نشریه علوم آبزی پروری پیشرفته
سال سوم شماره 2 (تابستان 1398)

The majority of plants and farm animal production is presently based on genetically improved seeds and stocks. Genetic improvement in aquaculture, however, lags far behind plants and farm animals. It is estimated that at present less than 10% of aquaculture production is based on genetically improved stocks, despite the fact that annual genetic gains reported for aquatic species are substantially higher than that of farm animals. In livestock, genetic gain in growth rate is typically 5 percent per generation, which is 5-6 times less than in aquatic species. The relatively high heritabilities and Large Phenotypic and genetic variation for growth rate and most other traits of economic importance combined with high fecundity and short generation intervals in most species explain the high genetic gains obtained in many aquaculture breeding programs. If genetically improved animals are used, production may be dramatically increased and feed conversion and survival were improved, that leads to better utilization of limited resources such as feed, labour, water, and land. Genetic improvement also reduces production costs as more animals can be grown using the same resources. There could be several reasons why use of selective breeding in aquaculture is far behind plants and terrestrial farm animals, including availability of  fry of wild stock, little knowledge about controlling reproduction of some pieces, lack of knowledge about the economic benefit of breeding programs, lack of knowledge about quantitative genetics and how to start and run breeding programs, substantial investments needed, many aquaculture farmers do not willing to cooperate with researchers, researchers working in the field have not effectively been able to promote the benefits of selective breeding and those extending knowledge to aquaculture lack information and knowledge about the potential of selective breeding.

Aquaculture diseases and its damages have affected the aquaculture industry around the world. Tilapia is newly introduced to the aquaculture industry of Iran. While tilapia is a tolerant fish, there are reports of infectious diseases, and it is essential to plan for their prevention and control. Health surveys of tilapia breeding indoor systems were carried out at the National Research Center of Saline Water Aquatics (Bafq, Yazd) in 2012-2014. Parasitic, bacterial, fungal and viral studies of eggs, fries, brooders and cultured fish were performed by observing abnormal movement, nutrition and symptoms of the fish as well as unusual mortality. Infection with parasitic agents Gyrodactylus sp. and Dactylogyrus sp., bacterial agents Streoptococcus sp. and Edwardsiella sp. and fungi of Penicillium sp. and Aspergillus sp. determined. The samples were negative for Herpesvirus, EHNV and BIV viruses. Although pathogens and disease factors have been rarely observed in the Nile tilapia Oreochromis niloticus and red hybrid tilapia, monitoring and enforcement of health guidelines is particularly important in preventing disease.

Crayfish is one of the most important and expensive aquatics of freshwater that in recent years,because of increasing in fishing activity ,its stoks in natural water resources had been threatened seriously and even been extinct. In order to help to rebuild the resources and producing Crayfish breeder, a project was done that named “producing Crayfish in the pool environment, with three treatment and repeating and with dencities of 3,5,7 pieces per square meter .The results of studying of Investigation and the number if eggs clinging to the swimming legs(Pleopodal eggs) and its relation to length,weight and age parameters, indicates their direct connection. That ,relative Investigation of three years old breeders have been more that two years old breeders,this difference have been statiscally significant. The breedres with more length, more weight and more age,have larger eggs and as a resuit, have less fecundity and are the opposite. Two years old female breedres with an average of 101/62 mm in length and 55.96g in weight,have relative fecundity of 2/08±0/53 and the breeders with an average,of 132/78 mm in length and 87/20g in weight,have relative Investigation of 2/18±0/64 . The Resulting data, statistically analyzed by using of spss14  software and with confidence level of 0/05 .

In this survey, the most important influencing factors on fish consumption behavior of Iranian households were determined and analyzed during 1995-2018. From 26 investigated studies , 21 factors were analyzed in order of frequency, including: price (15 items), smell (10 items), quality, market accessibility, awareness of benefits and nutritional values (9 items for each), taste (8 items), culture and acknowledge of  cooking (6 items), revenue (5 items), supply hygiene , consuming habit (4 items for each), freshness, packing (3 items for each), age, education, product variety (2 items for each), attitude, family size, protein resource, priority of consumed species, sexuality and supplying time (1 item for each). Results indicated, these factors are considered by producers and supplies management as production and supplier agents as well as Iranian fisheries organization and fisheries offices of Provinces as trustee of fish production. By progressing of society, consumption preferences and demand pattern of households would be changed and that affected their fish consumption behavior. Therefore, increasing nutrition awareness of community, introducing new processed fishery products, utilizing new packaging techniques along with market development could upgrade per capita consumption in Iran.

Ichthyophthirius multifiliis is a protozoan parasite that can cause catastrophic damage to fish farms and aquariums. This parasite can be transferred to a pool of fish, tanks, or other aquariums by introducing new fish or using equipments previously used in another farms. Therefore, the most effective way to prevent this disease is to use quarantine regulations. When this organism enters a system, during a short time cause severe deaths so that in severe infections, disease control is impossible and we ought to expect 100% fish losses. Unlike most parasitic diseases where the decision to treat sick fish depends on the severity of the infection, the treatment of fish infected with Ich parasite, although only one parasite has been observed in these fish, should begin immediately because of the speed of reproduction. One-step treatment is not sufficient to treat this disease because the life stage on the body of the fish (trophont) and the cystic stage in the environment (tomont) are resistant to chemicals and the only infectious Tront stage that is sensitive to treatment. Repeated chemical treatment can disrupt the life cycle and its spread. Fish surviving from Ich infection may act as parasite reservoir and may infect other fish. Ich can be controlled quickly and conveniently, but the cost of treatment for large farms will be high given the cost of chemicals and the amount of labor involved. Adequate attention to management methods, such as quarantine and multiple treatments when the disease occurs, can minimize the costs of the disease.

Shrimp is one of the fishery products that are being developed in the world. The expansion of this industry has created challenges. Shrimp production in earthen pools depends on a variety of factors, including pool preparation, provide nutrition with appropriate composition and quality, nutrition management and water management. Nutrition plays an important role in the management of production and water quality. Nutrition cause accumulates nutrients and organic matter in the pools and then leading to the growth of phytoplanktons. Phytoplanktons are appropriate life foods in bottom and column water to feed shrimp larvaes, produce oxygen and refinement water. Therefore, the composition of the plankton population in water of ponds culture is very important. Some species at high densities can cause inappropriate quality, toxicity, oxygen depletion or even mortality in water. Knowing the type and composition of the plankton population in addition to being aware of production levels, population dynamics and life cycle of organisms will provide growth control, production capacity, quality water management and create sustainable production conditions.