Biosecurity

Aquaculture Magazine Jul/Aug 2001Aquaculture Magazine Jul/Aug 2001Aquaculture Magazine Jul/Aug 2001Aquaculture Magazine Jul/Aug 2001Aquaculture Magazine Jul/Aug 2001
Volume 27, Number 4Volume 27, Number 4Volume 27, Number 4Volume 27, Number 4Volume 27, Number 4
© 2001 Aquaculture Magazine
T
he considerable impact of
viral diseases on
commercial shrimp
farming during the last decade has
significantly affected the
operation/management, and more
recently, farm design. This has led
shrimp farmers to look for better
husbandry methods in order to
reduce the risks associated with the
exposure to pathogens, and a
general acceptance of better
management practices to promote
and maintain shrimp health.
Shrimp farming is a relatively new
industry and has lagged behind in
the development of standard health
management practices, partly due
to the relatively poor level of
understanding of shrimp
physiology and the production
systems in which they are grown.
And until recently, limited
involvement by veterinarians and
animal health specialists to
develop health management
practices similar to those used in
the husbandry of many terrestrial
species (Fegan and Clifford,
2001).
Learning from Other
Industries
The modern poultry industry has
enjoyed considerable increases in
Comments on Biosecurity and Shrimp Farming
Darryl E. Jory
production along with decreases in
disease losses, which illustrates
economic advantages of biosecure
animal production. The
aquaculture industry must follow
this example to become more
competitive and environmentally-
friendly. Aquatic broodstock and
seedstock biosecurity, and
simultaneous protection of natural
stocks are necessary to sustained,
responsible, and profitable
aquaculture production (Lee,
2000). Biosecurity in shrimp
aquaculture refers to practices that
will reduce the probability of
pathogen introduction, and its
consequent propagation of disease.
Many shrimp farmers give only
limited attention to routine
biosecurity on their farms because
they lack the needed knowledge or
operate under the misconception
that the potential costs of
implementing biosecurity
measures will outweigh the
benefits. Implementation of
biosecurity protocols does require
greater levels of awareness and
discipline among all farm workers,
and a commitment by farm owners
to implement them. Knowledge of
shrimp viral diseases has increased
dramatically over the past 15 years
due to their serious impact on
commercial farming. The concept
of biosecurity is relatively new to
aquaculture and especially in
shrimp farming. In terrestrial
husbandry, “animal health” and
“herd health” indicate either
freedom from disease or minimal
levels of disease in individual
animals or in herds. Biosecurity is
a less familiar term, generally
referring to management practices
that protect the herd from the
introduction of new diseases along
with minimizing the spread and/or
adverse effects of diseases in the
herd (Fegan and Clifford, 2001).
Zero Exchange Production
Systems
There are several successful
examples of the implementation of
zero exchange production systems,
including those in Belize and
Panama.
Belize Aquaculture, Ltd.
The Belize Aquaculture, Ltd.
(BAL) project is probably the best-
known closed system in the
Western Hemisphere.According to
McIntosh (2000), BAL developed
a zero water exchange and recycle
strategy to reduce the effluents and
sediments that would be released
into the environment by a typical

intensive shrimp farm, and as a
methodology to increase farm
biosecurity. This zero water
exchange/water recycling
technology has resulted in
sustained high yields, the reduction
of nutrients released into the
environment, along with an
increase in feed and pond
utilization efficiency. Nutrients are
not flushed from the ponds as they
do when water is exchanged but
are recycled within the pond, with
a higher percentage of the nutrients
becoming assimilated into the
shrimp carcass biomass. In typical
ponds, the amount of nitrogen that
is retained in the shrimp carcass is
less than 25% of the total nitrogen
added to the pond. In ponds that
combine a zero exchange water
management with that of recycling
water between crops, like those at
BAL, nitrogen retention can be
greater than 40%. And because
recycled water is already fertile,
there is a reduction in the amount
of time required to prepare pond
water for stocking. With the
combined use of recycled water
and ponds lined with HDPE
plastic, restocking can take place
as soon as five days after a pond is
harvested. BAL maintains pond
use efficiency of 96%, and
harvests of 2.5 crops/year from its
ponds using this method.
Agromarina de Panama Farm
Lawrence et al. (2001) reported on
the successful intensive culture of
Litopenaeus vannamei on the
White Spot Syndrome Virus
(WSSV)-contaminated farm in
Panama. Cultured shrimp
production virtually came to a
complete halt in 1999 and 2000 in
Panama due to this virus.
However, while WSSV is the
major reason for decimated
production in Panama, Infectious
Hypodermal and Haematopoietic
Necrosis virus (IHHN) and
Necrotizing Hepatopancreatitis
(NHP) are also present and
affecting crop production. An
eighty percent average survival of
L. vannamei was achieved in 18
intensive 0.1 ha lined ponds in
Panama in a test designed to
exclude viruses from soil, water,
and postlarvae sources on a farm
with concurrently stocked
conventional earthen ponds known
to be heavily contaminated with
WSSV. This test, conducted
during the second half of 2000 by
the TexasAgricultural Experiment
Station, and Agromarina de
Panama (the oldest shrimp farm in
the Western Hemisphere, owned
by North American Agrisystems,
Inc., of Houston, Texas) using
newly constructed intensive ponds
in conjunction with the existing
contaminated earthen ponds. The
zero water exchange method in the
intensive ponds averaged 80%
survival in contrast with 8.34%
survival in the 600 ha traditional
earthen ponds. Additionally, two
sources of postlarvae were stocked
into the intensive ponds:
domesticated high health
postlarvae derived from the United
States Department of Agriculture
(USDA) Marine Shrimp Farming
Program and wild broodstock-
derived postlarvae. Both groups
achieved 80% survival in the
intensive ponds, but the growth of
the USDA program stocks was
42.1% higher. The USDA
program-derived stocks averaged
production of 29,192 pounds per
ha (per crop), while the wild
broodstock derived stocks
averaged 24,440 pounds per ha. A
broad range of potential vectors
have been implicated in WSSV
infectivity, including water-borne,
soil-borne, shrimp-borne, and
through organisms ranging from
copepods and crabs to many
microorganisms. This test was
designed to avoid most
contamination from these venues,
using water filtration of
approximately 25 microns, use of
pond liners, and comparison of
postlarvae sources. The test ponds
were also uncovered and adjacent
to infected conventional earthen
ponds. Results indicated that
management techniques, including
both design and operational
considerations, can overcome
WSSV contamination even in the
most heavily infected farms.
Acuipaula Farm
Grillo et al. (2000) reported on the
results of the first cycle at this new
farm in Panama. Survival rates
obtained are considered excellent
when compared to typical rates for

the rest of the country, averaging
80% and ranging from 52 to 95%
after a range of 112-129 days.
Growth rates averaged 0.70 g/
week (range 0.61-0.82 g/week).
The mean production for the 20
ponds was 4,941 kg/ha (range
3,515 -7,555 kg/ha), and a total of
39,530 kg of shrimp were
harvested in this first cycle of
operation. Production reflected the
stocking densities, with ponds
stocked at 50 PL/m2
averaging
4,736 kg/ha, at 60 PL/m2
averaging
6,028 kg/ha, and at 80 PL/m2
averaging 7,555 kg/ha. The main
objectives of this first production
cycle were accomplished which
were to maximize biosecurity by
excluding pathogens and their
vectors (particularly WSSV), and
to maintain pond conditions as
optimal as possible. Although the
FCR values can undoubtedly be
improved, no diseases were
observed and the economic results
were very positive and highly
encouraging. At 80 PL/m2
the
production cost US$2.49/kg, at 60
PL/m2
it was $3.10/kg, and at 50
PL/m2
the cost was $3.96/kg.
According to the authors, these
results show that it is possible to
grow shrimp commercially in
areas of Panama where WSSV is
endemic, using biosecure intensive
systems with zero exchange of
pond water.
Inland Shrimp Production
Shrimp farming at considerable
distances from the ocean is another
biosecure alternative.According to
Samocha et al. (2001), when
virulent pathogens are found in
shrimp farm water supplies and in
wild populations, avoiding
contamination of cultured stocks
becomes very difficult and costly.
One isolation strategy used is the
implementation of marine shrimp
culture in low salinity waters away
from the coastal zone. Several
researchers have reported the
successful implementation of this
practice in areas of the Far East
with Penaeus monodon. Inland
shrimp farming, using clean
seedstock, can provide a physical
barrier to spreading diseases.
Furthermore, when farms use low-
salinity water, effluent can serve
for crop irrigation, minimizing
effluent disposal issues, and in turn
creating environmentally-friendly,
integrated systems. These
emerging technologies offer
opportunities for establishment of
shrimp culture operations on
marginal arid agricultural sites,
reducing demand for shrimp
farming on limited, high-cost
coastal land. The studies
summarized in this paper show
that Pacific white shrimp can be
successfully raised in low salinity
ground water with varying ionic
composition and salt
concentrations. Furthermore,
successful culture at high densities
for both nursery and growout
phases in raceways and growout in
earthen ponds have been
demonstrated.
Biosecurity in Closed
Recirculating Systems
Lee (2000) recently reviewed the
development of biosecurity in
closed recirculating systems
(RAS). The design of a RAS
depends on the actual requirements
of the animals to be cultured. The
most common form of
environmentally-isolated system is
a RAS containing water derived
from isolated wells in the case of
freshwater animals or artificial sea
salts in the case of marine animals.
This water is then recirculated
through a variety of filtration
components so that it can be re-
used over and over again. A truly
closed RAS would be exactly that
– closed to all natural external
inputs. However, this is quite
impossible since some original
source of water must be used and
some external source of food will
be provided. In addition,
evaporation and incidental losses
from cleaning and maintenance
will result in some water loss. Most
RAS in operation today add >10%
system water volume per day.
Biosecure, closed systems can be
managed manually or by
automated means. For seedstock
and broodstock systems, the
choice will usually be manual,
because these animals must be

carefully monitored. However,
control of temperature, lighting,
and some feeding and filtration
components can be automated
effectively. Most intensive
aquaculture systems today use
automation, whether they are open
ocean cage systems or land-based
raceway systems.The goal of RAS
and other biosecure systems is to
significantly increase production
while simultaneously reducing
labor, as well as disease losses, and
offsetting the higher capital costs
of construction. The source of
seedstock for biosecure production
systems must be an SPF hatchery,
requiring extension of the
biosecure concept to hatchery
design and management. While
few hatcheries are truly closed
systems, some are geographically
isolated and many are increasingly
utilizing recirculation technology.
Maturation systems are becoming
the first to implement RAS
because of the low biomass, the
need for high water quality, and
improved ability to constantly
monitor mating and spawning
behavior. There are many
companies worldwide that are
contemplating the design and
construction of biosecure
seedstock and broodstock
facilities. The advent of
environmentally isolated,
biosecure hatcheries and
maturation facilities will, in fact,
mirror the compartmentalization
developed for modern poultry
production. The goal for seedstock
production will be increased
production with less labor and
fewer losses from disease. The
advent of biosecure RAS has been
spurred on by the recurring disease
problems associated with
aquaculture worldwide. The
advantages of RAS technology
are: (1) the environmental isolation
from natural waters and disease
vectors, (2) the degree of
monitoring and control that can be
applied and (3) elimination of
negative environmental impacts
(effluents quality and disease
transmission to natural
populations). The aquaculture
industry should be able to emulate
the development of biosecurity in
the poultry industry and reap the
same increases in productivity and
sustainability.
Reliable Diagnostic Tools
A cost-effective health
management and biosecurity
program requires reliable
diagnostic tools of which shrimp
farmers can use to make adequate
and timely decisions on
management procedures to control
or exclude pathogens. Virulent
pathogens can produce
catastrophic mortalities very
rapidly, and shrimp farmers need
this fast diagnostic capacity in
order to respond effectively.
Practical diagnostic methods that
are accurate, sensitive, rapid, and
economical to conduct are already
available, including PCR, dot blot
gene probes, and various methods
for rapid fixation and staining.
Conclusion
According to Fegan and Clifford
(2001), the most successful
strategies for controlling viral
diseases in shrimp ponds have
been based on a combination of
prevention by exclusion, and best
management practices that focus
on creating a healthy, non-stressful
environment for the shrimp. Viral
diseases have undoubtedly
affected the shrimp farming
industry globally, but have not
prevented its expansion and
technological development On the
contrary, these diseases are
directing the industry to develop
and implement a number of
biosecurity measures, and
implement more cost-effective
management procedures. Thailand
has managed to remain the top
farmed shrimp producer in the
world during the last decade, while
facing WSSV, and most countries
have recovered after being
seriously hit by WSSV. Both
Thailand and India are back to pre-
WSSV production levels. Cost-
effective, biosecure systems for
commercial production of shrimp
have been operating for several
years now, in countries like Belize
and Thailand, and more recently
in Guatemala, Panama, Malaysia,
and are being developed
elsewhere. Implementing

biosecurity is key to maintaining
the shrimp farming industry,
keeping it commercially viable,
and environmentally and socially
responsible.
References
Clifford III, H.C. 1999. A review
of diagnostic, biosecurity and
management measures for the
exclusion of White Spot Virus
disease from shrimp culture
systems in the Americas. In: T.R.
Cabrera, M. Silva y D.E. Jory.
Memorias, Tercer Congreso
Latinoamericano de Acuacultura.
Puerto La Cruz, Venezuela.
Noviembre 1999.
Fast,A.W. and P. Menasveta. 2000.
Some recent issues and
innovations in marine shrimp pond
culture. Reviews in Fisheries
Science 8:151-233.
Fegan, D. and H.C. Clifford III.
2001. Health management for viral
diseases in shrimp farms. In:
Browdy, Craig L. and Jory, Darryl,
E. editors. 2001. The New Wave,
Proceedings of the Special Session
on Sustainable Shrimp Culture,
Aquaculture 2001. The World
Aquaculture Society, Baton
Rouge, Louisiana, United States.
Grillo F. M., E. Grillo de Vega,
D.M. Dugger and D.E. Jory. 2000.
Zero-Exchange, Biosecure,
Intensive Shrimp Production in a
WSSV-Infected Area in Panama.
Global Aquaculture Advocate
3(6): 55-56.
Lawrence, A.L. W. More, W.A.
Bray and M. Royo. 2001.
Successful intensive culture of
Litopenaeus vannamei on a White
Spot Syndrome virus-
contaminated farm in Panama. In:
Rouge, Louisiana, United States
(abstract only).
Lee, P.G. 2000. Biosecurity and the
Development of Closed
Recirculating Systems. Global
Aquaculture Advocate 3(5):49.
McIntosh, R.P. 2000. Changing
paradigms in shrimp farming. Part
V. Establishment of heterotrophic
bacterial communities. Global
AquacultureAdvocate 3(6): 52-54.
Samocha, T.M., T. Blacher and E.
Estrada. 2000. High-density
nursery of Litopenaeus vannamei
in raceway system with limited
water discharge in a WSSV-
infected area. In: NP. D.E. Jory,
editor. Proceedings, 4th
Annual
Meeting of the Latin American
Chapter/WAS, Panama, Panama.
25-28 October 2000.
Samocha, T.M., A.L. Lawrence,
C.R. Collins, C.R. Emberson, J.L.,
Harvin and P.M. Van Wyk. 2001.
Development of integrated,
environmentally-sound, inland
shrimp production technologies
for Litopenaeus vannamei. In:
Rouge, Louisiana, United States.

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