فصلنامه شیلات
سال شصت و ششم شماره 1 (بهار 1392)

The present study examined the utilisation of seaweed extract as a source of natural antioxidantsfor retarding lipid oxidation in minced Kilka. The Kilka mince with two different concentrations(300 ppm and 600 ppm) of water extract obtained by microwave, one control sample with noadded extracts and one control sample with added vitamin C were prepared. The samples werestored at refrigerator (4º C) for 8 days. The measurement were undertaken at 0, 2, 4, 6 and 8days from the beginign of the experiment. The mince that containd the extract with 300 ppmconcentrate was found to be very effective in retarding lipid oxidation as it resulted in lowlevels of peroxide value (PV), tiobarbitoric acid (TBA), free fatty acids (FFA) and changeedthe fatty acids. Results showed that this alga is suitable to be used as a natural antioxidant.

In this research chemical composition of fillet of Anzaly Lagoon´s Pike and their changes were investigated during 120 days of frozen storage at (-20°C). The percentage of changes of the proximate composition over the analysis period for moisture was from 77.61±0.06 to 76.57±0.01, for ash was from 1.30±0.00 to 1.37±0.01, for bprotein was from 19.21±0.01 to 17.19±0.03 and for fat was from 2.29±0.01 to 0.98±0.00. Thirty fatty acids were indentified, i.e. 12 SFA, 6 MUFA and 12 PUFA. The percentage changes of fatty acids for SFA was from 22.94 to 27.83, for MUFA was from 22.61 to 31.35, for PUFA was from 51.16 to 34.96, for ΣUFA was from 73.75 to 66.31. This investigation on fatty acids of frozen Pike has shown that the percentage of n-3 and n-6 fatty acids has changed from 33.49 to 20.16 and from 17.85 to 14.80, respectively. All changes were statistically significant. The TVB-N and P.V as chemical deteriorative indices increased from 6.27±0.02 to 14.25±0.00 mg/100g and from 0.18±0.00 to 1.44±0.00 meq O2/kg, respectively.

Golden gray mullet (Lizaaurata) is one of the valuable fishes inhabited in Caspian Sea, which is captured in large volumes in northern parts of Iran. However, similar to other fishes, Golden gray mullet is susceptible to bacterial spoilage and the quality of the fish will be degraded during the storage time. Therefore, the purpose of the present study was to investigate the effects of gamma radiation, as a non-thermal fish processing method, on the microbiological properties and shelf-life extension of Golden gray mullet fillets during chilled storage (4° C).Experimental fish were filleted, irradiated at different doses (0, 1, 2, 3 and 5 kGy) and then stored in refrigerator for 35 days. Microbial quality changes were evaluated by enumeration of total viable count (TVC), Pseudomonas, Lactic acid bacteria (LAB), H2S producing bacteria and Enterobacteriaceae over the experimental period on the day of 1, 5, 10, 15, 20, 25, 30 and 35. The results obtained from this study showed that the shelf life of Golden gray mullet stored at the refrigeration temperature, as determined by overall microbial load, is 10 days for non-irradiated Golden gray mullet. However, samples treated with gamma irradiation showed better quality during storage. The results revealed that radiation at a high dose (5 kGy) was inhibited the growth of microorganisms, and irradiation at a medium dose of 3 kGy could be used to control the microbial load indices of Golden gray mullet for up to 35 days at the refrigeration temperature without adverse effects on the fish quality and acceptability.

Diversity, abundance and distribution of fishes in Tajan River were studied from March 2008 to July 2009. Tow sampling stations were selected along the River in up and down of the Shahid Rajaii Dam. A total of 2996 specimens were caught using electrofishing. The specimens were belonged to 9 species from 4 families: Capoeta capoeta gracilis, Alburnoides bipunctatus, Barbus mursa, Barbus lacerta, Luciobarbus capito, Squalius cephalus, Cobitis taenia, Paracobitis malapteruraandNeogobius fluviatilis. The results showed that species diversity and richness index coefficients of the upstream station of the dam were lower than those of the downstream station (P<0.05), but there were no significant differences in dominance and similarity indices between the two stations. The present study indicates that the dam, as a human-made construction, has influenced the fish diversity in up- and down-stream of the river.

Streptococcus agalactiae (group B, GBS) is an important human and animal pathogen that causes invasive infection in fish. The present study aims to investigate the detection of vertical transmission S. agalactiae using the PCR of the gene scpB in the ovarian tissues. A group of 48 fishes were injected intramuscularly (i.m) with 0.5 ml bacterial suspension containing 3.5×107 CFU/0.5 ml in normal saline, This group was compared with a control group of 48 fishesthat were injected with 0.5 ml sterile saline. In this study kidney tissue, ovarian tissue and ovarian fluid were sampled from the fourth day after injection. DNA was extracted from both the direct tissue and the bacteria isolated from the tissues, which were cultured in the BHI medium. The extracted DNA was then used in the PCR. The PCR confirmed the existence of this bacterium in 91.46% (44/48) and 68.75% (34/48) of the kidney and the ovarian tissues, respectively, and 95.83% (46/48) and 87.5% (42/48) of bacteria isolated from the kidney and the ovarian tissue cultures, respectively. The presence of S. agalactiaein rainbow trout ovarian tissue was confirmed by PCR and sequencing that can be the evidence for vertical transmission of this bacterium in rainbow trout brood stock.

In this study, the distribution, abundance and some growth parameters of Spirlin, Alburnoides eichwaldii in the Tilabad stream in the Golestan province was studied over 2009-2010. A total of 535 samples of Spirlins were collected by catching with Electroshocker. A total number of 205 samples was analyzed and the rest of the specimens were released. Spirlin was found only in stations 1 and 2 (the Headstream and next station) while station 2 had the highest number of summer Sprilin (0.889 # m-2). Catched fish were in three age-groups: 0, 1+, and 2+ years old with the longitudinal range of 25.34-110.16 mm. The exponential relationship between length and weight in both sexes indicated negative allometric growth. Growth equation was Lt= 12.45(1-e-0.248(t+0.39)) and Lt= 11.66(1- e-0.281(t+0.39)) for females and males of Spirlin, respectively. Apparently, Spirlinin in the Tialabad stream has no biotic suitability and faces severe environmental stress.

The influence of starvation and refeeding on the structure of liver was studied in the juveniles of Salmotrutta Caspius. 480 juveniles were stocked into 12 outdoor concrete tanks (40 fish per tank), with four levels of feeding: full-fed for 6 weeks, 3 weeks starved, full-starved for 6 weeks and 3 weeks starved and 3 weeks fed. The liver was then removed from five individuals taken from each tank (5fish/tank, 3tank/treatment) fixed for 24 h in Bouin´s fixative. The samples were dehydrated through a graded series of ethanol solution up to 100% and xylene, embeded in paraffin, sectioned using microtome at 4μm thickness, stained using haematoxylin and eozin and examined using a Nikon light microscope. The results showed that the starvation influenced significantly the liver structure of the both starved groups as hepatocytes atrophy and reduction of their size (P< 0.05). Cytoplasm was deteriorated and sinus enlargement was observed in the liver of starved fish. In addition, 3-week refeeding could be effective on liver regeneration leading to hepatocytes hypertrophy and increase of their size to the same size of the control group. In conclusion, food deprivation and consumption of energy resources caused tissue damage in the liver structure of Salmo trutta, but refeeding and fulfillment of energy resources may recover tissue damage.

To investigate water qualityin the Choghakhor wetland using BMWP and ASPT methods, ten stations were selected. Samples were collected every 45 days from April 2010 to March 2011 with 3 replicates at each station. The BMWP and ASPT were calculated after identification and counting benthic specimens using the BMWP and ASPT score system. The average BMWP measured in various sites and sampling times indicate that the water qulity of the Choghakhor wetland is classified as bad condition. However the eighth site and the first stage of sampling were found to be in the moderate quality class. Analysis of variance indicated a significant difference between all stations and stages (P < 0.05). The ASPT index takes the water quality of wetland in two pollution categories: moderate and severe. The ASPT index for different stations and stages agrees with the BMWP index as they have a positive correlation at the confidence level of 0.01

A larger proportion of energy intake for reproduction and also low food availability may decrease the growth rate of other organs during the late stage of the gonadal development. The main goal of this study is to examine the biological characteristics and organs growth pattern in Clupeonella cultriventris during the late stages of gonad development. Samples were collected by capturing 300-350 Kilka from a fishery area between Sari and Mahmod-Abad, every 2-3 weeks over October 2008 to April 2009. The length parameters such as fork length, stomach and intestine length and weight parameters such as fish weight, intestine weight and ovary weight were measured. The results showed that the slope of regression between weight and length for females increases At the beginning of sampling period, ovary was quit small, but grew up fast by the beginning of the reproduction and constituted a large part of the female body. The stomach and intestine grew faster than fish length over the study period. A reduction in length-growth of females indicates that greater energy was allocated to gonadal development by the end of reproduction. However, the gastro-intestinal growth pattern did not correlate with fish length, but showed faster growth.

The present study aimes to evaluate the effects of Eucalyptus camaldulensis, Mentha pulegium, Aloe vera (20, 40, 80, 160 and 320 μl/ml) and chloramine T (0.05, 0.12, 0.25, 0.5, 1 and 2mg/ ml) on the bacterial growth of Streptococcus iniae (8 isolates) and Lactococcus garvieae (12 isolates) after 30, 60 and 90 minutes and 1, 2, 4 and 10 hours post incubation at 25°C. The liquid dilution method was used to assess the minimum inhibitory concentration (MIC) using sub-culturing on the blood agar, after 30, 60 and 90 minutes incubation at 25°C. An increase in the concentration of Eucalyptus camaldulensis and Mentha pulegium caused that the bacterial growth decreased so that under the 160 and 320 μl/ml MIC of these essences after 60 and 90 minutes post incubation the growth was completely stopped. No effect was found for Aloe vera. Chloramine T proved to be the most effective substances to these bacterial strains giving a MIC of 0.5 and 2 mg/ml after 4 and 10 hours post incubation. The results also indicated that all strains of S. iniae and L. garvieae isolated from farmed rainbow trout are resistant to A. veraessence. However, E. camaldulensis, M. pulegium essences and chloramine T could be used as potential substances for reduction of bacterial loading in the water column in farmed rainbow trout.