نشریه علوم و فنون شیلات
سال یازدهم شماره 2 (پیاپی 38، بهار 1401)

In this study, the orangefin ponyfish (Leiognathus bindus) was hydrolyzed by alcalase in an enzyme to substrate ratio of 1: 100 for 300 minutes, and the degree of hydrolysis was measured for 5 hours. Also, the hydrolysate was fractionated by centrifugal having molecular mass cutoffs of 3, 10, and 30 kDa, and four peptide fractions were obtained. Then, the antioxidant activity (DPPH and ABTS free radicals scavenging activity) of peptide fractions, as well as hydrolysate, were measured at different hydrolysis times. The degree of hydrolysis was the highest (55.43 ± 2.11%) at a hydrolysis time of 240 minutes. The hydrolysate had a high amount of hydrophobic amino acids (50.6%) which cause antioxidant properties. The results of DPPH radical scavenging activity showed that the highest scavenging activity was obtained at a hydrolysis time of 240 minutes (75.59 ± 1.46). Also, among all the fractions, the 3-10 kDa fraction exhibited the highest scavenging activity compared to other fractions (80.58 ± 2.96% at a concentration of 5mg /ml). Based on the result of ABTS radical scavenging, the highest activity was reported at 240 minutes after hydrolysis (50.54 ± 0.63). Also, among all peptide fractions, the 3-10 kDa fraction had significantly higher scavenging activity than other fractions (84.58 ± 0.44 at a concentration of 5 mg /ml). The results of this study showed that the peptides obtained by enzymatic hydrolysis of orangefin ponyfish are a good candidate for providing antioxidant properties.

In addition to health effects, plant extracts can be used as natural preservatives with antioxidant and antimicrobial properties in the food industry. In this study, effect of antioxidant and antimicrobial properties of ethanolic extracts of watercress on the chemical and microbial quality of rainbow trout fillet at refrigerator temperature for 12 days was investigated. After drying the leaves at darkness and room temperature extract was extracted with 45, 65, 75 and 96% ethanol solvents for 24 hours at 65 °C. The results showed a significant difference (P≤0.05) in yields and phenolic content, 0.1 mg /ml of extract 65% with an extraction efficiency of 20% the highest amount of total phenol (88.60 ± 2.46%), DPPH (84.73 ± 0%); and ABTS (83.83 ± 0.06%) were. Also, the growth inhibition of the pathogenic bacteria Listeria monocytogenes, Escherichia coli, Staphylococcus aureus and Salmonella enteritidis in sample extracted with 65% ethanol had a significant difference with other extracts (P≤0.05). Rainbow trout fillet samples in 65% ethanol extract showed lower levels of TVB-N, PV and TBA to the control treatment during storage (P≤0.05). Rainbow trout fillet samples in 65% ethanol extract showed lower levels of TVB-N, PV and TBA indices of fillets compared to control treatment during storage (P≤0.05). Talking about bacterial index, the amount of total and pseudomonas bacteria in the treatment containing the extract did not reach the maximum allowable limit (106 cfu /g-1) by the twelfth day, Indicates the effectiveness of the extract on increasing the shelf-life of fillets compared to the control.

The DINEOF algorithm is a parameter free technique based on iterative EOF analysis that is used to calculate the missing data in a given satellite data set (without requiring any prior information). In this study, the DINEOF technique has been used to fill the gaps in chlorophyll-a data series in the Persian Gulf and Oman Sea. Level 3 data (4 km spatial resolution) of chlorophyll-a concentration obtained from MODIS sensor (2003- 2020) for the study area were used. In some of the images several gaps were found in different months of the year. Images with gap in the Persian Gulf and Oman Sea were reconstructed by rtsa.gapfill R-package and DINEOF algorithm in R software. The linear regression analysis was performed between the missing and reconstructed data, and also parameters such as RMSE, MSE, MAD and SNR were calculated to evaluate the validity and performance of the DINEOF algorithm. The maximum number of the gaps in data series were found in July. Hence, the images of July have been examined and reconstructed as the case study. The original maps of chlorophyll-a concentration showed that the maximum number of the gaps were in July 2009 and 2015. Evaluation of the results showed a high accuracy of DINEOF-reconstruction method (e.g. in July 2014, R2 = 0.83, RSME = 0.34, MAD = 0.14, MSE = 0.10). The results showed that the implementation of the DINEOF algorithm (in R) to reconstruct the gaps in chlorophyll-a concentration images could serve as a rapid and efficient technique.

Polysaccharides possess diverse biological properties, mostly owed to their structural complexity and molecular heterogeneity, that could be improved through engineering methods and application of structural modifications. The objective of the present study was the assessment of antioxidant properties of hydrolyzed fucoidan from seaweed Nizamuddinia zanardinii and the correlation of molecular weight with biological function. After the removal of pigments and low molecular weight compounds, crude extracted polysaccharide was hydrolyzed at 100 C for 10, 20, 40 and 60 minutes using 0.01N HCl. The average molecular weight of crude fucoidan 1254.4 × 103 g/mol and for hydrolysates FH10, FH20, FH40 and FH60 was 974.5, 891.8, 806.5 and 705.5 × 103 g/mol, respectively. With the decrease of molecular weight, hydrolysates, compared with the crude fucoidan, exerted considerable DPPH (61.27-84.54%) and ABTS (40.1-88.5%) radical scavenging and Fe3+ reducing power (0.49-0.81 Abs) activities. Among different samples, hydrolysate FH20 showed the greatest capacity for DPPH radical scavenging activity (70.45-84.54%) and Fe3+ reducing power (0.49-0.81 Abs). Overall, the results of the current study showed that hydrolysis and reduction of molecular weight significantly improved the antioxidant activities of the fucoidan while time did not result any significant differences in antioxidant properties of hydrolysates which could be due to alterations in functional groups. Hence, fucoidan isolated from the examined species could be utilized as antioxidant agents in forms of native or hydrolysates.

So far, very limited research has been done on Euryglossa orientalis parasites in our country. In the present study, helminthic infection of 50 digestive tracts of E. orientalis, were examined in Bandar Abbas in 2016. After procuring the fishes, they were transferred to the laboratory and different parts of their bodies were measured for a morphometric study. Then whole digestive tract of the fishes was removed, opened with a small scissor into a dish and the contents was searched for the presence of helminth. Then, the isolated helminth parasites were fixed in 5% formalin or 70% ethanol and stained with azocarmine. The parasites were identified with the aid of reliable sources. The results indicated that out of 50 fish tested, only 5 fish (10%) were infected with the parasite. Thus, in 10% of the fish, Plagiocirrus primus and in 2% of them, Lepocreadioides zebrini and Scolex pleuronectis were identified. This result shows that the infection of Euryglossa orientalis with helminths is mild in the coasts of Bandar Abbas in summer. P. primus is reported for the first time from Persian Gulf coasts.

This study was conducted from April 2017 to June 2018 in a Trout aquaculture farm in Firoozkoh, Tehran province, to distinguish environmental and managerial risk factors affecting incidence of viral diseases in the fish farm under study. Averaged visit from fish farm was 2 times a month and all biosecurity measures were advised and applied during every visit. Some of the physico-chemical parameters were recorded daily. Samples from all cargoes of eyed-eggs imported from abroad and also from larvae after active swimming and absorption of yolk sac were taken for RT-PCR test. Virology, bacteriology, parasitology and mycology tests in the farm and authorized laboratory were done. Clinical observations, macroscopic and microscopic examinations, checking all the sanitarian and productional managerial factors, also checking all the physical and chemical factors affecting the outbreak of viral diseases were done. During clinical observation of fishes, these symptoms were observed; anorexia, gathering at the raceway’s side and outlet, cachexia, one and two side exophthalmia, melanosis, integument ulcers, hemorrhage in ventricular and ocular areas, petechia in ventricular area, fecal casts, high mortality and also presence of a large number of moribund fishes. The result of the laboratory examinations was IHN positive of Rainbow trout fries. This disease caused about 80% mortality of the fries produced from the imported eyed-eggs cargo. The other fatalities with different reasons were also recorded such as; the Lutra’s attack at nights, the farm’s personnel running amongst other farms and transferrin pathogens, the transportation vehicles not being proper disinfected while inter to and exit from the farm and the severe food intoxication of fries. Regarding the results of this study, instruction of scientific and practical models has presented to decrease the effect of environmental and managerial risk factors in the incidence of the disease.

In this study, the effects of different levels of dietary supplementation with vitamin C, astaxanthin and lecithin on ionic (K+, Na+, Ca2+ and Mg2+) and biochemical (Total protein, cholesterol and glucose) indices of ovarian fluid, also its effect on sperm motility duration in Caspian brown trout (Salmo trutta caspius) were investigated. For this purpose, nine experimental diets: C0A0L0 (0 mg kg-1 vitamin C, 0 mg kg-1 astaxanthin and 0% soybean lecithin), C300A50L0, C700A100L0, C0A50L6, C300A100L6, C700A0L6, C0A100L9, C300A0L9 and C700A50L9 were formulated and broodstocks (2.51±0.05 kg) were fed for four months. After maturation and stripping, ovarian fluid was separated for ionic and biochemical indices. To evaluate sperm motility, 1 μl of milt was placed under a microscope with fresh water (as a control treatment) or ovarian fluid of experimental fishes. Sperm motility was measured with a chronometer. Results showed that the highest amounts of Na+, K+, Ca2+ and Mg2+ ions were obtained in ovarian fluid of C300A100L6, C300A100L6, C0A100L9 and C300A100L6, respectively, which were significantly different from C700A50L9 (p<0.05). Also, the highest levels of protein, cholesterol and glucose were observed in C700A50L9, C0A50L6 and C0A100L9 treatments, which were significantly different from C0A0L0 treatment (p<0.05). Lowest duration of sperm motility was obtained in fresh water (43.96±2.25 seconds) which was significantly different from other treatments (p<0.05); however, the highest sperm motility was observed in C300A100L6 and C0A100L9 treatments (80.76±2.03 and 80.7±1.76 seconds, respectively).