نشریه بهره برداری و پرورش آبزیان
سال ششم شماره 4 (زمستان 1396)

The utilization of natural preservatives has a great interest in the recent year food industries. In theis study the effect of common chitosan (acid soluble 1%), water soluble chitosan (1%), chitosan oligosaccharide (1%) and sodium acetate (1%) as a chemical preservative on maintaining Huso huso fillet during the refrigerated storage (4±1 0C) at days 0, 4, 8, 12 and 16 were assessed. The parameters of PV, TBA, PH and TVC, were determined. According to the results, acid soluble chitosan the lowest change and signification differences as compared to the other treatments (p

In this study the effects of high levels of ammonia on behavioral changes and determining of lethal dose (LC50) were examined in common carp. In this regard, 180 Common carp (Cyprinus carpio) fingerling with average weight of 3.1±0.4 g divided in 18 aquaria with a density of 10 fish (per tank) for 2 weeks (for adaptation to the environment), in this study 5 treatment and a control groups with three replicates were considered. Treatment groups were exposed to total ammonia at concentrations of 1.25, 2.5, 3.75, and 6.25 m/l respectively that were equal to 0.34, 0.66, 0.99, 1.32 and 1.65 m/l of unionized ammonia. According to the results, unionized ammonia 96 h median lethal concentration calculated as 1.17 m/l for common carp. Nervous and unbalanced swimming was the most behavioral sign in fish that exposed with 1.65 m/l of NH3, first mortality observed 16 hours post exposure in this group. In fish of treatment 4 and 5 (exposed with 0.34 and 0.66 mg/l of NH3) slow swimming, lethargy and bottom sitting were the most clinical signs after 24 h exposure but no mortality was observed in these groups during experiment. According to the results of this study maximumm sub-lethal concentration of NH3 for common carp calculated as 0.12 mg/l.

In this study the effect of polyethylene film impregnated with essential oils of thyme (T. daenesis) and savory (S. bakhtiarica) to control lipid oxidation fillet of rainbow trout (O.mykiss) during short-term refrigerated storage was studied. Sensory indices and lipid quality indices were assessed in three-day intervals and compared with control samples (uncoated polyethylene film). The hydrolytic corruption was limited by using essential oils of thyme and savory in packaging. The higher values of conjugated diene in control samples showed further development of lipid deterioration in this treatment. After impregnating film with essential oils of thyme and savory, increasing the primary products of lipid oxidation was inhibited respectively until the 12 and 15 days. The secondary lipid oxidation products rate was limited after using essential oils in packaging films. However, significant difference was not observed due to the type of essential oils. By using essential oils of thyme and savory, the taste and overall acceptance of the product was enhanced. During the storage period, the value of sensory evaluating indices was decreased in all samples while the changes rate much more progressed in control samples.

The conservation of genetic resources in aquatic animals needs awareness about genetic reserves and genetic diversity among one specie's individuals and also needs the conservation of genetic resources in the hatchery or wild and natural communities. It will lead to some threats such as inter- and intra-population genetic diversity loss and species extinction if propagation and sea ranching program being conducted improperly. Determination and calculation of inter- and intra-assay genetic diversity are of general goals of population dynamic studies and population genetic studies the genetic cross and population evolution. Different markers are used to estimate population's genetic diversity. In recent years, DNA-based molecular markers have been considered as suitable alternatives for old morphologic and cytogenetic ones. Mitochondrial genomic markers mtDNA belonging to non-PCR-based markers and microsatellite markers belonging to PCR-based markers show diversity and heterozygocity suitably, thus have wide use in population genetic studies. From the molecular markers at mtDNA level, 16SrRNA is widely used in fish phylogenetic studies. On the other hand, microsatellites markers are very efficient and worthy in inter- and intra-population genetic diversity studies.

Gorgan Bay is a semi-closed water area that has been exposed to water level decreasing in the Caspian Sea in recent years. In this research, the probable future of the Bay after separation from the Caspian Sea under two scenarios is examined.In the first scenario, the Bay was studied under the influence of the prevailing climate on it. In the second scenario, the Bay was studied under the influence of the climate and river inputs. The daily average of wind speed, wind speed, precipitation and evaporation data and the monthly average of rivers debi loading to the bay were used for modeling by Mike 21.The modeling results under the first scenario showed that, 551 days after the separation of the Bay from the Caspian Sea, the Bay would be dwarfed by the prevailing climate on it. The modeling results under the second scenario showed that the Bay affected by the prevailing climate on it and input rivers then reached the balance of 3 years and turned into an inland wetland. Following the separation of the Bay from the Caspian Sea, the stages of ecological successions will be carried out rapidly. If the Bay does not communicate with the sea and does not provide adequate supplies of rivers, ecological successions in the Gorgan Bay will be Disclimax. The results of the study show that in addition to water level decreasing and sedimentary process, eutrophication is also considered as the life threatening third factor in the Bay. The necessity of constructing a new channel through the Miankaleh Peninsula in order to increasing self-purification in the Bay and its withdrawal from Disclimax is proposed.

Hemiculter leucisculus is an exotic Cyprinid species for Iran and little is known about its biology. A total of 91 samples of the species (H. leucisculus) were collected between April and July 2013 using electro-shocker randomly and fixed by 10% formalin. The sex ratio of male to female in the studied population was 1: 1.53 indicating males are dominant. The maximum total length and weight were 107 mm and 12.17g for females, 112 mm and 12.50g for males. The maximum condition factor obesrved for males was in June (2/1) and for females in July (1/08). The highest instantaneous growth rate was observed for both sexes in younger age groups. The sampling period was only 4 months, so it seems that a longer sampling period, larger sample size including all size classes are needed to achieve detailed information on biological parameters. Anyway, the provided data could be used as basic information about one of the populations of the species in northern Iran.

Malachite green is used as a fungicide, bactericide and parasitic ide in the aquaculture industry, which is influenced on the environment as a pollutant. So, removal of this compounds before discharging to the water resources is very important. In this study, adsorption of Malachite green as a cationic dye onto SBA-15 was studied. SBA- was synthesized using Zhao method and then characterized by X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Effects of various process parameters including adsorbent dosage, contact time, initial pH of the adsorb and initial Malachite green adsorb were investigated under batch adsorption system. Results showed that maximum adsorption Capacity of SBA-15 (90.06 mg/g) accrued at initial concentration of 10 mg/l, adsorbent dosage of 200 mg/l, and solution pH of 10. In addition Malachite green removal percentage under this condition was 98%.