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  • 1
    Publication Date: 2018-10-08
    Description: For the first time white spot disease (WSD) was reported in shrimp farms of khoozestan province, in southwest of IRAN in 2002. Then in 2005 the neighbor province, boushehr, was contaminated. In 2008 WSD outbreak reported in sistan-bloochestan province in southeast of Iran. In 2015 all of southern shrimp farms of country except Hormozgan, the middle southern province, which has remained free of WSD, are being contaminated. White Spot disease suspended shrimp culture in thousands hectares of shrimp farms. Considering that white spot disease has not been observed in Hormozgan province yet, the question is; to what extent environmental and management factors participated in preventing WSD outbreak or cause WSD outbreak. In this study (20102012), the effects of environmental factors and management, stressors that decrease immune system function of shrimp are discussed. In addition, the role of pathogen as the main factor of outbreak is discussed. The goal of this study is to define environmental parameters and management practices associates with outbreak of white spot disease in affected provinces and discover reasons of being Hormozgan province free of this disease. In this study the role of the local environmental factors and management practice stressors in susceptibility to WSD was determine. Both the effects of environmental factors in water of ponds including total ammonia, nitrogen, dissolved oxygen, pH, salinity, transparency, and temperature and management issues related to biosecurity are studied. There were overlaps on physical and chemical parameter values obtained in clear areas with contaminated areas .Results of the data analysis suggest that lack of association with WSD incidence was 7 times greater than WSD incidence despite of disease outbreak in sistan-bloochestan province, so other sources of white spot disease virus incidence was suspected in affected areas. Histopathological examinations and polymerase chain reaction (PCR) tests during project performance did not reveal white spot disease virus evidences in post larvae examined from khoozestan province stocked in farms but disease outbreak was happened in that farms , so we suspected to management practice include feed , pond preparation and carrier of disease. Recorded values of temperature and salinity in some months during inspection in Hormozgan province specified stressful condition that may lead to WSD outbreak, however the disease did not appear. Therefore the hypothesis that the water physical and chemical conditions are reasons to prevent disease outbreak in Hormozgan province is being rejected. The policy of Hormozgan’s fishery authorities, to replaced Fenneropenaeus indicus with specific pathogen free Litopenaeus vannamei, that is more resistant to some of diseases, before incidence of WSD in farms and to before being endemic in the Hormozgan province, made an advantage compare to affected southern provinces that introduced Litopenaeus vannamei after WSD prevalence to their farms. However it does not guarantee to maintain current trend of being Hormozgan province farms free of white spot disease. Therefore establishing the principals of biosecurity are strongly emphasized. Strategies taken by the proficient authorities in preparation of SPF shrimp broodstock can be the most important factor in preventing WSD. Regarding biosecurity principals purchased feed must be free of shrimp head powder. Construction the new shrimp farms should be as far as it could be away from contaminated areas.
    Keywords: Aquaculture ; Ecology ; Health
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
    Format: application/pdf
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  • 2
    Publication Date: 2018-10-13
    Description: In this study, after determining history of origin entering white leg shrimp of broodstocks at hatcheries of country, finally, two population of Molokaei and High health were considered as shrimp broodstocks of specific disease free (SPF) zero generation. After inbreeding and cross breeding among adult males and females of two population above, three storage different were produced in the first generation: H♂ × M♀, M♂ × H♀ and H♀ × H♂. The second generation were produced from selective breeding of M♂ × H♀. The aim of this study was to determine genetic differences between different generations of specific pathogenic free shrimp by evaluation of 16S rRNA region mitochondrial of different generations. Result of this study showed that of 486 sites have been identified 484 sites were conserved. Also, monomorphic sites ranged between 482 - 486 sites and was consists 2 polymorphic sites and 2 transitional sites. The number haplotypes, haplotypes diversity, nucleotide diversity revealed in this region were 2, 0.356±0.159 and 0.00147, respectively. Due to the high genetic identify and reduce of genetic distance of shrimp between different generations of SPF shrimp, genetic differentiation and gene flow (Nm) between them were -.142 and -2.00, respectively. This rates clearly shows a low level of polymorphism in this region of mitochondrial of different generation of SPF. This may be occurred because of small effective populations and genetic drift. Thus, offspring had inherited mitochondrial genome from your mother, therefore, it is expected that rate of variation in this genome is influenced by several factors, including genetic drift, due to unavailability of new-broodstock from different areas. It was observed that due to high conservation sites in 16S rRNA region of mitochondrial genome, nothing genetic differentiation was observed among different generations of SPF.
    Keywords: Aquaculture ; Biology
    Repository Name: Aquatic Commons
    Type: Monograph or Serial Issue , NonPeerReviewed
    Format: application/pdf
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