Considerations in Site Selection for Fish Farming
Choosing
the right site ranks second after identifying markets for your
product. Locating land that meets your needs is usually less costly
than trying to make a readily available site fit the requirements
later. The three most critical criteria are adequate water (supply and
quality), suitable soil type and the appropriate topography.
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| fish farming |
Water
Aquaculture
requires large volumes of good quality water. While you may be able to
fill a pond with your garden hose, it may take six months to do
so. Normally, a well or surface water source (river, stream or spring)
is required. Surface sources may be polluted, intermittently available
(affected by weather, e.g. drought) or contain wild fish populations
which might be introduced into your pond. Wild fish can be a source of
disease and will often compete with cultured fish for feed. Many of the
most successful aquaculture operations in the U.S. depend on large
aquifers (underground water supplies) for water needs. Typically,
commercial aquaculture requires a water flow rate of 25-40
gallons/minute, on demand, for every surface acre (4 acre-feet) of pond
water.
Water
must be of high quality and free of pollutants, sewage and toxic
contaminants. Generally, water that is safe for livestock and domestic
use or that supports wild fish populations is safe for
aquaculture. However, livestock and aquaculture do not mix. Manure
from just a few farm animals can pollute a pond.
There
are several chemical characteristics of water that are desirable for
good fish growth. Water should have a pH of 6.5-9.0, total alkalinity
of 75-250 mg/l and total hardness of 75-250 mg/l. Total hardness and
alkalinity should not be less than 20 mg/l. Low alkalinity and acid
water are usually related to acid soils. Agricultural limestone can be
used to raise pH, alkalinity and hardness to the minimum required levels
in soft, acid water. If striped bass or red drum are being
considered, calcium hardness and total alkalinity between 100-250
mg/l are preferable; a calcium hardness value of 250 mg/l is
ideal. Often, well water contains no oxygen and high levels of carbon
dioxide and nitrogen, necessitating aeration before use or pH testing.
Soils
Second,
the site must have soils that hold water and can be compacted. If pond
levees are constructed with soil that has high water permeability
(leakage), the cost of pumping water could become prohibitive. Soils
should contain no less than 20% clay. Soils with high sand and silt
compositions may erode easily and present a piping hazard -- soil-water
flow along pipes -- which could wash out a levee. Anti-seep collars can
help minimize that problem. The following list can be used as a
general guide to the clay content of various soil textures:
Texture | Clay (%) |
Clay | >40 |
Silty clay | 40-60 |
Sandy clay | 35-55 |
Silty clay loam | 27-40 |
Clay loam | 27-40 |
Sandy clay loam | 20-35 |
Heavy silt loam | >20 to 27 |
Silt loam | 12-27 |
Loam | 7-27 |
One
can see that soils classified between sandy loam and sand do not
contain enough clay for pond construction. Silt loams and loams may or
may not have adequate clay. Texture classifications are based on per
cent compositions of clay, silt and sand. It is particle size that
determines how soil is classified:
Soil | Particle Size |
(millimeters) | |
Very fine sand | 0.05-0.1 |
Silt | 0.002-0.05 |
Clay |
If
you think your soil may be acceptable for building ponds, it is
important that you check with your County Agricultural Extension Agent
and the Natural Resource Conservation Service to be certain. Clay
content is not the only factor. Soil distribution, particle form and
composition, uniformity, and layer thickness are equally
important. Suitable soils should be close to the surface and extend
deep enough that construction, harvest activity or routine pond
maintenance will not cut into a water permeable layer, causing a
leak. Soil analysis and the services of an engineer may be
necessary. The following are examples of soils that can be found in
west Kentucky:
Soil Series | Depth (inches) from Surface | Texture |
Alligator | 0-8 | Silty clay |
8-60 | Clay | |
Sharkey | 0-65 | Silty clay |
Dubs | 0-13 | Silty clay loam |
13-38 | Silty clay | |
Dundee | 0-25 | Silty clay loam |
25-52 | Silty clay | |
Lindside | 0-60 | Silty clay loam |
Newark | 0-60 | Silty clay loam |
Nolin | 0-108 | Silty clay loam |
Arkabutla | 0-36 | Heavy silt loam |
36-60 | Silty clay loam | |
Rosebloom | 0-52 | Heavy silt loam |
52-72 | Heavy silty clay loam | |
Cascilla | 0-65 | Heavy silt loam |
Memphis | 0-12 | Silt loam |
12-24 | Silty clay loam | |
24-60 | Heavy silt loam | |
Colp | 0-12 | Silt loam |
12-18 | Heavy silt loam | |
18-65 | Silty clay | |
Okaw | 0-13 | Silt loam |
13-18 | Heavy silt loam | |
18-62 | Silty clay to clay | |
Loring | 0-12 | Silt loam |
12-34 | Heavy silt loam | |
34-46 | Silt loam fragipan | |
Grenada | 0-7 | Silt loam |
7-25 | Heavy silt loam | |
25-50 | Silt loam fragipan | |
Calloway | 0-26 | Silt loam |
26-50 | Silty clay loam fragipan | |
50-70 | Silt loam | |
*Brandon | 0-12 | Silt loam |
12-32 | Silty clay loam | |
32-75 | Very gravelly sandy loam |
*
The Brandon series is a good example of a thin layer of suitable soil
overlying a thick layer of soil with high water permeability. It would be easy to break through a weak section of the silty clay loam during construction, discing or seining. Building ponds on soils like the Brandon series would not be advisable.
Topography
Large
commercial fish farms are typically built on flat land. Pond bottoms
drop approximately 0.2 foot for every 100 feet of length, a slope of
0.2%. Topography with slopes of 0-2% is better for pond
construction. Extensive earth moving may be required on land with slopes
greater than these; increasing construction costs. Some innovative
farmers use terracing -- stair-stepping -- for pond layouts in hollows
or on land with slopes greater than 2%. However, the economics of that
method should be carefully examined. It is important that ponds have an
adequate drainage area for harvest. The site should be above the
25-year flood plain. If the pond site is situated within the 100-year
flood plain, a permit will be required before construction from the
Division of Water, Water Resources Branch -- Flood Plain Management, in
Frankfort, Kentucky.
Important Considerations
Other
considerations include former land use, agricultural activities in
surrounding areas, accessibility and migratory birds. New ground may
contain roots and stumps which make operation of earth moving equipment
difficult. The presence of roots or stumps in pond levees is likely to
create leaks. If the site was previously used for crops that required
heavy pesticide or herbicide applications, there may be too much toxic
residue in the soil for fish production. Likewise, wind drift from
extensive aerial applications of pesticides or herbicides on neighboring
farms could result in the loss of a fish crop. Land for commercial
aquaculture should have access to all weather roads and 230 volt or
preferably, three phase electricity. Finally, fish farms should not be
sited where fish-eating birds are likely to be a problem (e.g. near
migratory bird refuges and wintering grounds).
Tags:
Fish Farming