IKENWEIWE Bolatito Nafisat (PhD) DEPARTMENT OF AQUACULTURE AND FISHERIES MANAGEMENT UNIVERSITY OF AGRICULTURE, ABEOKUTA

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IKENWEIWE Bolatito Nafisat (PhD)DEPARTMENT OF
AQUACULTURE AND FISHERIES MANAGEMENTUNIVERSITY
OF AGRICULTURE, ABEOKUTA

• AQUACULTURE

titobola2007_at_yahoo.com, 08033770265
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AQUACULTURE

• FIS 309
• (3 Units)

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Course Outline

• Sources of water for Aquaculture
• Fertilization and Liming

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Sources of Water

• There are two principal sources of water that can
  be used in fish farming
• ground water and
• surface water

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• Surface waters have the advantage of being well
  oxygenated although they may be polluted from
  different sources.
• Surface waters include
• lotic waters (steams, brooks, rivers),
• lentic waters (lakes, ponds) and
• salt or brackish waters.
• Rainfall and run-off may also be included but
  since they are highly seasonal, they should be
  used with caution if they are the sole source of
  water.

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• Lotic waters have high oxygen content because the
  water turbulence encourages gaseous exchange,
  except when they become slow flowing.
• They usually have some form of organic
  allochthonous production which may serve as food
  for the cultured species.
• However, they often carrying a high load of
  suspended solids, some of their natural fauna may
  be parasitic or the cultured species and the
  indigenous species may be carriers of disease.

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• Salt and brackish waters share the problems of
  both lotic and lentic waters, and, in addition,
  are corrosive to many metals.
• Consequently, special materials will have to be
  used for pipes, tanks and other equipment.

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• Ground waters are usually pollution free although
  some may contain noxious gases like hydrogen
  sulphide and methane, as well as toxic metals.
• The level of noxious chemicals contained in
  groundwater is highly correlated to the geology
  of the area.
• The major disadvantage of groundwaters is their
  low dissolved oxygen content.

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• Ground waters include
• springs,
• depressions below the water table and
• wells.
• Depressions are uncommon and their use is
  questionable since water disappears when the
  water table drops.
• Wells can be free-flowering (artesian) or pumped.

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The Quality and Quantity of Water

• Water quality
• The quality and quantity of available water is of
  utmost importance in fish culture.
• The quantity of water required will depend on
• the fish species to be cultured and
• on the management practices (static or
  flow-through, intensive or extensive

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• If total losses from seepage and evaporation
  amount to 5.0cm day the additional minimum daily
  requirement to maintain the level of the hectare
  pond described above is 500m3 or 500,000litres or
  5.81 sec-1

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• If the water supply is from borehole, the
  discharge capacity of the borehole will indicate
  whether or not sufficient water will be
  available.
• The exact yield of a borehole may not be known
  until after money has been spent.
• It is therefore best to seek the advice of a
  geologist with a working knowledge of the area or
  to get some information form other people who own
  boreholes in the area.

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• If the water source is a stream, the quantity of
  water available can be calculated from the
  continuity equation.
• Q A.V
• Where Q is the quantity of water available (m3),
  A is the cross sectional area (m2) and V is the
  velocity (msec-1).

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• Table 1 Discharge rate in a canal of different
  depths and cross-sectional area.

Water-depth (m) Wet cross section are (m2) Water transported Msec-1) (m3)
0.1 0.11 23 2800
0.2 0.26 78 5700
0.3 0.43 120 11100
0.4 0.64 192 16500
0.5 0.87 260 24400
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• Thus, if a 0.2m deep canal is used to fill 1ha
  pond (including water to compensate for the
  initial saturation of the pond) it will take
  18750/5700 3.3days to fill the pond. If there
  were 20 ponds, it would take approximately 66
  days to fill them.
• This may be undesirable and consideration will
  have to be given to providing a reservoir to
  supply the water.
• When pipes are used for the canal, a much greater
  volume can be supplied. The volume of water
  passing through a pipe is
• Water flow (cross section x 100) / 100
  (r2x3.14 x 100)/1000

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• Table 3.2 Water flow in pipes of various diameters

Pipe diameter (cm) Water flow 1sec-1 (m3day-1)
2.5 0.5 43
5.0 8.0 150
10.0 11.5 690
15.0 18.0 1500
20.0 31.0 2600
30.0 70.0 6000
40.0 130.0 11000
50.0 196.0 17000
60.0 280.0 24000
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Water quality

• Criteria for water quality depend on the use to
  which the water is intended.
• Hence, what is good for one situation may not be
  good for another.

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• It must be mentioned that water for aquaculture
  should be adequate in
• dissolved oxygen,
• pH,
• temperature and
• should not contain
• excessive dissolved and suspended solids or
• toxic substances.
• It is possible that some water quality problems
  can be easily solved, hence quality may not be as
  critical as quantity

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• It is generally agreed that the growth of fish
  produced in an extensive system without
  supplementary feed is at the expense of the
  nutritive flora and fauna of the water body.
• However, few scientific works have successfully
  related primary production to fish production
  (Ryder, 1976). Consequently, prediction of the
  ability of a natural body of water to produce
  fish is based on empirical methods

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• The most applicable are the leger-Huet formulae
  (Huet, 1986). These are the productivity of
  running water and artificial ponds as
• K B x L x k (for running waters)
• K 0.1Na x B x k (for artificial ponds)

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• Where
• k is the annual productivity (kgkm-1) of water
  course or kgm2,
• B is the biogenic capacity,
• I is the average width of the water course (m),
• k the coefficient of productivity and
• Na the size of the ponds.
• The biogenic capacity is an expression denoting
  the nutritive value of the water examined for its
  feeding qualities for fish.

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POND PREPARATION AND MANAGEMENT
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Liming

• About two weeks before refilling the pond a layer
  of lime should be spread over the pond bottom
• Although not a fertilizer, it helps to accelerate
  decomposition of waste materials and the
  mobilization of nutrients from the pond soil.
• It raises the pH above the tolerable limits for
  disease vectors or eggs and spores of parasites,
  thus assisting in their eradication.

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• Lime comes in several forms and the application
  rates depend on the pH of the soil and the type
  of time used.
• In ponds where the soil pH is around neutral the
  application rates are of the order listed below.
  
• Crushed limestone-CaCO3 1200kg ha-1
• Agricultural lime- CaCO3 2500 kg ha-1
• Hydrated lime -Ca(OH)2 100kg ha-1
• Quicklime-CaO 200 kg ha-1

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• If the pond has a pH of about 4.5 or less,
  approximately 4.5 tonnes of agricultural lime
  will be required.
• If the pond had been limed before, subsequent
  annual liming are usually much less, i.e 20-25
  of the initial application rate.
• Hydrated lime is the best because it tends to be
  the most concentrated and cheapest form.
• Care should be taken if quicklime is used because
  it can burn on contact with the skin

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Fertilization

• The yield of any fish pond depends on its natural
  productivity, which is linked to nutrient
  availability in the pond soil and water. It thus
  allows an increase in fish density without the
  need for supplementary feeds.
• The most important nutrients for growth of food
  organisms are phosphorus (P), nitrogen (N) and
  potassium (K). if there nutrients are in short
  supply or absent they can easily be increased by
  fertilization using organic and inorganic
  substances.

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• Fertilizers are applied to the pond water or soil
  to stimulate and maintain plant growth and
  establish the secondary food chain.
• However, the mechanism of organic and inorganic
  fertilizers in achieving this production are
  quite different.

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INORGANIC FERTILIZERS

• Inorganic fertilizers are usually of chemical
  origin that dissolve in the pond water and
  provide nutrients almost immediately. This
  stimulates phytoplankton (algal) growth and
  zooplankton production, both of which are direct
  sources of food for fish

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• the main limiting element in established ponds is
  phosphorus and this can be provide in several
  forms, including basic powdered single
  superphosphate or granular triple superphosphate

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ORGANIC FERTILIZERS

• Organic fertilizers are usually waste plant or
  animal products include manure from cows, sheep,
  ducks, chickens and humans and grasses the
  non-utilized parts of crops such as rice husks
  that have rotted down this mechanism of
  fertilization is the basis of integrated fish
  farming.
• The important points to remember about organic
  fertilizers are slowly as they rot down and
  release the nutrients.

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Applying the fertilizer

• There are several ways of applying the
  fertilizer.
• In drained which are just about to be filled both
  organic and inorganic fertilizers can be spread
  over the pond bottom.
• In a pond which has been filled and stocked with
  fish the usual way for inorganic fertilizers such
  as superphosohates broadcast it evenly over the
  pond surface.

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NON DRAINABLE PONDS

• In ponds that cannot be drained or insufficient
  water is available to refill it, conditioning is
  no less important.
• In this case sediments wastes which have
  accumulated on the bottom of the pond during the
  grow-out season should be scraped out and placed
  on the bank or surrounding fields.

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• If necessary quicklime is broadcast over the
  ponds at a rate of approximately 600kg ha-1 and
  then fertilized according to the procedures
  described for drainable ponds.

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Water Quality Maintenance

• The survival, growth and consequent production o
  fish depend, to a large extent, on the physical,
  chemical and biological status of the water in
  the culture enclosure.
• Every cultured fish species has its own peculiar
  water quality requirements

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• Man has very little control over salinity of fish
  ponds. It is therefore imperative to culture a
  fish in a salinity medium in which it naturally
  occurs
• Other critical features of the holding unit that
  will influence production include water depth,
  transparency, dissolved on concentration,
  alkalinity, free dissolved carbon dioxide, odour
  and levels that will favour high fish production

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DEPTH

• Depth of water in the pond must be kept steady
  through regular replenishment with fresh and
  clean water to top up for water lost by seepage
  and evapotranspiration.
• If water level is not uncontrolled, it may
  overflow and eventually break down the dam or the
  dyke.

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TRANSPARENCY

• The Secchi disc is the instrument sued for
  measuring turbidity or transparency.
• A high transparency (gt80cm) is an index of low
  production. This can be improved by adding
  fertilizers.
• Low transparency (lt20cm) may be de to suspended
  silt, clay, plankton or organic matter. This also
  encourages low fish production.

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DISSOLVED OXYGEN

• High phytoplankton production may reduce
  dissolved oxygen content in the pond water at
  night because they use oxygen for respiration but
  do not product it by photosynthesis.
• The dissolved oxygen content is inversely
  proportional to temperature, and high temperature
  during the early afternoon may cause the oxygen
  content to fall below the critical level.
• It is recommended that the dissolved oxygen level
  is measured in the early morning and again around
  14.00 hrs. For minimal stress and good growth it
  should be above 4-5mg 1-1.

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Aeration

• Aeration can be achieved in a number of ways, but
  the method used will depend on financial
  resources, access to electricity and intensity of
  production.
• It can be achieved with electrically driven
  paddle wheel agitators or similar device which
  cause good mixing of the water and allow gaseous
  oxygen to dissolve in the water and carbon
  dioxide to escape.

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pH

• Water with a pH range of 6.5-8.0 is most suitable
  for fish production
• low pH can be improved through the addition of
  lime
• high pH can be lowered through addition of
  ammonium sulphate, ammonium nitrate and urea
  fertilizers.

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POLLUTANTS

• With industrialization, intensification of
  agriculture and widespread industrial and
  agro-chemicals and detergents, it is inevitable
  that some waste products of these ventures find
  their way into local surface underground water
  bodies by run-off or seepage, and eventually into
  ponds.
• As a rule, water flowing ponds must be analyzed
  routinely for pollutants.
• If the water in the found to be polluted, it
  should be drained and replenished with fresh
  clean water, preferably from an alternative
  source.

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Weed control

• Weeds are macroscopic plants and macrophytes
  whose existence, especially in large quantities,
  may interfere with pond management operations
  such as feeding, test cropping and testing.
• They compete with phytoplankton for available
  nutrients depriving planktivorous fishes of their
  natural food,
• provide havens pests and encourage
  evapotranspiration.

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• Aquatic weeds include plants, e.g Pistia
  stratiotes (water lettuce), pond weed (Lemma sp)
  filmentous algae, submerged weeds, e.g
  Ceratophyllum,emergent water lily (nymphea lotus)
  and marginal or fringe vegetation
• Submerged and emergent weeds can be effectively
  checked through fertilizer application.

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• Copper sulphate and synthetic algicides e.g.
  simazine and Aquazine can be used to control
  excessive growth of filamentous algae and
  phytoplankton.
• The use of copper sulphate and synthetic
  algicides also create low dissolved oxygen levels
  after their application.
• Synthetic algicides tend to have longer residual
  action when compared with the use of copper
  sulphate in the control of filamentous algae and
  phytoplankton.

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• Biological control of aquatic weeds through the
  introduction of grass eating fish such as grass
  carp (Ctenopharyngodon idella), Tilapia zillii
  and Heterotis niloticus is most often recommended
  in polyculture systems.
• Aquatic weeds can also be controlled through
  manual removal or mechanically through the use of
  specially designed amphibious machines.

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Routine production activities

• Stocking
• The main objective of fish farming is the
  sustained production of a good yield of fish from
  the production unit,
• For sound production scheduling the stocking rate
  should be calculated accurately base on the
  expected grow increment and mortality over the
  growing season.
• Expected output from pond
• Number to be stocked -------------------------
  --------------- x survival rate
• Expected increase in weight of individual fish

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• General rules which apply when transferring fish
  from one place to another.
•  Check the disease status of the fish prior to
  introduction to avoid contamination.
• If possible starve the fish for 24 hours before
  movement
• Handle the fish as little as possible
• Prevent the fish form becoming too warm through
  exposing to sunlight.
• Stock or transfer the fish in the early morning
  when the temperatures are lower and the fish less
  active.
• Provide the fish with plenty of oxygen/air if
  they are being transferred over long distances.

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Further Readings

• Olokor, J.O., J.A. Ihuahi, F.S. Omojowo, B.A.
  Falayi and E.O. Adeowo (2007). Hand book of
  Practical Fisheries Technology. Fisheries
  Technology Division, Remi-Thomas Press
• http//www.fishbase.org/summary/species

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Thank you