نشریه علوم و فنون شیلات
سال هشتم شماره 1 (پیاپی 25، زمستان 1397)

Considering the high importance of food poisoning bacteria in terms of public health threats and economic damages, this research aimed at evaluating food poisoning bacteria in some commercially important fish species collected from markets in Mazandaran, Iran.

For this purpose, 200 frozen fish belonging to 4 species were purchased from the stores and transferred to the laboratory. Samples were tested for total counting of aerobic bacteria, Escherichia coli count, Staphylococcus aureus count, Vibrio parahaemolyticus and detection of Salmonella according to Iranian national standard methods.

In the studied samples, Salmonella, and Vibrio parahaemolyticus were not observed. Comparing the results with the Iranian national standards, the total number of aerobic bacteria and Staphylococcus aureus in all samples was in normal range. The number of E. coli in 14% of samples of Rain bow trout, 20% of Clupeonella Cultriventris, 20% of Hypophthalmichthys molitrix and 10% of Scomberomorus commerson samples was higher than the standard range, due to the importance of pathogenicity of different strains of E. coli in humans, microbial control of the packed fish is very important.

The results of microbial investigations of frozen raw fish collected from stores in different cities of Mazandaran province can be defined satisfactorily, since the majority of samples conform to reference standards.

In this study, the physical and mechanical properties of tragacanth film incorporated with different antioxidant compounds including Hypericum perforatum extract, Ferulago angulata extract and vitamin C 25% (w/v) were studied. Adding Hypericum perforatum extract, Ferulago angulata extract and vitamin C reduced the moisture content and the solubility of the tragacanth film (p<0.05). The lowest amount of the solubility was observed in the tragacanth film containing vitamin C (51.59%) and Hypericum perforatum extract (52.05%). The amount of water vapor permeability (WVP) decreased in the tragacanth film containing vitamin C (1.68±0.06×10-7 gs-1m-1Pa-1 ), and in the films containing extracts increased significantly (p<0.05). Adding both extract and vitamin C to the tragacanth film decreased the mechanical properties of the film. Also, the lowest amounts of opacity were observed in the tragacanth film and tragacanth film containing vitamin C 1.72 and 0.98, respectively (p<0.05). The lowest amount of light transmission was observed in the tragacanth film containing Hypericum perforatum and Ferulago angulata extract (p<0.05).

In this research, we investigated the effects of stocking density on growth performance and survival rate of Persian sturgeon and Beluga.

Stocking densities for treatments 1-5 of Persian sturgeon in stages 1 were 6, 8, 10, 12 and 14 fish/l (initial weight: 116mg) and in stage 2 were 1, 2, 3, 4 and 5 fish/l (initial weight: 2218/6mg). Stocking densities of five months old Beluga juveniles (initial weight: 109.95g) for treatments 1-5 were 80, 100, 120, 140 and 160 fish/m3 in each 250-liter tank respectively.

Growth and feeding parameters were affected as the stocking densities increased in both species. In stage 1 in terms of weight, SGR and food efficiency, treatments 1 and 2 showed significantly higher values (p<0.05) comparing with treatment 5, treatments 4 and 5 and all treatments respectively. In stage 2, there are significant differences amongst the all treatments in terms of weight and SGR except treatments 3 and 4. Food efficiency in treatment 1 was significantly higher (p<0.05) than the rests except treatment 2. In Beluga, there were significant differences amongst all treatments except treatments 3 and 4 in terms of weight, SGR, and food efficiency and the highest values were observed in treatment 1.

The best stocking densities for stage 1 and 2 of Persian sturgeon were 8-10 and 1-2 fish/l respectively and for Beluga, juveniles were 80-100 fish/m3.

Malathion is one of the agricultural organophosphate pesticides used in agriculture that may be found in aquaculture centers. The aim of this study was to investigate the effects of different levels of dietary vitamin C on improving the situation of growth, digestive enzymes activity and blood stress factors of Nile Tilapia (Oreochromis Niloticus) under sub-lethal toxicity of malathion.

In this experimental study, 180 Nile tilapia with weight average of 12.5±5g were subjected to 25% concentrations of Lc50 96h of malathion for 28 days and during this period, the fishes were fed with different levels of vitamin C (0, 300, 600, and 900mg/kg of feed). Data were analyzed by Duncan's new multiple range test and one-way analysis of variance through SPSS 24 software.

The weight gain and specific growth rate of fish fed by the highest vitamin level (900mg/kg of feed) were significantly higher than other groups (p<0.05), while the feed conversion ratio in the fish under mentioned treatment significantly decreased compared to other treatments. Trypsin and chymotrypsin digestive enzyme activities were significantly increased in treatments of 600 and 900mg/kg vitamin C in diet, respectively. The activity of other enzymes at different concentrations of vitamin C in the diet did not show a significant difference (p>0.05). Blood glucose level was significantly higher in control treatment in comparison to the other treatments.

Vitamin C as an anti-stress agent reduces the stress in Nile tilapia subjected by Malathion pesticides and improve the metabolic status and growth performance of Nile tilapia.

The aim of the present study was to investigate the immunoval prebiotic performance on growth indices, hematological parameters, and rainbow trout carcass composition.

Immunoval prebiotic was added to the diet in 4 levels of 0.05%, 0.1%, 0.15% and 0.2% and a diet without prebiotic was used to feed the control group. Each diet was randomly used for fish with an initial weight of 13.66±0.54g in three replicates.

After 8 weeks of feeding, the final weight of fish fed with 0.1%, 0.15%, and 0.2% prebiotics was significantly higher than the fish of the control group (p<0.05). The food conversion ratio in all treatments fed with prebiotic was significantly lower than the control group (p<0.05) and the lowest amount was in 0.15% treatment. The specific growth rate in fish fed with prebiotic was higher than the control group (p<0.05). Also, there were significant differences in the parameters of red blood cells, white blood cells, lymphocyte and neutrophil in fish fed with prebiotic diet and the control group (p<0.05). In the carcass analysis, protein content was significantly higher than the control group and the highest amount was seen in 0.1% treatment. The amount of fat and carcass ash decreased significantly in the control group and the lowest amount was observed in 0.15% treatment.

Addition of immunoval prebiotic with 0.2-0.15% rate to rainbow trout diet had positive effects on growth indices, blood parameters, and carcass composition

Determining bioavailability fraction of the elements in sediments is an important topic in toxicology. Considering the specific conditions of the Persian Gulf and the impact of pollutants, the aim of the present study was to evaluation of toxic elements bioavailability from the total amount of surface sediments in the Persian Gulf.

In the present study, the total concentration and bioavailability fraction of copper, lead, zinc, cadmium, nickel, and chromium were measured at 14 coastal stations of Hormozgan province and Qeshm island. Nitric acid and perchloric acid were used to measuring the total concentration and K protease enzyme solution was used to measuring the bioavailable fraction.

Zinc and chromium have the highest mean of total concentration, respectively. Qeshm island has more pollution than Hormozgan. The higher bioavailability and higher percentage of components were observed in lead and chromium than the other elements. With increasing concentrations of lead, chromium, and copper, the bioavailability of these elements also increased. As well as, zinc and nickel showed the lowest bioavailability. The concentration of copper, lead, and nickel was also higher than the sediments world average and the WHO / US EPA maximum, and the nickel concentration was above the ERM, PEL, and SEL.

Due to the low accuracy of determining the total concentration of metals in sediment toxicity for aquatics and the need to pay attention to bioavailability fraction, the probability of ecological risk of lead and chromium elements is higher than the other elements for aquatics of Persian Gulf. Zinc and nickel, have the lowest risk to the environment despite the high total concentration

The aim of the present study was to investigate the effects of ascorbic acid and density on reproductive performance and steroid hormones in rainbow trout (Oncorhynchus mykiss). In this regard, six treatments were considered included three diets containing 0, 100, and 1000mg ascorbic acid as L-ascorbyl-2-polyphosphate per kilogram of food in contrast to two densities 4.33kg/m3 and 2.16kg/m3. Triplicate groups of fish were fed one of the test diets for 16 weeks. A total of 81 females with an average weight of 812.1±1.5g were introduced to tanks (910 liters). At the end of the 16th week and when preparing fish for spawning, from each replication of high and low densities, 4 and 2 fish after bleeding of fish to measure the concentrations of progesterone, testosterone, and estradiol were spawned. After that, reproductive parameters such as work fecundity, ova per gram, and ova diameter were measured and then fertilized. During the incubation period, fertilization and mortality rates were recorded. The results showed the interaction between ascorbic acid and density and also the significance of this effect in reproductive parameters (number per gram of egg, oocyte diameter, coagulation, and fertilization percent; p<0.05). In the case of steroid hormones, the effect of treatments on the amount of each of the three hormones and their interaction on the level of estradiol and testosterone were significant (p<0.05), but the effect of density and diet on progesterone was not significant (p>0.05). The results of this study confirm the use of higher levels of ascorbic acid in breeders compared to grow-out period and also the positive role of this vitamin in reproductive indices.