Gain an appreciation for the key organ systems in fish
responsible for excretion, respiration and the control of
osmolality
Know the main physiological differences between saltwater
and freshwater fish
Gain a basic understanding of the importance of
maintaining good water quality for aquarium fish and how this is
achieved
Be able to develop a basic clinical approach for a
diseased fish presented for examination
Gain an awareness of the environmental concerns affecting
aquaculture and wild fish stocks
1.2. Suggested review for this section
Please review the 1st Year Comparative Anatomy notes on
fish prior to attending lecture
Interactive anatomy and necropsy video at
www.aquanic.org/real/necropsy/
2. Introduction - Why bother??
2.1. Ornamental fish popularity continues to rise
Zoo/Aquarium
Pet
Home aquarium and pond (sales over $500
million/year)
Goldfish are statistically most popular pet
80% of fish owners own other pets
Commercial aquarium setting
2.2. Expectations of care similar to domestic species
Owner will expect you as veterinarians to be able to help
them when their fish are sick or die.
2.3. Fish as a food source becomes more and more important
More and more veterinarians deal with fish
diseases
Food born diseases from fish meat (e.g. sushi) have
zoonotic potential
2.4. Plentiful variety!
Leafy seadragon
Scientific literature and medical knowledge increases at a
fast pace
> 20 000 species
Smallest fish is 0.4 inches (10 mm)
Largest fish (Whale fish) 45 feet (14 m)
Anatomy and physiology varies with habitat of fish
3. Fish Anatomy
Approximately 20,000 different species of fish each with
its own physiological and anatomical variation to fit its niche.This makes the
class of fish the most versatile (and interesting) group to study.
3.1. Organs which are found in both fish and mammals but can
have anatomical variation
As you go down the list, there are more anatomical
differences
Liver
Spleen
Stomach
Intestines
Brain / spinal cord
3.2. Organs found in mammals but not in fish
Pancreas (Pancreatic tissue found in liver)
Adrenal Glands-instead there is
Interrenal organ (cortical) anterior
Suprarenal organ (Medulla) near sympathetic
ganglia
Lymph nodes
Bone marrow-Diffuse lymphomyeloid tissue in mesenteries,
spleen, and head kidney
Lungs
Parathyroids
3.3. Organs which are found in mammals but are distinctly
different in fish
Kidneys (divided into head and tail kidney)
Gonads-seasonally variable
Skin-no stratum corneum
Heart-two chambered
3.4. Organs which are present in fish but not in mammals
Fins
Lateral line
Swimbladder
Physostomous-connected to the g.i. tract
Physoclistous-sealed off from the g.i.
tract
Gills-gas diffusion and waste dumping
Ultimobranchial bodies-calcitonin production
Pseudobranch-???-May have physiological connection with
eye gas diffusion
Corpuscle of Stannius (bony fish only)-electrolyte
balance
Pyloric appendages
Spiral colon-elasmobranchs (sharks and rays)-increased
surface area
Rectal gland-elasmobranchs-electrolyte balance
3.5. Fins
Dorsal fin :Stabilizer, Courtship, Defense
Pectoral fin : counteract
Pelvic fin : stabilizer
Caudal fin : Motor
Anal fin : Stabilizer, Gonopodium
3.6. Integument
Bony scales of fish are overlapping plates
of bone produced in the dermal layer.
Epidermal cells cover the dermal plates. The outermost
cells of the epidermal epithelium contain microridges of uncertain
function.
Analogue to terrestrial animal
Epidermis consists of 6-8 layers of cells
Glassfish: collagen is arranged in uniform pattern
(cornea)
Rapid metabolism
Mucous (glycocalyx)
Full of antibiotic / antifungal enzymes and
antibodies
Protective coating
Slough off pathogens
Can be detrimental in high amounts
Alarm cells (pheromone)
Taste buds-some fish
to feed youngsters
to sleep (Parrotfish creates cocoon)
to protect from drying out (Lungfish)
3.7. Circulatory system
Blood cells formed in liver, spleen, kidney
Leukocytes may be normal at 10%
Some fish lack hemoglobin (white blood)
Lymph vessels but no lymph nodes
Capillaries in gas bladder (exchange gas)
Heat exchange in red muscles of lateral body wall (Tuna
raises 4-6F)
Fishes in high-risk habitats evolved various mechanisms
(mouth breeders, sex changes)
The reproductive tracts of most teleosts are specialized
for the production of large numbers of gametes that undergo fertilization and
development in the external environment.
Female teleost have ovaries with a central cavity which
collects large numbers of ova before they are expelled via an oviduct to a
genital pore. The ova lack the characteristic follicular development seen in
mammals.
Male teleosts have testes which may vary in size with the
breeding period. The sperm are delivered from the seminiferous tubules to the
external environment via a sperm duct which may join the most caudal end of the
urinary (archinephric) duct in some species.
3.11. Musculature
Most fibers are white - rapid contractions, short
stamina
Clinical relevance: White muscle
disease due to Vit. E /Se deficiency
3.12. GI system
GI tract is longer in herbivorous fish than carnivorous
fish
Digestion is temp dependant
Mouth is limiting factor
Barbels have tactile and gustatory function
Fish lack a muscular tongue, but have one formed by the
hyoid arch. Teeth and taste buds may be present throughout the oral
cavity.
Stomach is highly variable from no stomach to blind
sac
The stomach contains cells that produce both the
secretions of chief and parietal cells found in mammals. Some fish lack a
histologic stomach.
Pancreas/gall bladder evident
The intestinal ceca may be numerous and are located just
after the stomach.
The liver is large, tubular and has pancreatic tissue
within it.
4. Physiology (Breathing & Excretion)
The Big
Three Organs to Know
Gills
gas transfusion, osmotic
regulation, waste excretion
4.1. Breathing & Dealing with the External
Environment
O2 is as important to fish as to
terrestrial animals
The Water environment
Oxygen poor, H2O contains only 3%
O2
Osmotically unfriendly, H2O is 800 times
denser than air
A soup of pathogens
Cory aeneus
4.2. Osmoregulation
4.2.1. Diffusion and Osmosis
Diffusion: Movement of molecules from a higher
concentration to a lower.
Osmosis is diffusion through a semi-permeable membrane
4.2.2. Freshwater fish
Freshwater fish are hypertonic in
comparison to their environment.
Water passes through the gills and ions diffuse into the
water
They have to eliminate water constantly from their
body
In freshwater fish with large lesions on epithelial
layer or gills, fluid therapy is contra-indicated.
Most important task of the kidney is to
eliminate excess water
Larger glomeruli
4.2.3. Saltwater fish
Fish in the marine environment are
hypotonic and lose water at a high rate.
They have to drink seawater and excrete
minerals
Even when fish rest, they have a high energy requirement
due to the ATPase dependant processes.
Most important task of the kidney is to
eliminate excess electrolytes (Mg, So4)
Some species have aglomerular kidneys
4.2.4. Practical implications for fluid
therapy
In marine fish with large lesions on epithelial layer or
gills, fluid therapy is indicated.
In freshwater fish with large lesions on epithelial
layer or gills, fluid therapy is contra-indicated.
4.3. The Gill
4.3.1. Gill Physiology
Respiration
Hemoglobin varies in fish species
Goldfish-high affinity for oxygen
Trout-quick release of oxygen.
Some fish lack hemoglobin (White blood)
Efficiency
Under ideal conditions 80 % of O2 is
removed(Humans use 25 % of inhaled O2)
This efficiency will also harm the fish
(supersaturating- gas bubble disease)
Can accumulate concentration of toxic material of
100 (to 1 million) times higher than concentration found in water
Surface of gill is 6-10 times greater than surface of
fish
Lung surface is 100 times greater
Important second function as excretory organ - loss of
ions and water
Problems with abnormal water quality: Decreased pH and
increased CO2 cause quick release of oxygen-Bohr effect.
Bohr effect: Hb not only furnishes oxygen to
tissues, but also transports the waste products of metabolism from the tissues.
So there must be some regulatory interplay between these two functions, and the
mechanism of this regulation of Hb is called the Bohr effect. At the tissues
there is high [carbon dioxide] and [H+] i.e. low pH, and this
lowers the Hb affinity for oxygen
H2O must constantly been drawn over the gills
(but: Fish do sleep!)
Mostly water is drawn in per the
mouth
Sharks have slits on first gill branch
Tuna, trout etc. just keep mouth open when swimming
(1 mph)
Excretion of ammonia
Passive and active
transport.
Mostly concentration gradient dependent high
environmental ammonia = prevents ammonia from being excreted out the fish =
toxic
Energy required, even if fish is dormant
Acid base balance: Enzyme function, molecular
function.
Necrosis/Trauma: No semipermeable membrane anymore;
noosmotic regulation or protection from pathogens.
Hyperplasia (increased number of cells): Same
effectmucous build-up
Heavy mucous, necrosis, and hyperplasia,
prevents all the normal physiological functions!
4.4. Skin Pathology
Break in the skin barrier
Breech in osmotic barrier-stress
Breech in pathogen defense-mucous tries to
compensate
4.5. Kidney
Osmotic Balance: Saltwater verses
Freshwater
Immune response
Blood production
Excretion of cations (Ca++,
Mg++, excess water, etc.)
Freshwater fish are
hypertonic in comparison to their environment. They have to eliminate
water constantly from their body. In fish with kidney disease, ascites is very
common, as the elimination of water from the body is impaired ("Pine
cone" look).
Fish in the marine
environment are hypotonic and lose water at a high rate. They have to
drink seawater and excrete the minerals mostly via the gills.
4.6. Other important physiological organs
Rectal gland in sharks and rays - Elimation of excess
Na
Olfactory organ - Homing process in salmonids
Lateral line organ - Mechanoreceptors
Ear
5. Water Quality
The Key to Keeping Fish healthy!
5.1. Basic Water Quality Parameters
Salinity
Temperature
Dissolved oxygen
Ammonia
Nitrite
pH and hardness
Other parameters
5.2. Types of Filtration
Water changes
Mechanical
Biological
Chemical
Carbon
Ion Exchange
5.3. Disinfection
UV light
Ozone
5.4. Water Quality Monitoring Equipment
Test kits run from $ 20 to $ 2000. The accuracy of the
result is reflected in the price of the test. (See list of test kit
manufacturers at end of chapter)
Refractometer
Thermometer
Colorimetric tests
Ammonia
Chlorine
Dissolved oxygen
Nitrite
PH
Alkalinity/hardness
6. Principle Causes of Disease and Mortality
6.1. Definition of disease
A pathological entity characterized usually by at
least by two of these criteria: a recognized etiologic agent(s), and
identifiable group of signs or symptoms, or consistent anatomical
alterations.
6.2. Disease continuum
Because of all the factors involved, fish diseases can
be very confusing and frustrating. Also some diseases manifest in fish with
very different signs (e.g. mycobacterium marinum) and lots of diseases manifest
with the same clinical sign (e.g. cataract). Therefore, identification of the
causative agent(s) and the nature of the predisposing condition(s) are both
important in disease control and long-term prevention.
Consider the physical properties of water as
the primary environment of fish:
Fish are much more closely connected with their immediate
environment than terrestrial animals (water vs. air)
Water transports all kind of pathogens much more
efficiently than air
Water will keep pathogens alive better than air (drying is
one form of sterilization)
6.3. Stress
Stress is the sum of the biological reactions to any
adverse stimulus, physical, internal or external, that tends to disturb the
homeostasis of an organism. Should these reactions be inappropriate, they may
lead to disease states. The term is also used to the stimuli that elicit the
reaction e.g. heat, nutrition, confinement, transport etc.
6.3.1. Causes of Stress
Know your animals' natural
histories!
Improper housing (lighting, temperature, water quality,
improper hiding places)
Improper social structure
Improper food
Inadequate cleaning, etc.
Tank mate aggression: Contrary to common beliefs, fish
are very aggressive and usually very territorial. It is not uncommon that fish
do not get along in an aquarium set up and one will try to chase the other one
out of the territory. This will be a constant chase and the stress will
eventually kill the fish.
6.3.2. Reactions to Stress
Decreased reproduction
Decreased weight gain
Decreased immune function
Death!
7. Common Husbandry Problems of Captive Fish
7.1. Environmental
All the chemistries are closely related to each other.
A certain concentration of ammonia or nitrate may be tolerable at the optimum
temperature but toxic at 5 10 degrees higher. Remember fish are
poikilotherms!!!!! The immune system and all physiological processes need the
species-specific optimal temperature to work best.
KNOW THE AMMONIA CYCLE!see
below
New Tank Syndrome
Ammonia
Nitrite toxicity
Supersaturation-Gas Bubble
Disease
Chlorine toxicity
Low dissolved oxygen
7.2. Other common mistakes and pitfalls encountered in the
aquatic patient:
Failure to know your animal
Failure to allow a system to age and come into balance
before adding organisms.
Overcrowding, which taxes the oxygen supply and the waste
processing capacity of the system and increases traumatic injury,
territorialism, and cannibalism.
Overfeeding
Failure to rinse recently disinfected vessels and
implements
Failure to quarantine newly arrived stocks or to isolate
animals undergoing treatment.
Failure to rinse dust from activated carbon, dolomite, or
crushed shell when recharging a system.
Clogged seawater lines due to accumulation of fouling
organisms and resulting in decreases in water flow rates.
Failure to remove dead animals or decaying food.
Use of plastics impregnated with insecticides and
fungicides (certain bathroom sealers).
Use of toxins or solvents in or around aquaria (floor
stripping, pest control).
Failure to separate certain species (placing the predator
with its prey or the parasite with its host).
Failure to check the pH and specific gravity of culture
solutions.
Inadequate nutrition due to underfeeding or an unbalanced
diet.
Failure to keep adequate records of water quality data or
other significant events and failure to review the data
Failure in anticipating the onset or duration of
reproductive activity or in misinterpreting reproductive behavior as aberrant
Use of brass, bronze, or copper valves or piping which can
corrode and slough off or leach toxic copper salts. Copper is especially
injurious to invertebrates.
Failure to provide proper substrates, shelter, or support
of commensal organisms.
Improperly secured electrical equipment, frayed wires or
outlets not protected by ground fault interruption.
Failure to observe all pipes, fittings, and equipment on
the suction side of pumps for air leaks. Supersaturated water can
kill.
The belief that antibiotics will solve all your
problems.
7.3. The ammonia cycle:
A very common mistake done by the novice aquarist, is
setting up the system and not allowing time enough for the ammonia cycle to go
through all its phases until it is safe for fish and invertebrates. This common
mistake is often referred to as new tank syndrome. As the
system is set up and plants and one or two fish are introduced, an initial
built-up of ammonia will occur due to fish excrements, dead plant material and
food leftovers. Slowly a bacterial population (nitrosomas
sp.) will build up and transform the ammonia into nitrites which are
slightly less toxic than ammonia. A second population of bacteria
(nitrobacter sp.) will change the nitrites into nitrates,
which are not very harmful to the fish.
#1 Cause of infectious diseases
Lack of or Improper
Quarantine
For a good diagnostic work up, it is necessary to work
with a living fish or a freshly killed specimen. A dead fish will only be good
for histology if at all!!
Get live fish for diagnostics! External parasites will
leave or die when the host dies.
Avoid having invertebrates (esp. snails) in tank as
they are intermediate hosts for lots of parasites!
8.1.1. External parasites
8.1.1.1. Protozoa
Ich (Ichthyophthirius
multifiliis): Skin scrape, gill clip, see ciliate on
cytology
Treatment for Ich: Malachite green at 0.1 mg/l q3d x 3
Trichodina spp.: Skin scrape, gill
clip
R/O fungal diseases
8.1.1.2. Crustaceans
Lernaea spp.(Anchor worm):
Skin and gill exam
Argulus
spp.(Fish lice): Skin exam
Only a little knob
Animals are irritated (show
flashing, scraping)
Treatment
Potassium Permanganate (traditional, very
caustic) OR
Lufenuron (Program, Anchor Away) can be used
(chitin inhibitor) at 1 tab (490 mg) per 1000 US gal. (0.1-0.2 mg/L)
The veterinarian should be aware of a
possible risk to native aquatic arthropods from waste water runoff
8.1.1.3. Trematodes
Skin and gill exam
Gyrodactylus-live bearer
Dactylogyrus-egg bearer
Digenetic trematodes
8.1.1.4. Leaches
Skin examination
8.1.2. Internal parasites
Myxosporidia: Squash prep, histopathology
Myxobolus cerebralis
(Whirling Disease)
Nematodes: Squash preparation of liver, stomach, and
intestines
Trematodes: Squash prep of liver, intestines
Cestodes: Exam of muscle (grubs), stomach, and
intestinal content exam.
8.2. Bacterial Diseases
Remember that fish live in a bacterial
soup and are constantly challenged by their presence. A lot of
infections are opportunistic.
Common sign is hemorrhages in fins and scales
Fin rot
Fin rot is a bacterial disease involving opportunistic
bacteria such as Aeromonas, Pseudomonas or Flexibacter that abound in all
aquatic environments + Stress
It is usually self-resolving as they settle in, but
does demonstrate just how sensitive fish can be to stress and how fin erosion
is often a sign that all is not well.
Investigation into a underlying cause should
continue!!
Injected vessels in the tail fin
Finrot
Mycobacteria
Improperly called Fish T.B.
Probably the most frequent disease
All species are susceptible
Found in the water
Squash of liver, spleen-acid-fast stain
Culture will take 1 month - make sure the lab knows
the sample is from a fish, so that they culture under the right conditions and
look for fish mycobacteria
Zoonotic potential
Always wear gloves when handling
fish or cleaning an aquarium
Treatment difficult, culling and disinfection,
Kanamycin might be best
Fish tank granuloma - a frequently
misdiagnosed infection of the upper limb. Ryan JM, Bryant GD. J
Accidental Emergency Medicine,, 1997. 14(6): 398-400.
Five patients attended the accident and emergency
(A&E) department with fish tank granuloma caused by an infection with
Mycobacterium marinum. All patients had forearm symptoms which were initially
misdiagnosed. They were later recognised by the presence of superficial
cutaneous lesions in a sporotrichotic distribution. Definitive diagnosis was
confirmed by the histological appearances of a biopsy and or culture of the
organism. All patients responded to oral minocycline and had uncomplicated
recoveries once the diagnosis was established. A&E doctors need to be aware
of the possible diagnosis of fish tank granuloma especially when treating
forearm infections which have been resistant to
antibiotics.
Aeromonas
hydrophila: Culture of blood, liver, kidney; zoonotic
Vibrio spp: Culture of blood, liver,
kidney; zoonotic
Edwardsiella tarda: Culture of deep
ulcers, blood
Columnaris: Squash prep of
gills
Anaerobes
8.3. Viral
Infectious salmon anemia (see article
on APHIS
site)
Lymphocystis: Squash prep and histopathology
Viral Hemorrhagic Septicemia - Viral isolation
Once diagnosed in pet fish, concentrate on immune
modulators (Vit.C, levamisole, best aquarium conditions)
8.4. Fungal
Usually true opportunistic invaders. Also
check for underlying stressor.
Saprolegnia
can act as a primary pathogen
infecting fish that havent shown signs of previous damage
It is believed that such attacks are
temperature-dependant, usually occurring at low temperatures, possibly as a
consequence of a reduced immune response
Diagnose with skin scrape and gill clip (looks like
cotton wool)
R/O Ich
Identification of the causative agent and the
nature of the predisposing condition are both important in disease control and
long-term prevention.
Saprolegnia infection in a fish
9. Basic Approach to Fish Medicine
9.1. Different settings
Pond vs. Aquarium
Individual (small animal medicine) vs. Herd
health
Big differences, but same physiology, same
environment
9.2. History
How long have you been keeping fish?
What are the problems with the fish today?
When did you first notice these problems?
How long have you owned the sick fish and where were they
obtained/purchased?
Are there other fish in the same tank or pond with the
sick fish, and if So, how are they?
What is the size (volume) of the pond and how is it
heated, filtered, and aerated?
Do you have a water test kit, and if so, how often do you
test the water?
What are your most current results?
What and how often do you feed your fish?
Have the fish already been treated? If so, by whom and
with what medications?
Is there a possibility that the fish were exposed to some
type of toxin?
9.3. Aquatic Environment
Fish are ectothermic
Pond vs. Aquarium
Every reaction is governed by temperature of
system
Improving the water quality and environmental
conditions are key to success
Most diseases are related to disturbance of the balance
between waste production by the fish and its metabolism by the bacteria in the
biological filter.
9.4. Feeding
9.4.1. Pond
Starved below 7C ( 45F)
Half ration 7-14C (45-57F)
Full ration > 14C (> 57F)
Food eaten in 5 min tid
9.4.2. Aquarium
3 times daily
Food eaten in about 2 min
9.5. The different disease patterns
Sudden onset + all species affected = Environmental
Problem
Some clients will not be willing to come to your
clinic and might just want some telephone advice (free, of course); to avoid
bigger disasters you can tell them to:
test water quality (ammonia, nitite, nitrate,
pH)
change 1/3 of tank/pond water to dilute poor
environmental conditions
add salt at 2 g/l (equals 0.2 % solution) to reduce
physiological stress in freshwater fish
stop feeding immediately to avoid more ammonia build up
and it improves the acceptability of medicated foods
improve aeration
Isolate diseased individual
use immuno-stimulants (vitamin C,
levamisole)
9.7. The physical exam
Generally the clinical signs are very non-specific and
sometimes not uniform!!
Exophthalmus
Cataract
Dropsy
Strange breeds vs. tumor
Trauma/Furuncle
Emaciation and Dropsy in Zebra Danio
Pinecone appearance from several angles
9.8. Diagnostics
9.8.1. Tank-side assessment
If you cannot perform a house call then have the
owner take a picture. Look for chemicals over tank; improper electrical
circuits, lighting, heat sources; improper mixing of fish species.
9.8.2. Water Quality
Hach kit
Save water of chemical analysis
9.8.3. Direct microscopic examination at 10X, 20 X and
40X
New Methylene blue stain, Gram stain
Gill biopsy
Mucous smear
Fin biopsy
9.8.4. Hematology and Blood Chemistry
Phlebotomy
9.8.5. Culture
Remember water contamination
9.8.6. Other tests
Colon wash
Stomach sample
Radiographs
Ultrasound
Coelomic taps
9.8.7. Necropsy
Review all organs
Culture from head kidney, brain, spleen
Freeze for toxin or virus isolation
9.9. Treatments
Depending on the severity and circumstances of the
situation (pet fish in one aquarium vs. 1000 of fish in commercial aquarium or
pet store) different forms of delivering the medication might be chosen. Apart
from the direct medication by injection or topical application there are
different indirect ways to medicate the fish. See next section for specifics on
pharmaceuticals.
9.9.1. Isolation
Know dynamics of fish - some need to school,
some can be isolated.
Treatment tank
Hanging baskets
Dividers
9.9.2. Hands-off methods
In-water medication
In-food medication
9.9.3. Tank or pond treatments:
The advantages are less stress and no
handling.
Disadvantages are that biological filtration may be
affected.
Treatment dosages can be difficult to calculate unless
the exact water volume is known
Variances in water composition; particularly pH,
hardness, and organic load may interfere or affect the chemical activity of the
treatment
Some treatments, for example antibiotics, cannot be
applied via the pond.
Overdoses or situations where there is a bad reaction
can be difficult to remedy, particularly in large ponds
Treatment costs can be high in large ponds
9.9.4. Bath treatments
They can be easily calculated.
Higher doses can be used (for shorter
periods)
Filtration is not affected
Less interference with treatment reaction
If there is a bad reaction, it is easy to remove the
'patient'
Disadvantage is the need for handling and except in the
case of short treatment periods, a relatively large treatment tank may be
needed if several fish are treated at the same time.
9.9.5. Food top dressing usually antibiotics
Advantage: no stress or handling
Disadvantages include: difficult to calculate doses or
target specific individuals, treatment may wash off the food, very sick fish
may not eat
9.9.6. Injections
Intramuscular in longissimus dorsi
Intracoelomically
IM Injection
9.9.7. Some problems with treating fish
The Pathogen
Not all ectoparasites are easily eliminated with one
dose (e.g. white spot requires repeated treatments)
Drugs can be difficult to obtain (e.g. lice and
anchor worm usually require organophosphates)
Not all bacteria can be treated easily (e.g.
Mycobacteria are found deep inside lesions.)
Drug Resistance - Bacterial resistance
to antibiotics is now an important factor in the treatment of bacteria diseases
of fish. Culture and sensitivity tests may take too long to complete but it is
often essential to start treatment as soon as possible to avoid a disease
"explosion"
In-contacts - many fish pathogens are infectious or
potentially infectious, therefore all in-contact fish should be treated
enmasse.
The Patient
Small fish and fry may be too small to inject
safely.
Severe illness - too ill (e.g. gill disease) to
inject or handle without causing serious stress.
Unpalatable drugs (e.g. some antibiotics) and
anorexic fish limit the use of in-feed medications.
Shoaling - Some fish prefer company particularly in
isolation facilities, even if it is with other species.
9.10. Nutritional support
For the most part, captive fish are overfed and fed an
inappropriate diet
Increase to allow for increased metabolism
Oral intubation-no worry about aspiration but water
fowling and coating gills are problems. Some animals will regurgitate when
tubed under anesthesia. Make sure you have fresh water around to flush over
gills if they are covered with food material.
Clove oil (Eugenol) (Mix 1:10 with 95
% ethanol for stock solution) 25 50 mg/l will anesthetize fish. Recovery period
is longer than with MS-222.
Isoflurane-special ventilation to decrease human
exposure.
Make sure recovery water is available (temperature and pH
matched)
Preparation for surgery
Induction
9.12. Surgery
Anesthesia set-up
Absorbable monofilament. Remove suture after 3 weeks
!!
Standard surgical technique.
Surgery in a goldfish
Ophthalmic surgery for exophthalmos in a
fish
9.13. Imaging
Radiology
Can be done awake or under anesthesia
Fish will struggle initially but then remain calm
To protect the fish at all times is
utmost importance
Ultrasound
Water is best medium for utlrasound exam
10. Pharmaceuticals
Methods of delivery are different and
dependent on fish species
Injectable
Oral
Bath
10.1. Antibacterial
Oxytetracycline
Ciprofloxacin
Enrofloxacin
Amikacin
Trimethoprim-sulfas
Watch salt water and antibiotic baths-salts
(Ca++, Mg++ may bind such antibiotics such as
tetracycline rendering the antibiotic functionless)
10.2. Antiprotozoal
10.2.1. Freshwater
Salt (1-3 g/L) (if you use table salt, use the
non iodine version)
Formalin (37%) - very stressful, never use after recent
stress such as transport. Do not use formalin when paraformaldehyde (white
precipitation) is present.
Temperature modification (slowly!)
10.2.2. Saltwater
Copper (watch toxicity to fish and invertebrates and
elasmobranchs!), corals can act as a sponge and soak up and store copper and
then suddenly release it, causing a sudden copper toxicity
Hyposalinity
Metronidazole for intestinal problems
10.2.3. Malachite green at 0.1 mg/L q3d x 3, treatment for
Ich
It is only the free-swimming stage of
the parasite that is susceptible to treatment; neither the trophonts under the
epithelium or the tomont cysts can be killed. So any treatment plan has to be
carried out over a period of time in order to kill the emerging parasites. This
in turn depends on temperature. At 7degrees C the life cycle will take six
weeks, whereas at 25 degrees C it will be complete in a week.
An alternative treatment is prolonged salt immersion at
1-2 ppt (parts per thousand), i.e. 1-2 grams per liter. Water should be
monitored during the treatment course in case there is any loss of filter
activity.
It is also believed that fish that survive an attack of
Ich have an increased immunity against future attacks
Beware: remove filter before treatment and use
activated charcoal to remove from system after 3rd tx. Otherwise risk
killing off good Nitrosomas bacteria.
10.3. Antiparasitic
Fenbendazole
Praziquantel (bath or injection)
10.4. Antifungal
Salt bath
Temperature
Manual removal
Methylene blue
Malachite green
10.5. Viral Tx.
Isolation of fish
10.6. Tx. for noninfectious diseases
Lateral Line Disease: multifactorial
New Tank Syndrome: water changes
11. Fish Kills
(see examples in TUSK supplemental reading )
11.1. Reasons for investigating fish kills
Immediate alleviation of disease: Clean up site, stop
polluting, adding chemotherapeutic drugs for pathogens, management techniques
(thinning populations, modifying habitat)
Prosecution purposes
Data collected for future prevention through management
techniques, or to aid in future investigations.
11.2. What to do in case of a fish kill
Contact state and federal government
agencies
Examine dead fish pattern in the water. kinds of fish. Are
they spread out throughout the water body, or are they in one
location?
Examine the live fish: Are they at the surface, are they
behaving abnormally, do they have any abnormal lesions (eroded fins, increased
mucous)?
History: Interview local residents to determine if this
has happened before, length of time, time of day, water temperatures, unusual
weather (high winds, heavy rains (call weather service), smells, unusual events
(trucks over turning, crop fertilization)).
Geographic location: Look at map: head waters, location of
industry or agriculture, currents.
Water and soil samples: Information on water and soil
chemistries and organisms (indicator species).
Examine habitat:
Type of water body, plant growth, and soil
type.
Types of animals affected: fish (types: age, species,
bottom dweller verses mid column), amphibians, insects (indicators species of
current health of the water body), birds. If many different species are
affected then think toxin.
Example: Menhaden die-off involving sea
birds.
Necropsy exam (necropsy 5-10 fish for a disease survey):
Wear gloves (zoonotic potentials-mycobacterium, botulism, and vibriosis). Post
fresh fish; dead fish give very little information since they decompose
rapidly.
Necropsy technique (post within 1/2 hour of death):
Visual exam (abnormalities?), skin scrape, gill clip, fin clip, sterile entry,
liver/kidney swab, assess the viscera, tissue squashes, intestinal contents,
formalin 1 cm X 1 cm in 10% buffeted formalin.
Sending 5-10 fish off: Package fish off federal express
(not on a Friday!) in water with ice packs.
Deep freeze 5-10 fish and send off for toxicology if
necessary.
11.3. Examples of diseases
Seasonal water turnover
"Winter Kill"
Low water table
pH and alkalinity/hardness: Acid rain (Midwest v. East
Coast)
Tumors from polluted waters: Water sample, fish samples,
investigation.
Environmental contaminants (Heavy
metals, PCBs, herbicides, pesticides, and fertilizers): Water and soil samples,
interview any local farmer or industry up stream.
Dinoflagellates (red, brown tides):
Water sample
NOTE: These problems can, in themselves, cause fish
kills. They can also be primary contributing factors, along with other factors
such as spawning, overcrowding, temperature extremes, low food supplies, which
can lead to disease from "secondary invaders".
12. Aquaculture
Important
Aquaculture Fish in the US
Salmons
North
Catfish
South
Tilapia
South, Some indoor North
Striped Bass
North and South
Tropical Fish Industry
South
Bait fish (Shiners)
North and South
12.1. Types of Systems
Net pens
Raceways
Ponds
Recirculating systems
12.2. Important Considerations on Environmental
Impact
12.2.1. Introduction of exotic diseases
Carp-at last count common carp harbor 170 disease
organisms, 138 of which have been introduced to the United States.
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