Site Selection
Selection for a suitable site is a critical activity and must be carefully determined
before establishing of a shrimp farm. Site evaluation is not only undertaken to
determine if a site is suitable for shrimp farming. It is also valuable in determining
what modifications are needed concerning layout, engineering, and management practices
to make shrimp farming possible at a given site. No site will have all the desirable
characteristics, so a number of judgements have to be made for every site.
There are several factors involved during site selection.
Topography and Climatic
Condition
Topographically, the best areas for shrimp culture are those with average natural
ground elevations of about 1-3 m above mean sea level or at least 1 m above the
highest high tide level to allow drainage and harvesting. The cost of pumping increases
in highly elevated sites. The sites should have minimum vegetative cover, be near
the sea or other natural waterways such as rivers and streams, have easy access
to roads, a sparse population and be nearly square or rectangular in shape.
In terms of climatic conditions, areas having short and not as pronounced a dry
season with moderate rainfall distributed throughout the year are the best suited
for shrimp farming. A pronounced long dry season may cause an increase in water
temperature and salinity, which will promote excessive growth of algae and result
in oxygen depletion at night.
Infrastructure
Accessibility
The farm must have good accessibility either by road or water, and communication
systems throughout the year in order to facilitate supervision and transport of
materials and products. It is important that the farm be within 3-6 hrs traveling
time from the hatchery to avoid excessively long transportation time of the larvae
and should be within 10 hrs from the processing plant to avoid deterioration of
the product.
Electricity
Availability of relatively cheap and reliable power source is a major consideration
in site selection. In areas where electricity supply exists, it is practical and
beneficial to utilize electric power to run the farm, especially for the intensive
culture system. It is advisable to have a back-up electricity generator as a secondary
power source.
Security
Areas free from security risks result in favorable working conditions, productivity
and less extra costs.
Availability of Labor and Other Factors
The availability of labor, equipment and commercial feed and supplies ensure smooth
operations and successful crop.
Water Supply
Site should have good pollution free water supply of both freshwater and brackish
water. Water quality parameters required for maximum feed efficiency and maximum
growth of Penaeus monodon are given below:
Water Parameters
|
Dissolved Oxygen
|
3.5-4 ppm
|
Salinity
|
10-25 ppt
|
Water Temperature
|
26-32 (oC)
|
pH
|
6.8-8.7
|
Total nitrite nitrogen
|
1.0 ppm
|
Total ammonia (less than)
|
1.0 ppm
|
Biological Oxygen Demand (BOD)
|
10 ppm
|
Chemical Oxygen Demand (COD)
|
70 ppm
|
Transparency
|
35 cm
|
Carbon dioxide (less than)
|
10 ppm
|
Sulphide (less than)
|
0.003 ppm
|
Water from polluted areas containing high concentrations of suspended solids and
organic wastes such as effluent water from industry; urban areas, agricultural and
other farm locales should be avoided. A settling pond or a large reservoir should
be used in such areas for sedimentation and treatment. In saline areas, a source
of freshwater is useful for adjusting the salinity in the ponds and for domestic
use by farm staff. The freshwater should be good enough for use and adequate throughout
the year.
Soil Conditions
The type of soil is the most critical in site selection, since the shrimp will spend
most of their time on the pond bottom during the culture period. Usually, clay or
loam-based soil containing more than 90% clay and pH between 6.5-8.5 is preferable.
Sites with sandy or silty soil should be avoided due to their porous nature that
may lead to erosion, seepage of water and easy infiltration of waste into the soil.
Prior to construction of ponds, samples of soil should be taken randomly from 5-10
spots at the surface and at 1 meter deep and sent to a laboratory for the analysis
of soil texture and pH. Such data will be useful during pond construction and preparation.
Mangrove or acid sulfate soils are not suitable for shrimp pond culture due to their
high organic matter contents and acidic nature that require a high water exchange
rate and low stocking density. A pond built on mangrove soil will also encounter
the problems of hydrogen sulfide and ammonia accumulation in the pond bottom. In
the acid sulfate soil areas, the soil will develop high acidity when dried and then
flooded which will lead to difficulty in stabilizing the pH of the pond water and
in inducing the growth of plankton during the culture period.
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