فصلنامه شیلات
سال هفتاد و هفتم شماره 1 (بهار 1403)

From an environmental point of view, one of the major problems of the fish meal industry is discharges of stickwater (SW), an intermediate product from pressing process of fish meal, which is rich in organic matter and nutrients and can be used as a substrare for Recovery and valorization such as single cell protein and lipid. In this study, Yarrowia lipolytica and Aspergillus niger were used to produce single cell protein (SCP) and single cell oil (SCO) using Kilka stick water as the source of medium. The pattern of the yeast and fungus growth was studied by plate count method. Also the amount of remaining oil and remaining protein was analyzed for values of total protein, and total lipid. Data was analyzed by randomized complete block design and the results showed that yeast, as a fat-storing microorganism, had a higher ability to grow on SW, compared to protein-storing fungus within 120 hrs and produced more microbial biomass in a shorter time. 100% yeast treatment had the highest SW lipid reduction rate (more than 50%, equivalant to 21.7 mg/L) in 120 hrs, while 100% fungus treatment showed the lowest rate. Regarding SW protein reduction, 75% yeast-25% fungus treatment had the highest rate. Overally, Yarrowia lipolytica in single culture had the highest growth and SCO production and 75% yeast-25% fungus mixed culture treatment had the highest SCP production. Based on the results obtained from this study, application of pure Kilka stick water is suitable for production of SCP and SCO and reduction of its organic matter as wastewater.

Density and seasonal changes of polychaet communities in Tiab estuary, located in Hormozgan province, were studied at different seasons in 2015. Sampling from 4 stations was performed using Van vin Garb (0.04 m2) in triplicates. The average total density of Polychaetes (±sd) was 226.04±193.06 per square meter. 21 families, 28 genera and 39 species were identified. The Cossuridae family had the highest frequency (38.8%). The highest average of Margalef index recorded in station 1 (4.6) and those lowest in station 2 (2.8). Regarding Shannon index, the maximum and minimum value were recorded in station 3 (2.7) and station 1 (2.2), respectively. The results of multivariate CAP analysis showed the effective relationship between environmental parameters and dominant Polychaetes. It was found that Aglaophamus malmgreni was the indicator species of station 4 in all seasons and the most important parameters affecting the distribution of this species were TOM, Silt and NO3. It was also shown that Cossura longocirrata is the dominant species of station 2 in spring and the amount of oxygen and increasing its concentration showed a close relationship with the distribution pattern of this species in the presence of the predominant presence of Prionospio steenstrupi at the same station in summer. Chlorophyll a was as an effective factor in distribution of this species. In the case of Cossura spp. and Nephtys spp. It was found that higher temperature with high concentration of PO4 and at the same time the species are resistant to oxygen deficiency and finally PO4 was identified as the most important factor affecting the distribution of Prionospio banyulensis as the dominant species in stations 1 and 3. The results showed Tiab Estuary with high biodiversity, balanced distribution of Polychaets and dominant sensitive species to pollution and environmental stress and the fluctuation of Polychaete communities is influenced by seasonal fluctuations and quality of water and sediment parameters in this aquatic ecosystem.

Despite the development of polystyrene nanoplastics (PSNPs) in different fields, including nanotechnology, environment, industries, and their possible approach to aquatic ecosystems, a few studies have been conducted on nanoecotoxicology in aquatic animals. Therefore, this study was designed and conducted to measure the effect of toxicity of the PSNPs while transferring from the diet to the body of the fish (food concentrations= 0.1, 10, and 100 mg/kg) on juvenile rainbow trout (Oncorhynchus mykiss) in a 28-day chronic treatment and the control group (food concentration = 0 mg/kg) after the 7-day adaptation period, in three repetitions (15 juvenile trout were included in each repetition per concentration). Depending on the target test, fish sampling in the treatment group was taken after 24 h without food. According to the results, the survival rate (SR) (84.44 ± 3.14%) was significantly reduced with the highest dose of PSNPs compared to other treatments (P<0.05). But other growth indices did not show statistically significant difference (P>0.05). From the point of view of tissue pathology of polystyrene nanoplastic in the liver tissue in treatment 3 and 4, injuries such as vacuolation, necrosis, sinusoidal expansion and pyknotic nucleus were observed in rainbow trout. Based on the obtained results, the negative effects of polystyrene nanoplastic release on health and immunity at the cellular level were seen in liver histology in the studied aquatic sample. In general, this study showed that the entry of nanoplastic particles through the digestive tract causes changes in the histological parameters of the liver. However, more comprehensive studies are needed in this field.

The aim of this study was to find the effect of initial feeding with different live feeds in the larval stage on growth, hematological and blood biochemical indices of Persian sturgeon (Acipenser persicus) after the stage of adaptation to dry food. In order to carry out this study, 900 Persian sturgeon with an average weight of 263.8 ± 2.3 mg (mean ± standard error) were selected from each larval stage treatment, and 300 larvae were selected in each tank with 4 treatments and 3 replications. During 21 days, they were acclimated to dry food using chironomid and formulated diet. These Persian sturgeon fries were reared in the larval stage in 4 treatments includes: 1 (Artemia + Daphnia), 2 (Artemia), 3 (Artemia + chironomid) and 4 (chironomid). Final weight, growth rate, feed efficiency and daily growth rate in treatment 4 were significantly higher compared with the other treatments. Specific growth rate and weight gain in treatment 4 were higher than that of all treatments and food conversion ratio in this treatment was lower than the other treatments (P < 0.05). After adaptation of fries to commercial dry food, total protein and albumin were the highest in treatment 3 (Artemia and chironomid) and the lowest in treatment 1 (Artemia and Daphnia) (P>0.05). In terms of hematological indices, the number of white blood cells and mean corpuscular hemoglobin concentration were the highest in treatment 1 (Artemia and Daphnia) and lowest in treatment 2 (Artemia) (P<0.05). According to the results of the present study, feeding with chironomid larvae in the larval stage has a great effect on the growth and blood biochemical indices of Persian sturgeon fry after getting used to dry food, which chironomid larvae was used to feed Persian sturgeon larvae. The use of chironomid larvae is recommended for the initial feeding of Persian sturgeon fry and the transition stage from live feed to commercial dry food.

Red seaweeds contain compounds such as agar and hormones that have many uses in industry. This research was done to determine biomass and extract two hormones and agar from Gracilaria corticata algae. Methods Sampling was done from December 2014 to November 2015 in Bushehr port, one month apart. Biomass and environmental parameters were measured and algae harvested in the selected transect. After the extraction steps, hormones are separated by the HPLC method and identified by standard injection. The highest amount of agar occurred in July with 63.3%, Zeatin in September with 21.9% and indole butyric acid with 19.21% in January. The highest fresh weight of this algae was measured in March at 423.33 grams per square meter. The results of the ANOVA and Chi-squared statistical tests showed a significant difference in 6 months of sampling in all samples (P<0.05). The amount of agar showed a significant correlation with the biomass. Also, among environmental factors, agar was correlated with salinity and temperature. Butyric indole of acid in January caused the growth of alga, but Zeatin did not show a significant effect on the growth of this species. In general, in order to extract these materials, harvesting can be done in the months that have the highest amount. Considering the exorbitant price of these hormones and the need to use them in algae extracts and algae liquid fertilizer, this research is a starting point for extracting all kinds of hormones from these algae.

To investigate the effect of hydroalcoholic extract of rosemary (Rosmarinus officinalis) on chemical, microbial and sensory indices of grouper (Epinephelus coioides) in refrigerated conditions, four treatment groups: control treatment (uncoated fillets), fillet coated with rosemary 0.1%, Fillet covered with rosemary 0.2% and fillet covered with 0.4% rosemary were run. The 100 gr of samples were stored at refrigerator (4ºC) for 15 days. The measurements were undertaken at 0, 5, 10 and15 days at the beginning of the experiment. Generally, peroxide value (PV), thiobarbituric acid (TBA), total volatile base nitrogen (TVN), pH, counting total bacteria, counting cold-loving bacteria were significantly increased with storage time (P<0.05). The results showed that the use of rosemary extract improved the quality of chilled grouper.

Cyanobacterial blooms cause huge and irreparable financial losses to fish farmers every year. One of the most effective methods for managing water cyanobacterial bloom is biological control by adding pathogenic agents to break down cyanobacterial cells. Therefore, this study investigated the possibility of using Pseudomonas putida bacteria to control the bloom of cyanobacteria Chroococcus sp., Oscillatoria sp., Microcystis sp. and Gloeocapsa sp., isolated from fish Culture ponds was done in the laboratory. The results of this study showed that Pseudomonas putida bacteria have a significant effect on controlling all 4 cyanobacterial species. So, for the cyanobacterium Chroococcus sp. In the experimental group containing 106 CFU/ml of Pseudomonas putida bacteria, there was a moderate 80.7% reduction and also in the group containing 104 CFU/ml of this bacterium, there was 63.1% reduction compared to the control group models on the 10th day. Also, for the cyanobacterium Oscillatoria sp. at the 10th day, 78.9% reduction occurred in 104 CFU/ml and 87.7% in 106 CFU/ml. Next, for the cyanobacterium Microcystis sp. On the tenth day, there was 61.7 percent decrease in the group containing 104 CFU/ml and 70.5 percent decrease in the group containing 106 CFU/ml of Pseudomonas putida bacteria. Finally for the cyanobacterium Gloeocapsa sp. A decrease of 72.3% was observed in the experimental group containing 104 CFU/ml and an 83% decrease in the group containing 106 CFU/ml. Although the control group show an increase of 37-78 percent (P˂0.05). The results of this research showed that the bacterium Pseudomonas putida has a high efficiency in controlling the bloom of cyanobacteria.

Over many years, with the increase in population, the increasing human demand for food consumption and the importance of maintaining environmental security, researchers have paid attention to the use of microorganisms to increase the amount of product per unit area more than in the past. Some species of Trichoderma fungus are known as growth promoters in plants. The sensitivity of different species of fish to toxic substances is different, so toxicology tests are done on different fish. In this experiment, 120 pieces of rainbow trout (Oncorhynchus mykiss) with 3 types of Trichoderma fungi (Trichoderma afroharzianum, Trichoderma ghanens, Trichoderma lixii), treatment 1 (TC-1), treatment 2 (TC-3), treatment 3 (TC-4) and control treatment (CL) were fed completely randomly. Finally, growth factors (daily growth rate, weight gain percentage, specific growth factor, food conversion factor), approximate carcass analysis (protein, fat, ash, and moisture), and hematology (hemoglobin, hematocrit, white and red blood cells, neutrophils, Monocyte, lymphocyte, mean hemoglobin red blood cells (MCHC), size red blood cells (MCV), mean hemoglobin red blood cells (MCH)) were evaluated. The investigation growth factors showed that the treatment (TC-3) had significant difference with other treatments and the control group. Also, the evaluation of blood parameters in this research showed that Trichoderma significantly reduces the level of these factors in rainbow trout. The analysis of the rainbow trout carcasses in the treatments fed by different strains of Trichoderma showed that the amount of protein, fat and moisture in the control groups and the treatments were not significantly different; but the lowest amount of cholesterol and triglyceride was observed in the control. Considering the changes in the hematological factors of fish treated with Trichodema, the measurement of these factors can be used as biological index, a tool for monitoring and evaluating the health of aquatic ecosystems. Since it is necessary to use chemical pesticides and their toxicity even in very small concentrations on fish, it is important to investigate the adverse effects of chemical pesticides on aquatic health from the perspective of fisheries and environment.