فصلنامه بوم شناسی آبزیان
سال دوازدهم شماره 3 (پیاپی 46، زمستان 1401)

The aim of this study was to evaluate the effect of substituting the dietary fish meal with blood powder on some blood immune factors of Nile tilapia. 150 speciemns of tilapia (30 ± 0.5 g) were fed diets containing 0 (control group), 25, 50, 75, and 100 % of blood powder, each in three replicates for 8 weeks. After this period, fish were anesthetized and the blood samples were taken from the caudal peduncle of fish with a heparinized syringe for evaluating the blood immune indicators. No significant differences were observed in ACH50, glucose, and triglyceride among the blood powder-fed fish and the control group (P>0.05). The highest reported value of ACH50 (148.36±23.13), was observed in 75% treatment and the highest values of glucose (145.72±21.44) and triglyceride (451.68±49.61) were observed in 100% blood powder fed treatment. However, there were significant differences in the activity of lysozyme, immunoglobulin, total protein, and cholesterol in the groups receiving blood powder with different percentages compared to the control group (P<0.05).  The results of this research showed that it is possible to replace fish meal with blood powder in the diet of Nile tilapia due to its strengthening effect on immune system.

The aim of this study was to investigate the changes in the structure of the plankton community in the southwestern Caspian Sea and its relationship with the reduction of Rutilus frisii and Chelon auratus catches. The current study was conducted seasonally in the coasts of Guilan provience from 2020 to 2021. A total number of 48 genera and species of phytoplanktons were identified. Tthe findings showed that the non-native species Pseudo-nitzschia seriata from chrophyta and the toxic species Nodularia spumigena from cyanobacteria formed the highest density. The increase of water temperature and nutrition and the decrease of wind speed were directly related to the bloom of phytoplanktons, especially cyanobacteria in the Caspian Sea, which caused the third bloom of N. spumigena in Anzali shores in July 2021. The results showed an increase in the abundance of phytoplankton by more than 7-folds compared to 1996. The highest abundance of phytoplankton was observed in Anzali shores in 5 m depth. The pattern of phytoplankton abundance and the abundance of R. frisii and C. auratus juveniles were similar to each other.  The food eaten by C. auratus and R. frisii juveniles showed that these fish species fed on phytoplankton detritus. Probably the reduction of Cerastoderma glucaum biomass, illegal fishing with gillnet, the quality and quantity of R. frisii release by Iranian fisheries, and the lack of restoration of the rivers where the natural reproduction occurs are the factors affecting the reduction of the R. frisii catch in recent years.

In an investigation of the effects of the effluent of fish farms on the water quality of the Marbor River in Isfahan province based on biological indicators, some cases of infection of macrobenthos with horsehair worms (Nematomorpha: Gordiidae) were observed. About 76% of the observed worms were observed to leave their hosts. the horsehair worms were identified in only three families of aquatic insects, including Hydropsychidae, Limoniidae, and Chironomidae. About 24% of the observations were free living worms in the sediments. The highest and the lowest frequencies of observations were recorded in spring (47.7%) and autumn (0.92%), respectively. The seasonal abundance of free-living mature and fertile worms was a coincidence with increasing the reproductive activities of aquatic insects. Aaccordingly, it can be concluded that the ecological rules enforced such a simultaneous phenomenon to ensure that the worm larvae can find a proper host.

In this study, the trophic status of the Bustan dam reservoir was investigated using Palmer and Carlson indices. Biological parameters including phytoplankton and environmental factors such as phosphate, nitrate and chlorophyll were sampled at the depth of 0.5 meter in five stations in three replicates seasonally in 2019, repetitions and Then the Palmer and Carlson indices were determined. The Palmer index in Bustan dam was estimated as 24, 31, 27.6, and 28.8in spring, summer, autumn, and winter, respectively.  According to the Palmer index classification, in all four seasons, Bustan dam water is in the category of water with high organic matter. The highest value of Palmer's index was obtained in summer (31) and its lowest value was obtained in spring (24). The highest nutritional status of Carlson's index was related to summer (60.46 eutrophication) and the lowest level was found inwinter (52.44 eutrophication), which indicates that the reservoir has moved to semi-nourishing condition in winter season. Also, the highest nutritionism status was observed in station 3 (54/23). According to Palmer's and Carlson's indices and the ratio of phosphate to total nitrogen, the main factor of nutritionism in the reservoir of Bustan dam was phosphorus compounds that enteres the reservoir from external sources of the dam and ultimately causes the decrease of water quality.

The aim of this study was to investigate the body shape and morphological comparison between the populations of wild (marine) and farmed common carp using geometric morphology. For this purpose, 65 pieces of fish including 23 wild common carp and 42 farmed common carp were sampled. The samples were then photographed and 16 landmarks were identified on the images. Procrast analysis was used in order to remove the amorphous data from coordinate landmarks. Principal component analysis (PCA) and discriminant function analysis (DFA) tests were used. The results showed that the two populations of wild and farmed common carp are completely separated from each other using PCA and the first three components accounted for about 64.41% of the total changes. Based on DFA for morphometric characteristics, individuals were correctly placed in their original population. The results of this study showed a significant difference in body depth and body width of wild and farmed common carp using geometric morphometric method, so that the farmed common carp had deeper body (related to the displacement of landmarks 5 and 12), a wider body (related to the displacement of landmarks 5,6,10,11 and 12) and also a shorter tail stem (related to the displacement of landmarks 6, 7, 9 and 10) than wild common carp.

The aim of this study was to assay the antibacterial activity of Scenedesmus obtusus on some pathogenic bacteria. Microalgae S. obtusus were obtained from Algae Bank of Iran, and the methanol, ethyl acetate, chloroform and n-hexane extract of the microalgae were prepared using the maceration method. Bacterial strains were cultured in a solid culture medium, and antibacterial activity of the the different extracts of S. obtusus, were investigated using well diffusion method, and the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), against Staphylococcus aureus, Streptococcus agalactiae as gram-positive bacteria and Escherichia coli and Klebsiella pneumonia as gram-negatives. According to the results, methanolic and ethyl acetate extracts of S. obtusus, showed growth inhibitory effects against all examined bacteria at concentrations of 200, 300 and 400 mg/ml. The chloroform extract was effective only against S. aureus and E. coli, but n-hexane extract had no effect against any of the bacteria. The highest inhibitory effect of S. obtusus extract was observed on methanolic extract against E. coli (16 mm), while the least inhibitory effect belonged to ethyl acetate extract against S. aureus (6.8 mm). The results also showed that the extract of S. obtusus contains antibacterial compounds, and the solvent which used for microalgae extraction significantly affected the antibacterial potential of the extract.

The aim of this study was to detect different populations of Pacific White Shrimp (Penaeus vannamei: Boone, 1931) in farmed broodstocks and to determine their genetics indeces in hatchery centers of Bushehr province. First, the origin of the farmed broodstocks was determined based on the historical information of the different stocks. Then, DNA was extracted from muscle tissue of 30 broodstocks from 11 different stocks using a commercial kit. The repeated sequences were amplified using 10 specific primers by PCR in Iranian Shrimp Center. The results showed that the number of alleles was in range of 4.5-5.5 in studied stocks. The most allele frequency was observed in the farmed broadstocks of the third stock in H2 hatchery center, 5.2±0/359. Also, the average of observed heterozygosity in the farmed broadstocks of the second stock in H5 hatchery center obtained 0.669±0.152 that was more than other stocks among all centers. The results of the present study showed that genetics indeces of of third stock in H2 hatchery center were increased compared to other stocks in Bucher province. The inbreeding coefficients of the first stocks in H1 (0.595±0.105) and H3 (0.547±0.145) hatchery centers were significantly higher than other stocks. The inbreeding coefficient increase in farmed broadstocks in these stocks could be related to the small size of founder population and the bias selection programs. However, according to the information from other hatchery centers in Bushehr province and other countries, this amount is acceptable. According to the obtained results, it can be concluded that to increase the genetic indicators in the centers, breeders with higher diversity should be used.