فصلنامه شیلات
سال شصت و چهارم شماره 3 (پاییز 1390)

In this research work the production of sweet product from Thunnus albacares known as yellow fin tuna and it’s shelf life was studied. From fillet f tuna two sweet sampled in laboratory were prepared. One of them from raw and second one from cooked fillet. As the results of the orgenoleptic test showed the first sampled was rejected and second one was acceptable. The moisture, protein, fat, ash content and organoleptic score for this samples were 15.26%, 66.7%, 8.5%, 10% and 7 respectively. According to a time table, the shelflife of this product was determined by monitoring the changes of TVB-N, PV, total bacterial count and organoleptic properties of the samples which kept at 3-4?C in a laboratory frige for 30 days. The results showed that, the sample had a natural had a natural flavor, smell, color and texture for 15 days. The number of bacteria increased from 4.7?103 To 9?103 colonies per gram, TVB-N and PV also increased from 48.3 to 60.3 mg/100g and 0.2 to 3.4 meq/kg. Then peroxide value started to decreased, According to these results, the sheflife for this product recommended to be 15 days at 3-4?C.

In this study, proximate composition and sensory evaluation of Giant gourami compared with Rainbow trout and Common carp. Brightness (L*) was significantly higher than the other species and this leads to the highest score in sensory evaluation of the fillet color. Moreover ECI index of carp was significantly higher than that of the other two fish, in body part. Between the species, hardness, chewiness and gumminess of the gourami was significantly higher. Lipid and ash values were the highest (6.29± 0.16 and 1.6± 0.39 percent of flesh) and protein was the lowest (16.53± 0.18) in the gourami. Also color, flavor and total acceptance of the gourami fillet obtained significantly higher scores than two others. Finally in respect of the results obtained, flesh properties of the gourami are compatible with other two fish.

To investigate the hispathological characteristics in liver, kidney, spleen and gills of rainbow trout, Oncorhynchus mykiss following experimental infection with Aeromonas hydrophila, septicemia agents in fishwere infected through injected intraperitoneally and direct contact with 107 bacteria per liter solution. Mortality and clinical diagnostic were recorded in experimental periods. After 14 days, blood and tissues were sampled of survival fish. A significant decreased in RBC, Hb, lymphocytes and monocyte (p <0.05) and significant increase in WBC and neutrophile (p <0.05) is the most important changes in hematological index of infected fish by A.hydrophila. Presence of bacteria in the tissues were confirmed the by biochemical tests. Tissues were normal in the control group. The apparent disorganization of live cells, cytoplasmic and nuclear material deposition, the rupture of blood sinuses, hypertrophy of hepatocytes, degeneration, hemorrhage, vacuolization of cell cytoplasm in liver tissue; a significant deposition of hemosiderin granules in a melanomacrophage center and morphological alterations in ellipsoid cells in spleen tissue; degeneration and necrosis of renal tubules, glomerular lesions, shrinking of the glomerulus and enlargement of space inside Bowman’s capsule, dwindling of the tubular lumen in kidney tissue; hyperplasia, necrosis of epithelial filament, shortening of secondary lamellae and lamellar fusion in gills are important histopathological damage observed in tissues of infected fish with A.hydrophila.

This study was conducted to compare the body fatty acid composition of Caspian trout (Salmo trutta caspius) parrs in different nutritional statuses. 900 Caspian trout parrs 12.5 (SD± 1 g) were kept at various nutritional statuses, i.e. six weeks of full feeding (FFF), three weeks starvation and three weeks of refeeding (SF), three weeks of feeding and three weeks of starvation (FS), two weeks of feeding, two weeks of starvation and two weeks of refeeding (FSF), two weeks of starvation, two weeks of feeding and two weeks of starvation (SFS) and six weeks of full starvation (SSS). After feeding with various nutritional status, body fatty acid composition was analyzed by GC/FID. Total Monounsaturated Fatty Acids (MUFA) were decreased than control treatment (35.14%) with increase in periods of starvation and reached to 32.32% in SSS treatment, while Saturated Fatty Acid (SFA) and Polyunsaturated Fatty Acid (PUFA) were increased from 27.25% and 27.10% in FFF treatment respectively to 32.81% and 31.54% in SSS treatment (P < 0.05). Linolenic acid (LNA) content and PUFA C18/C20,22 index (1.62 and 0.27% in FFF treatment respectively) were decreased with increase in periods of starvation and reached to 1.19 and 0.22% in SSS treatment, Icosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) were increased significantly (P < 0.05) inversely and reached to 4.55 and 14.12%in in FFF treatment and 6.46 and 15.6% in SSS treatment. In refeeding periods, fatty acids have an invert trend and were closed to their levels in control treatment. Therefore, Caspian trout stores, converts or uses fatty acids selectively in different nutritional statuses to provide its own requirement for energy and essential fatty acids.

Mercury is one of the most toxic heavy metal which can enter the human body mainly through consumption of seafood contaminated with mercury. In this study, the human health risk due to consumption of kutum (Rutilus frisii kutum), in the Caspian Sea, were evaluated by measuring the concentration of mercury in muscle samples using Atomic absorbtion spectrophotometer (Perkin Elmer FIAS-100) and cold vapor technique. A total of 60 fresh kutum were collected by local fisherman from 12 stations on the southern coast of Caspian Sea in Mazandaran province. The average concentration of mercury in kutum muscle was 0.112 μg/g of fresh weight 0.382 μg/g dry weight) which was less than the allowable amount for human consumption determined by the international organizations such as USEPA, WHO, FAO and the FDA. HQ Index was below 1 (0.48). Also, the calculations indicated that daily and weekly mercury uptake for Iranian consumers, according to FAO (the amount consumed per capita) is lower than the guide values (PTWI and PTDI) provided by WHO, USEPA and JECFA. Therefore, the consumption of the kutum is not a serious threat to the consumer’s health and a consumption permitted rate of 62 g is recommended.

In this study, some of biological parameters of Vimba vimba from February 2009 to June 2010 were examined. In total, 281 fish samples were caught by gill- net. In two regions had of five age groups that, the most frequent age groups were related to 2+. Sex ratio of male to female were in Gorganrud population 67% ♂ to 33% ♀ and in Mahmoudabad population 57% ♂ to 43% ♀ (p 0.05). There was no significant differences (p>0.05) between the average length and weight of the two populations,. Growth pattern for populations of Gorganrud and Mahmoudabad were negative allometric and isometric, respectively. Within the two populations, the asymptotic length (L∞) in males was higher than females, but the growth rates (K) in females were relatively higher. Mean absolute fecundity in Gorganrud and Mahmoudabad populations were 11970.8±8381/03 and 6728.49±2488.5 eggs per fish, respectively. There was significant difference between the two populations (p≤0.05) in mean absolute fecundity, average egg diameter and condition factor. The results showed that, in many biological parameters, there were significant differences between the two populations due to environmental differences in two regions.

This study was investigated reproductive differences in fall and spring migrants of Caspian lamprey (Caspiomyzon wagneri) in the Shirud River (Southern Caspian Sea)in 2008. 89 and 15 specimens were sampled in in spring and fall, respectively. Generally, fall migratory fish had a significantly lower condition factor (CF) compared to the spring migrants. There was significant relationship between fecundity-length and fecundity-weight in both spring and fall seasons. No significant differences was found in fecundity, oocyte diameter as well as hepatosomatic index (HSI) between fall and spring migrants. However, fall migratory females had a significantly higher HSI compared to the spring migratory females. Nodifferences were also found in gonadosomatic index (GSI) between fall and spring migratory males, and fall and spring migratory females. Sex ratio of spring and fall migrants was 1:1.