FAU Institutional Repository http://purl.fcla.edu/fau/fauir
This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute.
Notice: © 2002 The Haworth Press, Inc. This manuscript is an author version with the final publication
available and may be cited as: Samocha, T. M., Hamper, L., Emberson, C. R., Davis, A. D., McIntosh, D.,
Lawrence, A. L., & Van Wyk, P. M. (2002). Review of some recent developments in sustainable shrimp
farming practices in Texas, Arizona, and Florida. Journal of Applied Aquaculture, 12(1), 1-42. doi:
10.1300/J028v12n01_01
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Review of Some Recent Developments
in Sustainable Shrimp Farming Practices
in Texas, Arizona, and Florida
Tzachi M. Samocha
Louis Hamper
Craig R. Emberson
Allen D. Davis
Dennis McIntosh
Addison L. Lawrence
Peter M. Van Wyk
ABSTRACT. The world shrimp-farming industry is currently experiencing major crop losses due to disease outbreaks, which are often associated with environmental degradation. Such losses can be minimized
through the adaptation of technologies that enhance biosecurity and environmental control. Current technologies suggest that a shrimp yield as
high as 10 kg/m2/crop can be achieved in indoor, super-intensive, closedrecirculation systems in which environmental parameters are controlled.
Nevertheless, high construction and operating costs make the financial
Tzachi M. Samocha, Texas Agricultural Experiment Station, Shrimp Mariculture
Research Facility, 4301 Waldron Road, Corpus Christi, TX 78418.
Louis Hamper, Arroyo Aquaculture Association, Route 2, Box 1040, Rio Hondo,
TX 78583.
Craig R. Emberson, Wood Brothers Farms, 77 Biltmore Estates, Phoenix, AZ
85016.
Allen D. Davis, Auburn University, Department of Fisheries and Allied Aquaculture, Auburn, AL 36849.
Dennis McIntosh, University of Arizona, Tucson, AZ 85705.
Addison L. Lawrence, Texas Agricultural Experiment Station, Shrimp Mariculture
Research Laboratory, 1300 Port Street, Port Aransas, TX 78383.
Peter M. Van Wyk, Harbor Branch Oceanographic Institution, 5600 Highway US 1,
Fort Pierce, FL 34946.
Journal of Applied Aquaculture, Vol. 12(1) 2002
 2002 by The Haworth Press, Inc. All rights reserved.
1
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JOURNAL OF APPLIED AQUACULTURE
viability of these systems questionable. Production of shrimp with reduced water exchange in outdoor ponds is another promising method to
minimize monetary losses and environmental degradation. Data from
commercial shrimp farms in south Texas suggest that significant reduction in water exchange and nutrient release is feasible with no impact on
production when an adequate level of aeration is provided. Researchers
of the Texas Agricultural Experiment Station, Corpus Christi, Texas, are
currently testing other potential management tools for intensification of
outdoor pond productions. These trials demonstrated the feasibility of
producing a yield of almost 0.9 kg/m2 of marketable size shrimp with no
water exchange. Inland production of shrimp in low-salinity ground water can provide another potential solution to disease and environmental
problems, as production is conducted in isolated areas away from other
host species and where effluent water can be used for crop irrigation. Recent studies with this water showed that high-density nursery and growout of Pacific white shrimp, Litopenaeus vannamei, are feasible, with excellent survival and yield. [Article copies available for a fee from The
Haworth Document Delivery Service: 1-800-342-9678. E-mail address:
<getinfo@haworthpressinc.com> Website: <http://www.HaworthPress.com>
 2002 by The Haworth Press, Inc. All rights reserved.]
KEYWORDS. Pacific white shrimp, Litopenaeus vannamei, closedrecirculation system, culture
INTRODUCTION
Viral disease outbreaks in farm-raised shrimp have resulted in severe
crop losses all over the world. In some cases, these losses have been associated with shrimp farming intensification and receiving-stream degradation. When virulent pathogens are found in wild populations and in
natural waters, disease control in cultured stocks becomes difficult and
sometimes very costly. Farmers and researchers are interested in developing cost-effective shrimp production methods to reduce the risk of
these disease outbreaks.
Aquaculture, by definition, uses resources from, and interacts with
the environment. Many aquaculture operations generate metabolic waste
products (e.g., feces, ammonia, uneaten food, etc.) that are being released into receiving waters. Consequently, some cases of environmental degradation in coastal areas have been documented in Europe,
Southeast Asia, and Latin America due to intensive aquaculture activi-
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Samocha et al.
3
ties (Phillips et al. 1993). In most cases, the organic particulate waste
will accumulate on the seabed in the immediate vicinity of the farm,
while the soluble waste will eventually end up in the receiving waters.
Organic enrichment of the benthic ecosystem may result in formation of
anoxic conditions. Under extreme cases, reduction in macro fauna biomass, abundance, and species composition may also follow (Barg
1992).
In semi-intensive and intensive pond systems, it is not uncommon to
exchange 40% of the pond volume daily. For example, old shrimp production practices in Taiwan required up to 43 m3 of water for every 1 kg
of shrimp produced (Chien et al. 1989). Hopkins and Villalon (1992)
found only small correlation between estimated water usage per unit
weight of product and shrimp production rates. Often on large farms,
water exchange is based on a set schedule, with occasional emergency
flushes (Macia 1983), rather than as an ongoing response to changing
pond conditions. Water exchange rates are seldom based on well-conceived nutrient and algal population monitoring. Often, pond-flushing
removes phytoplankton, nitrifying bacteria, and natural productivity
that could have otherwise benefited the pond water quality and the cultured organism. Hopkins et al. (1993) studied the effect of water exchange rates on production, water quality, effluent characteristics, and
nitrogen budgets of intensive shrimp ponds. They reported that reducing typical water exchange is feasible without negatively affecting
shrimp survival or growth, thereby decreasing economic costs and potential negative environmental impact. Furthermore, Hopkins et al.
(1995a, 1995b) stated that high shrimp yield was achieved without water exchange (7,000 kg/ha/crop). To avoid nutrient release during harvest, they suggest storing the water for reuse with subsequent crops.
Although the efficiencies of water recycling systems are still far from
perfect, more and more shrimp producers are incorporating this technology on their farms. One of the main reasons for this increased activity is the farmer’s effort to reduce the risk of losing their crops due to
viral disease outbreaks. A good example is the recent White Spot Syndrome Virus (WSSV) disease that affected shrimp production in the Far
East. Several organisms (especially crustaceans such as crabs, copepods,
Artemia, etc.) have been found to be potential carriers of this virus. To
minimize the risk of introducing these carriers into the culture systems,
water is treated before stocking. This water is recirculated within the
farm and every effort is made to avoid bringing new, untreated water
until harvest. Unlike farmers in the Far East, the initial driving force for
the Texas shrimp farmers to use the closed recirculating system was
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JOURNAL OF APPLIED AQUACULTURE
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their need to meet effluent water quality standards set by regulatory
agencies. Furthermore, effluent waters from coastal shrimp farms have
created a serious growth-limiting factor for the shrimp farming industry
in Texas. It is particularly true for Texas coastal areas, in which the discharge is going into bays and estuaries behind barrier islands that have
limited water exchange with the Gulf of Mexico. This paper reviews
management practices used by producers and researchers in Texas, Arizona, and Florida to reduce both water usage and pollution from shrimp
production operation.
INDOOR SUPER-INTENSIVE
SHRIMP PRODUCTION TECHNOLOGY
Current technology advancement suggests that a high shrimp yield
can be achieved in indoor, super-intensive, closed-recirculation production systems with “zero water exchange.” These systems can serve as an
alternative to conventional pond culture, in which environmental regulations and user conflicts of coastal land and water sources can be addressed more effectively. The University of Texas at Austin, Marine
Science Institute, Fisheries and Mariculture Laboratory, has employed
water reuse systems for over 20 years for both research and intensive
production of fish and shrimp. Arnold et al. (1990) and Reid and Arnold
(1992) provide a general description of the basic recirculating system
used for shrimp production. In these prototypes, post-larvae are stocked
directly into a raceway type culture tank. Airlift pumps and a biological
filter, made of vertical filter plates, served to maintain adequate water
quality in the culture chamber. Davis and Arnold (1998) have recently
published a paper with detailed description of this system along with
several alterations of procedures and system design to increase the efficiency of waste removal, minimize labor requirements, and maximize
biomass loading.
The following is a brief description of the culture systems that have
been used for intensive culture of the Atlantic white shrimp, Litopenaeus
setiferus, and the Pacific white shrimp, L. vannamei. Unlike the prototype, a separation is made between the nursery and the grow-out phases.
Nursery is conducted in 10-m3 circular tanks. Culture water is circulated via a settling box with foam fractionation into a biological filter
and a secondary settling area before the final return into the tank. Instead of vertical filter plates, the biological filter is composed of polypropylene packing material (1.6 cm Flexrings®, Aquatic Ecosystems,
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Samocha et al.
5
Apopka, Florida1). Grow-out production trials are conducted in three
sizes of raceways (with 25, 35, and 72 m3 of operational water). The
25-m3 and 35-m3 systems each consists of three separate components: a
fiberglass raceway; a fiberglass reinforced plywood filter box housing a
rotating micro-screen filter; and a fiberglass filter box divided into four
equal compartments, consisting of a foam fractionation/settling chamber, two biological filter compartments, and a secondary settling chamber/ozone reactor. For each system, the effluent water from the culture
chamber is discharged into a micro-screen barrel. Suspended solids are
collected on the rotating screen and washed into a catch basin for discharge. The filtered water is then air-lifted out of the rotating micro-screen filter box into two foam fractionators. The water passes
through a settling chamber, two reverse-flow biological filter chambers,
and a secondary settling chamber/ozone reactor. After treatment, the
water is pumped back into the culture chamber. Aeration to the raceway
(via ten porous plastic diffusers and airlift pumps) is provided by a regenerative blower. The biological filter consists of two chambers, each
containing 0.9 m3 of 5.8-cm Lanpac® polypropylene packing material
(Lantec Products Inc., Agoura Hills, California1) and supplemental aeration. Filtered water entering the secondary settling chamber is treated
with ozone (5.6-11.3 L/hour or 2-4 SCFH). Ozone is produced with a
corona discharge ozone generator (Innovative Water Technologies Corporation, San Antonio, Texas) with oxygen feed. Ozone and oxygen are
injected via venturi aspirators powered by a 1/10 horsepower (HP) submersible pump. When needed, a second pump that is equipped with two
oxygen-fed venturi aspirators and a screened intake achieves an increase in dissolved oxygen level in the culture tanks.
The 72-m3 system, has a similar design but the culture system and filters are constructed out of wood with a liner. In this system, effluent water leaving the raceway can be directed through two micro screens or
directly into the settling basin. All water, either from the micro-screens
or directly from the raceway, enters a common settling chamber. Water
entering the settling chamber is exposed to a stream of ozone, which is
introduced to facilitate flocculation of particulate material. Suspended
solids that have settled are discharged through a drain line running
along the bottom of the settling chamber or by manual siphoning. The
settled water is then airlifted into each of three parallel biological filters.
Water exits each filter box and enters a common foam fractionation/
ozone reactor chamber. Ozone is introduced into the reactor via three
1. Use of trade or manufacturer’s name does not imply endorsement.
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JOURNAL OF APPLIED AQUACULTURE
venturi aspirators. Treated water then travels via a common 15.2-cm
PVC pipe into the retention chamber for degassing and final settling.
Treated water is air-lifted into the top of the culture chamber at a rate of
720 L/minute. A summary of selected water quality parameters measured in the nursery and the grow-out trials can be found in Table 1.
Table 2 provides a summary of nursery and grow-out production trials with the Pacific white shrimp and the Atlantic white shrimp over a
six-year period (Davis and Arnold 1998). The nursery studies suggest
that the nursery system has supported a yield as high as 2.8 kg/m3 when
used with the Pacific white shrimp. High survival rates were obtained
for both species. Survival rates in the grow-out trials were lower than
those obtained in the nursery. Nevertheless, these trials showed that the
raceway-system could support biomass loads of 5.7 kg/m3 when used
for the production of live bait Atlantic white shrimp. When used with
the Pacific white shrimp, the system supported a yield of 9 kg/m3 of
marketable size and 11.23 kg/m3 of juvenile shrimp (Table 2). Their results suggest that the system can be operated with either 10-15% or with
as low as 0.2% daily water replacement. To optimize loading of the culture system, Davis and Arnold (1998) suggest using a three-phase system with nursery, post-nursery and grow-out.
Harbor Branch Oceanographic Institution (HBOI), Fort Pierce, FL
USA has been working for the last three years to develop a commerTABLE 1. Summary of water quality parameters for the major phases of production (adapted from Davis and Arnold 1998).
Species
System
pH
TAN (mg/L)
Litopenaeus setiferus
Nursery
27.7
5.5
7.7
0.17
0.17
28.3
(6/93)
35 m3
28.1
6.5
7.5
0.30
0.74
31.0
L. setiferus (8/93)
L. vannamei (6/94)
L. vannamei (6/95)
L. vannamei (2/96)
Temp. (°C) DO (mg/L)
NO3 (mg/L) Salinity (ppt)
Nursery
27.2
5.3
7.5
0.32
0.30
33.2
25 m3
24.7
7.0
7.5
0.18
0.12
29.2
Nursery
28.0
6.0
7.6
0.38
0.31
22.6
25 m3
27.5
6.8
7.4
0.41
0.43
31.8
25 m3
27.7
7.0
7.4
0.37
0.60
31.6
35 m3
26.1
6.2
7.6
0.36
0.30
29.3
Nursery
29.5
6.1
7.5
0.76
0.31
29.5
25 m3
29.5
6.7
7.4
0.66
0.98
33.1
72 m3
27.5
6.4
7.5
0.54
0.79
28.0
Nursery
24.0
6.4
7.6
1.16
0.51
31.3
72 m3
28.9
5.6
7.5
0.50
1.48
23.9
Samocha et al.
7
TABLE 2. Summary of shrimp production under various culture conditions at
the University of Texas Marine Science Institute, Port Aransas, Texas (adapted
from Davis and Arnold 1998).
Species
System
Litopenaeus setiferus (6/93) Nursery
35 m3
L. setiferus (8/93)
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L. vannamei (6/94)
2,100
28
0.18
582
Mean
Harvest
weight (g)b (kg/m3)c
EFCE
(%)d
Survival
(%)
0.36
85.1
96.9
99.0
99/111
5.2/6.4
3.41
49.4
5,000
32
0.14
0.63
69.5
87.0
25 m3
1,739
120
4.3
5.70
56.9
76.4
Nursery
6,000
34
2.29
110.6
84.8
25 m3
1,018e
161
16.1
6.51
25.4
44.8f
25 m3
1,018e
161
17.7
9.00
35.9
56.4f
0.45
19.5
89.8
165
161
2.90
36.0
Nursery
8,300
31
0.37
2.85
96.2
96.0
25 m3
3,189
77
3.46
11.23
81.2
87.8
8.95
24.3
78.3
1.22
94.1
92.4
7.26
29.6
66.7
72 m3
L. vannamei (2/96)
Daya
Nursery
35 m3
L. vannamei (6/95)
Stocking
shrimp/m3
Nursery
72 m3
902
172
8,200
21
700
175
12.7
0.16
15.6
a All shrimp were received as PL8-15. Day denotes the number of days from receipt of the population and indicates
the culture day that the population was moved or harvested.
b Mean weight at harvest of at least 30 individuals, towel dried and weighed individually.
c Kg shrimp harvested per cubic meter of culture water.
d Estimated feed conversion efficiency (EFCE) = biomass gain/total feed offered ⫻ 100.
e At day-90 a portion of the shrimp (2,896) having a mean weight of 8.6 g were transferred to the 35 m3.
f Shrimp jumping out of the culture system was estimated to result in 11.8% mortality.
cially viable freshwater recirculating system for the production of Pacific white shrimp in greenhouses (Van Wyk 1999a, 1999b). Scarpa and
Vaughan (1998) demonstrated that Pacific white shrimp can be successfully acclimated to freshwater, provided that the water has a minimum of 300 mg/L of chloride ion, and 150 mg/L as CaCO3 of total
hardness. Water with chloride levels this low is generally classified as
freshwater and can be used to irrigate most crops. The significance of
this is that the ability of Pacific white shrimp to grow and thrive in hard,
freshwater means that shrimp can be produced on cheaper, non-coastal
agricultural land. There are many locations in Florida where freshwater
wells meet these minimum requirements for culturing Pacific white
shrimp, including at Harbor Branch. The well water used in the HBOI
greenhouse production systems has a salinity of approximately 0.5 ppt
(300 mg Cl⫺/L) and a total hardness of 400 mg/L as CaCO3. Salinities
in the HBOI production trials averaged 0.7 ppt, chloride concentrations
averaged 400 mg Cl⫺/L, and total hardness and alkalinity as CaCO3 av-
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JOURNAL OF APPLIED AQUACULTURE
eraged 400 mg/L and 150 mg/L, respectively. The salinity of the water
in the culture systems (0.7 ppt, 400 mg Cl⫺/L) was slightly higher than
that of the well water. This was due to the periodic addition of small
amounts of seawater to the system to replace calcium, magnesium, and
trace minerals that were depleted as a result of uptake by the biological
components of the system.
The objective of the researchers at HBOI has been to develop a
cost-effective indoor, freshwater recirculating production system capable
of growing shrimp at moderately high densities (up to 150 shrimp/m2).
These densities are significantly lower than the densities (> 600 shrimp/
m2) that have been achieved for Pacific white shrimp in more sophisticated recirculating systems (Davis and Arnold 1998). However, the
profitability of a system is not strictly a function of carrying capacity.
The systems with the greatest profit-making potential will be those that
utilize capital, labor, energy, and other inputs most efficiently (Van
Wyk in press). The focus of the HBOI research effort has been on developing relatively inexpensive indoor production systems that make efficient use of space, energy, and labor.
In 1998, HBOI set up two prototype greenhouses measuring 9.2 m ⫻
29.2 m. Each greenhouse encloses two 70.7-m3 (4.4 m ⫻ 26.8 m ⫻ 0.60
m) culture tanks, which occupy 90% of the area enclosed by the greenhouses. The two culture tanks share a common interior wall. A catwalk
mounted on top of the interior wall provides access to the entire length
of the culture tanks. The culture tanks consist of a wooden frame supporting a black 30-mil high-density polyethylene liner. The tanks are set
up in a “racetrack” configuration with a central baffle and drain outlets
at opposite ends of the baffle (Figure 1). The water in the tank flows in
an elongated oval pattern, with a semi-circular flow pivoting about the
drain outlets at either end of the central baffle. This flow pattern generates centrifugal forces as the water circles the drain, concentrating the
suspended solid wastes in the area around the drain outlets. The drain
outlets are connected to a common drainage pipe, which carries water
from the culture tanks to the filtration system.
These culture systems feature a low-head filtration consisting of an
upflow static-bed bead filter for solids removal and an aerated submerged-bed biofilter. The solids filter, designed and built at HBOI, consists
of cylindro-conical sump (1.22 m diameter ⫻ 1.22 m deep, 1,200-liter
capacity), filled with 0.5 m3 of positively buoyant Kaldnes® biofilter
media (Water Management Technologies, Baton Rouge, Louisiana).
Solids-laden water from the culture tank enters the solids filter from below. As the water flows up through the filter bed, suspended solids con-
9
30%
Intermediate
10%
Nursery
Three-Phase Production System
Central Baffle
Single-Phase Production System
Final Growout
60%
Central Baffle
Spray Bar
Solids
Filter
Submerged
Bed
Biofilter
Pump
Solids
Filter
Submerged
Bed
Biofilter
Pump
FIGURE 1. Layout for single-phase and three-phase production systems at Harbor Branch Oceanographic Institute.
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JOURNAL OF APPLIED AQUACULTURE
tact and adhere to the sticky surfaces of the filter media. Filtered water
exits the solids filter at the top of the filter bed through a slotted pipe.
Head loss through the solids filter is less than 5 cm. The solids filter is
backwashed every three days. Approximately 2,000 liters, or about 3%
of the system volume, is discharged during each backwash operation.
Total water exchange rates average about 1% of the system volume per
day.
Nitrogenous wastes are removed by an aerated, submerged-bed
biofilter. Water flows by gravity from the solids filter to the biofilter.
The biofilter consists of a 2,700-liter rectangular polyethylene tank
(1.22 m ⫻ 1.83 m ⫻ 1.22 m) filled with 1 m3 Kaldnes® biofilter media
(effective specific surface area = 492 m3/m2). The biofilter media is
tumbled by air bubbles introduced through a grid of 10 medium pore
airstones (1 cubic feet per minute, CFM, airflow per airstone). Total
ammonia nitrogen levels averaged 0.25 mg NH3-N/L (S.D. = 0.46 mg
NH3-N/L) in three production trials carried out in 1998, while nitrite
levels averaged 0.56 mg NO2⫺-N/L (S.D. = 1.15 mg NO2⫺-N/L) (Table 3).
The water in the culture tanks is circulated through the filtration system once every 2.5 hours. At a flow rate of 500 LPM, there is less than
10 cm of total head loss through the solids filter and biofilter. Water
flows by gravity through the filter system, and is pumped back to the
culture tanks by a low-head 3/4 horsepower (HP) centrifugal pump. The
water returning to the culture tanks is introduced through spray bars,
which span the raceways. The sprays bars aerate and de-gas the water as
it is returned to the culture tank. In addition, the spray bars generate a
circulating flow of water within the culture tank. The circulation of waTABLE 3. Summary of daily water quality parameters of three freshwater recirculating production systems stocked with Pacific white shrimp at Harbor
Branch Oceanographic Institute in 1998.
Water Quality Parameter
Value±SD
Salinity (ppt)
0.7±0.5
Total hardness (mg/L as CaCO3)
390±145
Total alkalinity (mg/L as CaCO3)
132±8.4
Dissolved oxygen (mg/L)
6.9±0.9
Temperature (ºC)
27.2±1.8
pH
7.82±0.45
Total ammonia nitrogen (mg NH3-N/L)
0.25±0.46
Nitrite (mg NO2-N/L)
0.56±1.15
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Samocha et al.
11
ter within the tank is important because it suspends the solid wastes in
the water column and facilitates the transport of solid wastes to the
drains.
Aeration for the two greenhouses is supplied by a 2.5-HP regenerative blower. The blower provides 0.16 CFM of air per kilogram of anticipated shrimp biomass. The air diffusers serve both to aerate the water
and to help keep solid wastes suspended in the water column. During
the 1998 production trials, dissolved oxygen levels averaged 6.97±0.87
mg/L, and rarely dropped below 5 mg/L.
The effluent from the shrimp production operation is discharged into
a series of three, 0.11 ha, retention ponds at Harbor Branch. All effluent
from the facility discharges into a corner of the first pond in the series.
Overflow pipes pass through the levees separating each of the three
ponds. Nitrogenous wastes are removed from the water by algae and
aquatic plants. Evaporation and seepage account for all of the water loss
from the retention ponds. There is zero discharge of effluent from the
retention ponds to surface waters.
During the nursery phase, shrimp were fed specially formulated diets
(Bonney, Laramore, and Hopkins, Inc., Ft. Pierce, Florida) with 50%
and 45% crude protein levels and elevated levels of calcium, phosphorus, potassium, vitamin C, and other vitamins and minerals. Shrimp in
the grow-out phase were fed a commercial diet with 35% protein and
2.5% squid meal (Rangen, Inc., Angleton, Texas). Feed was offered
ad libitum four times a day. Feed conversion ratios (FCR) are summarized in Table 4.
A focus of the research performed at HBOI has been to compare the
productivity and economics of single-phase and three-phase production
systems. The two shrimp greenhouses at HBOI were set up in two different configurations (Figure 1). In one greenhouse, the culture tanks
were set up as non-partitioned single-phase culture tanks, while in the
other, a raceway was partitioned into a nursery, an intermediate, and a
final grow-out section. In the three-phase system, the shrimp spend 50-60
days in each phase of the grow-out. The area assigned to each section
was calculated so that the shrimp would reach a density of approximately 2.5 kg/m2 at the end of each culture phase. The nursery section
occupied approximately 10% of the culture area, while the intermediate
and final grow-out sections occupied 30% and 60% of the culture area,
respectively. Shrimp were transferred from one section into another by
draining the volume of one section into the next through 10-cm bulkhead fittings that pass through the partitions between sections. Trans-
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JOURNAL OF APPLIED AQUACULTURE
TABLE 4. Summary of the results obtained in production trials carried out at
Harbor Branch Oceanographic Institution comparing single-phase and threephase production systems.
Parameter
Percentage of culture area harvested (%)
Three-Phase
100
60
77±14
61±12
Feed conversion ratio (FCR)
1.59±0.24
1.74±0.11
Harvest density (shrimp/m2 of area harvested)
153±38
128±21
Survival (%)
Days to harvest
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Single-Phase
Average shrimp weight (g)
180
14.1±2.6
180
15.9±3.05
Growth (g/week)
0.55±0.10
0.62±0.12
Yield (kg/m2/crop) per area harvested
2.07±0.40
2.00±0.35
Yield (kg/m2/crop) per total area
2.07±0.40
1.20±0.21
2
6
4.14±0.80
7.20±1.26
Crops/yr
Yield (kg/m2/yr) per total area
fer-related mortality was minimized by the elimination of handling of
shrimp during transfers. The nursery, intermediate and final grow-out
sections of the culture tank were set up in a stairstep configuration, with
approximately 15 cm of elevation difference between adjacent sections.
A series of paired production trials were carried out in which single-phase and three-phase culture systems were stocked simultaneously
with high health postlarvae that had been acclimated to freshwater. The
tanks were stocked at an average density of 206 postlarvae/m2 of final
grow-out area. In the three-phase tanks, this resulted in an average nursery density of 1,236 postlarvae/m2. The shrimp were harvested after 180
days in all trials. The results of these trials are summarized in Table 4.
Survival in the three-phase systems (61%) was significantly lower
than in the single-phase systems (77%). This was primarily due to an increased frequency of cannibalism in the nursery and intermediate phases.
This problem was more severe in systems that were very shallow (30
cm deep) in the nursery sections. This problem has been largely overcome by using deeper nursery tanks (50 cm deep) and artificial substrates. Growth rates were slightly higher in the three-phase systems
(0.62 g/week) than in the single-phase systems (0.55 g/week), but the
difference was not statistically significant. Harvest densities per unit
area of final grow-out area were nearly identical, averaging 2.00 kg/m2
in the single-phase systems and 2.07 kg/m2 in the three-phase systems.
The final grow-out area occupies only 60% of the total production area
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Samocha et al.
13
of a three-phase system, so the harvest density per unit of total production area is only 1.22 kg/m2. However, six crops per year can be harvested from the three-phase system, compared to only two crops per
year for the single-phase system. The annual productivity of the threephase system was 7.2 kg/m2 of production area, versus only 4.00 kg/m2
for the single-phase system. These results demonstrated that the annual
productivity of greenhouse production systems could be increased by
70-80% by adopting a three-phase production strategy. This gain in productivity was obtained with little additional capital or operating cost.
An economic analysis was performed to examine the economic feasibility of a twelve-greenhouse hypothetical commercial facility using a
three-phase production strategy (Van Wyk 1999c). This analysis used
production data and cost information obtained from the prototype facility described above. The analysis assumed a stocking density of 221
PL/m2 of final grow-out area and a harvest density of 135 shrimp/m2
(61% survival). The analysis assumed that 180 days were required to
grow an 18-g shrimp. The cost of production for this hypothetical commercial enterprise was $4.28/lb of whole shrimp. This cost of production is high when compared to the cost of production of shrimp in
semi-intensive pond production systems. The capital requirements for
building indoor recirculating production systems are high relative to
their productivity. In addition, the energy costs and labor requirements
are much higher than are typical for typical pond production operations.
The challenge for shrimp recirculating system designers is to increase
system productivity while reducing capital, energy and labor costs.
Because of this fact, shrimp produced in recirculating production
systems cannot compete directly with foreign-produced shrimp on the
wholesale frozen tail market. Rather, these shrimp must be direct-marketed to restaurants and specialty seafood markets as premium fresh
product in order to bring a higher price. Based on the assumptions of the
economic model (Van Wyk 1999c), these shrimp would have to be sold
at a price of $6.00/lb in order to earn an internal rate of return of 26%.
This was the minimum rate of return that the project would have to earn
to justify the risk of the investment.
A sensitivity analysis showed that if the survival could be improved
from 61% to 70% and the time required for grow-out could be reduced
from 180 days to 150 days, the cost of production could be reduced
from $4.27/lb to $3.32/lb (Van Wyk 1999c). These goals appear to be
achievable with only slight modifications in system design and operation.
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JOURNAL OF APPLIED AQUACULTURE
Recent observations at HBOI suggest that survival rates in raceway
nursery systems may be improved by deploying artificial substrates.
Artificial substrates may also allow stocking densities to be substantially increased with little or no decline in growth or survival rates (Peterson and Griffith 1999).
During the production trials reported in Table 4, the HBOI greenhouses were covered by a 95% shade cloth to limit algal growth in order
to prevent diurnal fluctuations of dissolved oxygen and pH. While the
shade cloth effectively stabilized water quality, it appears that it also
slowed shrimp growth rates by lowering water temperatures and inhibiting algae growth. In a recent uncontrolled production trial at HBOI,
the average weekly growth rate of shrimp grown in an unshaded raceway averaged 1.1 g/week (VanWyk, unpublished data). This was nearly
double the average growth rates of the shrimp grown in shaded raceways in the 1998 trials. Other observations at HBOI indicated that water
temperatures in unshaded raceways average 3.2°C higher than in the
shaded raceways (Collins, pers. comm.). The low light levels in the
shaded greenhouses may also have affected growth rates by suppressing the growth of algae in the raceways. Very little algal growth was observed in the shaded raceways. In contrast, dense blooms of green algae
were typical in subsequent crops grown in unshaded raceways. Moss
(2000) demonstrated that shrimp growth is enhanced by the presence of
microalgae in the water.
In conclusion, the intensive water reuse systems have many desirable
attributes. They allow freedom from site limitations, improved environmental control, increased product quality and availability, and facilitate
the control of stock and effluent management (Rijn and Shilo 1989; Lee
1993). Another reason for the strong interest in indoor recirculating systems is the high degree of biosecurity these systems provide (Ogle and
Lotz 1998; Leung and Moss 1999). Nevertheless, businesses based on
this technology will only be profitable if project planners design their
facilities so that resources such as space, labor, and management are utilized as efficiently as possible. Facilities will need to take full advantage
of economies to scale wherever possible, and adopt production strategies that maximize productivity per unit inputs of capital and labor (Van
Wyk in press). This can be accomplished either by designing ultra-intensive systems capable of supporting extremely high standing crops
(Davis and Arnold 1998), or by adopting a three-phase production strategy (Van Wyk in press). Although the economic viability of recirculating production systems for bait or food shrimp has yet to be proven, the
Samocha et al.
15
consistent results, low water usage, and ease of waste management are
encouraging and warrant further economic and marketing evaluations.
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BIOSECURE SHRIMP NURSERY TECHNOLOGY
Researchers of the Texas Agricultural Experiment Station, Shrimp
Mariculture Research Facility in Corpus Christi, Texas, have evaluated
a variety of management strategies for intensive shrimp production. Recent studies have been designed to develop a biosecure shrimp production nursery and to develop grow-out practices that lower the risk of
viral disease outbreaks in cultured stocks while reducing the potential
negative impact from shrimp farm effluent waters on receiving streams.
The nursery studies were conducted in greenhouse-enclosed raceways,
each with a bottom area of 68.5 m2 and an operating volume of 45 m3.
Sturmer et al. (1992) and Samocha et al. (1993) provide a detailed description of the system. Figure 2 provides a schematic description of
this system. Every raceway is equipped with a rapid sand filter and a
center partition positioned over a 5.1 cm PVC pipe. Spray nozzles are
attached to this pipe to enhance water circulation near the raceway’s
bottom. Eighteen, 5.1-cm airlift pumps, grouped into six banks, are positioned on both sides of the center partition to enhance water column
circulation. In addition to the aeration provided by the airlift pumps,
three 1-m long air diffusers provide supplemental aeration and a venturi
injector operated by the same pump used for running the sand filter
(Figure 2). Nursery trials have been conducted with three native shrimp
species (the Atlantic white shrimp; the Atlantic brown shrimp, Farfantepenaeus aztecus; and the Atlantic pink shrimp, F. duorarum) and
with the exotic species the Pacific white shrimp. The following is a
short summary of studies with the Pacific white shrimp and the Atlantic
brown shrimp, which were conducted with reduced water discharge.
All shrimp were fed a 45% protein diet with 10% squid meal (“45/10”
Rangen, Inc., Buhl, Idaho) supplemented for about two weeks with
newly hatched Artemia nauplii and with a 50% protein diet (“PL
Redi-Reserve” Zeigler Bros., Inc., Gardners, Pennsylvania). Diet was
offered four times a day while daily rations were adjusted based on
growth and feed consumption. To reduce the risk of introduction of
pathogens with the incoming water, after adjustment of salinity, culture
water was treated with liquid chlorine solution (10 ppm active chlorine
initial-concentration). Raceways were stocked with post-larvae only
when no chlorine residue could be detected in the culture water. Trials
16
Sand filter
Multiport
valve
Pump
15.2 cm Outlet
20.3 cm Filter pipe
Venturi injector
20.3 cm
Filter pipe
Airdiffusers
Current
5.1 cm Water return pipe
2.54 cm
Center
partition
5.1 cm air supply line
27.3 m
5.1 cm
Airlift pumps
Valve
3m
FIGURE 2. Planer view of the nursery raceway used by the Texas Agricultural Experiment Station, Shrimp Mariculture
Research Facility, Corpus Christi, Texas.
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2.5 m
7.6 cm air pipe
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Samocha et al.
17
were conducted with/without inoculation of the water with the diatom
Chaetoceros muelleri. Throughout the nursery trials, only small volumes
of freshwater or chlorinated seawater were used to compensate for evaporation, leaking and losses due to sand filter backwash. Table 5 provides
a summary of selected water quality parameters for these nursery trials.
The water quality data indicate that under the conditions tested,
post-larvae of the Pacific white shrimp can tolerate a total ammonia nitrogen level as high as 10.4 mg/L without adverse effects on survival. A
summary of the nursery production trials with the Pacific white shrimp
and the brown shrimp is provided in Table 6. Feed conversion ratio
(FCR) values in all of the nursery trials were below 1. These studies
demonstrate that a yield of 1.48 kg/m2 or 2.23 kg/m3 with good survival
can be achieved when post-larvae of the Pacific white shrimp were
stocked at a density of about 2,000 PL/m2 under reduced water discharge. Furthermore, Cohen et al. (2001), in a more recent study in this
nursery system, reported 100% survival of Pacific white shrimp under
similar stocking density (2,200 PL/m2 or 3,300 PL/m3). The mean
weights of the juveniles harvested after seven weeks varied between 1.1
and 1.2 g with excellent yield (4.1-4.2 kg/m3), low FCR (< 1) and very
limited water renewal (1.1%/d).
“ZERO WATER EXCHANGE” POND TECHNOLOGY
Other studies at the TAES facility have evaluated the feasibility of
producing marketable size Pacific white shrimp under “zero water exTABLE 5. Summary of selected water quality parameters (mean±standard deviation) for nursery production trials with Pacific white shrimp in raceways under reduced water discharge at the Texas Agricultural Experiment Station,
Corpus Christi, Texas. RW = raceway
RW ID
(date)
DO (mg/L)
a.m.
p.m.
Temperature (°C)
a.m.
p.m.
pH
a.m.
p.m.
Salinity
NH4
(ppt)
(mg/L)
R1 (6-7/98)
7.3±0.6
7.1±0.6
27.9±0.4
29.3±0.4
8.1±0.4
8.3±0.3
20±1.2
0-4.2
R2 (6-7/98)
6.8±0.5
7.2±0.7
27.9±0.3
29.3±0.4
8.0±0.3
8.2±0.3
21±1.4
0-10.4
R3 (6-7/98)
6.6±0.5
7.3±0.7
28.5±0.4
29.9±0.4
8.1±0.3
8.3±0.3
20±1.1
0-7.8
R1 (4-5/99)
7.2±0.4
7.2±0.6
26.9±1.4
28.6±1.6
7.9±0.3
8.0±0.3
16±2.8
0-3.0
R2 (4-5/99)
7.0±0.5
7.3±0.6
27.0±1.2
28.2±1.4
7.8±0.3
8.1±0.2
16±2.7
0-3.0
R4 (4-5/99)
6.9±1.4
7.0±1.2
28.5±0.2
29.2±1.3
7.8±0.4
8.0±0.4
16±1.2
0-5.2
18
JOURNAL OF APPLIED AQUACULTURE
TABLE 6. Summary of shrimp nursery production trials in raceways under reduced water discharge at the Texas Agricultural Experiment Station, Corpus
Christi, Texas. RW = raceway
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RW ID (date)
Species
WtTia
(mg)
PL Density
(/m3)
1,370
Daysb WtTfc Survival Yield (kg)
FCR
(g)
(%)
(/m2) (/m3)
35
0.70
86.8
0.61 0.83 0.61
Water
usaged
R1 (6-7/98)
Litopenaeus
vannamei
1
(/m2)
1,000
R2 (6-7/98)
L. vannamei
1
1,000
1,370
35
0.58
99.7
0.58
0.79
0.65
0.4
R3 (6-7/98)
L. vannamei
1
1,000
1,370
35
0.42
111.1
0.47
0. 64
0.68
0.7
R1 (4-5/99)
L. vannamei
1
1,460
2,220
42
0.54
82.1
0.64
0.98
0.68
1.1
R2 (4-5/99)
L. vannamei
1
1,460
2,220
42
0.60
59.2
0.52
0.79
0.97
1.3
R4 (4-5/99)
L. vannamei
1
2,020
3,070
48
0.81
89.9
1.48
2.23
0.92
4.7
R1 (3-4/99)
Farfantepenaeus
aztecus
1
3,390
5,150
15
0.067
75
0.17
0.26
0.52
0.8
R2 (3-4/99)
F. aztecus
1
3,390
5,150
15
0.054
84
0.15
0.23
0.57
0.8
R1 (5/99)
F. aztecus
1
3,240
4,940
34
0.27
100
0.87
1.33
0.8
0.8
R2 (5/99)
F. aztecus
1
3,240
4,930
34
0.23
100
0.75
1.14
0.8
0.8
R6 (5/99)
F. aztecus
1
3,240
4,940
34
0.27
100
0.87
1.33
0.8
0.8
0.3
a Mean weight at stocking.
b Nursery duration in days.
c Mean weight at harvest.
d Percent of the total volume of culture water added daily.
change.” These trials were also designed to evaluate the effect of two
low-protein diets and a commercial bacterial supplement on selected
water quality parameters and shrimp performance. The studies were
conducted in outdoor tanks and in HDPE-lined ponds. The following is
a short summary of study conducted in the outdoor tank system. Eighteen 10.5-m2 round tanks (3.66 m ⫻ 1 m) were provided with a 15 cm of
sandy clay loam soil. Tanks were positioned under a shade (73% light
reduction) to avoid water heating in excess of optimal limits for shrimp.
Prior to stocking, tanks were filled with water from a nearby saline lagoon to an average water depth of 65 cm (6.8 m3/tank) and salinity was
adjusted to 15 ppt using municipal freshwater. Aeration was provided to
each tank with ten air stones (5.3±1.6 L/minute/stone), fed by a regenerative air blower. Municipal freshwater was added periodically to avoid
an increase in salinity due to evaporation. All tanks were stocked with
Pacific white shrimp juveniles (average weight of 1.69±0.58 g) at a density of 40/m2. Tanks were randomly assigned into three treatments of
six tanks each. Shrimp in the first treatment (21%) were offered a 21%
protein feed. Shrimp in the second treatment (21%+) were offered the
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Samocha et al.
19
same 21% protein diet but culture water was enriched with a bacterial
inocula (Bacillus sp., BioStart® Advanced Microbial Systems, Inc.,
Shakopee, Minnesota). This bacterial inocula was applied five times/week.
The manufacturer’s instructions for brewing and applying the bacteria
were followed. Shrimp in the third treatment (31%) were offered a 31%
protein diet. Shrimp in all treatments were fed twice a day, receiving
50% of the ration in the morning and 50% in the afternoon. The ration
was adjusted weekly, based on weight sampling of one tank from each
treatment. The combined average weight of the three treatments was
used to determine the weekly ration. Both diets were produced by a
commercial feed mill (Rangen, Inc., Buhl, Idaho). Selected water quality parameters were measured daily (dissolved oxygen, temperature, salinity, pH, and secchi disk reading) while total ammonia nitrogen,
nitrite-nitrogen, nitrate-nitrogen, total phosphorus, reactive phosphorus, five-day carbonaceous biochemical oxygen demand, chemical oxygen demand, total suspended solids, and volatile suspended solids were
monitored weekly. The study was terminated after 94 days, at which
time the shrimp were harvested manually and individually weighed.
This information was used to calculate mean final weight, survival, and
FCR. Repeated measures of analysis of variance (ANOVA) was used to
compare data associated with daily and weekly water quality of the
three treatment sets. Survival, mean final weights, and FCR were analyzed using the one-way ANOVA. Percent survival data were arcsine
transformed prior to conducting the analysis. Tukey’s HSD was used to
determine which treatments were statistically significantly different.
The same significance level (P = 0.05) was used for all tests.
No statistically significant differences were found in the daily water
quality parameters among treatments (Table 7). Table 8 summarizes the
weekly changes in water quality for each treatment. Among the weekly
water quality parameters, total phosphorous and reactive phosphorous
levels in the 21%+ treatment were significantly higher than the 31%
treatment. No statistically significant differences were found in weekly
water quality between the 31% and the 21% treatments (Table 8). Furthermore, the regular application of the bacterial inocula did not significantly improve the water quality in the treated tanks. It is interesting
that even though there were significant differences among the treatments in survival, mean final weight, and FCR (Table 9), there were
very few statistically significant differences in the water quality parameters measured. Survival was high in all treatments, ranging between
91% and 93% in the 21% treatments and 96% in the 31% treatment. The
difference in survival between the 21% and the 31% treatment was sig-
20
JOURNAL OF APPLIED AQUACULTURE
TABLE 7. Summary of daily water quality parameters (mean±standard deviation) in a 94-day study with Pacific white shrimp in outdoor tanks with “zero water exchange” under stocking density of 40 shrimp/m2 when fed diets with 21%
and 31% protein and treated with bacterial supplement.
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Dissolved Oxygen (mg/L)
Temperature (°C)
pH
Salinity
Secchi disk
a.m.
p.m.
a.m.
p.m.
a.m.
p.m.
(ppt)
(cm)
6.7±0.8
6.8±0.7
27.4±1.9
28.7±2.1
7.7±0.3
8.1±0.3
14.5±2.2
13.8±7.6
TABLE 8. Summary statistics of weekly water quality parameters (mean±standard deviation) in a 94-day study with Pacific white shrimp in outdoor tanks with
“zero water exchange” under stocking density of 40 shrimp/m2 when fed diets
with 21% and 31% protein and treated with bacterial supplement.
Parameter
Treatment
Mean±SD
Maximum
Minimum
Ammonia (mg/L)
21%
21%+
31%
0.4±0.72a
0.4±0.89a
0.4±0.66a
3.9
4.7
3.9
0.0
0.0
0.0
Nitrite (mg/L)
21%
21%+
31%
0.5±0.92a
0.6±0.92a
0.8±1.05a
6.2
4.2
4.3
0.0
0.0
0.0
Nitrate (mg/L)
21%
21%+
31%
0.1±0.29ab
0.1±0.25a
0.3±0.60b
1.3
1.6
3.0
0.0
0.0
0.0
cBOD5 (mg/L)
21%
21%+
31%
7.1±4.82a
6.6±4.30a
6.1±3.32a
23.6
21.6
13.6
0.4
0.2
1.1
Chemical oxygen demand (mg/L)
21%
21%+
31%
443±86a
470±110a
510±131a
Reactive phosphorus (mg/L)
21%
21%+
31%
2.0±2.11ab
2.5±2.52a
1.5±1.74b
8.4
8.6
7.5
0.0
0.0
0.0
Total phosphorus (mg/L)
21%
21%+
31%
4.7±4.76ab
4.8±4.22a
3.9±3.72b
28.6
14.2
14.8
0.1
0.2
0.1
Total suspended solids (mg/L)
21%
21%+
31%
257±187a
264±212a
330±298a
648
1,097
1,147
9
17
2
Volatile suspended solids (mg/L)
21%
21%+
31%
80±49a
86±48a
89±55a
200
217
254
⫺12
1
⫺93
1,010
767
646
321
244
281
a Note–Treatment means sharing the same letter are not statistically significantly different (P > 0.05) using Tukey’s
HSD method.
Samocha et al.
21
TABLE 9. Summary statistics of survival, mean final weight (mean±standard
deviation) and FCR of Pacific white shrimp in 94-day trial in outdoor tanks with
“zero water exchange” under stocking density of 40 shrimp/m2 when fed diets
with 21% and 31% protein and treated with bacterial supplement.
Parameter
Survival (%)
Treatment
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FCR
Maximum
Minimum
91±4a
95
83
21%
93±5ab
98
87
96±2b
99
93
11.80
31%
Mean final weight (g)
Mean±SD
21%+
21%
12.17±0.28a
12.53
21%+
11.69±0.63a
12.79
10.93
31%
14.04±0.58b
14.86
13.25
21%
2.15±0.11a
2.31
1.99
2 1%+
2.19±0.11a
2.10
2.39
31%
1.75±0.07
1.85
1.66
a Treatment means sharing the same letter are not statistically significantly different (P > 0.05) using Tukey’s HSD
method.
nificant. However, no significant differences were found between the
21%+ and the 21% or 31% treatments. Mean final weight was lowest in
the 21%+ treatment (11.7 g) and highest in the 31% treatment (14.0 g).
The 21% treatment had a mean final weight of 12.2 g. Significant differences were found between the 31% treatment and both the 21% and
21%+ treatments. No significant difference was found in mean final
weights between the 21% and 21%+ treatments. The FCR for the 31%
treatment (1.75) was significantly lower than either the 21% treatment
(2.15) or the 21%+ treatment (2.19). There were no significant differences in FCR when comparing the 21% and the 21%+ treatments.
In a more recent study that was conducted in the same tank-system,
juveniles (0.68 g) of the same species were stocked at higher density
(50/m2) in six 10.5 m2 tanks and were raised with no water exchange.
Shrimp in three tanks were offered a 30% protein diet, while shrimp in
the other three tanks were offered a diet with 40% protein. As in the first
study, the diets used were commercial shrimp diet produced by Rangen,
Inc. Shrimp were fed a fixed ration four times a day at approximately
08:00, 11:00, 13:00 and 16:00. Rations of the 40% protein diet were fed
on an equal nitrogen basis (e.g., daily ration was 75% of the ration provided to the shrimp which were fed the diet with 30% protein). The
measured daily and weekly water quality parameters were similar to
those mentioned previously. Preliminary analyses suggest no statistically significant differences in daily and weekly water quality between
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22
JOURNAL OF APPLIED AQUACULTURE
treatments. Table 10 summarizes the information collected in this
study. These studies suggest that the Pacific white shrimp can be cultured at high densities with no water discharge with good survival and
growth.
A similar study was conducted to evaluate the effect of “zero discharge” on shrimp performance in two 1,700-m2 HDPE-lined ponds.
Shrimp (average weight of 0.64 g) were stocked at the same density
(40/m2) tested in the tanks with soil substrate. Ponds’ aeration was provided by paddlewheel aerators (6 HP/pond). Prior to stocking, culture
water was treated with chlorine as described earlier. Shrimp in two
ponds were fed commercially available diets containing 21% and 31%
protein (Rangen, Inc., Buhl, Idaho). Municipal freshwater was used to
maintain salinity at 20 ppt. A third similarly sized pond was stocked
(30/m2) with juvenile shrimp (3.49 g) seven weeks after the stocking of
the other two ponds. These shrimp came from the same population
stocked into the other two ponds. Shrimp were fed a 45% protein diet
(Rangen “45/10”). The daily and weekly water quality parameters monitored in this study were identical to those described for the tanks with
the soil substrates. Diet was offered four times a day, seven days a
week. Daily ration were adjusted based on shrimp growth and feed consumption. Water releases from the ponds throughout the production cycle was minimal (e.g., less than 0.6%/day). These discharges were
needed due to heavy rains. Table 11 summarizes the mean values of the
daily water quality parameters found in the three ponds. Few differences were found between ponds.
Table 12 shows the weekly changes in water quality parameters in
the ponds offered the 21%, 31%, and 45% protein diets. Slightly higher
ammonia, nitrite and nitrate levels were found in the 31% protein treatment than the 21% protein treatment. Ammonia levels in the pond that
was offered the 45% protein diet were lower than in the other two
ponds. The smaller amount of diet and the shorter operating period are
TABLE 10. Results from a high-density (50 shrimp/m2) outdoor tank study with
Pacific white shrimp under no water exchange when offered commercial
shrimp diets with 30% and 40% protein.
Duration
Survival
Growth
Stocking
Mean Shrimp Size (g)
Harvest
(days)
(%)
(g/week)
30%
0.5
17.97
111
94.5
1.15
2.44
40%
0.5
19.34
111
92.4
1.24
1.72
Treatment
FCR
Samocha et al.
23
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the main reasons for these differences. The pond with the high protein
diet was harvested after 48 days while the other two ponds were harvested after 100 days. Table 13 summarizes the average initial and harvest sizes, survival, weekly growth rates and FCR values for the shrimp
in the three ponds. Shrimp survival and mean average weight in the
31% protein diet were higher than in the lower protein diet (86.0% vs.
81.4% and 20.2 g vs. 16.1 g). A slightly better FCR was observed in the
pond that was offered the 31% protein diet (1.75 vs. 1.86). The shrimp
mean weight after 50 days in the pond that was offered the 45% protein
TABLE 11. Daily mean values for dissolved oxygen, temperature, pH, and salinity for three ponds stocked with Pacific white shrimp and fed one of three diets with different protein levels.
Mean Temp. (°C)
DO (mg/L)
pH
Treatment
Salinity (ppt)
a.m.
p.m.
a.m.
p.m.
a.m.
p.m.
21% (40/m2)
27.7
30.1
6.4
8.8
8.0
8.4
18.6
31% (40/m2)
27.8
30.0
6.4
9.1
8.1
8.4
19.1
45% (30/m2)
26.7
28.5
6.9
10.7
8.0
8.6
22.6
TABLE 12. Water quality parameter in a pond under no water discharge
stocked with Pacific white shrimp (40 shrimp/m2) and fed diets with 21%, 31%,
and 45% protein levels.
Diet
cBOD5
COD
NH4
NO2
NO3
TP
RP
TSS
VSS
(mg/L)
21%
18±12
757±504
0.9±1.2
0.1±0.1
0.7±0.7
5.0±4.0
2.0±2.0
91±49
80±63
31%
15±9
817±314
1.3±1.8
0.5±0.9
0.9±0.7
3.9±3.5
1.9±1.7
84±71
85±67
45%
10±5
922±348
0.2±0.2
0.1±0.0
0.8±0.5
6.3±2.3
1.6±1.2
77±69
54±21
TABLE 13. Mean initial and harvest weights, trial duration, growth, and FCR of
Pacific white shrimp stocked at 40 and 30 shrimp/m2 and fed three diets with
different protein levels under no water discharge.
Duration
Survival
Growth
Stocking
Mean Shrimp Size (g)
Harvest
(days)
(%)
(g/week)
21% (40/m2)
0.64
16.1
100
86.0
1.1
1.86
31% (40/m2)
0.64
20.2
100
81.4
1.4
1.75
45% (30/m2)
3.49
16.8
48
96.1
1.9
1.00
Treatment
FCR
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diet was 16.8 g. Excellent survival (96.1%) and FCR (1:1) value were
obtained in this pond. This study shows that the Pacific white shrimp
can be cultured to marketable size at high stocking density (40/m2) with
no water exchange with good survival and yields using a diet with 31%
protein level. The low FCR (1:1) and the good water quality obtained
when the shrimp were stocked at lower density (30/m2) and fed a 45%
protein diet suggest that additional studies are needed to determine the
optimal feed to be used under “zero water exchange” strategy.
INLAND POND SHRIMP PRODUCTION TECHNOLOGY
Inland production of shrimp in low-salinity water can provide another alternative to disease and environment problems. This technology
is currently being implemented by commercial shrimp producers in Arizona, Florida and Texas. Smith and Lawrence (1990) documented one
of the first attempts to raise the Pacific white shrimp in saline ground
water. These authors reported successful culture (86.7% survival) of
juveniles (1.2 g) to marketable size (19.9 g) in 120 days in inland ponds
stocked at a density of about 25 juveniles/m2 using saline (28.3 ppt)
ground water.
A preliminary test in the early nineties by researchers from the Texas
A&M University System demonstrated the ability to successfully grow
shrimp in west Texas using low salinity (11 ppt) ground water. Following this test, two small farms (one with 14 ha and the other with 20 ha)
were built in 1994 and 1995. One of the major differences between
these farms and the farms along the Texas coast is the short growing
season of mid-May through mid-September. Although there are other
shrimp production operations in this area, this summary will focus on
the information received from the Regal Farm. The farm has fourteen
rectangular 1.45-ha earthen ponds with an average depth of 1.2 m. Each
pond is provided with paddlewheel- and aspirator-type aerators (8.3-12.5
HP/ha). Ponds are generally stocked with “high health” eight-day-old
(PL 8) at a density of about 40 PL/m2. Pond bottoms are disked three to
four time after harvest. Due to the low salinity, dragonflies can sometimes create a problem. After filling, ponds are fertilized with cottonseed meal, nitrogen, and phosphorus sources. Diet (35% to 38% protein)
is offered up to three times a day using an air blower. Rations are adjusted based on weekly growth samples. Feed trays are used (1 per
pond) mainly for health evaluation and for monitoring growth during
the early stocking phase. For the first few months ponds are maintained
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Samocha et al.
25
with limited exchange. About 5% daily water exchange is employed towards the harvest. Shrimp are harvested by a fish pump. FCR is generally 2:1 with a typical survival of 65% and an average yield of about
4,500 kg/ha of 17.5 to 21 g average shrimp size. All effluent is kept on
the property and is used to create a lush natural area that becomes a
part-year wetland. Thus far, this farm has shown only one year of profitability (Mr. Morris, Regal Farms, pers. comm.). The one crop per year
limits the revenue for the invested capital compared to tropical climates.
The overall expenses are higher than for most other shrimp farming areas of the world. Nonetheless, it is believed that economic viability is
possible, even if not yet demonstrated. The area presents these special
problems:
• A short growing season of four months (mid-May through midSeptember). Some years, stocking at the first of May has been successful, but major losses have occurred as well. Therefore, to minimize risk, ponds’ stocking has to take place in mid-May. Another
option is to stock the PL mid to late-March in greenhouse-enclosed nursery systems. These systems not only extend the growing season, but also enable production of two shrimp crops a year.
At this time, risk management and economics don’t give a clear
advantage to any of the three solutions.
• Midsummer daytime air temperatures of 43°C are not uncommon
in the area. These high temperatures can negatively affect oxygen
solubility and shrimp growth. Due to the evaporative cooling effect generated by paddlewheel aerators, a greater use of these
types of aerators rather than the aspirator-type aerators should help
lower water temperatures.
• Limited water availability and high pumping costs. A dropping
water table is now a major concern. In past years, under maximum
pumping of all wells, the water table dropped from a static depth of
6-9 m in the early season to 18-27 m late in the season. This drop
was attributed to higher demand by a nearby cotton farmer.
• Exposure to pesticides due to proximity to agricultural lands. On
both sides of the farm, there are cotton fields participating in the
boll weevil eradication program that relies on the heavy use of
malathion.
• Biosecurity and sustainability issues have arisen: several new operators in the area either have already done so or intend to violate
both good husbandry practices and the applicable regulatory standards. This will place the whole region in jeopardy for importing
26
JOURNAL OF APPLIED AQUACULTURE
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viral diseases and degrading water quality of the aquifer. It is obvious that this area will not be able to support high-density shrimp
farming, but it certainly should be able to provide important diversification for the area.
Samocha et al. (1998, 1999a, 1999b) provide a short summary of the
studies conducted in an intensive nursery system using low-salinity
geothermal water in Arizona. Preliminary data suggest that the Pacific
white shrimp can be raised in low salinity water without negative effects on growth and survival. The following is a short summary of nursery and grow-out studies conducted in raceways of a shrimp farm
located in the Sonora Desert, Arizona.
These studies were conducted in greenhouse-enclosed, concrete raceways of the Wood Brothers Farm, Gila Bend, Arizona. Design of these
raceways was similar to the one presented in Figure 2. Each raceway
had a bottom area of 97.5 m2 with an operational water volume of 147.6
m3, and a center partition extended 2 m from the end-walls. Raceways
were built with 1% bottom slope and 0.3-m-deep settling basin at the
deep end. Water depth of the raceway at the deep end was 1.8 m and 1.2
m in the shallow end. A PVC filter-pipe (30.5 cm in diameter), at the
center of the settling basin, served for water exchange and pump-driven
water circulation. A 30.5-cm PVC return line delivered water from the
settling basin into a concrete reservoir at the shallow-end of the raceway. A 3-HP pump delivered water from this sump back into the raceway, with an optional loop directing the water via a rapid sand-filter
and/or a venturi injector. Water was forced into the raceway by a PVC
spray-pipe (5.1 cm in diameter) and/or a bottom PVC pipe (7.6 cm)
manifold with spray nozzles. Three banks of four airlift pumps (7.6 cm
in diameter), were positioned on each side of the center partition to provide a counterclockwise current. Supplemental aeration was provided
by six 3-m-long air diffusers positioned along the sidewalls. A flat-laying polypropylene heat exchanger supported by solar energy and/or a
gas-fired boiler was used to increase culture water temperature when
needed. Table 14 provides a summary of the ion composition analysis
of water samples taken from the two geothermal wells of the farm.
Although several nursery trials were conducted in these raceways,
results are summarized for one trial only. In this trial two raceways
(Raceway 3 and 4) were filled to about 10% capacity one day before the
scheduled stocking and salinity was adjusted to 17 ppt with artificial sea
salt (Marine Enterprises Int., Baltimore, Maryland). Raceway water
was fertilized with urea (46-0-0), triple superphosphate (0-45-0), and
Samocha et al.
27
TABLE 14. Ion composition of the two geothermal wells at the Wood Brothers
Farm, Gila Bend, Arizona.
Parameter
Well 1
Well 2
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(ppm)
Fe
0.22
Zn
< 0.01
< 0.01
Sulfate-S
115
230
0.4
Phosphate-P
0.01
0.05
Pb
0.25
0.29
Br
0.66
2
TOC
< 1.0
< 1.0
Ca
124
250
Mg
Na
K
Carbonate
8.5
22
627
820
11
14
0
0
Bicarbonate
153.7
248.4
Cl
796
985
NH4-N
0.3
1.1
NO2
< 0.02
< 0.02
NO3
7.7
22.3
Total N
8.2
23.4
pH
7.6
7.3
1,843.6
2,591.8
20.8
33.6
Total soluble salts
Ca+Mg hard. (meq/L)
sodium silicate to provide a final nutrient concentration of 10, 1, and 1
mg/L for the N, P, and Si, respectively. In addition, each raceway was
inoculated with mono-culture of the diatom Chaetoceros muelleri at an
initial cell concentration of 50,000 cells/ml. “High Health” PL 8 of the
Pacific white shrimp were received from a commercial hatchery in
Texas (Harlingen Shrimp Farms). Mortality due to shipping stress was
estimated at 1.9% and 2.9% for Raceway 3 and 4, respectively. Stocking
densities of live PLs in these raceways were 19,200 PL/m2 (12,700
PL/m3) and 20,400 PL/m2 (13,500 PL/m3), respectively, with PL mean
weight of 0.0025 g. Dissolved oxygen, temperature, pH, and salinity in
the raceways were monitored twice daily. Ammonia, nitrite, and nitrate
were monitored three times a week using Hach DR 2010 procedures
(Hach Company, Loveland, Colorado). Algal cell-counts were taken
every other day starting about seven days after stocking. Shrimp were
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JOURNAL OF APPLIED AQUACULTURE
fed a 45% protein dry diet (“45/10,” Rangen, Inc., Buhl, Idaho) that was
supplemented for the first eight days with newly hatched Artemia
nauplii. Diet was distributed five times a day. Rations varied between
4.5% and 11% of the total estimated shrimp biomass in the raceways.
Shrimp growth was monitored three times/week from a group sample.
Shrimp biomass at harvest was recorded after water was allowed to
drain for 20 seconds. Percent survivals and average weekly growth rates
were calculated from the harvested biomass and the shrimp mean
weight as determined from group weight samples. Individual weight
samples were also taken during the harvest from each raceway. An Independent T-Test with significant level of P = 0.05 was used to determine differences in water quality and mean weights between raceways.
Individual weight records were used for the statistical test. Raceway
water salinities were reduced gradually (over a 28-day period) from the
initial 17 ppt to 2 ppt. New water was added to both raceways with no
water discharge until day 12 of the study. The raceways’ daily water exchange was increased from 10% on day twelve to 84% starting on day
25th of the study. Good algal density was noticed in both raceways on
the fourth day after stocking with algal density reaching 167,000 and
375,000-cells/ml for Raceways 3 and 4, respectively. No statistically
significant differences (P > 0.05) were found in water quality parameters between the two raceways. The mean values of these water quality
parameters are summarized in Tables 15 and 16. Differences in mean
weights at harvest were not statistically different. The calculated FCR
values for both raceways were low with 0.7 and 0.71 for Raceway 3 and
4, respectively (Table 17). Shrimp survival in both raceways was high
(100%) with yields of 2.34 and 2.10 kg/m2 for Raceways 3 and Raceway 4, respectively. These results suggest that nursery of the Pacific
white shrimp can be conducted at low-salinity ground water with excellent survival and yields.
In addition to the nursery trials, another grow-out trial was conducted
in four raceways. Raceways were stocked with two-month-old juveTABLE 15. Summary of daily water quality parameters in raceway water during
a nursery trial with Pacific white shrimp in low salinity geothermal water.
DO (mg/L)
Temp. (°C)
pH
Culture Tank
a.m.
p.m.
a.m.
p.m.
a.m.
p.m.
Raceway 3
5.86±0.32
6.52±0.97
24.66±1.42
26.41±1.02
7.71±0.40
8.00±0.43
Raceway 4
6.01±0.26
6.69±0.97
24.28±1.34
25.93±1.12
7.75±0.39
8.09±0.38
Samocha et al.
29
TABLE 16. Ammonia, nitrite, nitrate, and algal density in raceway water during
a nursery trial with Pacific white shrimp in low-salinity geothermal water.
Culture Tank
NH4 (mg/L)
NO2 (mg/L)
NO3 (mg/L)
Algae (cell/mL ⫻ 106)
Raceway 3
0.779±0.499
0.376±0.283
11.93±2.20
260,600±154,300
Raceway 4
0.610±0.426
0.340±0.249
11.49±1.78
327,700±174,400
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TABLE 17. Summary of stocking and harvest information from a nursery trial
with Pacific white shrimp using low salinity geothermal water.
Stocking
Culture Tank
shrimp/m2 shrimp/m3 Size (g)
Duration
(days)
Harvest
Mean Wt. (g)
kg/m2
kg/m3
Survival (%)
FCR
Raceway 3
19,200
12,700
0.0025
34
0.103±0.078a
2.34
1.54
100
0.70
Raceway 4
20,400
13,500
0.0025
35
0.091±0.069b
2.10
1.39
100
0.71
a Mean weights with different letter within a column are significantly different at
P = 0.05.
niles (0.5 g) at a density of 74, 93, 107, or 346/m2. Temperature, dissolved oxygen, and pH were monitored twice daily; ammonia, nitrite
and nitrate at least twice weekly. Shrimp were fed four times/day a
commercial diets (Rangen, Inc., Buhl, Idaho) with either 40% or 45%
protein. Daily rations were adjusted based on weekly shrimp growth.
Table 18 summarizes the minimum and maximum range of selected
water quality parameters in the four raceways along with the daily water
usage. Differences among raceways were small; however, the daily water
discharge from the high-density raceway was much higher. Information
concerning shrimp survival, FCR, and yields in this study is presented
in Table 19. Survival in the high-density raceway was much higher than
in the low-density raceways. Although the mean average weight of the
shrimp at harvest for the high-density was the lowest among the raceways, the yield was almost four times higher. FCR value for this raceway was a little lower than the other three raceways. This study showed
that juvenile shrimp could be raised to marketable-size in 107 days with
good survival and excellent yield (4.39 kg/m2), using low-salinity geothermal water. A relatively high volume of water was used to maintain
the high yield in the high-density raceway. However, since effluent water was used for crop irrigation, no effort was made to conserve water.
In addition to the nursery and grow-out studies in raceways, other
production trials were carried out in fourteen rectangular earthen ponds
of the farm. Emberson et al. (1999) provide a short summary of this
30
JOURNAL OF APPLIED AQUACULTURE
TABLE 18. Minimum/maximum values of selected water quality parameters in
a grow-out trial of Pacific white shrimp in raceways using low salinity geothermal water.
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Density
Temp. (°C)
(shrimp/m2)
pH
DO
NH4
NO2
NO3
Water Discharge
(% total
volume/day)
21
(mg/L)
74
24.7-31.3
6.8-9.1
4.2-9.2
0.0-0.36
0.08-0.5
6.4-12.8
93
23.7-30.9
6.8-9.1
4.9-10.6
0.0-0.34
0.08-0.4
6.6-12.8
21
107
24.0-31.5
6.7-9.0
5.1-10.5
0.0-0.60
0.1-0.6
7.4-11.3
21
346
24.5-30.9
6.6-8.8
4.5-9.7
0.0-0.79
0.05-0.6
7.2-13.6
133
TABLE 19. Summary of stocking and harvest information from a grow-out trial
with Pacific white shrimp using low-salinity geothermal water.
Stocking
Culture Tank
shrimp/m2 shrimp/m3 Size (g)
Harvest
Duration
(days) Mean Wt. (g) kg/m2
kg/m3
Survival (%)
FCR
Raceway 1
74
49
0.5
107
19.53
1.00
0.67
69.4
2.66
Raceway 2
93
61
0.5
94
17.26
1.16
0.76
72.1
2.37
Raceway 3
107
71
0.5
107
18.66
1.18
0.78
59.2
3.22
Raceway 4
346
228
0.5
107
14.72
4.39
2.89
86.1
2.11
study. The pond size varied between 0.11 and 1.06 ha with an average
water depth of 1.6 m. Water was provided from four low-salinity
(1.6-2.6 ppt) geothermal (25°C) wells. Aeration was provided by double-bladed paddlewheel aerators (2-HP each) or by air diffuser system.
An average of 20.4 HP/ha of aeration was used in the large ponds and 13
HP/ha in the small ponds. Compressed air was supplied (24 h/day) by
three air blowers (100 HP total) that delivered air at a rate of 28.3
m3/min (1,000 CFM). Air was distributed via three 5.1-cm floating
tubes with outlets positioned 8 to 10-m apart; each outlet had 4 air
stones (7.8 L/air stone). All paddlewheel-aerated ponds were provided
with one air supply line. Table 20 summarizes the experimental design
of this study. Ponds were fertilized before stocking with a liquid ammonium phosphate (33-5-0) until a rich algal bloom has developed. Temperature, dissolved oxygen, and salinity were monitored twice daily;
secchi disc readings were taken in the afternoon; ammonia and algal
counts were measured weekly. Daily rations were adjusted based on
shrimp growth and water quality. Shrimp were fed a 40% protein diet
(“40/5” Rangen, Inc., Buhl, Idaho) for 14 weeks and a 25-30% protein
Samocha et al.
31
TABLE 20. Experimental design for production of Pacific white shrimp in
earthen ponds at Wood Brothers Farm, Gila Bend, Arizona (AD = Airdiffuser,
PW = Paddlewheel aerators).
Pond Group ID
Parameter
Total # of ponds
Pond size (ha)
Density (juvenile/m2)
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Shrimp size (g)
Aeration (HP/ha)
A
B
C
3
4
4
D
3
0.75
0.74-0.96
0.82-1.06
0.11-0.18
71, 90, 109
34-37
61-70
40-52
0.4
0.18-0.22
0.11-0.22
0.12
AD (14.7)
PW (15-27)
AD (17.3-20.3)
AD (26.7-43)
AD (6.7-9.9)
PW (11-18)
diet for 6 weeks (Zeigler Bros., Inc., Gardners, Pennsylvania). Shrimp
in one pond were fed a combination of the two diets with 30% diet replacement by wheat flour. Diet was distributed twice a day (0800 and
1900) using an air-powered feeder mounted on a flatbed truck.
Due to setup limitations, up to 50% of aeration generating capacity
was lost in the air diffuser aerated ponds, as only half of the 4 air stones
per outlet were operating at full capacity. A heavy clogging of the air
stones with bryozoans (up to 0.3 m thick) was noticed during the last
two months before harvest. All ponds were affected by Haemocytic Enteritis disease outbreak; severity varied among ponds. Water temperature of the paddlewheel-aerated ponds was 1°C lower than the ponds
aerated with air diffusers. Many dragonfly nymphs were noticed in
Group C ponds (ponds that were provided with air diffuser aeration
only) a few days after stocking. The average daily farm exchange rates
by month were as follows: May 5.3%; June 6.0%; July 10%; August
16.7%; and September 8.3%. No significant differences (P > 0.05) were
found in water quality parameters among the four groups. Table 21 provides a monthly summary of the water quality data collected from the
ponds in Group A. As no significant differences were found among
ponds in water quality, these data are provided only to characterize the
culture water in this study. The mean-morning pond water temperature
in the early season was lower than 25°C required for adequate shrimp
growth. The mean afternoon water temperature during July was above
32°C. Good algal blooms were found in all four months. This may explain the low ammonia levels in these ponds (below 0.2 mg/L).
It is interesting to see that the mean afternoon pH levels in the ponds
were below 9.3 even under the high algal bloom conditions. Table 22
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TABLE 21. Monthly summary of selected water quality parameters in earthen
ponds (Group A) stocked with Pacific white shrimp in Wood Brothers Farm,
Gila Bend, Arizona.
Temp. (°C)
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DO (mg/L)
Secchi
disk
(cm)
NH4
(mg/L)
Algae (⫻105)
a.m.
p.m.
a.m.
p.m.
min
pH
p.m.
min.
max.
May
23.4
26.2
8.8
11.5
7.7
8.9
67
0.04
1.3
3.0
June
25.2
28.0
6.1
10.8
5.8
9.3
65
0.12
0.4
1.0
July
30.0
32.3
4.2
10.5
4.0
8.7
47
0.19
0.5
1.4
August
29.6
31.5
4.7
12.0
4.5
9.1
40
0.03
0.6
2.2
September
28.4
30.0
5.1
10.1
5.0
9.3
44
0.11
N/A
N/A
Month
TABLE 22. Mean production data for Pacific white shrimp in earthen outdoor
ponds at the Wood Brothers Farm, Gila Bend, Arizona.
Pond Group ID
Parameter
A
Density (shrimp/m2)
Average final weight (g)
Yield (ton/ha)
Biomass at harvest (kg/m2)
Growth (g/week)
B
C
D
34-37
61-70
40-52
72-109
18.0-19.5
17.7-20.5
15.8-27.7
20.7-22.6
19.8
4.0-5.1
3.4-6.8
3.0-5.5
6.7-12.4
4.6
58
0.40-0.51
0.4-0.7
0.3-0.6
0.7-1.2
0.53
1.1-1.5
0.9-1.0
0.8-1.1
0.9-1.1
1.0
Survival (%)
62-75
27-55
34-57
42-53
FCR
1.3-2.2
2.0-3.8
2.1-2.8
2.4-2.6
AD*
PW**+AD
AD
PW+AD
Aeration type
Farm’s
Average
46
2.4
* Aeration by air diffusers
** Aeration by paddlewheel aerators
summarizes the production results from the four groups of ponds. The
highest group average survival (69.6%) and growth rate (1.34 g/week)
was obtained in Group A (ponds stocked at the lowest densities that
were aerated by air diffusers). The mean FCR value (1.79) for these
ponds was the lowest among all other groups. The highest yield (5.5
ton/ha = 4,850 lb/ac) in the diffuser-aerated ponds was achieved in the
pond with the highest aeration rate (20.3 HP/ha) that was stocked at 49
shrimp/m2. The highest yield (6.8 ton/ha = 6,000 lb/ac) in the paddlewheel-aerated ponds was achieved in the pond with the highest aeration
rate (27 HP/ha) that was stocked at 70 shrimp/m2. The highest yield on
the farm (12.4 ton/ha = 10,930/ac) was achieved in 0.11-ha pond
stocked at 109 shrimp/m2 with 61 HP/ha of aeration (PW-18 HP/ha,
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Samocha et al.
33
AD-53 HP/ha) and about 30% water exchange/day. It is interesting to
note that a high yield (9.6 ton/ha = 8,470 lb/ac) was obtained in another
0.11 ha pond stocked at 90 shrimp/m2 with the same aeration regimens
when 30% of the diet was replaced by wheat flour, with only 5% water
exchange/day. A cost-breakdown for direct farm operating costs showed
that pumping cost accounted for 7% of the estimated total operating
costs. Since all effluent water from the farm was re-used for agricultural
crop irrigation, the actual pumping cost was much lower.
The nursery and grow-out studies suggest that the Pacific white
shrimp can be raised to marketable-size at high densities in raceways
and earthen ponds using low-salinity geothermal water. Unlike coastal
producers that often use contaminated water that result in disease outbreaks, inland shrimp farming using non-polluted ground water can
help reduce this risk. Furthermore, when water salinity is low, effluent
water from these facilities can be used for crop irrigation, negating potential negative environmental impact from effluent water.
OUTDOOR SHRIMP POND PRODUCTION TECHNOLOGY
WITH REDUCED WATER USAGE
In south Texas, much progress has been achieved with outdoor pond
production systems operated with reduced, or with no, water discharge.
In most cases, these systems employ heavy aeration to maintain adequate dissolved oxygen levels. Significant reductions in water usage,
nutrient, and pollutant releases were achieved when these farms started
to use sedimentation basins, water recirculation, lower stocking densities, low-protein diets, and high aeration rates. The following is a brief
description of one of the farms (Arroyo Aquaculture Association Farm,
Rio Hondo, Texas) along with a short summary of the farm’s past and
current management practices.
The Arroyo Aquaculture Association (AAA) farm is located on the
far southeast region of Texas, near Arroyo City along the Gulf of Mexico. The farm pumps its water from a nearby creek (Arroyo Colorado)
into two distribution canals that feed the ponds by gravity. Out of 85
two-ha earthen ponds at the farm, only ten ponds are not being used.
Each pond is equipped with twelve to eighteen 2-HP paddlewheel aerators. Typical production management during the early 1990s included:
high stocking densities (50 PL/m2) of the production ponds with the Pacific white shrimp, use of high-protein diets (40-45%), heavy water exchange (up to 380,000 m3/day with about 10%/day water discharge),
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high fertilization rate, and minimal aeration. The effluent waters generated by this and other shrimp farms had created a serious growth-limiting factor for the emerging Texas shrimp farming industry. It was
particularly true for Texas coastal areas, in which the discharge is going
into bays and estuaries behind barrier islands that have limited water exchange with the Gulf of Mexico. Farms were required to limit their volume of discharges and to meet certain effluent water quality standards.
Under these conditions, the farmers were looking for cost-effective
methods to improve effluent water quality and reduce the nutrient releases to receiving water.
In early 1994, researchers from TAES and Texas A&M University-Kingsville, together with the farmers, launched an intensive sampling
program to characterize the farm’s effluent water quality. Preliminary
testing was also carried out to identify potential methods to minimize
pollutant releases to receiving waters. Lopez (1996) and Samocha and
Lawrence (1997) provided a detailed summary of the data collected in
this study. The study showed that dissolved oxygen, ammonia, and total
suspended solids (TSS) levels were in most cases above the limit set by
the state regulatory agency. The main conclusions from these studies
were: (1) drainage ditch soil erosion was one of the main sources of the
high TSS levels in the farm’s effluent waters; and (2) the farm’s drainage ditch could serve as a primary settling basin to reduce TSS and to
improve the water quality in the grow-out ponds.
Based on the data obtained from this study, a few modifications were
implemented by the farm to improve the effluent water quality. To reduce effluent TSS levels, sections of the drainage ditches with high soil
erosion were lined with geotextile membrane; primary drainage ditches
were deepened, widened, and partitioned to enhance settling. Drainage
canals were also equipped with aeration devices to improved dissolved
oxygen and enhance nitrification. Furthermore, to minimize TSS release, water drained from the ponds during harvest was pumped into
empty ponds for initial settling. Although a trend toward reduction in
water exchange was noticed throughout the years, a significant reduction was implemented after massive crop losses due to the Taura virus
syndrome outbreaks in 1995. To minimize the risk of spreading pathogenic viral diseases in the state of Texas, shrimp farms are only allowed
to use certified viral pathogen-free seed. After the initial Taura disease
outbreak, shrimp farmers have realized that reduced water exchanges
not only reduce the potential negative environmental impact from effluent waters, but also minimize the risk to their cultured stocks from contaminated incoming water.
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Samocha et al.
35
To reduce the introduction of competitors and disease-carrier organisms, the farm has started to filter all raw water with 250-micron
screens. Further decreases in water exchange were achieved by increasing ponds’ aeration rates up to 18 HP/ha. A secondary pumping station
was installed to pump water from the discharge canal back into the distribution canal. Discharge and distribution canals were equipped with
mechanical aeration to improve water quality. For the first two months
after stocking, ponds are kept under no discharge. When shrimp biomass load increases (generally 0.2 to 0.4 kg/m2) and based on water
quality data, water is released from the ponds into the discharge canal
system. This water is pumped back into the distribution canals and
eventually returned to the ponds. Thus, the widening and deepening of
the discharge canals along with installation of supplemental aeration,
enable enhancement of the ponds’ effluent water quality. The improvement in water quality makes this water suitable for reuse without negative impact on the shrimp performance. Although some ponds are
operated with no water release until harvest, other ponds may require up
to 30% daily water release into the discharge canal system. In general,
the farm’s average water recirculation rate varies between 10 and 15%
of the pond volumes per day. Only limited volume of new water
(1%/day) is being pumped from the river to compensate for evaporation
and seepage losses. During harvest, water is pumped into empty ponds
for storage. This water is released back into the river only when water
quality meets the standard set by regulatory agencies.
Another modification implemented by the farm to institute the “zerodischarge” management was the reduction in stocking density from the
initial 50 PL/m2 to a density between 30 and 40 PL/m2. Furthermore, to
improve diet utilization, the farm is currently using feed trays (2 per
pond) to monitor diet consumption. In addition, diet is offered three
times a day using a tractor-mounted feed-blower rather than the once/day
practice used in the past. Unlike past practices, fertilizers are added to
the newly-filled ponds on an “as needed” basis. Under this no-discharge
management, the farmers have found that the same growth and survival
results can be obtained when a low-protein (30%) diet is fed rather than
diets with 40 to 45% protein levels.
Figure 3 shows the decrease in water usage over five-year period at
the AAA Farm. Current practice requires about 2,500 L of water for the
production of 1 kg of shrimp compared with about 38,000 L used during
the 1994 production season. Figure 4 shows the reduction in effluent
TSS from 3.5 kg for every 1 kg shrimp produced in 1994 to 0.05 kg in
36
JOURNAL OF APPLIED AQUACULTURE
FIGURE 3. Reduction in water usage (L/kg of shrimp produced) by Arroyo
Aquaculture Association Farm, Arroyo City, Texas.
40,000 Liters
35,000
30,000
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25,000
20,000
15,000
10,000
5,000
0
1994
1995
1996
1997
1998
FIGURE 4. Reduction in effluent total suspended solids (TSS) (kg/kg of shrimp
produced) by Arroyo Aquaculture Association Farm, Arroyo City, Texas.
4.00
Kg
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
1994
1995
1996
1997
1998
Samocha et al.
37
FIGURE 5. Reduction in effluent ammonia levels (kg/kg of shrimp produced) by
Arroyo Aquaculture Association Farm, Arroyo City, Texas.
0.06
Kg
0.05
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0.04
0.03
0.02
0.01
0.00
1994
1995
1996
1997
1998
1998. Figure 5 shows the reduction in total ammonia nitrogen over the
years. Ammonia level decreased from almost 0.05 kg for one kg of
shrimp produced in 1994 to 0.0004 kg in 1998. A similar reduction
trend was noticed in the five-day carbonaceous biochemical oxygen demands (cBOD5). Figure 6 shows a reduction in cBOD5 from 0.18 kg for
each kg of shrimp produced in 1995 to 0.01 kg in 1998. Figures 7 and 8
show the differences in selected water quality parameters between the
farm’s intake water and the water in the recirculation system. As expected, an increase in salinity, ammonia, nitrite, and nitrated TSS and total
P were observed in the recirculating system. While further modifications can help improve water quality in this system, the slight increase
in salinity is unavoidable. Figure 9 shows the changes in average pond
production of the farm over a five-year period. It is interesting to note
that although reduction in dietary protein level and water usage was noticed for the last five years, the farm production was not affected. Aside
from the decrease in pollutant-load due to lower water usage and the use
of low-protein feeds, a significant improvement was noticed in the
farm’s FCR value (overall reduction from 2.3 to 1.75).
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JOURNAL OF APPLIED AQUACULTURE
FIGURE 6. Reduction in effluent cBOD5 (kg/kg of shrimp produced) by Arroyo
Aquaculture Association Farm, Arroyo City, Texas.
0.20 Kg
0.18
0.16
0.14
0.10
0.08
0.06
0.04
0.02
0.00
1994
1995
1996
1997
1998
FIGURE 7. Differences in selected water quality parameters between the incoming water and the recirculating system water of the Arroyo Aquaculture Association Farm, Arroyo City, Texas.
60
Intake
Recirculation
50
40
Units
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0.12
30
20
10
0
Salinity
pH
cBOD5
TSS
VSS
Samocha et al.
39
FIGURE 8. Differences in selected water quality parameters between the incoming water and the recirculating sytem water of the Arroyo Aquaculture Association Farm, Arroyo City, Texas.
2
Intake
Recirculation
1.8
1.6
1.2
mg/L
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1.4
1
0.8
0.6
0.4
0.2
0
Nitrite
Nitrate
Ammonia
Total P
Reactive P
SUMMARY
The world shrimp farming industry is currently experiencing major
crop losses due to disease outbreaks. In some cases, these disease outbreaks were associated with degradation of water quality in receiving
streams. The paper reviewed several shrimp production systems and
management strategies that can be used to minimize crop losses and environmental deterioration. Based on the results from both research and
commercial production facilities, it is clear that considerable improvements in biosecurity and sustainability can be obtained by retrofitting
old facilities and incorporating new design concepts into new operations. Consequently, commercial producers are encouraged to adapt
these technologies into their production systems. Based on the positive
results, continued research to optimize operational parameters and develop/evaluate new technologies are warranted.
40
JOURNAL OF APPLIED AQUACULTURE
FIGURE 9. Changes in average pond production (kg) over five-year period in
the Arroyo Aquaculture Association Farm, Arroyo City, Texas.
12,000
Kg
10,000
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8,000
6,000
4,000
2,000
0
1994
1995
1996
1997
1998
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