مجله علمی شیلات ایران
سال سی و سوم شماره 2 (پیاپی 142، خرداد و تیر 1403)

Considering the increasing speed of destruction of natural aquatic habitats in the rivers leading to the southern basin of the Caspian Sea and the importance of investigating the habitat conditions of the release sites of juvenile fish with economic value, in this research for the first time (at the national level) in order to investigate the suitability of Tajan River from the point of view of releasing Caspian kutum fingerlings, habitat suitability index (HSI) was used. Considering that currently the only available option of the Iran Fisheries Organization for the release of the fingerlings in the Tajan River is in the estuary of this river, therefore, in the current research, this area was selected to sample the fingerlings and investigate various biotic parameters (phytoplankton and zooplankton) and abiotic (water temperature, pH, salinity, dissolved oxygen, turbidity, total suspended solids, total dissolved solids, electrical conductivity, total hardness, ammonium nitrogen, NH3, biochemical oxygen demand, chemical oxygen demand, nitrite nitrogen, nitrate nitrogen, total nitrogen and total phosphorus). The above-mentioned biotic and abiotic parameters were determined during the months of July, August and September 2022 and August and September 2023. The highest selectivity index values for R. frisii were related to NH3. HSI values of Tajan River estuary for R. frisii fingerlings in the studied time period was calculated as 0.592. Therefore, on this basis, the study area can be classified as "suitable habitat" for the fingerlings. Nevertheless, the comparison of the range of changes of the habitat variables measured in this research with the respective permitted ranges showed that the conditions of the release area of the fingerlings were not suitable from the point of view of the range of changes of some parameters (including total suspended matter, total nitrogen, total phosphorus, ammonium nitrogen, electrical conductivity and turbidity) during the study period.

In 2022, the world trade of tuna fish was 42.63 billion dollars, which is expected to reach 52.85 billion dollars in 2028. The three countries of Thailand, Taiwan, and Spain in terms of quantity and the three countries of Thailand, Spain and Ecuador in terms of value are in charge of 40% of world trade, respectively. Fresh tuna (USD 672 million), frozen fillets (USD 1.65 Billion), whole frozen fish (USD 4.116 Billion) and prepared and packaged fish (USD 6.765 Billion) have been traded in the world trade. In fact, 58.6% are prepared and packed, 35.6% whole and frozen and 2.4% whole and fresh are exchanged in the world. In the twelve years ending in 1401, the amount of exploitation of tuna stocks in Iran has reached 289 thousand tons with a growth of 4.8%. Iran's tuna fish export, despite being the first in the west of the Indian Ocean and the second in the Indian Ocean, has reached 2604 tons with a value of USD 425 thousand to 2604 tons with a value of USD 2.3 million, which is 30.8% and 15% growth in terms of quantity and value, respectively. Imports have also arrived from 66.8 thousand tons with a value of USD 59.4 million to 10.2 thousand tons with a value of USD 20.9 million and have grown by -14.5 and -8.3 percent, respectively. The share of these fish in the total catch of Iran is 38.5% and its export is 1.4% of the country's aquatic exports. The 33% increase in the domestic price of fish tuna in this period and the difference in its price with the imported price in 2024 have created special conditions in Iran. Currently, the article examines the country's strengths and weaknesses, opportunities and threats, quality of fishing, improvement of the fleet and transportation, reduction of waste in the missing links of the industry, diversification of processed products, as well as constructive interaction with international organizations and It suggests continuous presence and monitoring in the world market and having a comprehensive plan and road map for the development of tuna and tuna-like species industry in Iran.

Listeriosis, an important illness with a high mortality rate (up to 30%), is caused by Listeria monocytogenes. Nowadays, there are several reports that display the prevalence of L. monocytogenes in fisheries products. Therefore, it is important to investigate and control the expression of virulence genes and adhesion-related genes in different strains of this bacterium in foodstuffs. In this study, the expression levels of inlA, hly, lmo1634, lmo1847, sigB, and prfA genes in two isolates (food and clinical) were investigated under the influence of NaCl and lime juice in the shrimp broth. The results of the independent t-test for the prfA gene demonstrated that the expression level in the treatments of clinical strain was significantly higher than the food strain (p<0.05). Similarly, the average expression of both adhesion genes (lmo1847 and lmo1634) and stress gene (sigB) in the studied treatments for the clinical strain was significantly higher than the food strain. In both strains, the role of lime juice in increasing the expression of virulence and adhesion genes was significantly higher than in NaCl treatments (p<0.05). Overall, it can be stated that the transcription level of virulence- and adhesion-related genes upon exposure to preservatives may be different in the various L. monocytogenes isolates.

In this research, population characteristics and length-based spawning potential ratio (LBSPR) of longtail tuna (Thunnus tonggol) were investigated. For this purpose, information was collected from 4 fishing grounds on the coasts of Sistan and Baluchistan Province, including Bris, Pasabandar, Pezam and Kanarak. In total, more than 700 fish were bio-measured in the research stations (catch loading areas), and the growth indices were infinite length L∞=132(cm), annual growth coefficient K=0.39, annual natural mortality M=0.61, the annual fishing mortality F=0.88, the total annual mortality Z=1.49 and the annual exploitation coefficient E=0.59 and the time of zero length to=-0.28 and the amount of growth performance index Φ'=3.84. The ratio of length-based spawning potential ratio (LBSPR) in 2022 for this species was LBSPR=0.21(0.16-0.27). This research showed that this species has medium vulnerability and medium stock status, and also the annual harvest of this species is in the stage of overfishing.

This research was conducted with the aim of measuring and investigating the relationship between heavy metals (mercury and zinc) and some biochemical factors of blood and gill tissue of sea bass (Lates calcarifer) grown in cages in fall of 2022, located in Kangan port. After fixing the samples with alcohol, they were transferred to the laboratory. The biometric indexes of the fish including weight in grams were measured using a scale and total length in centimeters using a biometric board. Then, a sample of the gills of each piece of fish was prepared and the concentration of each metal was obtained by flame atomic absorption spectrophotometry. To evaluate histological analysis, gill tissue samples were separated and stained by hematoxylin and eosin method. Blood biochemical factors were measured according to the instructions of the commercial kit. The results of this research showed that the average metal mercury and zinc were 0.1 and 7.5 microgram/g respectively in the fish blood serum of the samples. which was lower than WHO and FAO standards. The average concentration of cortisol, glucose, albumin, total protein, cholesterol and triglycerides were 50.55 ng/l, 154.33 mg/ dl, 1.19 g/dl, 3.36 g/dl, 194 mg/dl and 244 mg/dl were obtained, respectively. In the examination of the gill tissue sample of Asian seabass, complications such as hyperemia, bleeding, hyperplasia, cell necrosis and destruction of the epithelium layer of the primary and secondary strands of the gill were observed. The concentration of heavy metals mercury and zinc in the gill tissue of the studied seabass was lower than the standard limit determined by FAO and WHO.

A 70-day study was conducted to examine the effects of dietary butyric and probiotic (Lactobacillus plantarum) supplementation on growth, digestive and antioxidant enzymes activities in Arabian yellowfin seabream (Acanthopagrus arabicus). In this regards, butyric (BA) and L. plantarum were used to design six experimental feeds as follow: 1-control (diet without supplements), 2- probiotic (1.6 × 108 CFU/g) 3-BA 0.5 (0.5% BA supplementation), 4- BA 1.0 (1% BA supplementation), 5- PRO+BA0.5 (probiotic+0.5% BA), 6- PRO-BA 1.0 (probiotic+1% BA). Five hundred and forty fish with initial weight of 2.7 ± 0.1 g were distributed among 18 polyethylene tanks (300 L). Fish were fed with the experimental diets three times a day up to visual satiation making sure no feed remain at the bottom of the tanks. Water temperature and salinity were 31.3 °C and 46 ppt, respectively. Fish fed control and probiotic diets had higher growth rate and feed efficiency than other groups. Fish in PRO-BA1% group had higher total length than other groups. Alkaline phosphatase and chymotrypsin activities in fish fed mixture of probiotic and BA was higher than the other treatments. Amylase activity in fish fed BA1%, PRO-BA0.5 and PRO-BA1% was higher than other groups (P < 0.05). Protease, trypsin and lipase activities did not affect by dietary treatments. Glutathione level in the liver of fish fed control and PRO-BA0.5% was higher than other treatments. Superoxide dismutase activity in fish fed BA1% diet was lower than the other treatments. Catalase activity in fish fed mixture of probiotic and BA was higher than other groups. The findings of the present study demonstrated that inclusion of dietary BA alone might marginally compromise growth in A. arabicus juveniles, but using a mixture of probiotic and BA in both 0.5 and 1% can improve digestive enzyme activity and antioxidant capacity in this species.

In this study, the effects of different levels of biofertilizer containing phosphate solubilizing bacteria on aerobic digestion of Nile tilapia (Oreochromis niloticus) sludge were investigated in vitro under a completely randomized design. Three experimental treatments including aerobic digestion of Nile tilapia solid sludge without adding biofertilizer (control) and aerobic digestion of solid sludge with adding biofertilizer containing phosphate solubilizing bacteria (Pseudomonas putida strain P13 and Pantoea agglomerans strain P5) at levels of 0.1% and 0.2% were used in triplicate. The aerobic digestion containers with a capacity of 1 L (9 containers) were kept in a shaker incubator at 30ºC for 28 days. The results showed that the concentration of phosphate, potassium, and iron nutrients on the 14th day of the experiment in the biofertilizer treatments were significantly higher than the control, but their concentrations on the 28th day in the biofertilizer-0.1% treatment were significantly higher than other treatments )p<0/05). The manganese concentration on the 14th and 28th days in the biofertilized-0.1% treatment was higher than other treatments (p<0/05). The results of the present study indicated that the aerobic digestion of fish sludge for two weeks with adding biofertilizer containing phosphate solubilizing bacteria (P. putida strain P13 and P .agglomerans strain P5) by counting 107 of each bacteria per mL (CFU/mL) at 0.1% improved the release and dissolution of nutrients.

In the present study, the nutritional value of Asian seabass grown in cages was evaluated based on the measurement of proximate compounds and minerals according to AOAC standard method and UV-Vis spectroscopy, respectively, and protein quality indicators were evaluated based on the amino acid analysis using acid hydrolysis and chromatography. According to the results, the levels of moisture, protein, fat, and ash were determined as 77.78, 17.36, 3.21 and 1.56%, respectively, and the energy content was 98.33 kcal/100 g. The results of minerals indicated a high content of sodium and potassium at 371.41±50.98 and 230.26±40.23 mg/100 g and manganese had the lowest level at 0.29±0.11 mg/kg. A total of 18 amino acids were identified, of which 9 were identified as essential amino acids. Glutamic, aspartic, and lysine amino acids were dominant in this profile. The values ​​of protein quality indices including essential amino acids index, biological value, nutritional index, and protein efficiency ratio in this species were obtained as 58.955, 52.53, 10.23, and 2.90, respectively.

Continuous monitoring and evaluation of surface water quality is necessary to protect the global ecosystem and human health. One of the most critical ways to estimate water quality is the WQI method. In order to check the water quality of the Maroon Dam lake located in Khuzestan province (15 km from Behbahan city), five sampling stations were selected at the inlet, outlet and inside of the lake. Sampling to measure the water temperature factor (with intervals of five meters by five meters from the surface to the bottom of the lake) and other factors such as dissolved oxygen, pH, biochemical oxygen demand, total phosphorus, total nitrogen monthly and from the surface to a depth of 60 meters (with distances of 20 meters by 20 meters) were carried out from October 2014 to September 2019 and finally the WQI index was calculated using qualitative parameters. The results of this study showed that the trend of changes in WQI index in different months of sampling in different stations in the quality class was medium to relatively good and the range of changes of this index was calculated between 49 in June to 66 in October. The depth measurement of temperature showed that in the lake behind the dam thermal stratification was created in spring (0 to 20 meters), summer and autumn (0 to 40 meters), but in winter, there is no such difference between surface and depth. According to the evaluation of the WQI index values of the reservoir water, it is suitable for all kinds of drinking purposes for domestic animals, agricultural purposes and raising resistant species of fish.

Since shrimp white spot virus has infected shrimps of all ages and caused widespread loss of shrimps in Iran and across the world, and the pandemic has caused great loss for shrimp farmers, many studies have been carried outto this day in order to identify the reasons and the risk factors regarding this fact. Regarding the importance of the subject and also the different opinions on the results of the past researches, in this study, we have tried to carry out a retrospective review on past studies in Iran and other countries especially on the target tissues for shrimp white spot virus in order to specify the tendency of the white spot virus generally. In this survey, the accomplished studies and researches in the Shrimp Research Center (Bushehr Province), other research centers, universities and higher education centers in Iran and other countries, were collected and the studies carried out on hepatopancreas, intestine, gill and other tissues were examined. Most of the target tissues for white spot virus in Penaeus vannameiwith high intensity are; hemolymph, posterior intestine epithelial cells and cephalothorax epidermis.Some researchers have claimed that the epithelium tissue is the most targeted tissue for white spot virus in penaeus vannamei. The lowest mean values of severity index (SI) were found to be from hemolymph, posterior intestine epithelial cells and cephalothorax epidermis. This could be due to more contact surface of the epidermis with the virus and also more receivers for the virus or lower operation of the immune system especially in horizontal transmission.It seems that hemolymph is the most probable early target tissue for the virus in vertical transmission because the virus replication is at a higher level compared to the other tissues.The most of researchers have pointed out in their researches that tissue of gill, stomach, hepatopancreas and intestine of shrimp are the most important tissues in relation to the white spot virus infection.