Selven,S; Dr.Rosamma,Philip(Cochin University of Science and Technology, May , 2008)
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Abstract:
Aquaculture has developed to become one of the fastest growing food producing sectors in the world.Today India is one among the major shrimp producing countries in the world.There are extensive and intensive shrimp culture practices. In
extensive shrimp culture, shrimps are stocked at low densities (< 25 PLs m'2)in large ponds or tidal enclosures in which little or no management is exercised or possible. Farmers depend almost entirely on natural conditions in extensive cultures. Intensive shrimp culture is carried out in
high densities (>200 PLs m'2). Much of the world shrimp production still comes from extensive culture.There is a growing demand for fish and marine products for human and animal consumption. This demand has led to rapid growth of
aquaculture, which some times has been accompanied by ecological impacts and economic loss due to diseases. The expansion of shrimp culture always accompanies local environmental degradation and
occurrence of diseases.Disease out breaks is recognised as a significant constraint to aquaculture production. Environmental factors, water quality, pollution due to effluent discharge and pathogenic invasion due to vertical
and horizontal transmission are the main causes of shrimp disease out breaks. Nutritional imbalance, toxicant and other pollutants also account for the onset of diseases.
pathogens include viruses, bacteria, fungi and parasites.Viruses are the most economically significant pathogens of the cultured shrimps world wide. Disease control in shrimp aquaculture should focus first on preventive measures for eliminating disease promoting factors.ln order to design prophylactic and proactive measures against shrimp diseases, it is mandatory to understand the immune make up of the cultivable species,
its optimum culture conditions and the physico chemical parameters of the rearing environment. It has been proven beyond doubt that disease is an end result of complex interaction of environment, pathogen and the host animal. The aquatic environment is abounded with infectious microbes.The transmission of disease in this environment is extremely easy,
especially under dense, culture conditions. Therefore, a better understanding of the immune responses of the cultured animal in relation to its environmental alterations and microbial invasions is essential indevising strategic measures against aquaculture loss due to diseases. This study accentuate the importance of
proper and regular health monitoring in shrimps employing the most appropriate haematological biomarkers for application of suitable prophylactic measures in order to avoid serious health hazards in shrimp culture systems.
This study shows that the disease resistance and survival
rate of Penaeus monodon in a larval rearing systems
can be enhanced by supplementing with antagonistic
or non-antagonistic probiotics. The antagonistic mode
of action of Pseudomonas MCCB 102 and MCCB 103
against vibrios was demonstrated in larval mesocosm
with cultures having su⁄cient concentration of antagonistic
compounds in their culture supernatant. Investigations
on the antagonistic properties of Bacillus
MCCB 101, Pseudomonas MCCB 102 and MCCB 103
and Arthrobacter MCCB 104 against Vibrio harveyi
MCCB111under in vitro conditions revealed that Pseudomonas
MCCB 102 and MCCB 103 were inhibitory to
the pathogen.These inhibitory propertieswere further
con¢rmed in the larval rearing systems of P. monodon.
All these four probionts signi¢cantly improved larval
survival in long-term treatments as well as when challengedwith
a pathogenic strain ofV. harveyiMCCB111.
We could demonstrate that Pseudomonas MCCB 102
andMCCB103 accorded disease resistance and a higher
survival rate in P. monodon larval rearing systems
throughactive antagonism of vibrios,whereas Bacillus
MCCB 101 and Arthrobacter MCCB 104 functioned as
probiotics through immunostimulatory and digestive
enzyme-supporting modes of action.