مجله علمی شیلات ایران
سال سی و یکم شماره 1 (پیاپی 129، فروردین و اردیبهشت 1401)

Gillnets are sometimes abandoned or lost at sea due to sea storms, tearing by a hard object, or the failure of fishermen to find the fishing area. In this study, the data related to the frequency of illegal abandoned fishing nets in Golestan province were collected through field patrols and questionnaire information from spring to winter 2016. 88,465 abandoned fishing nets were collected in the coastal waters of Golestan Province. The results showed that 78.2% of the discovered nets belonged to Caspian kutum, carp, and common roach, 10.4% of them belonged to sturgeon nets, and 11.4% belonged to beach seines and other fishing nets. Among the interviewed fishermen, 49.2% believed that 10-20% of the nets were lost at the sea, and about 6% believed that more than 40% of the nets were lost. In investigating the causes of losing fishing nets in seawater, 52% of the people believed that the nets were stolen. In other words, human factors are one of the main reasons for the loss of the nets. 25.2% of the people consider strong waves and 15.3% of the fishermen, tearing by boat fins, 6.3% of not being able to find the location of the net, and 1.2% of other factors such as rot of nets are considered to be the cause of the gill nets loss.

Bacterial diseases are a major challenge and warning to the development of aquaculture industry. Vibriosis is caused by bacteria of the genus Vibrio, especially Vibrio alginolyticus, in warm and temperate regions, which cause severe damages to the marine fish production economy every year. The aim of the present study was to isolate and identify this bacterium from farmed marine fish with bacterial septicemia symptoms in the farms of the southern provinces of the Iran. A total of 130 fish were sampled and isolated bacterial samples by conventional methods. Isolates were examined for biochemical and molecular properties using specific primers of 16 S rRNA and Collagenase genes to identify Vibrio sp. and alginolyticus species by polymerase chain reaction, respectively. Molecular analysis showed that 109 isolates out of 119 suspected isolates of Vibrio genus were confirmed as Vibrio genus; also, 48 isolates belonged to V. alginolyticus. It is concluded that the cause of more than 44% of cases of vibriosis is caused by infection with V.alginolyticus. For the LD50 determination, 250 Asian sea bass were used and the lowest LD50 calculated for Vibrio alginolyticus isolates was 1.83× 10 8 fish/CFU. The results showed a significant role of vibriosis as well as a high percentage of V. alginolyticus in bacterial septicemia in the studied fish.

Chaetognaths (arrow worms) are strong predaceous mesozooplankton; which feed on other more abundant zooplankton’s groups; their most important preys are Copepods and Appendicularians. So they are considered as one of the most important groups among mesozooplankton communities, especially in the pelagic food web, also widely distributed in the neritic zone of all the oceans. Considering the fisheries activities and ecological aspects of economically and traditionally important ecosystems of the northern coastline of Bushehr, this study aimed to identify, introduce and assess the temporal and spatial distribution patterns of the Chaetognaths in the Persian Gulf, restricted to coastal waters of this area. Chaetognaths were collected during seven sampling programs, from Frake river-estuary, three sites of large creek-estuary of the Shif, one site in the sea, and one site in the Lashkari creek-estuary, at the middle and last day of each season. During all surveys, the depth of the sampling location, Secchi depth, water temperature, pH, and salinity were measured. Finally, 4 species were identified, Flaccisagitta enflata, Aidanosagitta neglecta, Aidanosagitta regularis, and Zonosagitta pulchra, with relative abundances of 56.56%, 29.42%, 11.25% and 2.87% respectively. The highest total density was observed in the sea station at the cold season, for two species of F. enflata and A. regularis. A. neglecta and Z. pulchra reached to the highest density in coastal stations and shif creek at summer. Based on dbRDA (distance based Redundancy Analysis), the depth of sampling location explained effectively the distribution pattern of F. enflata and A. regularis, with a positive correlation,   but salinity demonstrated a negative effect. Also based on the results of dbRDA, depth of the habitat is the most important factor which explains negatively the distribution pattern of A.neglecta and temperature was the correlated factor with the distribution pattern of Z. pulchra in our study area.

In the present study, growth indices, body composition and digestive enzymes of juvenile common carp (Cyprinus carpio) were investigated in biofloc system with different stocking rates. So, 825 juvenile fish (17±1.2g) were randomly transferred to 15 fiberglass 200 liter tanks in lab of Khorramshahr University of Marine Science and Technology. Twenty five fish were stocked in a tank (2.12 kg/m3) with water exchange (control), and also 25 (2.12 kg/m3, D25), 50 (4.24 kg/m3, D50), 75 (6.37 kg/m3, D75) and 100 fish (8.5 kg/m3, D100) were stocked in tanks as a biofloc treatments. The photoperiod included 12 h light and 12 h darkness and the duration of the experiment was 40 days. Control and other treatments treatment were fed with a commercial diet containing 35% and 25% protein, respectively for 40 days. The fish were fed manually, three times a day (8:30, 12:00 and 15:30) based on 3% of the body weight. In the control treatment, the water was exchanged 25% every two days. Dissolve oxygen, temperature, pH and salinity parameters were not significantly different in biofloc system compared to the control (P>0.05). Biofloc volume (BF) and total suspended solids (TSS) values were higher in biofloc treatments than the control (P<0.05).  Total ammonia and nitrite levels were lower in biofloc treatments than the control (P<0.05). The nitrate levels were higher in D100 treatment than other biofloc treatments (P<0.05). Final weight, percentage of weight gain, specific growth rate and feed conversion ratio were not significantly different in D25 and D50 treatments compared to the control (P<0.05). The protein efficiency was significantly increased in B25 and D50 treatments compared to the control (P<0.05). The lowest protein content was observed in D100 treatment compared to the other treatments (P<0.05). The lipase, amylase and alkaline phosphatase activities did not show significant difference in biofloc treatments compared to the control (P<0.05). The results of this study showed that biofloc system decreased the consumption of dietary protein while reducing the pollution load of nitrite and total ammonia.

Peeled oak acorn was soaked in tap water for 24 or 48 h. The 24 h soaked acorn was fermented by baking yeast for 24 h. The effect of four diets including treatments 1: diet without acorn, 2: diet containing not soaked and fermented acorn, 3: diet containing 48 h soaked acorn, and 4: diet containing 24 h soaked and 24 h fermented acorn was determined on common carp with an initial weight of 8 g for 61 days. The phenolic compounds in the acorn were significantly reduced by soaking and fermentation (P<0.05). Diet had no significant effect on total length, feed intake, carcass moisture and survival rate (P>0.05). Treatment 3 significantly increased weight and specific growth rate in comparison with treatments 2 and 4. The condition factor in treatment 3 was significantly higher than treatment 4. The best feed conversion ratio and protein and lipid efficiency rates were observed in treatment 3, which were significantly different from treatment 2. There was no significant difference in protein retention between the treatments fed with acorn, but treatment 4 compared to treatment 1 had significantly less protein retention. The highest lipid retention was observed in treatment 1, which had a significant difference with treatments 3 and 4. Acorn led to a significant reduction in carcass crude protein, crude fat and ash. There was no significant difference in terms of carcass ash between treatments fed with acorn. The negative effects of treatments 3 and 4 were higher on the percentage of carcass lipid and carcass protein, respectively. Soaked acorn for 48 h did not have a negative effect on growth and feed consumption and can be used up to 5% of diet, but the study of other soaking and fermentation methods is recommended to improve the carcass quality.

In the present study, the effect of dill extract in the diet of Green terror fish on growth indices as well as survival, blood and Immunological factors is investigated and albumin, total protein, cholesterol, triglycerides, and glucose were measured. For this purpose, 180 fish were prepared and randomly subjected to four experimental treatments containing levels of 0, 0.5, 1.5 and 2.5%. Biometrics were performed every 14 days. The highest values related to specific growth rate, body weight gain, weight gain percentage, daily food intake, protein efficiency ratio, and lowest feed conversion ratio were observed in the group containing 1.5% of dill extract, which was statistically significantly different from other The treatments were especially in the control group (p<0.05). In terms of obesity coefficient index, the highest rate was observed in the group containing 2.5% and the lowest rate was observed in the control group, which was statistically significant (p<0.05). The results of biochemical blood parameters in an eight-week period showed that there was a significant difference between the treatment of 1.5% dill and the control group in terms of total protein, globulin and albumin (p<0.05). Also in the present study, the highest triglyceride level was observed in the control group, which was significantly different from the 2.5 and 0.5% dill treatments (p<0.05). The highest and lowest glucose levels were reported in dill and control treatments, respectively. In this study, it seems that the use of dill supplements in Green Terror fish can have a significant effect on improving growth indices and biochemical parameters of the blood. The results of this study can be widely used in improving the production of this valuable species and creating new perspectives on breeding conditions.

Aquaculture has become one of the sustainable sectors with a bright and promising future to ensure the safety of human food. Due to the need to increase the production of this healthy food, intensive aquaculture has been welcomed, which causes many diseases, especially viral. In recent years, VHS virus has caused irreparable damage to the country's trout fish producers. Rapid diagnosis and elimination of infected fish in the early stages of the disease is essential to control the spread of the disease effectively and reduce cost wastage, and rapid diagnostic kits will be very useful. These kits are made out of  antibodies. In this research, the production of polyclonal IgG antibodies against VHS virus was investigated in a New Zealand rabbit animal model(Oractulagus cuniculus). In order to this , the stock of  VHS GenBank Accession No: AF345859) Prepared by European Reference Laboratory as  an antigen to stimulate the immune system with Freund's complete adjuvant in four treatments including negative control of distilled water, treatment one with a concentration of 1 cc virus Complete, treatment two with a concentration of 0.5cc virus and 0.5cc adjuvant Freund, treatment three with a concentration of 75% virus and 25% adjuvant, treatment four with a concentration of 25% virus and 75% adjuvant, for four months, once a month IM In 5 groups of New Zealand rabbits injected, after 15 days, the ratio of blood sampling from the peripheral vein and antibody absorption (OD) were measured. During 4 blood samples, the amount of IgG antibody absorption was significantly different between the groups P <0.05) showed. Antibody purification was then activated by Sepharose Protein G adsorption chromatography column 4B (Sepharose® 4B) ) and OD of antibodies purified by Nano-200-Ver1.0 at 280 nm in the second treatment were 2.60 and the third treatment was 2.38 and the antibody concentrations were 1.82 and 1.67 mg, respectively. This antibody is going to be used in the rapid diagnosis kit of this disease.

Unfortunately, the high diversity and high geographical spread of invasive species, e.g. tilapia species in Shadegan lagoon, has become one of the main challenges for the native fishermen and local communities in it. This study conducted field operations from October 2018 to September 2019. Laboratory experiments including the fish biometry, analysis of the biological parameters, the sexual maturity and nutrition were performed based on standard methods. The results of 898 sampling from different species of tilapia showed that fishing combination included 284 redbelly tilapia (Tilapia zillii) with 31.6 %, 578 Blue tilapia, (Oreochromis aureus), with 64.3% and Nile Tilapia, (Oreochromis niloticus), with 4%. The highest abundance of redbelly tilapia (Tilapia zillii) was observed in the length range of 11-13 cm, Blue tilapia, (Oreochromis aureus), with a wide length range of 7-23 cm and Nile Tilapia, (Oreochromis niloticus), in the length range of 13-16 cm. At present, the distribution of three invasive species of tilapia in Shadegan lagoon with more than 50% fishing during the most of months on the year along with unfavorable environmental conditions specially, reduction of quality and quantity of inlet water due to the agriculture and industrial Effluents and dam construction and reduction of water volume, lagoon become in a challenging situation.

In the present study, the effects of the different levels soybean meal replacement with sesame oil-cake in rainbow trout diet on growth performance, body biochemical composition and liver enzymes were evaluated. An 8-week feeding period were performed by Four experimental diets with different levels of sesame oil-cake 0% (S0), 5% (S5), 10% (S10) and 15% (S15), respectively, in a completely randomized design in triplicate. Growth and nutrition indices including final weight (FW), specific growth rate (SGR), weight gain (WG), feed conversion ratio (FCR), lipid efficiency rate (LER) and feed intake (FI) did not show significant differences between different treatments (p<0.05). However, there was a significant difference between S10 (0.23) and S15 (0.21) treatments in protein efficiency rate (PER). In contrast, hepato somatic index (HSI), visceral somatic index (VSI) and condition factor (CF), showed significant difference (p<0.05) between experimental treatments, so that most of them were related to the treatments (S10= 1.07), (S10= 6.29) and (S15= 1.05, respectively, and the lowest of them were observed in the treatments (S15= 0.98), (S15= 5.78) and (S0= 1.02), respectively. There was a significant difference in fillet protein, lipid and moisture (p<0.05) but the amount of ash did not show any significant difference. In addition, the activity of alanine amino transferase and aspartate amino transferase showed a significant decrease with increasing sesame meal and conversely, the activity level of alkaline phosphatase increased significantly with increasing replacement level (p<0.05). According to the results, it can be stated that not only the use of sesame meal instead of soybean meal up to 15% did not have a significant effect on rainbow trout growth and nutritional indices and also improved the health status and quality of the fillet biochemical composition.

One of the important factors in the use of natural pigments in various foods is their stability and preservation of their antioxidant properties under the production and storage conditions. Astaxanthin is one of these natural pigments that microalgae are one of its resources. In the present study, after the extraction of astaxanthin from hematococcus microalgae (Haematococcus pluvialis) by a combined method (HCL-Acetone), the effect of temperature, pH, and time parameters on its stability and antioxidant activity (DPPH free radical scavenging activity and reducing power of ferric) were evaluated. The results showed that the effect of temperature, pH and time factors alone and the interactions between the time and temperature were significant (p<0.05). However, the interactions of pH with time, pH with temperature, and the interaction of three factors together on the concentration and stability of astaxanthin were not significant (p>0.05). According to the findings, the antioxidant activity and pigment stability at 4 °C was more than 20 °C and with increasing the storage time, these properties were decreased. The pH changes did not have much effect on the pigment properties, although the results at pH=5.5 were relatively better than pH=4.5. Among the studied treatments, DPPH free radical scavenging activity as well as the reducing power of the extracted pigment ranged from 45.5-93.11% and absorption of 0.31-0.81 at 700 nm, respectively. This property makes it possible to use this pigment in food products as an antioxidant. However, use of various methods such as coating the pigment for using in heat-treated foods is recommended due to the low stability of the pigment at the higher temperatures.