Group Title: Circular
Title: Introduction to fish health management
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 Material Information
Title: Introduction to fish health management
Series Title: Circular
Physical Description: 3 p. : ill. ; 28 cm.
Language: English
Creator: Francis-Floyd, Ruth
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1991?
Subject: Fishes -- Diseases   ( lcsh )
Fish culture -- Florida   ( lcsh )
Fishes -- Parasites   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: Ruth Francis-Floyd.
General Note: Title from caption.
 Record Information
Bibliographic ID: UF00014505
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA6945
ltuf - AJG5670
oclc - 26846457
alephbibnum - 001752713
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Circular 921



Introduction to fish health management.

Ruth Francis-Floyd* ,

Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florid Woeste,ean

What is fish health
Fish health management is a
term used in aquaculture to
describe management practices
which are designed to prevent fish
disease. Once fish get sick it can be
difficult to salvage them.
Successful fish health
management begins with
prevention of disease rather than
treatment. Prevention of fish
disease is accomplished through
good water quality management,
nutrition, and sanitation. Without
this foundation it is impossible to
prevent outbreaks of opportunistic
diseases. The fish is constantly
bathed in potential pathogens,
including bacteria, fungi, and
parasites. Even use of sterilization
technology (i.e., ultraviolet
sterilizers, ozonation) does not
eliminate all potential pathogens
from the environment. Suboptimal
water quality, poor nutrition, or
immune system suppression
generally associated with stressful
conditions allow these potential
pathogens to cause disease.
Medications used to treat these
diseases provide a means of buying
time for fish and enabling them to
overcome opportunistic infections,
but are no substitute for proper
animal husbandry.
Daily observation of fish behavior
and feeding activity allows early

detection of problems when they do
occur so that a diagnosis can be
made before the majority of the
population becomes sick. If
treatment is indicated, it will be
most successful if it is implemented
early in the course of the disease
while the fish are still in good

The significance of fish disease
to aquaculture
Fish disease is a substantial
source of monetary loss to
aquaculturists. Production costs are
increased by fish disease outbreaks
because of the investment lost in
dead fish, cost of treatment, and
decreased growth during
convalescence. In nature we are less
aware of fish disease problems
because sick animals are quickly
removed from the population by
predators. In addition, fish are
much less crowded in natural
systems than in captivity. Parasites
and bacteria may be of minimal
significance under natural
conditions, but can contribute to
substantial problems when animals
are crowded and stressed under
culture conditions.
Disease is rarely a simple
association between a pathogen and
a host fish. Usually other
circumstances must be present for
active disease to develop in a
population. These circumstances
are generally grouped under the

umbrella term "Stress"(Fi e 1).
Stress is discussed in greater detail
in the IFAS publication "Stress Its
Role In Fish Disease". Management
practices directed at limiting stress
are likely to be most effective in
preventing disease outbreaks.

Host Disease

P thogen nviro, ment

Figure 1. Disease rarely results from simple
contact between the fish and a
potential pathogen. Environmental
problems, such as poor water
quality, or other stressors often
contribute to the outbreak of

Determining if your fish are sick
The most obvious sign of sick fish
is the presence of dead or dying
animals. However, the careful
observer can usually tell that fish
are sick before they start dying
because sick fish often stop feeding
and may appear lethargic. Healthy
fish should eat aggressively if fed at
regularly scheduled times. Pond
fish should not be visible except at
feeding time. Fish that are observed
hanging listlessly in shallow water,
gasping at the surface, or rubbing
against objects indicate something
may be wrong. These behavioral

*IFAS extension veterinarian, Department of Large Animal Clinical Sciences and Department of Fisheries and Aquaculture, Institute of Food
and Agricultural Sciences, University of Florida, Gainesville, FL 32611.

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abnormalities indicate that the fish
are not feeling well or that some-
thing is irritating them.
In addition to behavioral
changes, there are physical signs
that should alert producers to
potential disease problems in their
fish. These include the presence of
sores (ulcers or hemorrhages),
ragged fins, or abnormal body
conformation (i.e. a distended
abdomen or "dropsy", and
exopthalmia or "popeye"). When
these abnormalities are observed,
the fish should be evaluated for
parasitic or bacterial infections.

What to do if your fish are sick
If you suspect that your fish are
getting sick, the first thing to do is
check the water quality. If you do
not have a water quality test kit,
contact your county extension office;
some counties have been issued
these kits, and your extension agent
may be able to help you with this. If
your county is not equipped with a
water quality test kit, call the
aquaculture extension specialist
nearest to you (see the list at the
end of this publication). Anyone
contemplating commercial
production of fish should invest in a
water quality test kit and learn how
to use it. A complete kit can be
purchased for under $200, and can
save thousands of dollars worth of
fish with its first use.
Low oxygen is a frequent cause of
fish mortality in ponds, especially
in the summer. High levels of
ammonia are also commonly
associated with disease outbreaks
when fish are crowded in vats or
tanks. Separate extension fact
sheets are available that explain
oxygen cycles, ammonia cycles, and
management of these water quality
problems. In general, it is
appropriate to check dissolved
oxygen, ammonia, nitrite, and pH,
during a water quality screen
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associated with a fish disease
Ideally, daily records should also
be available for immediate refer-
ence when a fish disease outbreak
occurs. These should include the
dates fish were stocked, size of fish
at stocking, source of fish, feeding
rate, growth rate, daily mortality
and water quality. This information
is needed by the aquaculture
specialist working with you to solve
your fish disease problem. Good
records, a description of behavioral
and physical signs exhibited by sick
fish, and results of water quality
tests provide a complete case
history for the diagnostician work-
ing on your case.
Professional assistance is avail-
able to Florida residents through
the Institute of Food and Agricul-
tural Sciences (IFAS) at the Univer-
sity of Florida, the Department of
Agriculture and Consumer Services,
as well as several private laborato-
ries. A list of these resources is
included at the end of this publica-
If you decide to submit fish to a
diagnostic laboratory you should
collect live, sick fish, place them in
a freezer bag (without water), and
ship them on ice to the nearest
facility. Small fish can be shipped
alive by placing them in plastic
bags which are partially filled (30%)
with water. Oxygen gas can be
injected into the bag prior to sealing
it. An insulated container is
recommended for shipping live,
bagged fish as temperature
fluctuations during transit are
minimized. In addition to fish
samples, a water sample collected
in a clean jar should also be

Types of fish diseases
There are 2 broad categories of
disease that affect fish, infectious
and non-infectious diseases. Infec-
tious diseases are caused by patho-

genic organisms present in the
environment or carried by other
fish. They are contagious, and some
type of treatment may be necessary
to control the disease outbreak. In
contrast, non-infectious diseases are
caused by environmental problems,
nutritional deficiencies, or genetic
anomalies; they are not contagious
and usually cannot be cured by
Infectious diseases. Infectious
diseases are broadly categorized as
parasitic, bacterial, viral, or fungal
diseases. Parasitic diseases of fish
are most frequently caused by small
microscopic organisms called
protozoa which live in the aquatic
environment. There are a variety of
protozoans which infest the gills
and skin of fish causing irritation,
weight loss, and eventually death.
Most protozoan infections are
relatively easy to control using
standard fishery chemicals such as
copper sulfate, formalin, or
potassium permanganate.
Information on specific diseases and
proper use of fishery chemicals is
available from your aquaculture
extension specialist.
Bacterial diseases are often
internal infections and require
treatment with medicated feeds
containing antibiotics which are
approved for use in fish by the Food
and Drug Administration. Typically
fish infected with a bacterial
disease will have hemorrhagic spots
or ulcers along the body wall and
around the eyes and mouth. They
may also have an enlarged, fluid-
filled abdomen, and protruding
eyes. Bacterial diseases can also be
external, resulting in erosion of skin
and ulceration. Columnaris is an
example of an external bacterial
infection which may be caused by
rough handling.
Viral diseases are impossible to
distinguish from bacterial diseases
without special laboratory tests.
They are difficult to diagnose and

/ r

there are no specific medications
available to cure viral infections of
fish. The most important viral
infection which affects fish produc-
tion in the southeastern United
States is Channel Catfish Virus
Disease, caused by a herpes virus.
Consultation with an aquaculture
or fish health specialist is recom-
mended if you suspect a bacterial or
viral disease is killing your fish.
Fungal diseases are the fourth
type of infectious disease. Fungal
spores are common in the aquatic
environment, but are not normally
a problem in healthy fish. When
fish are infected with an external
parasite, bacterial infection, or
injured by handling, the fungi can
colonize diseased tissue on the
exterior of the fish. These areas
appear to have a cottony growth or
may appear as brown matted areas
when the fish are removed from the
water. Potassium permanganate is
effective against most fungal
infections. Since fungi are usually a
secondary problem it is important
to diagnose the original problem
and correct it as well.
Non-infectious diseases. Non-
infectious diseases can be broadly
categorized as environmental,
nutritional, or genetic.
Environmental diseases are the
most important in commercial
aquaculture. Environmental
diseases include low dissolved
oxygen, high ammonia, high nitrite
or natural or man-made toxins in
the aquatic environment. Proper
techniques of managing water
quality will enable producers to
prevent most environmental
diseases. There are separate IFAS
publications which address water
quality management in greater
Nutritional diseases can be very
difficult to diagnose. A classic
example of a nutritional disease of
catfish is "broken back disease",
caused by vitamin C deficiency. The

lack of dietary vitamin C contrib-
utes to improper bone development,
resulting in deformation of the
spinal column. Another important
nutritional disease of catfish is "no
blood disease" which may be related
to a folic acid deficiency. Affected
fish become anemic and may die.
The condition seems to disappear
when the deficient feed is discarded
and a new feed provided.
Genetic abnormalities include
conformational oddities such as lack
of a tail or presence of an extra tail.
Most of these are of minimal
significance, however, it is
important to bring in unrelated fish
for use as broodstock every few
years to minimize inbreeding.

There are many diseases of fish
which can be troublesome to
commercial producers as well as the
recreational pond owner. Many
disease outbreaks of captive fish
stocks are associated with stressful
conditions such as poor water
quality, excessive crowding or
inadequate nutrition.
There are two broad categories of
disease which relate directly to
selection of appropriate treatments:
1) Infectious diseases are
contagious diseases caused by
parasites, bacteria, viruses, or
fungi. These often require some
type of medication to help the fish
2) Non-infectious diseases are
broadly categorized as
environmental, nutritional, or
genetic. These problems are often
corrected by changing management
Fish disease outbreaks are often
complex, involving both infectious
and non-infectious processes.
Appropriate therapy often involves
medication and changes in hus-
bandry practices. Assistance from
IFAS aquaculture extension special-

ists is available to help you manage
disease outbreaks and develop
management programs to prevent
them. A list of state specialists is
provided for your convenience at the
end of this publication.

State specialists
University of Florida:
IFAS Aquaculture Extension
Department of Fisheries and
Aquaculture and College of
Veterinary Medicine
7922 NW 71 St. Gainesville, Fl.
32606 (904) 392-9617

Hillsborough County Extension
Office 5339 St. Rd. 579, Seffner, Fl.
33584 (813) 621-5605

Northwest Florida Aquaculture
Demonstration Farm P.O. Box 754,
Rt.1, Blountstown, Fl. 32424
(904) 674-3184

Florida Department of
Agriculture and Consumer
State Veterinary Diagnostic
P.O. Box 420460, Kissimmee, Fl.
34742-0460 (407) 847-3185

Live Oak

Drawer O, Live Oak, Fl. 32060
(904) 362-1216


Woeste, director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the
May 8 and June 30, 1914 Acts of Congress; and is authorized to provide research, educational information and other services only to
individuals and institutions that function without regard to race, color, sex, age, handicap or national origin. Single copies of extension
publications (excluding 4-H and youth publications) are available free to Florida residents from county extension offices. Information on bulk
rates or copies for out-of-state purchasers is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of
Florida, Gainesville, Florida 32611. Before publicizing this publication, editors should contact this address to determine availability.

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