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General Principles


Selection of species for aquaculture. Development of new aquacultural species ... Considerations for hatcheries (site selection, etc.) are similar as those for ... – PowerPoint PPT presentation

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Title: General Principles

General Principles (Chapter 2)
  • Non-graded Quiz 3

General Principles (Chapter 2)
  • General Topics
  • Culture system classification
  • Type of structures used
  • Intensity of culture operations
  • Water management strategy
  • Site selection and economics
  • Hatchery systems
  • Selection of species for aquaculture
  • Development of new aquacultural species

General Principles
  • Structures
  • Typically more than one structure will be used
    during the life span of a cultures species.
    Structures used in aquaculture include
  • Ponds
  • Tanks
  • Raceways
  • Cages
  • Pens
  • Substrate

General Principles
  • Structures
  • Ponds usually earthen impoundments (including
    natural ponds)
  • Oldest aquaculture structure
  • Hole in ground, enclosed waterway, embankment
  • Used mainly in culture of fishes and crustaceans
  • Water input and discharge primarily by gravity
  • Impermeable soils
  • Soils that support pond ecosystems (this is
    important feature that determines productivity)

General Principles
  • Structures
  • Tanks
  • Second to ponds as most commonly used structure
    in aquaculture
  • Usually above ground on a solid base
  • Indoors or outdoors
  • Wide range of sizes
  • Flow-through or recirculating systems (more
  • Uses include culture of microalgae, macroalgae,
    various stages of fishes and invertebrates

General Principles
  • Structures
  • Raceways elongated tanks with canalized flow
  • Usually continuous water flow from one end to the
  • Designed to keep unidirectional water flow along
  • Suitable for fish such as salmonids that live in
    shallow streams swimming against current
  • Need source of good water quality and quantity
    (most raceways are flow-through)
  • Potential problem deterioration of water quality
    along length
  • Typically used for high-value fishes

General Principles
  • Structures
  • Cages
  • Original cages poles or stakes driven into
    sediment with netting stretched around them (now
    known as net pens or hapas)
  • Modern cages are floating structures with net
    suspended underneath
  • Square, rectangular or round of variable sizes
  • Typically used for grow-out phase (months or
  • Require maintenance but not water pumping
  • Require location with good water quality
    (protected inshore locations, large freshwater
    lakes and ponds)
  • Potential problems net fouling , predators,
    diseases and parasites, algal blooms

General Principles
  • Structures
  • Pens or hapas
  • Used in shallow water, typically in ponds
  • Relatively small
  • Practiced typically in developing countries (low

General Principles
  • Structures
  • Substrates racks, suspended culture
  • Used to provide attachment surfaces for
    bottom-dwelling (e.g., bivalves) and attached
    species (e.g., seaweeds) that are grown in the
    field for most of their culture

General Principles
  • Intensity of culture operations
  • Definition The term intensity describes the
    density of cultured organisms per unit volume or
    unit area. It is meaningful for comparing
    culture levels for a given species or related
    species. It is not very useful for comparing
    culture levels for different groups of organisms.
    Tilapia at 100 kg/m3 in recirculating systems is
    considered intensive, whereas shrimp at only 1-2
    kg/m3 in ponds is considered intensive.
  • Energy (cost) considerations Natural aquatic
    ecosystems consist of primary producers
    (primarily plants, including phytoplankton),
    various levels of consumers (primary or
    herbivores secondary or carnivores tertiary or
    higher level carnivores), and decomposers. These
    various trophic levels are arranged into a food
    chain. As a rule of thumb, the amount of energy
    that can be transferred from one level to the
    next in the food chain is only 10 (the remaining
    90 is lost into metabolism, heat generation,
    waste, reproduction, etc.).
  • Implications for aquaculture The greater the
    intensity of culture operations, the greater the
    requirement for energy input into the system.
    For intensive operations, it is thus much more
    efficient and cheaper to grow organisms low on
    the food chain. Approaches differ between
    developed and developing countries.

General Principles
  • Intensity of culture operations
  • Classification
  • Intensive
  • Extensive
  • Semi-intensive

General Principles
  • Intensity of culture operations
  • Intensive systems
  • Requires high energy input (feeds, aeration,
    water filtration, water pumping, etc.)
  • No energy recycling (totally non-self-supporting)
  • All nutrition comes from introduced feeds, with
    no utilization of natural diets
  • Simple food chain feed ? cultured organism
  • Thus, low energy losses/high feed conversion
  • High rearing densities and production yields (per
    unit volume or area)
  • Water quality requirements for target species
    determines level of stocking (stocking ponds lt
    cages lt raceways/tanks).
  • Use of ponds, (shrimp), cages (marine fish),
    raceways (trout), tanks (eels) but remember
    that usually different structures are used
    depending on growth stage of cultured species.
  • Can be outdoor or indoor

General Principles
  • Intensity of culture operations
  • Extensive systems
  • Relies on natural ecosystem processes for
    maintenance of water quality and provision of
    most nutrients
  • Thus, limited energy input is needed to maintain
    animal growth and survival
  • Low stoking densities
  • Common structures for extensive culture include
    ponds (low value fish carp, tilapia) and
    substrate (bivalves, seaweeds)

General Principles
  • Intensity of culture operations
  • Intensive versus extensive systems
  • Example Feedlot cattle (intensive) versus
    free-range cattle (extensive)
  • Both can be profitable depending on difference
    between cost of production and value of product

General Principles
  • Intensity of culture operations
  • Semi-intensive systems
  • There is no clear line separating intensive from
    extensive culture
  • Middle ground semi-intensive
  • Semi-intensive culture systems rely to some
    degree on natural processes and productivity, but
    there is also supplementation, such as
  • Aeration
  • Addition of fertilizers (organic or inorganic)
  • Addition of feeds (supplemental feeds)
  • Semi-intensive culture is almost exclusively
    applied in ponds and allows for increase in
    stocking density relative to extensive systems

General Principles
  • Intensity of culture operations
  • Polyculture
  • Used in semi-intensive and extensive systems
  • Refers to the deliberate culture of target and
    complementary species. Complementary species
    differ from target species especially in regards
    to their nutrition so as to minimize competition
    for resources (e.g., detritivores that clean up
    waste and maintain pond quality)
  • Polyculture increases production by maximizing
    utilization of nutritional niches within the pond
  • A relatively new approach to polyculture culture
    of a second complementary species isolated from
    the main target species. For example, effluent
    from shrimp ponds (main target species) can be
    routed through separate ponds for culture of
    bivalves, plants, microalgae, etc. Second round
    of culture not only improves the quality of
    effluent water by removing waste but may also
    produce additional commercial crops.

General Principles
  • Intensity of culture operations
  • Integrated agri-aquaculture systems (IAASs)
  • Polyculture is based on the integration of target
    and complementary aquaculture species in single
    or separate bodies of water
  • Integrated agri-aquaculture systems involve
    traditional agricultural crops (plants, animal)
    and aquaculture. In these systems plant and
    animal waste is used to fertilize ponds, but
    sometimes aquacultural animals (fish and
    freshwater crustaceans) are grown directly in
    plant fields (e.g., rice fields)
  • IAASs are typically applied in the setting of
    semi-intensive operations, but intensive
    operations can also be incorporated into an IAAS.
    For example, when using aquacultural effluent
    from an intensive pond system for the irrigation
    of plant crops
  • Modern aquaculture has moved toward
    disintegration of aquaculture into monoculture
    systems, but problems of limited water
    availability seems to be reversing this trend in
    some places

General Principles
  • Water exchange/flow systems
  • Classification
  • Static
  • Open
  • Semi-closed
  • Recirculating (closed)

General Principles
  • Water exchange/flow systems
  • Static systems
  • Static system is one in which there is no water
    replacement during the growth of an organism
    (except for water added to offset evaporation)
  • Static pond culture is usually extensive because
    of difficulties in maintaining water quality
  • Most global aquaculture occurs in ponds using
    static systems

General Principles
  • Water exchange/flow systems
  • Open systems
  • The open environment (lake, ocean, etc.). There
    is no artificial circulation of water through or
    within the system.
  • Structures used in this system include cages,
    racks, etc.
  • In some cases, such as salmon culture in cages,
    the open system is intensive (high density of
    fish with artificial feeds)
  • In other cases, such as bivalve culture in racks,
    the open system is extensive (bivalves feed on
  • Operation costs of open system is usually low
    since no pumping is required
  • Capital costs are high for open intensive systems
    and low for open extensive systems.
  • Problems (1) lack of control over water quality,
    so site selection is a very important
    consideration (2) predation and disease.

General Principles
  • Water exchange/flow systems
  • Semi-closed systems
  • Systems where culture water is confined in
    discrete units and some degree of water exchange
    occurs are defined as semi-closed systems. These
    systems fall between static (no exchange) and
    open (in the open environment) systems in terms
    of water exchange.
  • Ponds, tanks and raceways where significant
    exchange of water are carried out are considered
    as semi-closed systems.
  • Since the farm is not located in the natural
    environment, there is some control over water
    quality by regulating the amount exchanged.
  • In large semi-closed systems with semi-intensive
    to intensive culture, water flow is generally
    high (5-10 per day for semi-intensive ponds and
    30-40 per day in intensive ponds)

General Principles
  • Water exchange/flow systems
  • Recirculating (closed) systems
  • Systems are characterized by minimal water
    exchange, but unlike static systems the water
    flows internally, usually through waste removal,
    biofilter, and disinfection units to help
    maintain water quality.
  • Costs of construction and operation are high, but
    yield and product value can also be high and
    offset costs.

General Principles
  • Hatcheries
  • So far we have discuss information primarily
    associated with the grow-out or production
    aspects of aquaculture (e.g., farming operations)
  • Hatcheries are those aquaculture facilities
    associated with reproduction, larval rearing, and
    supply of juveniles to farms
  • Considerations for hatcheries (site selection,
    etc.) are similar as those for nursery and
    grow-out facilities
  • General design requirements
  • Area for holding broodstock
  • Spawning area
  • Food production area (plankton, etc.)
  • Larval rearing area
  • Early nursery area
  • Hygiene is major concern. Must be designed to
    minimize possibility of disease transfer between
    different areas.
  • Water quality and feeding regimen are important
    management considerations

General Principles
  • Selection of species balance between biology
    and economics
  • Biology
  • Water temperature and quality requirements
  • Growth rate (fast or slow growing species?) rule
    of thumb, more than 2 years to market size not
    good (rule may be modified according to risks and
    final value of product)
  • Feeding habits and cost 3 phases
  • Hatchery/nursery
  • Juvenile
  • Grow out (usually similar to juvenile in fishes)
  • Reproductive biology reliable source of
    juveniles or seed is very important. Wild
    sources of feed sometime used (table oysters,
    milkfish in Asia) but availability can be
    unpredictable and affect aquaculture operations.
  • Hardiness adaptability to captive environments
    is important. Domesticated lines are very useful.

General Principles
  • Selection of species balance between biology
    and economics
  • Economics
  • Production objectives
  • Industrial products
  • Pharmaceutical products
  • Aquaculture products
  • Ornamental species
  • Wild stock enhancement (usually of concern to
    public agencies)
  • Marketing is there a market for the product
    being considered?
  • Cost-return analysis (computer software available)

General Principles
  • Development of new aquaculture species
  • If culture techniques are already established for
    target species, especially if the species is
    already cultured in the region, the establishment
    of an aquaculture operation is made easier.
  • If culture is desired for new species not
    previously raised in captivity, basic culture
    techniques need to be developed first.

General Principles
  • Development of new aquaculture species
  • Stages in the development of new culture species
  • Screening stage
  • Collection of available information about species
    life history, ecology, husbandry. Consider
    information obtained in relation to the
    characteristics of proposed aquaculture site.
  • Legal considerations
  • Market considerations local, global demand?
  • If market does not currently exist, can it be
  • Economics
  • Research biology and husbandry (water quality
    requirements, optimal stocking densities,
    reproductive physiology and broodstock
    management, nutrition and growth)
  • Pilot trial semi-commercial validation of
    aquaculture potential using small culture units
    and animal numbers
  • Commercial trial full-size culture units and
    larger number of animals identifies production
    costs and profits and problems of husbandry of
    large numbers of animals preliminary market
  • Full-scale production uses full number of
    commercial size culture units.

General Principles
  • Development of new aquaculture species
  • Time scale for development could be well over
    10 years
  • Screening stage up to 2 years
  • Research no less than 5 yeas for species not
    previously studied
  • Pilot trial at least 2 growing generations
  • Commercial trial at least 2 growing generations