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Formalin is a common disinfectant and therapeutic agent in fisheries-related activities. Considering large variation in susceptibility of different species to formalin toxicity, it is necessary to determine its toxicity and safety margins in different species, separately. Therefore, to investigate formalin acute toxicity and safety margins on Caspian roach, an experiment was conducted in 1g Caspian roachs Rutilus rutilus caspicus. Fish were exposed to 0, 30, 40, 45, 50, 55, 60, 70, 100, 150, 200, 250, 300 and 400 ppm formalin and mortality was recorded after 0.5, 1, 12, 24, 48, 72 and 96h. 0.5-96 h LC50 values were 49-246 ppm. The lowest observed effect concentrations (LOEC) were found to be 40-150 ppm at different periods. No observed effect concentrations (NOEC) were 30-100 ppm at different periods. According to regression model for NOEC versus time, concentrations of 88.4, 80.3, 51.2 and 40.1 ppm are suggested as the maximum concentrations for 0.5, 1, 12 and 24 h bath treatment, respectively. Results showed the recommendations for formalin safety in the literatures are not applicable and valid for Caspian roach. Such differences could be due to species or experimental differences which should be taken into account before treating.

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The aim of this study was to develop a biopreservation strategy for cold-smoked Caspian  roach by the use of Lactobacillus casei previously selected for their capability to inhibit the growth of Listeria monocytogenes in this product.  An application on commercial smoked Caspian roach was tested by spraying L. casei (10⁴ CFU g^-1) on slices smoked Caspian roach. Microbial and chemical characteristics were each ten days compared to a control during forty days of storage. No significant differences were showed in microbiological and chemical characteristics of  inoculated slices with  L. casei. The strain L. casei  inoculated in SCR in a biopreservation goal exhibits some interesting properties: it is able to grow at high level without giving major quality changes in the product. In conclusion, biopreservation of SCR using lactic acid bacteria such as L. casei is a promising way to inhibit the growth of pathogenic bacteria such as L. monocytogenes with low effect on the quality of the product.

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Due to the increasing demand for nanotechnologies, there is a rising concern about the potential risks of nanomaterials to human health, environment, and aquatic ecosystems. The chemical composition and small size of the nanomaterials are the most important factors in the toxicity of these materials. Histological study of gill and investigation of haematological parameters are important for monitoring of the health status in aquatic animals. Therefore, in this study, the effects of subacute concentrations of copper oxide nanoparticles were examined on some haematological parameters of Caspian Roach (Rutilus rutilus). The experiment was performed at 15 litres aquariums in three experimental groups including 10, 40, 80 ppm copper oxide nanoparticle and the control group for 42 days. Each treatment included three replicates consisting of seven juveniles carp with an approximate weight of 42± 2 gr. The results of this experiment showed that copper oxide nanoparticle caused hyperplasia, lamellar fusion, epithelial hypertrophy, lamellar aneurism, and reduces secondary lamellae length. In addition, red blood cells (RBC) was significantly decreased with the increase in the concentration of copper oxide nanoparticle (P<0.05). At the end of treatment, RBC had a significant reduction from 2.11±0.004 to 1.98±0.005. Hematocrit and haemoglobin reduced from 1.37±0.011 to 1.34±0.001 and 7.8±0.01 to 6.9±1.32, respectively (P<0.05). A significant reduction was recorded in hematocrit among the control groups and other treatments (P<0.05). Conclusion: Eventually it can be concluded that the sub-acute particles may causes damage to the surface of tissues, especially gill tissue, and changes in the level of blood factors in fish, which can be due to the destructive effects of this type of nanoparticle on hematopoietic organs such as liver and kidney. Therefore, a definite conclusion in this regard requires more and more extensive research on the same species and other species.

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Because of the importance of osmoregulation in success of the juvenile Caspian Roach (Rutilus caspicus) release, maintenance and their restoration, this study was performed with the aim of the evaluation of these fish (average weight of 1.4 g± 0.018 g) to the salinity tolerance of the Caspian Sea by abrupt and gradual transfer methods on two different occasions of short-term (24 hours) and long-term (21 days). For this reason, 360 juvenile roaches were distributed to 9 different experimental treatments (each of them with 3 replicates) with 1) increased abrupt salinity (direct transfer to the Caspian Sea water), 2) increased gradual salinity (3 ppt for every 24 hrs) and 3) the Control group (freshwater). In order to evaluate the ion regulation, osmolality, Na⁺, K⁺ and Cl^- were measured in fish. Some immune responses related to the increased salinity (immunoglobulin and lysozyme) and stress indices (cortisol and glucose) were also measured. Based on the obtained results, the fish in both treatments of increased salinity showed high percentage of survival. All parameters related to ion regulation were decreased after a primary increase. Furthermore, the trend of cortisol and immunoglobulin changes were negatively correlated showing decreased stress response and increased immune system for both salinity transfer methods. Thus, the roach juveniles (1-2 g) are able to be transferred into the Caspian Sea directly.