Diccionario acuicultura

INSTITUTO DEL MAR CAPITAN WILLIAMS
FUNDACION
ALMIRANTE
CARLOS
CONDELL

Diccionario En Inglés Acuicultura

A

Ablation

The process of removal of the eye in crustaceans. This is done to promote moulting and/or spawning. The eye stalk is a
source of GIH (Gonadotropin Inhibiting Hormone) and so it's removal, reduces or eliminates the signals which are
stopping gonadotropins (which start and control the maturation process) from being produced

ABS

See Acrylonitril Butadiene Styrene

Abscess

A localised area of dead tissue debris and white blood cells, surrounded by inflamed (and often infected) tissue.

Absolute

100%. See also nominal

Absolute pressure

Pressure measured on a gauge where zero on the gauge is equal to zero pressure i.e. a complete vacuum

Absorption

The process where gasses, fluids and other chemicals are taken in by the mucous membranes, blood vessels and skin.
Also refers to the transfer of nutrients across the cell membrane with required nutrients entering the cell and waste
matter being discharged.

Acanthopterygii

Superorder of fish including orders such as Beryciformes, Zeiformes, Syngnathiformes, Gasterosteiformes,
Scorpaeniformes, Perciformes, Pleuronectiformes and Tetraodontiformes. Largest of all superorders. Dorsal, pelvic and
pectoral fins usually have spiny rays, protractile mouth.

Acanthuroidei

Suborder of fish (part of the order Perciformes) including fish such as Surgeonfish (Acanthurua), Rabbitfish (Siganus)

Acclimation

DEPARTAMENTO DE INGLES: PABLO CORTEZ DIAZ – DAVID AMIGO HENRIQUEZ 2007

FUNDACION
ALMIRANTE
CARLOS The process by which fish become used to a given environment. For example fish which are usually held at one
CONDELL temperature, will take time to adjust to being held at a different temperature. During the acclimation period, fish may
be more susceptible to pathogens and may exhibit poor appetites and food conversion rates. Acclimation may be
required for changes in water quality, lighting regimes, husbandry practices etc. Bacteria used in biological filters also
require acclimation to changes in water quality, during which period they may perform their function at a reduced rate.

Acid

A compound that contains hydrogen and reacts with a base. pH<7.0

Acid Sulphate soils

Acid sulphate soils commonly occur in brackish water marsh lands, swamps and mangrove areas. The soils will often
contain iron pyrite and when exposed to air or well oxygenated water, sulphuric acid is formed which can reduce the
pond muds and water to pH of below 4.0 and make it unsuitable for fish culture. It can take many years of repeated
filling and draining of acid sulphate soil ponds to remove the acidity from the soil. Options are to try to manage the soil
with lime addition and bottom harrowing or by trying to maintain the pond full with water at all times. The oxidation of
the soils is much slower in water than in air due to the smaller amounts of oxygen available. Many such ponds are now
lined, as the management of such soils is very labour intensive and costly. The establishment of grass cover on the banks
of the ponds can also reduce the oxidation rate of the soils and reduce the acidification of the pond through run off.
Other suggestions are that in areas of acid sulphate soils, ponds should not be dug, but dams, banks and levees built
above the ground level using top soils from the inlet and outlet channel construction. the disadvantage of this is that the
ponds must be filled by pumping and are at increased risk from leakage and erosion of the banks.

Acidity

This refers to the amount of buffering that water requires to bring the pH to 7.0, neutral.

Acipenseriformes

Order of fish (of infraclass Chondrostei) which includes fish such as Sturgeon (Acipenser) and Paddlefish (Polydon)

Acrylonitril Butadiene Styrene

Type of plastic. Abbreviated as ABS. Often used for pressure pipes. Usually solvent welded. Can be directly solvent
welded to U-PVC. High impact strength. High abrasion resistance. Non toxic. Taint Free. Operating temperature range -
40oC to +80 oC. Not resistant to organic acids, ozone. Partially resistant to chlorinated water.

Sponsored link - Pisces Engineering for quality abs pipe and fittings

Activated Carbon

Available in granules (GAC) or powder. Granules are usually more practical for commercial use. Removes negative ions
o
from the water (such as ozone, chlorine, fluorides etc.) Once used it can be recharged by heating to 900 C. Not generally
financially viable for commercial systems. Sometimes used in small hatcheries, especially where mains water is being
used and chlorine and other chemicals added to the water must be removed.


FUNDACION
ALMIRANTE
CARLOS Activated Sludge
CONDELL

Process where nutrients are kept suspended in the water by pumping or more commonly aeration. A mixture of free
floating bacteria and algae utilise and convert the nutrients through processes such as nitrification and photosynthesis.
Fish are reared in the ponds, usually at stocking densities of below 15 kg/m3. The fish in such systems will often taste
muddy and must be kept in clean water for a period of up to one week prior to harvest. Such systems are used in some
countries for fish such as tilapia. They enable higher stocking densities than normal, static green water systems (ponds).
The systems are limited to areas where there is sufficient year round light and temperature for the bacteria and algae to
perform. The systems are more difficult to control and predict than more conventional water treatment systems such as
recirculation units, and due to the high B.O.D. in the water, the energy required to add oxygen to the water is often
higher than the pumping costs which would be associated with recirculating the water to a separate treatment system
where a lot of the B.O.D. could be removed from the system.

Acute

A rapidly developing disease or process. Used to describe a disease outbreak where the stock are rapidly affected, often
dying without showing many symptoms. The term acute is not used to describe how severe a condition is, only the
speed at which it is developing. See also Chronic

Acute catarrhal enteritis

Another name for Infectious Pancreatic Necrosis (IPN)

Acute toxicity

Causing death within 96 hours pr less after a brief exposure period.

Ad libitum

To the limit. In respect of feeding this term is used to describe when the fish are fed freely until they reach satiation
point

Adipose tissue

Body tissue which is able to store high amounts of neutral fats. For example the adipose fin found in Salmonids and
some other species.

Adjuvant

A compound added to a vaccine to increase the immune response.

Adrenal Glands

Glands responsible for production of some hormones. The inner section of the adrenal gland produces adrenaline and
non-adrenaline. The outer part of gland secretes small amount of sex hormones (androgens and oestrogens) as well as
corticosteroids. Located about the kidney.


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ALMIRANTE
CARLOS Adsorb
CONDELL
Formation of a thin film on a surface

Aeration

The process where air and water are mixed. This may be in the form of bubbling air into water, or letting water fall
through the air. The process is usually used to increase the oxygen concentrations in water. The efficiency of aeration
equipment is determined by the amount of surface area interface between the water and air and the energy required to
produce that interface. A summary of the devices used and their corresponding efficiencies is shown in the table. It is
also used for other processes such as degassing, mixing and destratification.

Aerobic

The name given to a process which requires oxygen. For example aerobic bacteria, require oxygen to live. The opposite
of aerobic is anaerobic.

Aeromonas salmonicida

Gram negative bacteria that is the causative agent of the disease Furunculosis.

Aetiology

The cause of a situation or problem.

Agitator

A device which causes turbulence such as a paddlewheel or other device with rotating blades / parts.

Air

Combination of gasses making up the earth's atmosphere Typically 78% nitrogen , 21% oxygen, 0.9% argon, 0.03%
carbon dioxide with the remainder being a mixture of trace gasses plus water vapour.

Air Cooling

This process uses towers or columns, packed with media to break up the water as it falls. The water forms a thin film on
the media as it runs across it. If air is blown through the tower, it will cool the water as it passes across it. Cooling is
achieved in two ways - Evaporative cooling, where heat is lost into the air as the water evaporates (the same way that if
you put a solvent on your hand it feels cool as it evaporates), and conductive cooling where, if the air is cooler than the
water, heat will pass directly into it. Trickle Biological Filters can also be used as cooling towers if air is blown through
them. Air cooling can be very efficient, depending on the relative water and air temperatures.

Air Curtain

see Bubble Curtain


FUNDACION
ALMIRANTE
CARLOS Air Dryers
CONDELL
Air dryers use either a heat source or a chemical (such as the silicon pouches, that are found in packaging for items like
shoes to protect the products from rotting) to remove the moisture from air. They are mainly used to dry air before it
enters machinery such as an ozone generator. Air dryers usually either use refrigeration techniques or chemicals which
absorb the moisture and require replacing. For large application, refrigeration is usually the choice because of the cost
and management time of the chemical replacement option..

Air - Friction loss

See Friction Loss - Air

Air Lift

see Airlift

Air Lock

Air locks are pockets of air that form in pipes, if there is nowhere for the air to escape to. Bubbles often get drawn into
pipes as a result of vortexes at inlet points, or if the pipe entrance is not fully submerged. Bubbles can also form in pipes
as a result of gas supersaturation. If the pipe travels in an upward slope at some stage, and then slopes down again,
there is a risk that the air will collect a the highest point in the pipe. This can then restrict or even stop the flow of water
through the pipe. The solution is to either ensure that pipes always slope downwards, an air vent, or air purger at the
point where the air collects in the pipe.

Air Purger

A device used to expel air from piped water systems. Typically the device has an internal float. As the air builds up inside
it, the float falls, opening a valve at the top. The water pressure in the pipe pushes the air out. As the device fills back up
with water again, the float rises and the valve shuts.

Air stripping

The removal of dissolved gasses from water by a mechanical means which involves the movement of air across water.
The stripping of carbon dioxide is relatively easily achieved, stripping of supersaturated gasses is easy down to a
saturation level of 103-105%, after this it becomes increasingly difficult, and requires increasing amounts of energy to
remove the gas. Vacuum systems can help achieve 100% or below. Stripping of ammonia from water is only cost
effective at pH levels of higher than 10.0 and therefore not relevant to fish farming. A small amount of ammonia can be
stripped by air at lower pH levels, but the amount is usually insignificant when the total ammonia production is taken
account of. See also degassing

Airlift

A contained column of bubbles and water used to pump, provide flow or current. The air lift uses a bubble source
(usually a diffuser) to supply bubbles to the bottom of a column (often a pipe or similar). As the bubbles mix with the
water, they create a mix which is less dense than water alone. Because of this, gravity has less effect on the water and it
rises higher than the water around the column, which has no air in it, and is therefore denser. An opening at the top of
the column allows the water/air mixture to escape. The head and amount of water that an air lift can pump is a function


FUNDACION
ALMIRANTE
CARLOS of the ratio of air to water, the amount of air pumped in, the depth of the diffuser, the ratio of the submerged part of
CONDELL the column to the part of the column that protrudes form the water and the diameter of the pipe. Air lifts cease to work
so well once the bubble to water ration becomes so high that the bubbles begin to join together and form much larger
slugs of air. Airlifts are also sometimes used on cage farms, taking the water and any feed / faeces in it, from the bottom
of the cage to the top, so that the farmer can see if his stock are eating all their feed. They have also been used in cages
as fish pumps.

Alevin

The life stage of a fish when the yolk sac is still present. Also called sac fry.

Algae

Algae are simple celled plants and (like all plants) contain chlorophyll. This traps energy from the sun and uses that
energy to convert nutrients and carbon dioxide (which are dissolved in the water) into growth. When grown in a
hatchery, the growing and multiplying algal cells are collectively known as a culture. The main form of algae that is of
interest to aquaculture is collectively known as unicellular. These consist of free floating cells of algae which make the
water look green or brown, depending on the colour of the algae. There are many different types of unicellular algae but
only a few are nutritionally suited for good growth. These are divided into two types; flagellates, which can swim by the
action of one or more flagellae and diatoms, which have an outer shell made of silica. Some of the more commonly
grown species and their sizes are listed in the table. Other forms include filamentous, which are strand like colonies of
algae, which usually form dense mats or clumps, and blue-green algae, more commonly referred to as cyanobacteria. As
well as being grown for food for the fish and also as food for zooplankton, which are then fed to the fish, algae impacts
on aquaculture in other ways. These include algal blooms, taints, oxygen depletion, supersaturation and fouling.

Algae control

Algae can be controlled by either chemical (see herbicides), mechanical or biological methods. The mechanical methods
generally involve light elimination (by floating black polythene or black bubble wrap). Filamentous algae can be removed
by netting or dragging out. Care should be taken when using light elimination as the dying algae can result in high
oxygen demands and lead to fish kills. Biological methods involve the used of species such as silver carp
(Hypothalmichthys molitrix) which eat the algae.

Algal bloom

An algal bloom occurs when light, temperature, water currents and water quality (especially the amount and type of
nutrients in the water) combine to form perfect growing conditions for a species of algae. The algae multiply very fast
and depending on their colour, the water turns green, blue, red or brown. Algal cell counts in the water generally exceed
5 million per litre. The algae can cause damage to the fish by suffocation as it takes all the available oxygen out of the
water for the purpose of photosynthesis or by causing the gills to become clogged with algae and function poorly.
Certain species of algae (e.g. the blue green algae's) can produce a toxin which is poisonous to fish and can cause
mortalities. Algal blooms are particularly common in areas where there is a nutrient build up in areas of poor water
exchange, such as beneath cages or in static ponds where fertiliser and/or artificial diets are used. The only method to
ensure that algal blooms do not occur is to remove the nutrient source. Once all the available nutrients have been used
up, the algae mass reaches a critical point where it can no longer sustain itself and dies off (often very quickly). In static
ponds, the algae cell mass is retained in the pond and is broken down, releasing the stored nutrients. This cycling of
nutrients leads to a recurrence of the bloom (although sometimes with different algae species) at a later date. Blooms
typically occur in the Spring, when the rising water temperatures, increased daylength and light intensity enable algae to
multiply and make use of any available nutrients that have built up in the water during the Autumn and Winter (either as
a result of breakdown of previous algae blooms or new nutrients entering the system). After the Spring, when all the
nutrients are used up, the algal mass dies off and is broken down into it's constituent nutrients and made available
again. This often causes a second bloom in the late summer / early Autumn. The term "red tide" is often used to
describe blooms of certain species of algae which contain red or orange pigments. these pigments can give the bloom a
vivid red / orange colour, especially when the bloom dies off and the green chlorophyll that masks the pigment is
reduced and the colour of the pigment shows through.


FUNDACION
ALMIRANTE
CARLOS Algal Scum
CONDELL
A floating mass of filamentous and/or unicellular algae which can restrict the penetration of light to the water column. It
can be removed either physically, by mechanical filtration or by biological filtration which will remove the nutrients that
it depends on for growth.

Alginates

Derivative substance of seaweed, used sometimes as a binder in feed formulation.

Alien

A non-native species for the area

Aliquot

A single dosage of a drug or a chemical which is in solution.

Alkaline

A compound which has an excess of hydroxide ions. A substance which combines with acid and neutralises it, forming a
salt. pH >7.0

Alkalinity

Alkalinity is a measure of the concentration of bases in the water and the capacity of the water to accept acidity (I.e. it's
buffering capacity). Alkalinity is usually measured as either mg/l (milligrams per litre) CaCO3 (Calcium Carbonate) or meq
(milli-equivalents). 1 meq = 50 mg/l CaCO3. The ideal range of alkalinity for fish farming is 20 - 300mg/l. Below 20mg/l
the water will have a very low buffering capacity, and any acids that are washed into the water (for example after heavy
rain has soaked through peat), will cause a big fall in pH. Such fluctuations of pH are harmful to fish. Water with low
alkalinity can be treated with lime. High alkalinity levels can sometimes lead to a condition in the fish called
nephrocalcinosis.

Allele

A gene (in a diploid fish) is supplied with a single allele from each of the parent fish. For example the gene may be
responsible for the expression of eye colour, with one allele giving a blue colour and the other a brown colour. One
allele becomes more dominant over the other (which is termed recessive) and this denoted the expression of the gene.
In the case of the eye colour, the blue allele may be dominant in which case the gene will make the eyes blue.

Altitude

Altitude has a bearing on the amount of dissolved gas (such as oxygen) that water is capable of holding. At higher
altitudes the water contains less oxygen than at lower altitudes.

Aluminium

Aluminium is used in many farms as screens, hatching trays and also as a construction material for some items of plant
such as filters etc. The material is generally long lasting, but use in very acid waters should be avoided as this can lead to
the build up of aluminium in the water, which is toxic to fish. It's use in seawater systems should also be avoided as the
seawater oxidises the aluminium. Where aluminium is not suitable, 304 or 316 stainless steel should be used. In some


FUNDACION
ALMIRANTE
CARLOS areas where there is an abundance of aluminium in the ground, and acidic waters prevail, dissolved aluminium can
CONDELL cause severe problems to fish. These problems most often occur where there is run-off from industry/mining activities

Ambient

The normal (natural) environmental conditions.

Amino acid

The building block of proteins. The quality of a specific protein source is down to it's make up of different amino acids

Ammonia

The unionised form of ammonia (although sometimes used to express the total ammonia (i.e. unionised and ionised).
Symbol NH3. Toxic to fish. See unionised ammonia for more details on toxicity. The amount of ammonia produced by
the fish is approximately 0.03 x feed (for commercial diets). Therefore for every 1000g of feed that is fed 30g of total
ammonia is produced. This is excreted by the fish in the urine and across the gills. The ammonia production will vary
throughout the day with the 0.03 value being the average. In systems where the feeding regimes are confined to a few
large feeds over a short period, the maximum ammonia production at any time may be twice this amount, with
corresponding periods of very low ammonia output.

Ammonia stripping

see Air stripping

Ammonia-nitrogen

Ammonia-nitrogen refers to the part of ammonia that is made up of nitrogen. The chemical symbol for ammonia is NH4.
This means that it consists of one Nitrogen atom (N) and four Hydrogen atoms (H). The atomic weight of Nitrogen is 7,
and that of Hydrogen is 1. Therefore a molecule of ammonia has a total atomic weight of 11 (7+1+1+1+1). Nitrogen
therefore comprises 63.6% of the total weight of ammonia (7 / 11 x 100%). When ammonia concentrations are referred
to as ammonia-nitrogen, they are only referring to the nitrogen part of the compound, which is only 63.6% of the
ammonia concentration. The term is used in aquaculture, as it is the nitrogen part of ammonia, which is used to
calculate how much nitrite and nitrate will be produced, following biological filtration of the ammonia. To convert
ammonia to ammonia-nitrogen, multiply by 0.636. To convert ammonia-nitrogen to ammonia, multiply by 1.57. See also
ammonia

Ammonium

The ionised form of ammonia, symbol NH4. Non toxic to fish. See also Unionised Ammonia, Ammonia nitrogen
Can be used in some forms as a herbicide against Elodia sp. (common name Canadian Pond Weed). Applied at 225kg / ha
to dry pond as a preventative measure.

Ammonium Chloride

NaCl. Chemical often used to start biofilters.

Ammonium Nitrate


FUNDACION
ALMIRANTE
CARLOS NaNO3 Chemical used in starting biofiltration system, especially where there is denitrification in the system which
CONDELL requires the nitrate source.

Amorphous

Without any fixed shape

Amplitude

Term used to describe the height of a wave. The measurement is taken from the crest to the mean half way point to the
trough.

Anabantoidei

Suborder of fish (part of the order Perciformes) including fish such as Gourami (Osphronemus). Able to breath air
through specially adapted respiratory organs

Anadromous

A fish which spawns in freshwater and lives most of it's life at sea e.g. Atlantic Salmon (Salmo salar)

Anaemia

A reduction in the number of red blood cells. Limits the ability of the blood to carry oxygen and other nutrients around
the body, and excretion of waste products (such as carbon dioxide). the reduction in the red blood cells results in the
starvation of tissues of oxygen and other nutrients. Anaemic fish typically show pale gills, due to the reduced number of
red blood cells.

Anaerobic

The term used to describe a biological process which occurs without the need for oxygen. Often used to describe types
of bacteria and bacteriological processes such as denitrification. Anaerobic bacterial activity can be seen in the bottom
muds of ponds, lakes etc., where organic matter is broken down without the availability of oxygen. The thin crust of the
surface muds, prevents the oxygen from penetrating through to lower layers. Such anaerobic breakdown in muds can
result in the production of hydrogen sulphide, which can be toxic to fish.

Anaesthetic

An agent (usually chemical) which can cause partial or complete loss of sensory awareness, ability to feel pain and ability
to carry out muscle movements. Not all anaesthetics achieve the full range of effects (e.g. hypnotics such as
metomidate and etomidate, which do not block pain well), and a number of the common drugs which have pain-
relieving (analgesic) ability may stimulate marked transient stress via their
depression of the subject's central nervous system.

Anaesthetics are sometimes used in aquaculture for the following purposes ; transportation, prior to slaughter,
broodstock handling/injections etc., administration of vaccines/drugs, tagging. If anaesthetics are to be used for
stripping broodstock, the fish must be rinsed and dried before stripping as any anaesthetic can affect sperm motility and
egg quality. A list of the more common anaesthetics used in fish culture are given below. Before using then one should
check the following: 1. If they are licensed for use in your country, 2. Test a few fish first as the speed and depth of
anaesthesia varies fish size, species and water quality, 3. Special licences may be required for the use of anaesthetics,
especially if they are to be injected, 4. Workers are protected from the effects. See also Sedation, Carbon dioxide

Analogue (1of 2) - Signal.


FUNDACION
ALMIRANTE
CARLOS A function which can give a proportional state. Unlike a digital signal which can only instruct a device to be on or off, an
CONDELL analogue instruction can tell a device to be at any number of states between on and off. For example a digital signal can
only turn a pump on or off., whereas an analogue signal can not only turn the pump on or off, but can also regulate the
speed of the pump (e.g. 20%, 30%, 40% of full operational capacity etc). Analogue signals are increasingly being used for
dosing functions using the feedback from a probe. For example an output from oxygen probe may give a tell a controller
that the oxygen concentration is changing in a tank. The controller will send out an analogue signal to partially open or
close the oxygen supply valve, in an effort to maintain a steady oxygen concentration at all times. This is more
preferable than having just an open or closed valve (as would be the result from a digital signal), as this can give rise to
peaks and troughs of oxygen which can stress the fish. Analogue outputs come in a variety of signal types, all of which
give a band of operation proportional to the controller output requirements e.g. 4-20mA band will give a value
anywhere between 4 and 20mA. Other common analogue outputs are 0-20mA, 0-1volt and 0-100mV.

Analogue (2 of 2)

A copy of....for example some artificially produced hormones are analogues of the naturally occurring hormones.

Anchor

Device dropped onto the sea bed to secure a floating vessel. The best type and size of anchor for a given situation
depends on the sea bed type and the angle of the anchor chain / rope. See also chain, cable and rope

Anchor Ice

The term given to a specific type of ice which forms under the water. The phenomenon occurs when water
temperatures are almost 00C (32oF) and air temperatures are below freezing (usually < -4oC). Bubbles of very cold air
are drawn into the water through water splashing (at weirs or pipe outlets) and as the air in the bubble is below
freezing, the bubbles become coated with ice. This reduces their buoyancy and causes the icy particles to travel in the
water column. The ice particles "stick" to each other in the water and also "stick" to the surfaces of pipes etc. Once there
is a coating of ice on a surface. Other ice particles readily stick and the coating builds up. Anchor ice can cause particular
problems in long pipe runs, where the bore of the pipe is gradually reduced by the thickening ice layer, and also on
screens (where maters are often worsened by the fact that many screen designs cause air to be drawn through with the
water.).

Androgen

A substance with a male hormone activity such as Testosterone

Androgenesis

This process involves the irradiation of the egg before fertilisation. This means that only the male parent contributes to
the genetic make up of the offspring. This process then results in the offspring being all male, a desirable attribute in
some species. It also allows cryopreserved sperm to be used to fertilise eggs. In this way a library of sperm from proven
broodstock could be held in storage and used in the future to create off-spring with the same characteristics as the
original broodstock which may have died years ago.

Androgenote

Offspring produced through androgenesis

Entry submitted by Shmuel Rothbard


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ALMIRANTE
CARLOS
CONDELL
Anguilliformes

Order of fish (part of the superorder Elopomorpha) which includes fish such as European eel (Anguilla anguilla), Moray
eel (Muraena). Absence of pelvic fins, reduced pectorals and elongated body.

Anion

A negative ion

Annulus

A growth ring that is found on scales, opercula and in otoliths. Like rings on a tree. Counting of the rings can assist in
determining the age of a fish and the number of times it has spawned.

Annunciators

Device which plays a message (e.g. as found in an alarm panel)

Anoxia

Oxygen deficiency in the blood cells or tissues of the body to such an extent that it causes physiological and/or
psychological disturbance

Anoxic

Deficient in oxygen. Anoxic areas are sometimes found a few inches down in silt and muds, where organic matter has
settles and has been broken down the bacteria. The upper layers of silt act as a barrier against oxygen transfer to the
lower layers and so the muds become devoid of oxygen. Such situations can often occur in the bottom of heavily stocked
ponds with a poor water turnover rate or beneath cages. The build up of such anoxic areas can lead to the production,
and release into the water of Hydrogen Sulphide which is toxic to fish. See also Azoic zone

Anterior

Towards the front (opposite of posterior)

Anthelmintic

A chemical which destroys or expels parasitic worms

Antibiotics

Chemicals used to treat bacterial infections. There are many different antibiotics available. Most are administered with
the feed, although some valuable fish may be injected. Antibiotics are usually given under the supervision of a veterinary
surgeon, and care should be taken to follow the complete course through, to prevent the build up of resistance in the
bacteria. If antibiotics are to be incorporated with the feed, this is most effectively done at the feed mill where more
controlled mixing can be carried out. If carried out on site, a cement mixer is often used to mix the feed with the dry
antibiotic, before finally adding a spray of vegetable or fish oil to bind the antibiotic to the pellet. The more common
antibiotics and their dose rates are listed below. Care should be taken to ensure the following when using antibiotics 1.
If they are licensed for use in your country, 2. Special licences may be required for their use or on farm mixing, 3. Special


FUNDACION
ALMIRANTE
CARLOS licences may be required for their injection 4. Workers are protected from contact as much as possible, 5 Proper
CONDELL Withdrawal periods are observed. See also Vaccines

Antibody

A protein which is produced by the fish, in an effort to neutralise the effects of a foreign material (such as a pathogen)
entering the body

Antifouling

Antifoulants are chemicals that are coated on to surfaces to prevent algae, seaweeds and marine organisms from
attaching to the surface. Some chemicals that have been used in the past and some that are still used, create conflicts
with environmentalists, ecologists and shellfish / crustacean farmers and fishermen. This is because the chemicals leach
into the water and affect the wild stocks.

Antigen

A substance which is not normally found in the body, but which, if added to the body, will produce an immune response.

Anti-oxidant

A chemical which is added to feedstuffs to stop fats breaking down. Vitamin E is a commonly used anti-oxidant in fish
feeds.

Antisepsis

The prevention of infection by administration of chemical agents (biocidal or biostatic) to damaged tissue.

Aquathol

Herbicide used to control submerged macrophytes. Applied at 18.8 litres / ha. See Herbicide

Aquifer

A formation of rock that holds a reservoir of ground water

Artemia

Proper name for the crustacean, the brine shrimp. Harvested from certain areas of the world (such as the Great Salt Lake
in the USA). The shrimps lay cysts which are packed dry and have a long shelf life. Contact with water activates the cyst
and the development and hatching process begins. The artemia are used to feed marine fish larvae and some freshwater
species (such as cyprinids). The nutritional make up of the artemia can be boosted by the addition of several
commercially available compounds. See also Live Feed

Artesian Well

A well where although the water table is below the ground level, geological pressures force the water up to the surface
when a borehole is sunk into the water bearing rock. (which underlies an impervious rock formation.). Ground water can
therefore be obtained without the need for pumping.

Ascites

Fluid accumulation in the peritoneal cavity.


FUNDACION
ALMIRANTE
CARLOS Ascorbic Acid
CONDELL

Vitamin C. Water soluble vitamin important for the construction of connective tissues. A lack of vitamin C can cause
abnormalities of the spine and a reduction in the ability of the body to heal wounds. Other deficiency symptoms may be
seen, depending on species

Asexual

Reproduction without eggs and sperm e.g. bacteria are asexual as they multiply by dividing.

Asphyxia

Suffocation as a result of too little oxygen or too much carbon dioxide in the blood. Can be brought on by high ambient
carbon dioxide concentrations which can restrict the ability of he fish to excrete carbon dioxide.

Aspirator

A device for aeration and water flow creation. The device consists of a float(s), a motor, a hollow shaft and a propeller.
The hollow tube is open to the air at one end and submerged at the other. The angle which the tube is mounted at is
adjustable. A motor turns the propeller and creates a directed current of water. The alignment of the end of the shaft
and the propeller are such that air is drawn down the shaft and mixed in with the propelled water. See aeration for
comparison of efficiency with other devices.

Assimilation

The conversion of digested food to body tissues and fluids.

Astaxanthin

Astaxanthin is a naturally occurring chemical in the family of carotenoids. It is the principal pigment that gives salmonids
their pink colour. It is produced for addition into fish feed in the latter part of the production cycle to ensure a good
flesh colour. Astaxanthin has largely replaced the use of Canthaxanthin as the main pigment used in salmonid diets, due
to adverse publicity about the latter. Pigment levels are typically in the region of 50 - 60 mg/kg feed. Modern feeds, with
higher energy levels and low FCRs mean that the pigment level often has to be increased, especially if the fish are
supplied to Japan or the French smokehouse markets which both demand a very deep colour. Much of the astaxanthin
used in fish diets is extracted from a yeast (Phaffia rhodozyma) which contains over 0.1% astaxanthin as a dry weight.

Asymptomatic carrier

An animal that shows no signs or symptoms of a disease but harbours it and is capable of transmitting it to others. Such
animals can be responsible for a disease, previously thought to be eradicated from a farm appearing again after a long
period. E.g. A wild fish in the water course supplying the farm can become infected by the pathogen, but as it lives in a
natural, stress free state it does not manifest itself as a disease. This can also be apparent in systems where different
species are held, where one species is largely unaffected by the pathogen but may harbour it, the other species may be
susceptible to it.

Atheriniformes

Order of fish (part of the superorder Atherinomorpha) includes fish such as Garfish (Belone) and Flying Fish (Exocoetus)

Atherinomorpha


FUNDACION
ALMIRANTE
CARLOS Superorder of fish including the order Atheriniformes. Generally small surface feeding fish with protractile upper jaw.
CONDELL
Atmospheric pressure

The pressure exerted by the weight of air above the measured point at any point on the surface of the earth.

Atrophy

Damage and wastage of tissue due to nutritional deficiency, disuse or nerve damage.

Atypical

Not usual in a normal condition; opposite of typical

Auger

Device for lifting materials. Uses a rotating, enclosed screw which lifts the material as a result of the screwing action.
Used with some success for lifting fish and water together. Not as flexible as a fish pump in that the angle of lift is
restricted and means that the auger sometimes takes up too much space. One advantage is that it can gently handle
very large fish (in excess of 5kg), which most other types of fish transportation systems will not. Also used for conveying
feed to and from hoppers.

Autodialler

An electronic device that is included into alarm panels to automatically dial a series of telephone numbers when an
alarm condition exists. Some are linked into annunciators, which play a taped message.

Autotrophic

Organisms not requiring carbon in their diet. Such organisms are able to grow on inorganic salts only.

Available oxygen

see oxygen

Axenic

Denotes the absence of bacteria; opposite - Xenix

Axial Flow pumps

See low head pumps

Axilla

The region immediately behind the base of the pectoral fin

Azoic Zone

The area of sea/pond bed directly beneath a cage farm. Large downward flow of nutrients (food and faeces), very little
life. May vary according to currents, tides etc.


FUNDACION
ALMIRANTE
CARLOS
CONDELL

B

B.O.D.

Biochemical oxygen demand. A measure of the organic substances/matter (and also chemicals which may use oxygen)
present in the water. Measured in terms of the oxygen requirements of the organic matter in the water in units of mg/l.
The oxygen concentration of a sample of water is taken before sealing it in a dark container, with no entrapped air,
where it is held for five days at 20oC. The oxygen concentration is then taken at the end of the five day period, and the
B.O.D. is the value of the oxygen at the start minus the oxygen at the end. For samples where the B.O.D. is thought to be
higher than 7mg/l, the sample should be diluted with distilled water to avoid a false result as all the oxygen will be used
up before all the organic matter is used up. Often several samples are taken at various dilutions to ensure a result. BOD
is sometimes written BOD5 which indicates that the BOD was measured over a 5 day period. Some users may use
different time periods, in which case the number of days is usually denoted (e.g. BOD3 = 3 days) but the 5 day period is
the usual one used. The initials BOD may also be suffixed by "ATU" i.e. BOD5ATU. This indicates that chemicals have
been added to the water to inhibit the oxidation of ammonia (nitrification). The amount of B.O.D. produced by fish is
dependant on the quality of feed and the efficiency with which it is fed and converted. Typical values for high quality
feed, which is fed well and converted well are in the region of 330 - 480 grams of B.O.D. for every kilogram of feed given.

Bacillariophyta

Also known as diatoms. Free floating, microscopic unicellular algae surrounded by a cell wall which is highly impregnated
with silica (SiO2 :nH2O). Around 10,000 different species, which comprise approximately 20% of all primary production.
Typically brown in colour (as a result of their containing the carotenoid - fucoxanthin). Impact in two ways in
aquaculture

1. Some species (such as Skeletonema costatum (6 microns diameter), Chaetoceros calcitrans (2.5 microns diameter),
and Thalassiosira pseudonana (5.5 microns diameter)) are cultured for feeding to rotifers and other zooplankton, which
are then fed in the larval rearing stages of some species.

2. Some of the larger species of diatoms in supply waters can also be responsible for damage to small fish, especially in
the gill lamellae. The silicon outer shell of some species is very sharp, and when water is drawn across the gill for
respiration, the diatoms can scratch and cut the gills. In extreme cases this can lead to mortalities. This can sometimes
be the cause of apparent respiratory problems in spring and summer, when the fish are producing a lot of gill mucus in
response, without any apparent pathogen or water chemistry problem. This problem is often mistreated as bacterial gill
disease, with limited success. Mechanical filtration of water can remove many of the diatoms and prevent the problem.

Back flushing

The general term used to describe the process where filters are cleaned. Also sometimes called back washing. The
washing can be either from flows in filters a being reversed, filter beds being agitated by air or some mechanical means,
or the jetting of water/air onto screens to clean them. Although many of these operations are not technically correct
under this heading, they all tend to be grouped into the back washing/flushing term

Back Washing


FUNDACION
ALMIRANTE
CARLOS see back flushing
CONDELL
Bacteria

Usually single celled microscopic organism about 1 micron in diameter. See biological filtration, bacterial diseases.

Bacterial diseases

Diseases caused by bacteria. Bacterial diseases fall into two categories, those that affect specific areas of the body
(localised) and those that affect the entire body (systemic). External bacterial diseases usually respond well to chemicals
such as Chloramin T and the quaternary ammonium compounds. Systemic infections (such as Enteric Red Mouth
Yersinia ruckeri) usually require antibiotic treatment. Many pathogenic bacteria are present in the body tissues and
environment all the time, a trigger such as stress is often responsible for lowering the fishes defence mechanism (see
Corticosteroid) allowing the bacteria to multiply.

Bacterial Gill Disease

A condition where the gill lamellae of the fish are infested by colonies of filamentous bacteria which cause the gills to
produce excessive amounts of mucous and stick together. Both of these have the result of limiting the transfer of gasses
across the gill surface and lead to respiratory stress. The disease, which in Salmonids and pond fish is usually caused by
the bacteria Flavobacterium branchiophila although in warm water fish, the bacteria Cytophaga (formerly Flexibacter)
columnaris is often the culprit. Small fish tend to be more susceptible to bacterial gill disease (BGD) and infections often
follow periods of stress. Fish can often be seen with their opercula sticking out due to the excess mucous build up of the
gills, and breathing seems rapid. Cause of most BGD outbreaks in salmonids. Infections are often reported following
exposure to high ammonia, but there can also be many other non-specific causes such as high suspended solids.

Treatment is usually by the use of quaternary ammonium compounds such as Benzalkonium Chloride at 1-2ppm (active
ingredient) and are often followed by a treatment of Chloramine T or a similar chemical. The rational behind this is that
the latter is better at killing the bacteria, but cannot effectively penetrate the thick mucous layers that have built up. In
addition to the antibacterial effects, the quaternary ammonium compounds have the added benefit of "washing" most
of the excess mucous off the gills). Care should be taken using quaternary ammonium compounds in soft water.

When BGD, caused by C. columnaris, occurs in pondfish, external treatments for the control of columnaris disease are
used. Diquat at 8.5ppm, Copper sulphate at 0.5 ppm, or Potassium permanganate at 2 to 4 ppm can be added to ponds
and allowed to dissipate over time. If copper sulfate or potassium permanganate are used, treatment levels may have to
be adjusted, depending on water chemistry. In soft water, 0.5 ppm copper sulfate may be toxic; and if pondwater is high
in organic material, potassium permanganate concentrations must be increased.

Bacterial kidney disease

Bacterial kidney disease (BKD) is a systemic infection, caused by the bacteria Renibacterium salmiarum that commonly
causes high mortality in populations of both wild and farmed salmonids. First recognised in wild salmon from the river
Dee in Scotland in1933. As a result of this it is sometimes called Dee disease. Brook trout (Salvelinus fontinalis) would
appear to to be the most susceptible species followed by Brown trout (Salmo trutta) and Atlantic salmon (Salmo salar).
Causes most problems in fish which have been infected and are transferred to sea, due to the damage caused to the
kidney, which makes the fish unable to cope with the changes in the osmoregulatory system. This can lead to rapid
mortality. In freshwater the disease is typically chronic, but acute outbreaks sometimes occur, especially at
temperatures between 13 - 18°C. Due to the grey/white lesions that occur in the kidneys, spleen, and liver; BKD has also
been called white boil disease. External blisters in the skin, exophthalmia and small ulcers are typical. Often associated
with infections of diphyllobothrium. Gram positive bacteria, resistant to most antibiotics. Some success has been found
with Erythromycin


FUNDACION
ALMIRANTE
CARLOS Bacterin
CONDELL
A vaccine that is prepared from bacteria which have been inactivated by a heat or chemical treatment which does not
affect the cell antigens.

Bacteriocide

A chemical that kills bacteria

Bacteriostat

A chemical which inhibits the multiplication of bacteria and so enables the animal to cope more easily with the infection.

Baffle

A device, such as a plate or screen, installed to alter / reduce the velocity of water.

Bag Filters

Enclosed vessels designed for the removal of fine solids. A mesh, or felt bag is inserted in the vessel and water passes
from the inside to the outside. Filtration to less than 1 micron is possible with such filters although the cost of
replacement of the bags, and the cost of pumping (due to the headloss) is high. Useful for applications such as marine
hatcheries where very finely filtered water, in relatively small volumes is required. Bags may be dried out and used
several times, but there is always some residue left in the bag, which limits it's performance the next time round.
Depending on solids loadings and how much the bag gets clogged before it is cleaned, one can typically get three to six
uses from a bag , before it needs replacing.

Bagging

See Net Bagging

Barbel

A fleshy protrusion from the body, usually the mouth. Used by some fish to feel for food.

Barometric pressure

The same as atmospheric pressure. The force exerted by the atmosphere at any point. Most commonly expressed in
mmHg (millimetres of mercury) from the original equipment used to measure this which consisted of a tube of mercury
which rose or fell with changes in the pressure.

Barr marks

Vertical strips of colour on fish

Base

A chemical that has the ability to react with acids to form salts

Base metabolism

The minimum amount of energy required for the body to perform it's vital life functions i.e. excludes the energy
required for growth, activity etc.

Bath Treatments


FUNDACION
ALMIRANTE
CARLOS Chemical treatments of the fish, where the flow to the tank/pond is closed off or a tarpaulin is pulled around a cage. The
CONDELL chemical is added to the water, and the tank remains without any inflow or outflow for a pre-determined period, (often
an hour or so). Oxygenation or aeration is usually applied to a tank, whilst the water flow is turned off. The main
advantage of bath treatments is that they are easy to administer, they require no special equipment (such as dosing
pumps) and they generally use less chemicals than flush treatments.

Batrachoidiformes

Order of fish (part of the superorder Paracanthopterygii) includes fish such as Toadfish (Opsanus)

Beer's Law

The light passing through a coloured liquid decreases as the concentration of the substance dissolved in the liquid
increases. See also spectrophotometer.

Bends

Gas bubbles formed in the blood stream and tissues. See gas bubble disease

Benign

Not a risk to health.

Benthos

Collective term for organisms living in or on the sediments.

Benzalkonium Chloride

Sometimes referred to as Roccal, or B.A.C.. A quaternary ammonium compound used as per Hyamine 3500. Typically
supplied as a 10,20 or 30% solution, so care should be taken when using the chemical to ensure that the right amount of
active ingredient is used. Dose rates are typically 1ppm in poorly buffered water to 4ppm in well buffered water for a
period of one hour.

Benzocaine

A commonly used and widely available anaesthetic (ethyl-4-amino-benzoate). Administered at a dose rate of 50mg/l,
with the benzocaine first being dissolved in a small amount of alcohol or acetone before adding to the water.

Beryciformes

Order of fish (part of the superorder Acanthopterygii) includes fish such as squirrelfish (Beryx)

Bicarbonate

A salt of carbonic acid (i.e.HCO3). Having an HCO3 group, such as sodium bicarbonate (NaHCO3)

Bile

Alkaline liquid produced by the liver and stored in the gall bladder. Assists in the digestion and absorption of fats by the
action of bile salts, which chemically reduce fatty substances an decrease the surface tension of fat droplets so that they
are broken down.

Binder


FUNDACION
ALMIRANTE
CARLOS A substance used in the production of feeds to help the pellet stay together. Such substances include alginates and
CONDELL molasses.

Biochemical Oxygen Demand

See BOD

Biocide

A chemical which will indiscriminately kill any life in the water. In addition to chemicals whish are simply toxic to all life
for (example derris), this also includes chemicals (such as cyanide) which take all the oxygen out of the water.

Biofilter

see Biological filtration

Biological Filtration

The growing of bacteria colonies on a media surface over which the water passes to remove nutrients form the water.
Used as an essential part of most water recirculation systems and also sometimes for treatment of outlet water from a
farm to reduce waste loadings entering a river or stream to comply with regulations. Although the process of biological
filtration handles many different types of waste, the main ones that we are concerned with in aquaculture are BOD,
ammonia and nitrite. The BOD is oxidised by a group of bacteria called heterotrophic bacteria. These are fast growing,
dominant bacteria which often comprise a high percentage of the "sewage fungus" found in tanks, pipes, sumps,
channels etc. The ammonia is converted to nitrite by a group of bacteria called nitrosomonas bacteria, the nitrite is
converted to relatively harmless nitrate by a group of bacteria called nitrobacter. The process of conversion of ammonia
to nitrite and then nitrate is commonly known ad nitrification. Because the heterotrophic bacteria are more dominant
than the nitrification bacteria, the fist 25% of biofilters often comprises a high percentage of heterotrophic bacteria and
a small percentage of nitrification bacteria, the rest of the filter being mainly nitrification bacteria. Because of the ratios
of BOD to ammonia in fish waste, and the way that a biological filter functions, it is generally held that if ammonia levels
are kept in check by biological filtration, then the BOD will also be kept in check. The ammonia is therefore used as the
main indicator that full biological filtration is taking place. There are three main types of biological filter ; trickle,
submerged and fluidised. The sizing of biological filters is calculated by knowing the surface area of the media which is
2 3
being used, for example pre-formed, plastic media typically has a surface area between 100 and 800 m m (depending
on the design). Once the amount of ammonia that the fish are producing has been calculated, the media surface area
2
required can be calculated by using the rule of thumb 0.4 - 1.0 g ammonia removed per day per m of media surface
o o
area. This figure equates to temperature operation of between 10 C - 30 C respectively. Although the process of
biological filtration involves changing the water quality, sudden changes in the incoming water quality to the biological
filter can "stress" the bacteria lead to poor performance. Such changes may include sudden changes in pH, flow rates,
temperature etc. The processes of oxidation of BOD and nitrification are aerobic processes. Another type of biological
filtration which is sometimes used in aquaculture, especially in high rate recirculation systems is denitrification.
Denitrification filters convert nitrate to nitrogen gas, the bacteria in such filters are anaerobic.

Biological Oxygen Demand

See BOD

Biomass

The total weight of all living organisms. Note that for a recirculation system, the biomass should include bacteria in the
biofilters. May sometimes however be used in texts to refer to the farmed stock, rather than the total of all living
organisms.


FUNDACION
ALMIRANTE
CARLOS Biostatic
CONDELL
A chemical which prevents organisms from multiplying without necessarily killing them, which makes it easier for the
body to rally it's natural defences and deal with them. The used of biostatic chemicals rather than those that kill the
organisms can result in increased immunity to subsequent outbreaks.

Biotechnology

Term used to describe the use of any living organisms in industrial and production processes.

Biotic index

A figure derived from tables of species with scores against them, relating to the quality of water. Used by many
authorities to determine the pollution effect that a farm is having on the watercourse. Points are awarded for the type
of species (those that prefer clean environments getting a higher score), the number of each species found in a sample
(higher scores for high numbers) and the number of different species found (higher scores for greater number of
species). The difference in scores between the inlet and outlet determines the level of impact on the watercourse. This
method is often preferred by farmers as it is more generally representative of the impact rather than water quality
samples, which may reflect a particular practice (such as tank cleaning) at the time of sampling. The results are open to
speculation as the method of sampling may differ between operators . For example if a kick sample from a stream is
taken (where the bed is disturbed and a net held downstream) the results will be dependant on the force used and
duration of agitation of the bed.

Biotin

One of the water soluble B-complex vitamins.

Birds

Fish eating birds can cause great damage to a fish farm. The damage is only partially in the animals eaten by the birds.
For each fish successfully caught and eaten, many others are damaged (see picture). In the case of shellfish (e.g. mussels
on ropes), species such as the Eider duck can strip the ropes, partly though consumption but mainly through knocking
several animals off the ropes for each animal eaten. Birds also present a threat through transmission of disease to the
farm from other farms and watercourses in the area. They can also play a role as an intermediary host in some diseases
such as eye fluke. Wherever possible, birds should be eliminated from entering the farm by use of netting or other
scaring devices. Netting is the only complete solution as birds will very quickly become used to most scaring devices and
choose to ignore them.

Bird Netting

Many farms are plagued by fish eating birds. These are best excluded by the complete covering of the farm with netting,
which although more expensive to install than wires or strings is more effective.

Biting

(see Nipping)

Bivalve

Common term for animals in the class Bivalvia Also sometimes referred to as lamellibranchs which is actually a sub-class
of Bivalvia, and contains most of the families and almost all the edible forms.

Bivalvia


FUNDACION
ALMIRANTE
CARLOS Class of animals. Part of the phylum Mollusca. Freshwater, brackish and marine forms. Shell is comprised of two hinged
CONDELL valves under which lie two large gills. Class includes fixed forms such as mussels and clams, and also burrowers such as
shipworm and razorshell.

BKD

see Bacterial Kidney Disease.

Black Spot

Often used to refer to the black cysts caused by the intermediate stages of trematodes in fish.

Blastula

A ball of cells seen in the early stages of development following fertilisation. See also Cell Division

Bleach

(Sodium Hypochlorite) Chlorine based chemical which is sometimes used in aquaculture for footbaths etc. Their
efficiency and period of effectiveness is not as good however as iodine based products as it is inactivated by organic
matter quicker. They are also used for disinfection of tank walls, floors etc., however the chlorine (which is the "active
ingredient") will often evaporate out of the solution as it is swilled around the tanks or across floors. The rapidly reduces
the effectiveness of the product, and can lead to incomplete disinfection. Very corrosive to metals, avoid contact.

Blenniodei

Suborder of fish (part of the order Perciformes) including fish such as Blenny (Blennius)

Bloom

See algal bloom

Blowers

Devices which provide pressurised air, typically at pressures between 50mbar and 500 mbar. Most blowers use a turbine
principle to provide the air pressure. Blowers have the advantage of being able to be all but closed off on the discharge
side of the blower without damaging the blower or the discharge pipe. This is not the case with compressors. Most types
of blower can also operate as low vacuum air suction pumps. Typical applications for blowers include; vacuum
degassing, aeration using coarse or medium bubble diffusers, aeration using some makes of fine membrane diffusers in
shallow water, provision of air for fractionation and bubble degassing of carbon dioxide. See also friction loss-air.

Blue sac disease

A condition of sac fry (alevins) in which the yolk sac takes on a blueish colour. Brought on by a lack of oxygen and / or
high Carbon dioxide concentrations which limit the uptake of oxygen into the bloodstream.

Blue tinge

Irritation of the skin on fish can cause an excessive production of mucus which can give the fish a pale blue colour,
especially when viewed from above in the water. Particularly associated with the parasite costia Can also be brought on
by malnutrition, especially a lack of biotin in the diet.. Should not be confused with the blue colour that some naturally
sterile and triploid fish (especially salmonids) can exhibit.

Blue-green algae


FUNDACION
ALMIRANTE
CARLOS see cyanobacteria
CONDELL
Bohr Effect

Discovered by C. Bohr (1855-1911). High concentrations of carbon dioxide in the blood, causes the blood to become
more acidic. This has the effect of inducing the haemoglobin to release any bound oxygen in to the tissues, but has the
opposite effect at the lungs/gills, where the haemoglobin is less inclined to take up oxygen. Can lead to respiratory
stress and exhaustion as the fish has to breath harder to maintain it's oxygen supply. Can be caused by high carbon
dioxide levels in the water, which inhibit the release of carbon dioxide from the haemoglobin into the water.

Bony Fishes

A common term used for Teleosts.

Borehole

A shaft drilled into a water bearing rock or fault line in an impervious rock formation. Water is then either pumped out
of the rock, or exits as a result of natural geological pressures (artesian well). Boreholes are usually sunk for freshwater
supplies, but some farms sink boreholes close to the sea where they can pump seawater as it is drawn inland through
porous rocks or sand / gravel. The pumping of seawater from boreholes can often bring about conflict with agriculture
as, the increasing salinity of the ground water around the borehole area (salinisation), can lead to crop failure. Borehole
water is sometimes wrongly assumed to be 100% disease free. Many borehole supply sources are from underground
streams and channels, which may carry viruses and other pathogens. This is especially so if they are located near to a
farm with earth ponds, where water from the ponds, seeps back into the ground. Borehole supplies are often high in
dissolved nitrogen and carbon dioxide and low in oxygen. As a result of this they should always be degassed before use.
The cost of pumping from borehole usually prohibits their use in ongrowing systems, but they are used widely in
hatcheries. Water quality from boreholes tends to stay constant with temperatures higher than ambient in the winter
and lower than ambient in the summer (for example almost all boreholes in temperate areas will have a temperature
between 9 and 11oC all year round). see also water table and aquifer

Brachyura

Group comprising the crabs. Includes important aquaculture species such as Scylla serrata, the mud crab. The culture of
crabs is at present restricted to either holding facilities, or facilities where the animals are held until they moult and are
then sold as soft shell crabs.

Brackish

Slightly salty. Used to describe waters which are nether freshwater or seawater, but have a salinity which falls between
the two (usually between 0 - 25 ppt.). It may also be used to describe areas (e.g. estuaries) where, due to tidal
exchanges, the environment fluctuates between seawater and freshwater.

Branchiae

The gills (singular - branchia)

Branchiocranium

The part of the skeleton that the gill arches are attached to

Branchiomycosis

see gill rot

Brine


FUNDACION
ALMIRANTE
CARLOS Salty water. Generally regarded as water with a salinity of greater than 45ppt.
CONDELL
Brine Shrimp

see Artemia

Bromine

One of the most common chemicals found in seawater (full seawater contains 65mg/l bromine). Often left out of
artificial seawater mixes where ozone is used in a system, as the production of hypobromous acid (a reaction of the
bromine with the ozone) can cause toxicity problems to the fish

Brood Chamber

An area formed on the underside of some crustaceans to carry fertilised eggs prior to hatching. Also occurring in flat
oysters, where the eggs are incubated on the gills.

Broodstock

A fish which is being kept with the intention of using it for reproduction. Broodstock are usually kept at very low stocking
densities in an effort to reduce stress, promote growth rates and reduce the risk of diseases.

Browsers

Animals which eat continuously. Bites are not very well defined. Includes mostly herbivorous species. See also Grazers

Bubble Curtain

A constant stream if bubbles provided by a submerged diffuser (usually a tube type), which surrounds a specified area.
the action of the bubbles forms a "wall" through which most fish will not swim. It is used for maintaining fish in an area,
when screens or nets cannot be used. Fish may swim through the "curtain" in a fright response.

Buccal Cavity

The mouth cavity

Buccal force plate

The plate feature at the bottom of the mouth which is controlled by muscles to pump water through the gills and also to
give a coughing action to prevent choking or clogging of the gills

Buccal incubation

The incubation of eggs held in the mouth by one or both of the parent fish. The movement of water through the mouth
and across the gills keeps the eggs supplied with oxygen and also keeps the eggs in motion, preventing the build up of
fungus or other infections. If stressed (especially if the fish feels threatened) the eggs may be swallowed. Common term
for this is mouthbrooding or oral incubation . Practiced in particular by some cichlids such including tilapia (e.g.
Oreochromis mossambicus)

Budget Quotation

An approximate quotation. Often used by companies in the initial dealings with a customer to give a guideline of the
price. The budget quotation saves companies the effort of detailed quoting, whilst giving the customer an idea of price.


FUNDACION
ALMIRANTE
CARLOS If the budget quote is in the region of the price that the customer expects to pay, more information is usually sought by
CONDELL the supplying company before a full quotation is offered. Used more often in the supply of systems, rather than
individual items of equipment where the price tends to be fixed

Buffering

The process of adding carbonate and/or bicarbonate ions to water to reduce acidity and increase pH. Buffering systems
are often used in recirculation systems , to counter the acidity produced during the nitrification process, and also the
acidity caused by the carbon dioxide in the water. Systems usually involve using a type of lime which is either dosed into
the water once it as been dissolved, used in a pelleted form with the water flowing through it (often in a fluidised bed),
or added directly to sumps etc. in granular or powdered form. The effect of a buffering system used on the farm is that
the operator will se a rise in the pH of the water. Systems may be manually controlled or automatically controlled by
feedback from a pH controller

Buildings

Almost any building type can be used to house an aquaculture facility, however some aspects which can improve
working and operating conditions are as follows; 1. Ventilation - poorly ventilated aquaculture buildings become very
humid, and provide a perfect breeding ground for fungal spores and bacteria on spilled food etc. They are very
unpleasant places for staff to work which can often result in poor staff performance. 2. Insulation - Note should be taken
on the temperature of operation of the farm, especially if water is being recirculated, which can lead to a build up of
heat in the system. The heat gain in to the building should be taken account of as well as the heat loss. 3. Wind loadings
and snow loadings should be taken account of. One of the most common cost effective means of housing aquaculture
facilities is in polytunnels. These can be built to varying degrees of insulation and lightproofness

Bund

An area of containment. Used to describe features such as dams, pond walls and flood banks. Also used to describe
areas for containment of chemical spillage.

Butt welding

A process of joining two pipe sections together using a heat source to melt the pipes, and allowing the melted plastic
form each pipe to amalgamate, and then letting the joint cool to form a hard plastic again. Special equipment is usually
required to provide the heat for an effective butt weld. The most commonly butt welded material are polypropylene and
polyethylene

Butterfly Fillet

A double fillet, which leaves both sides of the fish attached above the backbone

Butyl

Synthetic rubber compound often used in sheet form for lining ponds etc. Ability to vulcanise makes it more suitable for
large ponds where multiple sheets are required. Unlike some other compounds it degrades over time in sunlight,
especially where areas are exposed for long periods without covering of plants, soil or water

Byssus

The threads that some molluscs (such as blue mussels - Mytilus edulis) use for attachment to a substrate or cultch

C

C.O.D.


FUNDACION
ALMIRANTE
CARLOS See Chemical Oxygen Demand
CONDELL
Cable

See table for specifications of different cable types. See also chain, rope

Cadmium

Metal, falls into the category of heavy metals. Very toxic to fish, safe levels are 3.0mg in well buffered water, 0.4mg/l in
poorly buffered water. 0.2mg/l in seawater.

Cage

A fixed or floating enclosure used to contain fish. There are many designs of cage. Fixed designs are usually referred to
as Hapas and tend to be limited to an area of several square metres. Larger systems involve a net suspended from a
floating and supporting collar.

Calcinosis

The build up of calcium carbonate deposits in the tissues of the fish, often without harmful effects see also
nephrocalcinosis

Calcium carbonate

Chemical symbol CaCO3. g/eq - 50, Solubility - moderate. Most common naturally occurring form is chalk and limestone.
Used for increasing the alkalinity of water. See Lime for more details.

Calcium Cyanamide

Herbicide, used to control macrophytes. Applied at 750 kg / ha to filled ponds with no stock in. Pond should be fully
drained and refilled prior to stocking.

Calcium Hydroxide

Chemical symbol Ca(OH)2 . g/eq - 37, Solubility - high, has a high degree of alkalinity and therefore is often used as a
method of buffering systems. Applied to ponds at 1000-1200kg/ha See Lime for more details

Californian hatching systems


FUNDACION
ALMIRANTE
CARLOS Hatching system consist of a number of stacked hatching troughs or trays, with grids or baskets to support the eggs. The
CONDELL troughs then flow from one onto another, often with water cascading to aerate between the troughs. Used extensively
for salmonids and other species with large (>4mm eggs).

Calorie

Unit of energy. The amount of heat required to raise 1 gram of water by 1 degree centigrade. See Energy for conversion
tables

Canister Filters

Enclosed housings usually containing fine mesh baskets, into which filtration or other media ca be put. Often used in
conjunction with activated carbon and zeolite materials. Generally designed for small flow rates, although larger units
are sometimes custom built.

Cannibalism

The eating of ones own kind. Cannibalism can most often occur as a result of overcrowding, starvation and lack of
grading (through there being a size difference in the fish great enough to enable the larger of the fish to eat the smaller
fish). Some species which are left to spawn relatively naturally (e.g. tilapia) have been known to eat their young if
severely stressed. More prevalent in carnivorous fish such as eels (Anguilla anguilla) see also nipping

Canthaxanthin

Canthaxanthin is a naturally occurring chemical in the family of carotenoids. It is a pigment that is sometimes used to
give salmonids their pink colour. Synthetically produced canthaxanthin is available under the name of Carophyll pink,
EEC no.E161. Astaxanthin has largely replaced the use of Canthaxanthin in salmonid diets due to adverse publicity.

Carapace

The hard exoskeleton shell of crustaceans

Carbohydrate

General term for compounds such as sugars, starches and cellulose. Contain carbon, oxygen and hydrogen. Most
carbohydrates can be used as an energy source by animals, although some are difficult to digest (especially by
carnivores) and so release only small amounts of energy to the body

Carbon

Chemical symbol "C" - The essential building block of all organic compounds. Often needs to be added to the water
(often in the form of methanol) to supply bacteria in denitrification filters. See also Activated Carbon

Carbon Dioxide

Produced as a result of respiration by the fish and other aerobic organisms (including plants) in the system. The amount
of carbon dioxide produced is directly proportionate to the oxygen consumed. For every 1g oxygen that is consumed,
1.4g carbon dioxide is produced. Carbon dioxide has the effect of increasing the acidity of the water, it is present in
three different forms in the water : CO2 (free carbon dioxide, which is the toxic form), HCO3- (bicarbonate ion, and CO3-
- (carbonate ion). The concentration of each is dependant on the pH of the water. The table shows the effect of pH on
the proportions of different forms of carbon dioxide in freshwater. As free carbon dioxide is the form that is toxic to fish,
high toxic concentrations are only normally found in neutral or acidic waters. Most surface waters, in their natural
surface state contain low concentrations of carbon dioxide (<6 mg/l). There are situations however, where toxic levels
may be reached : 1. Acidic groundwater can contain very high carbon dioxide concentrations and require degassing prior


FUNDACION
ALMIRANTE
CARLOS to use 2. Ponds with large phytoplankton populations can be the cause; carbon dioxide may reach high concentrations
CONDELL during the night or during cloudy weather, as the plants consume oxygen as part of their natural respiration, 3.Fish
transportation - carbon dioxide build up can occur in transport tanks, especially when in enclosed tanks or bags
containing oxygen. Open tanks and aeration is much more preferable as it gives the carbon dioxide a chance to escape,
this is especially important when transporting fish in acidic water for long journeys.

High carbon dioxide concentrations are harmful to fish as the blood becomes less efficient in getting rid of it's carbon
dioxide across it's gills. This means that some of the carbon dioxide stays in the blood, taking up a space where an
oxygen molecule would otherwise have occupied. For example a carbon dioxide concentration of 25mg/l equates to
almost a 50% drop in the fishes carrying capacity for oxygen. This will limit growth and make the fish more susceptible to
any diseases. General guidelines for carbon dioxide concentrations are : <15 mg/l acceptable for most species, 15-
30mg/l sublethal effects including respiratory stress and the development of kidney stones (nephrocalcinosis) in some
species. >30mg/l lethal to many species with prolonged exposure. Carbon dioxide can be removed / controlled by using
aeration or degassing techniques, or adding lime to a pond (this should be carried out very slowly, as in acidic waters,
small additions of lime can lead to large increases in the pH, which will stress the fish), approximately 1meq of hydrated
--
lime can remove 2.25mg/l CO2 . Careful planning of stocking, feeding, fertilising and use of oxygenation can also help
prevent high carbon dioxide levels occurring. Shallow ponds are less likely to suffer carbon dioxide problems than deep
ponds.

Carbonate minerals

2-
A group of minerals containing the anion CO3 as the fundamental unit of their structure. Carbonate minerals are used
for buffering water to increase the alkalinity. See also lime

Carcinogen

Any substance that either produces or accelerates the development of cancer

Carnivore

An animal that feeds solely on other animals.

Carotenoids

A group of yellow, orange and red lipid soluble pigments. A form of vitamin A. See also Astaxanthin, Canthaxanthin

Carrier

An animal that harbours a disease without showing symptoms. see also asymptomatic carrier

Carrying capacity

The amount (either expressed in weight or number) of animals that a given system is capable for supporting. The
carrying capacity is limited by a factor which on farms is usually oxygen then ammonia and carbon dioxide / B.O.D.

Cartilage

A firm, flexible connective tissue. In vertebrates, the cartilage forms the skeleton in the early stages of development,
after which it is largely replaced by bone. Some cartilage remains at the joints to give flexibility and support. Some fish,
such as sharks remain with their skeletons made of cartilage, these are termed "cartilaginous". Some parasites (such as
Myxosomas cerbralis) can only enter the fish and complete their life cycle, if the skeleton is still cartilaginous. For this
reason, if there is a risk of infection, fish are often kept on spring or borehole water supplies until their skeletons have
hardened.


FUNDACION
ALMIRANTE
CARLOS Cartridge Filters
CONDELL
Enclosed vessels which house a replaceable filter membrane. The filter membrane is generally of a pleated or a woven
material. Cartridge filters are used primarily for filtration of water of 20 microns and below. Disadvantages of using
cartridge filters include the cost of replacement filter elements, the cost of pumping the water through the filters ( the
finer the membrane, the greater the headloss across the filter) and the maintenance of large numbers of filters, should
large flows be required. Cartridge filters do however have their applications in situations such as marine hatcheries,
where pre-filtration is often used and very low flow rates are required. see also mechanical filtration

Catadromous

A fish which spawns in the sea and lives most of it's life at freshwater e.g. European eels (anguilla anguilla) See also
Anadromous

Cataracts

An irreversible clouding of the lens of the eye. Appears as a grey / white colour in the normally black lens of the eye.
May be due to either physical damage sustained whilst handling, irritation from disease organisms such as Diplostomum
spathacaeum, or a result of incorrect nutrition. The cataracts impair the vision of the fish. In some species, such as sight
feeders like salmonids this can lead to a wasting away and eventual mortality. Some fish will however adapt and feed
from the bottom of a tank / pond. This will usually result in very poor FCR and lesions to the mouth parts which can in
turn lead to other infections. Poorly sighted fish are normally removed and killed to prevent them becoming stressed
and risking the development of disease conditions which could threaten the rest of the stock.

Catchment

see Watershed

Cation

A positive ion

Caudal Peduncle

The name given to the area where the tail of a fish joins the body. Sometimes also called the "wrist". Some operators
will use this area to hold the fish, although excessive struggling by the fish can cause damage to the spine and body
tissues if it is not also supported elsewhere. This can result in poor fillet quality.

CCVD

see Channel Catfish Viral Disease

Centrifugal Pumps

The workhorses of most applications, centrifugal pumps use a rotating impeller that draws water into it's centre and
through centrifugal action, throws it outwards through vanes in the impellor and out of the pump. Efficiencies are
generally in the 55 - 80% range depending on how closely the application fits the optimum curve of the pump.

Cell division

The process by which cells split into two copies of the original. Forms the basis of development of ova once fertilised.
The single cell divides into two, these two then divide resulting in four and so on.

Cephalopod


FUNDACION
ALMIRANTE
CARLOS Common term for animals belonging to the Class Cephalopoda, including squid and octopus
CONDELL
Cephalopoda

Class of animals, under the phylum Mollusca. Regarded as the most advanced of all the Mollusca classes. Mostly marine.
Possess a well developed head surrounded by a ring of tentacles. Includes squids, octopuses and cuttlefish.

Cerceria

Larval stage of flukes such as eye fluke (Diplostomum spathacaeum). The stage at which the flukes are released from
their mollusc host (usually a snail) and infect fish.

Cfs

Cubic feet per second. Measurement of flow. see Flow or click on software link to get conversion tables program.

Chain

See table for specifications of different chain types. See also cable, rope

Channel

An open water course i.e. not enclosed as a pipe would be. Several design factors must be taken into account when
designing a channel these are :
1 Material for construction - this has a bearing on the flow which will be achievable down the channel. Smooth surfaces
will allow greater flows than rough ones. See Friction loss. The material used must also be of sufficient structure that the
water flowing down the channel will not erode. The velocity at which a material erodes is known as the limiting velocity.
2 Gradient - The greater the gradient, the faster the water will flow down the channel
3 The scouring velocity. This determines whether silt and other particles will settle in the channel or be carried along
with it.

Channel catfish viral disease

Disease affecting primarily channel catfish (Ictalurus punctatus), but other species of catfish have been infected
experimentally. Confined to USA and Honduras.
Symptoms include high mortality among fry; outbreaks associated with high temperatures; high head posture; erratic
swimming; hemorrhages at fin bases; swollen abdomen; exophthalmia; pale gills.
Control of the disease is by using an available vaccine, selection of resistant strains (don't use wild fry), reduction of
stocking densities, maintenance of temperatures below 25°C and oxygen concentrations above 4 ppm Ponds should be
drained and/or chlorinated between batches of fry.

Channeling

The term used to describe the concentration of flow through some areas of a filter, whilst other areas become blocked.
This particularly applies to sand filters and some biological filters and degassers. The media in the filter gradually
becomes blocked with solids and bacterial floc, eventually forming clumps of bound up media. Unable to pass between
the individual pieces of media in the clump, the water flows around the clump. Channeling can dramatically reduce the
ability of a piece of equipment to perform to it's design specification. Once channeling has started, the only way to
remedy the situation, is to backflush or wash the filter media to remove excess floc/particulate matter.

Channoidei

Suborder of fish (part of the order Perciformes) including fish such as snakehead (Ophiocephalus)


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