, -ω3, -ω6, EPA+DHA,ω-3/ω-6 and PUFA/SFA between farmed wild carp and farmed carp. But following determination of fatty acid profiles in the Caspian Sea wild carp and farmed wild carp, fatty acid compositions in three groups of fish were found to be significantly different in terms of SFA,MUFA,PUFA, -ω3, EPA+DHA,ω-3/ω-6 and PUFA/SFA. PUFA, -ω3, -ω6, EPA+DHA,ω-3/ω-6 and PUFA/SFA were significantly higher in the Caspian Sea wild carp. Considering exceeding PUFA/SFA and ω-3/ω-6 ratios in Caspian Sea wild carp, farmed wild carp and farmed carp, all fishes were considered invaluable fisheries and nutritional resources. It is noteworthy that Caspian Sea wild carp is more nutritious than farmed counterparts thank to its higher rates of PUFA, ω-3, EPA+DHA, ω-3/ω-6 and PUFA/SFA.

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Considering the significance of sturgeon rearing and producing the meat and caviar which are one of the most development programs in aquaculture, it is necessary to investigate on hygiene condition of rearing environment to gather information about current rearing condition and to adopt the best method for prevention of disease and treatment in sturgeon. In this study, skin, gills, water and kidney bacteriaflora before transferring the farmed Husohuso(with average weight 103.45± 27.5 gr) and aftertransferringto the cage were determinedin fish washed with saline (0.85%NaCl) in the laboratoryunder sterile conditionssince 2011to 2012.Inorder tocounttheCFU (colony forming unit),1 square centimeter of skin, and 1 gram of fish gill were removedand washed for preparing of a homogeneous solutions of the decimal dilutions.In order to cultivate the kidney, the ventral surface of fish, disinfected and then the body aseptically opened for kidney sampling. Primary cultured on bacteriological medium was TSA. In addition to purification and identification of bacteria using standard bacterial identification, API 20E kit was used.Bacterial investigation results showed that total bacteria in rearing water tanks, fish gills and skin were 5.80-5.84Log cfuml-1, 3.28-3.41cfug-1 and 5.36-5.58 cfu (cm2)-1,respectively. The range of bacterial count insea water, skin and gill were 3.97-5.92 Log cfuml-1, 3.74-5.41 cfu (cm2)-1 and 2.01-3.40 cfug-1, respectively. Before and after releasingfish, isolated bacteria fromfish and rearing water were included Enterobacteriaceae,Aeromonassp., Pseudomonassp.,Acinetobactersp.,Staphylococcus, Halomunassp. andShewanellasp.

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This study was conducted to determine six heavy metals (Zn, Cu, Ni, Pb, Cd and Hg) concentrations in water (during four seasons) at eight transects (Astara, Anzali, Sefidroud, Tonekabon, Nowshahr, Babolsar, Amirabad and Turkman) in the southern coasts of the Caspian Sea in 2010-2011. 93 samples of water were collected at 10, 50 and 100 meters depths. All samples were prepared by extracting processes and then determined using Atomic Absorption Spectroscopy (AAS) instrument. Results of current study showed that maximum values of Zn, Ni, Pb and Hg were observed inspring and for Cd was inwinter. Also, at the west and center regions were more contaminatedthanthe east part. Annual mean contents and standard error (±SE) of water were registered 2.10 ±0.59, 1.64 ±0.18, 0.68 ±0.10, 0.11 ±0.01 mg/l and 3.30 ±0.40 µg/l for Ni, Pb, Cd, Zn and Hg, respectively. The mean values of the examined heavy metals with percentage (in parenthesis) in water samples during four seasons were obtained in this order Ni(46.3%)>Pb(39.1%)>Cu(15.0%)>Zn (2.5%)>Hg(1.0%). In conclusion, the results revealed that in the most transects the heavy metal concentrations of water were above the threshold levels associated with the toxicological effects and the regulatory limits (ANZECC, MPL and UKMPA) which represented polluted condition in this area. In addition, correlation between environmental parameters and heavy metals showed that the addition of different resources of metals,different behavior of bio-geochemical behavior was influenced on their concentrations.

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Common Kilka are distributed along the Caspian Sea, but at the depth less than 50m has more density. The fish is caught in commercial fisheries, but unlike previous decades, it is the main catch in the coasts of Iran. This study was conducted in the Kilka commercial catch area around the Anzali Port. A diet survey was conducted on 320 individuals of Kilka from summer 2011 to spring 2012, seasonally. The weight, length and age showed variation with 5.15-14.29 g (9.30±1.66) 8.3-12.9 cm (11.27±0.75) and 3-7 old years (4.82±0.86). The results showed that 26.87% of common Kilka had empty tract, and Copepods, Balanidae (Balanuscypris and larvae), Cladocera, Parasites (Nematoda&Trematoda) and Azolla were observedin the gut of fish.The number of prey were 94.5, 3.0, 1.8 percent for Copepods, Balanus(larvae) and Balanus(cypris), respectively and copepods with 61.6 percent as main food, Balanus(cypris) with 48.3 percent as second food item were considered. Also the other types of food were consumed randomly. For common Kilka the relative length of gut 0.73±0.11 and fullness intensive index 115.01±63.01 were estimated. The frequency of prey, fullness intensive index and relative length of gut did not show differences in unlike seasons and ages. In a conclusion, it can be expressed that in comparison with last studies, diversity of food for this fish was more limited, also fullness intensity index was decreased.

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In this study, the effect of beach-seine catching activitieson changesof sediment structure of bed in Rudsar and Chaboksar areas were investigated. Samplesof sedimentwere takenmonthlywithaVan Veen grabcoveringasurfaceareaof 225 cm2 from seining and non-fishing areasofRudsarandChaboksar stations in depths of 3, 6 and 10 meters with 3 repetitions in each depth, in autumn and winter 2011.The results showa significant difference between the percentage of silt-clayinthe various sampling depths of seining area and the percentage of silt-clay in the various sampling depths of non-fishing area, in each of Rudsar and Chaboksar stations and each of autumn and winter seasons(P< 0.05). So that, the amount of silt-clay in seining area has been more than the amount of silt-clay in non-fishing area. In the Rudsar station, the amount of Total Organic Matter of the seining area were 2.6 and 2.2percent in autumn and winter, respectively, and these amounts for non-fishing area were 2.3 percent in autumn and 1.7percent in winter.Also in the Chaboksar station, the amount of Total Organic Matter of the seining area were 2.5 and 2.2 percent in autumn and winter, respectively, and these amounts for non-fishing area were1.5 percent in autumn and 1.3 percent in winter. Results indicateda significant difference between the amounts of Total Organic Matter in seining and non-fishing areas(P< 0.05). Also, the amount of Organic Matter has significant and positive correlation with the percentage of silt-clay. The results of this study show the sedimenttexture of seining areasin the various sampling depths are different form non-fishing areas.

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Cadmium is one of the most important environmental pollutants that have been increased in parallel to population growth and industrial development in aquatic ecosystems such as the Caspian Sea in recent years. Marine invertebrates such as crustaceans and bivalves for the reason of sessile can absorb essential and non-essential heavy metals surroundings themselves and cause transfer them to top of the network food. This study was conducted to study filtration rate of Mytilaster lineatus and Palaemonelegans exposed to Cd (62 and 620 µgl-1) and its ability to remove these metals from water. The experiments were carried out in a designed mesocosm system. The results showed no significant different in filtration rate of M. lineatus and P. elegans exposed to Cd. These two species reduced the filtration rate and even they returned excess metals to the environment. It was also shown that the shrimp Palaemon elegans and bivalves Mytilaster lineatus can be the biological indicators for the assessment of cadmium in the aquatic environment.