فصلنامه شیلات
سال هفتاد و پنجم شماره 4 (زمستان 1401)

Due to the increasing of industries on the coast and the development of coastal cities, aquatic ecosystems and species are affected by discharged pollutants, especially heavy metals. After entering aquatic ecosystems, heavy metals accumulate in aquatic tissues, including fish, and eventually enter the food chain, which can enter the human body through feeding on contaminated fish. The aim of this study was to determine the amount of copper as a heavy metal and its transferring during the food chain of ornamental fish to estimate the presence of contaminants in the food chain. So the effect of copper sulfate (CuS04) and its transmission were investigated in the food chain of Artemia franciscana, Danio rerio (Zebra) and Astronotus ocellatus (Oscar).  Initially, lethal concentration of Cu on Artemia was obtained in 24 hours. At the first step, infected Artemia was fed to zebrafish Danio rerio as the second consumer in two separate environments (clean water and water containing 10% of CuS04). At the second step, zebra fish were fed Oscar fish Astronotus ocellatus as the third consumer in two separate environments (unpolluted water and water containing 10% of CuS04). In the last step, CuS04 was measured in the liver tissue of zebrafish and scar. Also, changes in glucose and alanine aminotransferase (ALT), aspartate aminotransferase (AST), and acid phosphatase (ACP) enzymes were measured. The results of this study showed a significant increase in zebra fish and oscar under different treatments exposed to this heavy metal. In addition, a significant increase was observed in different enzymes (ALT, AST, and ACP) and glucose, which indicates damage to body tissues..

This study aimed to investigate the changes and growth pattern of Beluga sturgeon fishing in fishing regions of Golestan and biological characteristics of this species over a period of 13 years. The highest amount of Beluga sturgeon fishing was in 2008, when a total of 95 pieces of this species were caught from five fishing grounds in Golestan province, and the lowest amount was caught in 2020, when 3 pieces of this species were caught. The results showed that the highest average total length was observed in 2020 and the highest total weight was observed in 2017 and the lowest average total length and total weight was obtained in 2011.The sex ratio of male to female elephant fish in the thirteen-year period was 0.66:1, which was significantly higher than the female population (X2=19.69, p<0.05). The range of growth coefficient (b) for the population of Beluga sturgeon between 2008 to 2020 years varied from 2.56 to 3.97. The results of Pauli test for the relationship between length and weight of Beluga sturgeon species showed that the growth pattern of this species in 2008 and 2010 were negative allometric, in 1393, 1396 and 1397 positive allometric and in 2009, 2011, 2012, 2013, 2015, 2016, 2019 and 2020 were isometric. In general, in a period of 13 years, the amount of elephant fishing in the coasts of Golestan province decreased by more than 90%, so in this region, this trend for Beluga sturgeon is among the most endangered species, concluding an alarm for conservation of this valuable species in Caspian Sea..

Aras dam has ecological and socio-economic importance in the West Azerbaijan province, which freshwater crayfish (Astacus leptodactylus) is one of the pristine and important sources of export. To investigate the stock status of this species, two models CMSY and BSM were used from 2013 to 2018 and catch data were analyzed in this respect. Sampling was performed in July 2021 in Aras Dam reservoir. The average catch weight was 88.91 g, total and carapace length was 13.88 cm and 7.5 cm, respectively. The amount of CPUE (Number per trap per day) calculated per day in Station I and SII were 0.06 and 0.013, respectively. Fisheries reference points obtained from CMSY and BSM models showed that the maximum sustainable yield of Aras Dam crayfish was between 18 and 24 t. These results indicated a sharp decline in stock and fishing over the sustainable yield, during the past years. Therefore, it can be generally concluded that the freshwater crayfish stocks of Aras Dam severely damaged. Considering the population parameters, and stock status, as well as the reasons of stock depletion, it can be hoped that if the stock rebuilding program and also the exploitation is defined based on sustainable harvest and maximum allowable catch planned gathered from the results of this study. Therefore, rebuilding of the stocks of this species and prevent its extinction are possible..

In this study, the possibility of using migratory locust as a source of protein in the diet of rainbow trout fry and its effect on growth performance, immunity and hematology of blood serum was investigated. 300 number of rainbow trout fingerling with an average weight (6.09 ± 0.22 gr) with diets of 0% (control), 15% (LM15), 30% (LM30) and 60% (LM60) of formulated locust meal. became Each diet was distributed in a completely random design in 3 replicates with 30 number of fish in each fiberglass tank with the same conditions. At the end of the experiment, the indicators of growth, immunity and blood serum hematology were calculated based on standard formulas and analyzed using Tukey's test. The results showed that the highest final weight was observed in the 30% treatment (616.20% ± 34.89%) and the difference between zero, 15% and 60% treatments was significant (p<0.05). In the 60% treatment, a significant increase in feed conversion ratio was observed compared to the control treatment (p < 0.05). In feeding fish with a diet containing locust meal, the values of glucose, albumin, globin and IgM did not show significant differences among different experimental treatments (p<0.05). However, the amount of total protein, triglyceride and blood cholesterol showed a significant difference in the experimental treatments compared to the control treatment (p < 0.05). Therefore, it can be concluded that the use of 30% of locust meal in the commercial diet of rainbow trout fingerling can improve the growth performance and have no negative effect on the desired level of blood and immune parameters..

In this study, the ability of the Sobeity fish to regulate and restore the capacity of digestive enzymes (trypsin, chymotrypsin, and lipase) during different periods of starvation and re-feeding was studied for 80- day period. 300 fish with an average initial weight of 28.47±0.24 g was stocked in twelve 300-liter polyethylene tanks. In four experimental treatments, including treatment 1 (T1), the fish were starved for two days and fed for eight days; in treatment 2 (T2), the fish were starved for four days and fed for sixteen days; in treatment 3 (T3), the fish were starved for eight days and fed for thirty-three days. The cycles were repeated eight times for the T1, four times for the T2, and two times for the T3 until the end of the experiment (80 days). The control treatment was also fed to satiety throughout the experiment. At the end of the period of starvation, the activity level of trypsin and chymotrypsin in the control treatment was significantly higher than other treatments (P<0.05). The lipase activity level in the first cycle of T1 and T2 did not significantly different from the control treatment. However, the lipase enzyme activity in the midpoint cycle of T2 was significantly lower than control (P<0.05). At the end of days 40 and 80, no significant difference was observed in the activities of three digestive enzymes between the control and the experimental treatments. The present study showed that Sparidentex hasta can cover their digestive capacity after overcoming various periods of starvation..

Biofloc system is a new technology that used in intensive and semi intensive aquaculture systems. The main advantage of this system is reducing the water use, along with increasing the intensity of production based on heterotrophic bacteria than autotrophic bacteria. The fish were divided into 4 groups in 3 replicates. The first group (A) was reared in normal culture situation as a control. In subsequent treatments, juvenile were rearing in a biofloc system containing various carbon sources, including: maize flour (B), Wheat flour (C) and barley flour (D) as different treatments. One hundred and twoenty fingerlings of common carp with initial average body weight of 15.18±2.07g introduced into the experimental treatments and cultured for 45 days. At the end of the experiment, water quality, growth preformance, and metabolic nitrogen excretion rates compared among treatments. Based on the results, water quality improved among all biofloc treatments compared to the control group (p<0.05). Growth indices significantly improved in all biofloc treatments (p<0.05). The highest growth rate and the lowest feed conversion ratio were recorded in the biofloc system containing barley flour (p<0.05). Ammonia and urea excretion in biofloc treatments were significantly higher than the control group (p<0.05). The highest ammonia and urea excretion rates were recorded in the biofloc treatment containing barley flour (p<0.05). Therefore, it was concluded that the use of barley flour as a carbon source in the biofloc system can be used for rearing of common carp. The use of this carbon source, in addition to improving of water quality, is effective in promoting the growth of common carp in the biofloc system..

Koi Herpes Virus (KHV or Cyprinid Herpesvirus 3, CyHV-3) is an etiological agent of an emerging and notifiable disease and one of the mostrisky factors affecting common carp and koi worldwide production with high mortality rates. Molecular methods have been developed and routinely used for the detection of KHV infections. These diagnostic tools are sensitive but still have some drawbacks: they require expensive and bulky apparatus, a large sample volume, and long sample preparation/detection times. Therefore, it is desirable to develop simpler, faster, cheaper and more portable detection methods. Loop-mediated isothermal amplification (LAMP) technique is a novel and next-generation tool which can amplify nucleic acids with high specificity, sensitivity and rapidity under isothermal conditions. In this study, a fragment of the CyHV-3 TK gene was amplified at 65°C in the presence of Bst DNA polymerase and a set of six specially designed primer mixture. The reliability, sensitivity and specificity of this assay for rapid detection of CyHV-3 was investigated and compared to conventional PCR. LAMP assay was successfully developed with the detection of KHV- generated product, and showed 100% specificity and sensitivity of 1.25 fg/µL, that is comparable to the most sensitive method reported to date. The assay was 8000 fold more sensitive and three times faster than conventional PCR. The LAMP assay described in this study revealed a highly sensitive, rapid and reliable diagnostic protocol for detection of CyHV-3..