Journal of Aquaculture Development
Year:2012 | Volume:6 | Issue:1|Papers Count:8

In this study different solutions like clay, chalk, talk and Kaolin applied to remove eggs adhesiveness and the main indices of artificial reproduction including fecundity percent, weight of eggs and larvae, fungal infections, hatching percent, mortality and survival rate investigated in various treatments. The effect of clay solution in removing adhesiveness compared in different treatments and the results showed significant differences (P £0.5). Moreover, chalk solution was not suitable in this regard. Applying talk showed that the survival rate is 9.3% less than using clay. Applying kaolin led to significant increase in various indices of incubation. Statistical analysis in kaolin treatment showed significant differences compared to other ones. Totally the mortality rate is less than other treatments and the survival rate is 19.6% more than using clay one. It shows that using kaolin solution in artificial reproduction causes higher productivity in sturgeon reproduction. Successful results obtained through using kaolin (10g/l) for 40 min which can efficiently remove the adhesion in sturgeon eggs.

Sturgeon fish with extremely great commercial value are belonging to one of the most ancient groups of the chondrostei. The highest concentration of the sturgeon fishes is in the Caspian, the Azov and the Black Sea. The Caspian Sea represents are unique. In recent years, great attention is given to artificial propagation. In order to preserve the diversity of sturgeon species and maintain their numbers. One of the most important points in propagation is environmental condition like oxygen, waterflow &… .in this study, Effect of water flow on larva of Acipenser persicus detected. Four speed of water (3,4.5,6,9.4lit/min) examined. In each pond 800 gr larva was poured. Then during a week several parameter recorded like weight, length , temperature, oxygen. The result showed 6 lit/min is the best speed of water flow for larva.

Viral Nervous Necrosis (VNN) is a serious disease causing significant economic damages to marine aquaculture industry. The disease has a wide geographical distribution having been observed in tropical and temperate climates. Up to now, more than forty species mainly of marine origin have been so far affected and this number is likely to rise in future following the introduction of new species and the increase of aquaculture trade. According to OIE all fish mortalities characterized by abnormal swimming behaviours associated with vacuolar lesions in the nervous tissues containing viral particles of the Nodaviridae family should be ascribed to one single disease, officially identified as viral nervous necrosis (VNN) also known as viral encephalopathy and retinopathy (VER). Affected fish may show different clinical symptoms depending on species, age and temperature, furthermore acute and sub-acute forms characterized by slightly different symptoms and mortality rates are also known. The most characteristic and common clinical sign observed among the different species is an abnormal swimming behaviour characterized by fish showing difficulties to maintain the normal static and dynamic equilibrium, speed and swimming direction and to control the swim bladder inflation. The viral aetiology has been confirmed following the identification of small, non-enveloped, RNA agents definitively assigned to the Nodaviridae family, genus Betanodavirus. The existence of four genotypes characterized by high homology has been proposed on the basis of the viral genome analysis. Although horizontal transmission undoubtedly represents the most common transmission route, vertical transmission has also been highly suspected, at least for some species. VER/VNN is commonly diagnosed after isolation of the causative agent in cell cultures followed by identification with immunological or molecular methods.The control of the disease is complicated by difficulties in both applying strict hygiene and preventive measures in open environments like the sea and in selecting broodfish free from infection. Although currently under study, commercial vaccines are unfortunately not yet available. VNN was identified in Golden grey mullet (Liza aurata) in the Caspian Sea as first time in 2005. A comprehensive research project was designed and carried out in IFRO from 2006 till 2010.Viral causative agent was isolated and identified by Cell culture, IHC, IFAT and RT-PCR and confirmed in Guppy fish as pathogenicity test.

A trial was conducted to evaluate the efficacy of Halamid on bacterial flora in gills and skin of Acipenser persicus fingerlings. Experiments were designed randomly. 450 healthy A.persicus fingerlings with an average weight of 7.3 ±1.6 g and an average total length of 13.7±1.1 cm were distributed in 9 fiberglass tanks (1×1×0.5 m) with 50 A.persicus fingerlings in each tank. The experimental design incorporated two treatment groups that were exposed to Halamid at 20 and 60 mg/l and one control group (without any disinfectant). Each treatment included three replicates. Disinfection was applied once daily for 30 minutes on five consecutive days to determine the effect of disinfectant bath exposures on gills and skin bacteria of Persian sturgeon fingerlings. The bacterial culture was conducted every other day. Water chemical parameters including temperature, pH and dissolved oxygen concentration were measured and recorded every day during the trial period. Other water chemical parameters including ammonium, hardness, nitrate, Co2, alkalinity and electric conductivity were measured and recorded every other day. Total bacterial count in terms of Colony Forming Unit (CFU) was determined in gills and skin of A.persicus fingerlings after exposure to the disinfectant used. Samples were collected under absolute sterile condition. Results obtained indicated significant effects (P<0.05) of Halamid on bacterial flora on gills and skin as compared to the control group. In gills 60 mg/l of Halamid was seen to be more effective than other treatments although no significant differences (P>0.05) were detected as compared with the other experimental groups. In skin samples studied Halamid at the dose of 60 mg/l produced similar results in reducing bacterial counts.

A investigation carried out for survey effect of different percentage replacement fish meal by blood meal in diets fingerlings Acipnenser stellatus on growth rate and body composition with percentage replacement 0, 20, 40, 80 and 100% in statistic complete random blocks for 8 weeks. Result showed increase replacement to above 40 % resulted a decrease on percentage body weight, final weight, specific growth rate , feed conversion ratio and protein efficiency ratio (P<0.05). The total replacement showed non appetite and mortality in fishes. Also in treatments 80 and 100 % replacement showed an unwilling to consumption diet and decrease appetite. Fishes belonged to treatment 20 and 40 % replacement truly feed diets. Parameters final weight, percentage body weight, feed conversion ratio and specific growth rate in fish fed diets 20 and 40 % replacement did not significant difference with control diet (P>0.05). increase replacement fish meal by blood meal higher 40% led to decrease body protein and a lipid deposition lipid in body (P<0.05). But body protein fishes fed diets (20 and 40% replacement) don’t difference significant with control diet (P>0.05). Result of these present study indicated that protein from fish meal could substations levels 20-40% by protein from blood meal without influencing adverse effects on the growth rate and biochemical composition of the body fingerling Acipenser stellatus.

Fungal infections in the fish hatchery are well known as problematic diseases. The aim of the present study was to isolate and identify fungi which caused Caspian kutum eggs mortality and evaluation the effects of water physical and chemical factors on their prevalence. Kutum eggs with fungal hyphea and water samples were collected from hatcheries three times in propagation seasons from 2004 to 2007. Finally 1350 eggs and 45 water samples were examined (totally 4050 infected eggs and 135 water samples). The soluble oxygen, temperature, pH, NO2-1, NO3-1 and NH4-1 were measured as water physical and chemical factors. The eggs were inoculated in culture media (YGC agar and SD agar) and incubated at same hatchery temperature. The results showed Saprolegina species were only aquatic fungi isolated from kutum eggs in examination time, whereas the most important saprophytic fungi species based on incidence were Fusarium sp., Penicillum sp., Aspergillus sp., Moucor sp., Pscilomyces sp. and Alternaria sp. respectively. The most and the least incidence percent of Saprolegnia sp. were observed in 2005 and 2007 respectively. However, incidence percent of saprophytic fungi completely showed the opposite results. The results of water physical and chemical factors were shown that temperature, soluble oxygen, pH, NO2-1, NO3-1 and NH4-1 had a significant difference between 2005 and another two years. It is clear from the present study there may be straight relations are between water physical and chemical factors and incidence of aquatic and saprophytic fungi.

In this study Bacillus subtilis is used for control of streptococcosis with the agent of Streptococcus iniae in Rainbow trout. The experience was carried out in 2 groups (Control and Treatment) and 3 replicates. In Control group, probiotic was not applied in diet but in Test group, Bacillus subtilis was administered in feed at a concentration of 107 cells per gram. In the day of forty five, 0.1 ml intraperitoneally injection of S.iniae with 2×107 cells ml-1 dosage was done for both of groups and were checked for the rest of the survey duration (2 weeks). At the end of the time which took about two months, 5 blood samples were caught for hematological and biochemical experiments from every replicate for realizing the effect of B.subtilis feeding on resistance of fish against S.iniae infection. After injection of S.iniae, there was no significant difference among control and treatment groups considering parameters such as erythrocyte count, hemoglobin, hematocrit, mean cell volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration and percent of monocyte (p>0.05). But significant difference was seen in the leukocyte count, percent of lymphocyte and neutrophile, serum total protein, serum albumin, IgM and lysozyme in both groups (p<0.05). The leukocyte count, percent of lymphocyte, serum total protein, serum albumin, IgM and lysozyme were higher in T group and neutrophile percent was lower in comparison with the control.

Feeding, the highest costs in aquaculture, are included. By food components and low-cost alternative to high levels can help to develop aquaculture. Probiotics, live microorganisms that are favorable or its or their metabolites as dietary supplements are used in farm animals. The use of probiotics in aquaculture is for two reasons: To improve the aquatic environment and to introduce beneficial microflora to the gastrointestinal tract. Probiotics, produce vitamins, toxic compounds in the diet and desensitization of non-digestible particles can stimulate appetite and improve nutrition in the host. This study was conducted for 6 weeks in the center propagation of fish bone in Syjuval, Bandar Turkman, Golestan province. The tests conducted on 4 treatments and 3 replications were as follows: control treatment that was used SFK food, treatment 2: 106 colony forming units, treatment 3: 107 colony forming units, treatment 4: 108 colony forming units. Feeding rate was 10% of total body weight of fingerlings. Physical and chemical factors were so controlled through the experiment that the amount of dissolved oxygen was fixed on 5.5 - 6 ppm, the temperature 26±2 0C and pH 7.5 - 8. Rutilus rutilus caspicus were fed during the experimental period with SFC foods containing: 8.7 % moisture, 11.2 % ash, 32 % protein and 10.5 % fat. According to the results of this study, it was shown that various color tanks affect body weight and length gain of fish and these differences are significant (p < 0.05). Maximum weight and length of body was in treatment 4 with black. Results also showed that there is significant difference in the rate of SGR, BWI%, GR and CF (p<0.05). However, there were no significant deifferences with regard to the amount of FCR and survival (p >0.05). This study showed that use of black tanks make better growth in Rutilus rutilus caspicus. According to the results of this study, there were shown that between treatments means of body weight of fish observed differences are statistically significant (P<0.05). Maximum weight and length were the treatment 2 with 106 colony forming units. Also no significant differences in FCR and CF rate were observed (P>0.05) while no significant difference in the rate of GR,% BWI, SGR and survival were observed (P<0.05). Results showed that use of the yeast Saccharomyces cervisiae is better growth in Rutilus rutilus caspicus.