فصلنامه تغذیه آبزیان
سال سوم شماره 1 (پیاپی 5، بهار و تابستان 1396)

The aim of this study was to investigate the effects of short term starvation periods on growth, feed efficiency and chemical composition of rainbow trout (Oncorhynchus mykiss) larvae cultured at two salinity levels; 0.5 ppt (fresh water) and 1.95 ppt (brackish water). Fish larvae averaged 300 ± 10 mg in weight were exposed to three different feeding regimes for 40 days: one group (control) which continuously fed and the two other groups including T1 (5 days feed + 2 days starvation) and T2 (2 days feed + 2 days starvation). The growth performance results indicated that there are significant differences (P<0.05) between the treatments. The maximum body weight (1935.47 mg) was obtained in control group. These results indicate that protein, lipid and energy efficiency ratio in control group were significantly enhanced in comparison with T1 and T2 (P<0.05). The highest PER, LER and EER amounts (1.70, 5.26 and 0.56, respectively) were also obtained in control. Body composition was also analyzed at the end of the experiment. The highest and lowest crude protein levels were obtained in control (74.65%) and T2 (59.72%), respectively. The results showed that food deprivation has a negative impact on the growth performance and body composition in the fish larval stage.

This study designed to evaluate blood parameters of 3-4 years Huso huso on pen in the center of the fishing and processing Ashuradeh (Chalasht) from the Gorgan Bay in different seasons.Blood samples from 10 Huso huso withaverage weight2698.01 ± 757.32 g and length 77.98 ± 5.53 cm were collected in each season (autumn 2014 to summer 2015) and activity of alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and variation in hematological parameters such as hemoglobin, erythrocyte count, leucocytes count, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) in the blood samples of fish were measured in each season. There is significant difference in the enzymes levels were observed. (P<0.05). The lowest activity of aminotransferases and alanine aminotransferase were also observed in autumn. With the exception of mean corpuscular hemoglobin concentration (MCHC) that was the highest in the spring, the other blood parameters mentioned were highest in the autumn. The number of WBC (6.67 ± 0.35×103 mm3), RBC (0.97 ± 0.01×106 mm3) and hemoglobin values (6.96 ± 0.15 g/dl) had its lowest level in winter. But the levels of hematocrit (%21.80 ± 0.62), hemoglobin, MCV and MCH values respectively 187.50 ± 3.87 fL and 63.36 ± 1.45 pg/cell showed the lowest level in spring. The results of this study showed seasonal variations effect on haematological parameters in Huso huso and should be considered when these parameters are utilized to evaluate fish health status.

In the present study, the influence of deep-frying with plant oil on the amount of heavy metals, minerals and vitamins grass carp were studied. Different plant oils (corn oil, grape seed oil and olive oil) were used for deep-frying of grass carp fillets. Fried fillets had higher pb content. Cr and Ni contents of fried grass carp fillet decreased significantly. Co and Cd contents in raw and fried treatments were below the limits of detection. Na content of fried fillets with olive oil was higher than the other treatments. K content of fried fillets decreased in comparison with raw fillet. There was no significant difference in the Ca and Fe contents of fillet between raw and fried samples. Mg content in fried fillet with grape seed oil and Mn, Cu and Zn contents in dried fillet with olive oil decreased (P<0.05). Vitamin A content in fried fillets increased. Vitamin D content in different samples of raw and fried in oil did not show significant differences. Vitamin B1 and B3 contents in the fried fillets in plant oil decreased significantly (P<0.05). Considering the quality properties showed that corn oil is the best deep-frying.

Antimicrobial properties of diethyl ether and methanol extracts of algae Scenedesmus dimorphus against Gram positive bacterium Micrococcus lutesus and Gram negative becterium, Aeromonas hydrophila were evaluated. The algae was pure cultured and once the required volume and number of cells achieved coli using agar well diffusion method diethylether and hexane extracts of the algae cells were extracted. Antibacterial properties of the extracts were evaluated using well diffusion method. The results showed inhibitory activities of methanol and ether extracts of Scenedesmus dimorphus against M. luteus and A. hydrophila with 11-13 mm and 13-21 mm diameters of inhibition zone, respectively. In case of diethyl ether extracts also the inhibitory activity observed with diamaters of inhibition zone in the range of 9-23.7 mm and 21.6-6.3 mm respectively against M. luteus and A. hydrophila. Gas chromatography mass spectrophotometry was used to identify different substances within diethyl ether and methanol extracts with hydrocarbon and ester with highest perentage among other substances. The results confirmed antimicrobial activities of extracts from S. dimorphus against bacteria used in this study.

In order to processing white fin wolf-herring (Chirocentrus nudus), fish burger prepared using two formulas; standard (A) and proposed (B). According to the results of sensory assessment of fish burger including physical indexes such as color and appearance, consistency of tissue, taste, flavor and smell, fish burger A obtained higher acceptance than the fish burger B, therefore fish burger A selected to storage in frozen condition. Chemical and microbial experiments were conducted in zero time and after 5, 10, 15, 20, 25 and 30 days of storage at -18 °C. Results showed that peroxide value (PV) increased to 2.4 meq O2 per kg meat until fifteenth day, and then decreased to 2 meq O2 per kg meat in final storage period (30 days). The value of total volatile nitrogen (TVN) was 8.4 mg TVB-N per 100 g flesh in zero time and reached to 21 mg TVB-N per 100 g flesh at the end of the storage period. The total count of bacteria decreased from 6.75 log cfu/g in zero time to 3.85 log cfu/g at the end of the storage period. Investigation of quality parameters showed that this product is consumable with good quality at the end of 30 days of storage in freezing condition (-18 °C).

Biochemical composition of seafood is important in order to present some nutrition recommendations. In this study, the fatty acid composition of barracuda was investigated. Pickhandle barracuda (Sphyraena jello) and Yellowtail barracuda (Sphyraena flavicauda) were caught in autumn and spring from the Oman Sea during 2015 Total saturated fatty acids (SFAs) in both species were higher in spring (P<0.05) than in autumn. The most monounsaturated fatty acids (MUFA) were found in autumn (P<0.05). Sum of EPA + DHA was the least in spring, while highest in autumn. The omega 6 content in the Pickhandle barracuda in autumn did not show any significant difference in comparison with that of Yellowtail barracuda in spring (P>0.05). The most omega 3 fatty acid in both species was observed in specimens caught in autumn and had a significant difference with that of the spring (P<0.05). The maximum n-3/n-6 ratio was found in Pickhandle barracuda in spring (9.33 ± 0.53). Thrombogenecity index in Pickhandle barracuda in spring was the highest (0.62 ± 0.24) (P<0.05). Barracuda spawning starts from spring through summer, so, significant differences in the biochemical content may be due to the sexual requirements and also the nutrition conditions as well as the availability of food items. In conclusion, both barracudas are valuable in the human health nutrition especially in adults.