مجله علوم و فنون دریایی
سال دهم شماره 1 (بهار 1390)

This study was carried out to evaluate the use of synthetic hormones (ovaprim,hCG) to induce spawning of snow trout(Schizothorax zarudnyi) fish. Wild broods (45 females and 53 males 1328±45, 632±17.6 g, respectively) caught from Chanimeh reservoirs (Sistan, Iran) were transported to Zahak Hatcheries Complex (Sistan Fishery Department). The brood fishes were randomly distributed among five treatment groups:1- females treated with quadruplet injections(0.2, 0.5, 0.5 and 0.3 ml ovaprim/kg B. W.) every 24 hrs. Simultaneously to second injections males were injected with 0.3 ml Ovaprim/kg B. W. 2- Females were injected with combination of ovaprim(0.2, 0.5 and 0.5 ml/kg B. W.) and hCG 1000,2000,2000 IU/kg B.W) and simultaneously to the 2nd injection of females, males were injected with 0.3 ml/kg B. W. ovaprim and 1500 I.U. hCG/kg B. W. C). 3- In the third treatment females were injected with ovaprim plus hCG (0.2, 0.5, 0.5 and 0.3 ml/kg B. W. + 200, 400, 400 and 300 I. U. /kg B.W. respectively every 24 hours) and males received 0.3 ml/kg B.W. ovaprim + 200 I.U. hCG /kg B.W., at the second dose of females via injection. 4- In the fourth treatment females were injected triplet injections of different doses of hCG (400, 800 and 800 I.U. hCG/kg B.W.) every 24 hours and also males (500 I.U./kg B.W.) synchronized to second injections to females.5- Finally,in the fifth treatment 0.3 ml/kg B.W. saline was injected to all males and females belonging to control group. The results showed mean working fecundity for 1, 2, 3, 4 and 5 groups was 39531±7802, 18625±9704, 15682±5982, 0 and 0, respectively. Latency period was 36.2±3.77, 12.33±0.66 and 30.2±2.95, conversion percentage of dry egg to eyed egg was 88.97±0.9, 73.19±2.04 and 75.26±3.90, conversion percentage of eyed egg to larvae was 81.93±1.15, 75.67±0.19 and 71.03±1.03 for a, b and c groups, respectively. There were significant differences in the fecundity, latency period and other parameters mentioned above between the group treated with only ovaprim and the control group (P<0.05). Based on the results it could be concluded that treatment of Snow trout with ovaprim is effective for spawning induction.

In order to study the feeding biology of the Japanese Threadfin Bream in the Northern parts of Oman Sea (Chabahar Area), a total of 212 specimens were collected in 2009-2010, and different indices of VI, FP and GSI were taken into consideration. Of total stomachs, 51, 44 and 117 numbers were full, semi-full and empty, respectively. The VI index was estimated 55.2%, and amount of Food Preference Index were estimated as: Crustacean (63.2%), Fishes (38.9%), Molluscs (36.8%), Nematoda (25.3%), Polychaeta (8.4%), Sipuncula (7.4%), Foraminifera (6.3%), Phytoplanktons (4.2%), Seeweeds (2.1%) and Nemertean worms (1.1%). The maximum and minimum Gastro-Somatic Index for males were in autumn and winter season; and for females in summer and spring. It was concluded that N.japonicus is a moderate feeding fish and it’s main food is Crustacean and minor foods are Molluscs and Fishes.

For many aquatic animals olfactory has an important role in food searching and intake. Amino acids are the large group of olfactory stimulants in feeding behavior of aquatic organism. The aim of the study was to determine the olfactory preference in crayfish (Astacus leptodactylus). Crayfish juveniles (6 to 8cm L) were exposed to 20 amino acids, and two positive and negative controls, in laboratory condition. Experiments were carried out in 6 replicates. In the qualitative evaluation of crayfishs responses, Aspargine and Sistine stimulated a significant and obvious feeding reaction. The quantitative evaluation confirmed the effect of Asparagine but showed weak response for Sistine. Phenylalanine, threonine, tyrosine, methionine, and lysine promoted low positive response. The quantitative evaluation verified this result except for tyrosine and phenylalanine. Other amino acids didn’t show considerable attractive effects on feeding behavior. The quantitative evaluation confirming the results of pervious observation showed the well apparent response for glycine and thriptophan. The responses for aspartic acid, serine, acid glutamic and proline were sufficiently positive. According to the results asparagine could be considered as a suitable appellant for Astacus leptodactylus.

Availability of brood fish with high quality is one of the main aspects in sturgeon rehabilitation programs. The present study was conducted to compare different biological parameters and reproduction indices in 397 of Persian sturgeon broodstocks caught in the Sefidroud River and the Caspian Sea using beach seine and gillnets. A total of 74 Persian sturgeon broodstocks were caught in the Sefidroud River, and in the sea 199 spawners were collected using beach seine and 124 collected using gillnets. Results obtained showed that the minimum mean weight (26.5 ± 5.1 kg) recorded belonged to fish caught in beach seine whereas maximum mean weight (30.0 ± 4.0 kg) recorded belonged to fish caught in the river which were significantly different (P<0.05). No significant differences were detected in the weight of gonad from different groups of broodstocks (P>0.05). The highest polarization index (PI) (10.6 ± 2.6) in broodstocks belonged to the groups caught in beach seine and minimum PI values (6.6 ± 0.9) were observed in broodstocks caught in the river (P<0.05). Highest fertilization rate (92.2 ± 3.3 %) belonged to broodstocks caught in the river which was significantly higher than broodstocks collected from the sea (75.1 ± 4.8 %) (P<0.05). It is evident from the results obtained that higher values for reproduction indices were recorded in broodstocks caught in the river. Therefore, it is suggested that in order to improve artificial breeding programs in hatcheries and also to increase fertilization rate and survival rates of eggs and larvae, more attempts should be made to facilitate the migration of these spawners into the Sefidroud.

Successful management of sturgeon population requires knowledge of stock composition with regard to sex and gonadic stage. Measurement of sex steroid concentration has proven to be a reliable and less invasive method in compare to convention methods. In this study we have examined the possible role of plasma testosterone (T), estradiol (E2), progesterone (P), cortisol (C) and morphometric parameters as indicators of sex and stage of gonadal development in immature (4-5 years old) Great sturgeon cultured in brackish water. Biometry of fishes, blood sampling from caudal vein was performed every three month and plasma was frozen until analyses. Glucose was measured with auto analyser, calcium and magnesium with spectrophotometer and sodium and potassium with film photometer, Hormone levels were measured by radio immunoassay (RIA). Histological preparation was stained with hematoxylin and eosin. In sex determination, result show that total length (L) and weight (W) had no significant elevation in different sexes and can not be used as an indicator sex determination. Among hormones only T had significant elevation, so it could be stated that level of T in immature Great sturgeon could be used to identify sex. In case of gonadic stage result show that total L and W just in male had significant correlation with gonadal stage and among hormones just T in male and C in female had significant correlation. So it could be concluded that in male and female respectively based on T and C measurment gonadic stage in immature Grate sturgeon could be identified.

Study was conducted to investigate the effects of various energy levels on growth performance, food conversion ratio (FCR) and whole body composition in Gattan, Barbus xanthopterus fingerlings (12.12±0.28 g) for 8 week. Feeding trial was conducted using 3 semipurfied diets containing 3 levels of digestible energy (DE 2.5, 3 and 3.5 kcal/g) and same protein level 35%, in a flow-through system (1L/min) at 26.2 ± 0.460C. Triplicate groups of 15 fish (12.12±0.22 g) each, were stocked in 300-L circular polyethylene tanks and fish were fed to satiety thrice daily throughout the feeding trial. The best of total weight gain (146.67 g), FCR (2.21), protein efficiency ratio (1.31), apparent net protein utilization (ANPU%) (34.69) and condition factor (CF) (1.26) were observed in diet containing 3 kcal/g DE. The viscerosomatic index (VSI) and hepatosomatic index (HSI) did not show any significant difference between treatments (P>0.05). The final whole body moisture content decreased significantly with increasing energy levels in diets (P<0.05). Although whole body lipid and protein contents did not show significant variation among treatments (P>0.05), but the highest lipid and protein deposition were observed in diets containing 3.5 and 3kcal/g DE, respectively. Comparison between varying levels of dietary energy on the growth, feed utilization and whole body composition of Gattan indicated that 3 kcal g-1 DE could be the preferential dietary energy levels in fingerlings of this species.

This project was carried out in order to increase the shelf life of Kilka Fish and prevent color changes during cold storage. Edible film made of sodium alginate (1% concentration) was used for fish packaging. This project was carried out in four treatment and in triplicates. Treatments were coated samples at intervales times of 0, 2 and 4 hours shelf life in sodium alginate solution and uncoated Kilka (control samples). The coated and control samples were kept at -18 oC. Examination were carried out for a period of six months. Examination was conducted on 21 packs from each treatment on day 1 after processing and from first month untill sixth month after processing.Total bacterial counts and Staphylococcus bacteria count were lower in the coated samples compared to the control samples. Coliform, Escherichia coli and Pseudomonas bacteria contamination were not observed until the end of storage period in the coated samples. Moisture was less in the coated samples at time = 0 and was highest in the coated samples at time = 4 hour. Peroxide value, free fatty acids, thiobarbitoric acid, TVN and pH were higher in coated samples at time = 0 compared with other samples and in coated samples at time = 4 were lower compared with other samples. Statistically significant (p<0.05) decreases were observed in the coated and control samples during cold – storage. Sensory analysis carried out based on ranking method. Over all there was a significant difference (p<0.05) between the coated samples and control ones. The coated samples at time = 0 had the best quality. The coated samples at time= 4 hour had lower quality. According to the results, the coated samples had good quality until the end of storage period. Based on the results of sensory analysis the coated samples maintained quality for a period of three months.

The effect of light intensity and photoperiod on growth and survival of juvenile Fenneropenaeus indicus shrimp was investigated for 40 days. After adaptation, 3 months juvenile shrimps with initial mean weight 8.13±0.20g were stocked (12 shrimps/tank) in 300 liters fiberglass tanks. Two light intensities (50 lx,1500 lx) with two photoperiods (24L/0D, 12L/12D) were provided in four treatments (50 lx, 24L/0D; 50 lx, 12L/12D; 1500 lx 24L/0D; 1500 lx, 12L/12D) useing fluorescent lamps.Water temperature and salinity were maintained between 29 and 310C and 25-26 ppt, respectively. The results indicate that maximum and minimum SGR occurred under 50 lx, 24L/0D and 1500 lx, 24L/0D, respectively(P<0.05). The treatment 50 lx, 12L/12D had the second highest SGR between treatments. However, no significant differences in SGR was found between 50 lx, 12L/12D and other treatments (P>0.05). Light intensity and photoperiod did not significantly affect survival of juvenile shrimp (P>0.05). Our study suggest that light intensity of 50 lx provide conditions for better growth rate and photoperiod could be adjusted to 12 or 24 h light.

By attention to the increased application of Aluminum alloy in various industries, essentiality of excreting suitable surface preparation in order to increase the resistance to the corrosion is inevitable. Meanwhile using special materials in various groups of alloys (alloy groups of 7000, 2000) their problem of the corrosion is higher. Different kinds of coatings are used. In marine environment and other places with higher humidity exerting the anodizing coats, Is the best method to prevent the exfoliation corrosion of aluminum alloy. In this research the effect of different currents (1.6 and 2.6) and the importance of sealing on increasing the corrosion resistance to anodizing alloys 7075-T6, 2024-T3, 6061-T6 and 5083-H34 by using the salt spray in accordance with the ASTM B117 standard is investigated and the results reveals the importance of the current density and the process of sealing on increasing the resistance to corrosion of the anodized coating.

In order to effect of prebiotic Immunoster was performed the experiment in period of 8 weeks in 0, 2, 4 percent levels on growth, survival, blood cells count and body compositions of mahi sefid fingerlings with initial weight of 0.350.02gr. The experiment was performed with use of compeletly accidental design in one control group and two treatments groups each with 3 replicates and with 150 kutum fingerlings in each tank. Feeding was varied 15-20% of biomass. At the end of experiment, however there was no significant difference in 2 and 4 percent level of Immunoster in camparing with control group (P > 0.05), but mahi sefid fingerlings fed by Immunoster containing diet showed slightly better growth function. Survival rate didn’t have significant difference between treatments. The amount of red blood cells (R.B.Cs) and the amount of white blood cells (W.B.Cs) in one cubic millimeter of blood showed significant difference between control and fingerlings fed with 2 and 4 percents levels of Immunoster (P ≤ 0.01). As 2 percent level of Immunoster had highest of R.B.Cs and W.B.Cs in compare with control group. Also there were significant difference between control and experimental groups the view of protein, fiber and carbohydrate of carcass (P ≤ 0.05).