نشریه آبزیان دریای خزر
سال پنجم شماره 1 (بهار و تابستان 1399)

In the aquaculture industry the production of sterile polyploid fish is an advantage due to the elimination of sexual maturity during rearing to produce fish meat. Polyploidy having more than two complete sets of chromosomes in each cell which is rarely seen in nature in the fish, but can occur in controlled conditions through induction. The production of triploids in salmonids have emerged with methods such as chemical (Cytochalasin B, Colchicine and nitrous oxide), high temperature (26-29 0C), and hydro static pressure (650– 700 kg/cm2 of hydrostatic pressure) that interfere with and prevent the release of the second polar body during metaphase II of meiosis and the use of fused sperm for fertilization. By crossing a tetraploid fish with a diploid mate, 100% triploids would result. Salmonidae tetraploid containing two additional chromosome sets induce by chemical or hydrostatic pressure treatments of eggs before the first mitotic division of the zygote. In practice, there have been varying degrees of efficiency and acceptance of these methods for producing triploid salmonids for aquaculture. Polyploidy induction is important for the production of sterilized fish, increasing of growth rate in maturity age, introducing fish in water resources for sport fishing and the production of transgenic fish in aquaculture

Silkworm pupae powder is obtained as a by-product after separating silk strands from cocoons. This powder can be used as a suitable protein source for terrestrial and aquatic animals because of its amino acid structure. In this study, the effects of diets containing 0, 5, 10 and 15% silkworm powder instead of fish meal on growth performance of rainbow trout were investigated in a completely randomized design. 360 juvenile rainbow trout (average weight 55±3.42 g) were used. They were divided in 4 groups and 3 replication. At the end of the experiment; total length, weight gain, condition factor, feed conversion ratio, and protein efficiency ratio were not significantly different (P>0.05). Specific growth rate and nutrition protein utilization were significantly higher in control group compare to other treatment groups (P<0.05). Results of the present study showed that silkworm pupae meal could replaced up to 15% of fish meal diet in rainbow trout culture without adverse effect on growth performance.

Due to the global problems of supplying oil and fish meal, plant oils are the only suitable alternative to the aquatics diet. In this scrutiny, the levels application of vegetables compounds with flour and fish oil in the diet of aquatic animals were compared by researchers in Iran during years 1998 to 2019. Soybean and its processed and modified products (10 to 50% level), canola meal (20 to 100%), flaxseed meal (10 and 15%), rice protein concentrate(25%),cotton seed meal(20 and 35%), irradiated Chickpea (40%), Azolla meal (15 and 21%) ,corn gluten meal (60%), Sargassum meal(15%),barely protein concentrate (25%), and wheat Gluten (no effect) as alternatives to fish meal and rapeseed oil (60%), canola (50%), Flax (75%), grape seed (50%), soybean (10%), canola and soybean combination (50 and 100%), mixture of cotton seed, soybean and grape seed (100%), combination of canola, flax, sunflower and safflower (80%), mixture of canola, flax and safflower (100%) were Fish oil substitutes in aquatics diet. The results showed that in the aquatics diet, vegetable oils can be replaced at a higher level than vegetable proteins. Due to the development of cultivated surface area of oilseeds in Iran, this potential could be used to reduce the dependence of fish oil in aquatics diet.

*, This study carried out to determining the normative of artificial and semi-artificial reproduction of wild common carp (Cyprinus carpio. L. 1758) in 2019. In this study, 70 samples were caught from Gomishan region. Mean weight and length of 29 wild males were 1146±151.62 g and 44.79±2cm, and for 41 wild females were 1152.25±235.14 g and 44.87±2.4cm, respectively. Mean age of males were 7.16±0.75 and females were 9.5±0.67 years old, respectively. Artificial and semi-artificial propagation methods were performed. Artificial propagation was done by Ovulin injection in two steps for females at 1 ml / kg fish weight and half the dose was injected at the same time in the second stage of female infusion after 12 hours for males.14 males and 13 females broodstocks for artificial, and 7 and 10 for semi-artificial propagation were selected. The number of eggs per gram was 783±53. The fertilization rate was 91±4 and hatch rate was 58±7.23.Maximum and minimum relative fecundity were 209707 and 61200 per kilogram of body weight and Maximum and minimum working fecundity were 325728 and 53244 respectively. Mean relative and working fecundity was 104795.6±49663.32 and 128981.5±84102. Hatch rate was 58±7.23. A total of 729800 larvae were transferred to the Sijaval Center pond . 200000 juveniles with 0.8g weight and 36500 juveniles with 2.6g weight producing of semi artificial propagation rearing in Gharasu River in order to restocking. For reproduction of wild common carp, choosing the broodstocks in right time (in winter), region of catching, transfer it from the sea to breeding centers are the most important effective point. Therefore, the manipulation, relocation and transfer of these newly catch wildlife from the shores of the sea or river requires equipment, handy net, disinfect materials, anesthesia, Oxygen tank and time table.

The cesium-137 (Cs-137) is one of the most dangerous fission fragments from fissionable nuclides U-235, which it half-life is about 30/17 years. The Chernobyl accident was diffused a high concentration of radioactive pollutants especially Cs-137 in different areas. Since Iran is very close to accident area, it is necessary to study the contamination of radioactive material in the environment and living organisms. The research covers the health of muscle tissue of liza aurata to pollution of Cs-137 of center region in southern part of the Caspian sea in 2008. In this study 60 piece of liza aurata were obtained from fishing sites in Mazandaran province (in the central region of the southern coasts of the Caspian Sea). The Cs-137 activity measurement of muscle tissue was carried out by using of gamma spectrometry. The results of Cs-137 was compared by the International Atomic Energy Agency (IAEA) and the World Health Organization (WHO) at 10 Bk/Kg. Based on the results, Cesium-137 levels in muscle tissue were less than the detection limit in more than 90% of the fish samples. The radioactive material was within the permissible and standard range in the rest of the fishes (8.3%). This study has been confirmed the health of muscle tissue of Liza aurata muscle to pollution of radioactive Cs-137 in period and area of stud

Beluga )Huso huso ( years, is distributed in the Caspian, Black, Azov and Adriatic seas as well as the Volga and Danube rivers; In recent years the amount of its reserves and catching has been declining due to biological, non-biological and human interventions, and it is still on the list of highly endangered species. However its breeding is expanding in the world and in Iran. This fish can be raised in some rainbow trout farms. In this study, 800 pieces of juvenile of fish Huso huso with an average weight of 100 gr were transferred from Yousefpour Siahkal farm to a trout farm concrete suburb Siahkal city (pools dimension: 30× 3×1m). The fishes were reared for Four years. Trout pellet feed was used to feed (Huso huso). Fish biometrics was performed during the period and end of each year, and growth index parameters were calculated with the corresponding formulas. The average weight of fish was 1.270 kg in the first year, 2.890 kg in the second year, 5.840 kg in the third year, and 8.850 kg the fourth year . The daily growth rate increased from 4.79 g / day to 12.53 g / day in 2015 and the feed on version ratio decreased from 2.37 to 1.2 unite. The weight gain percentage (BW %), of Beluga fish decreased by half in four years. The survival of the fish during the rearing was 100%. Therefore, Beluga Fish farming is economically justified, , taking into account the growth rate, the initial investment, the selling price of fish in or outside the country.