Aquaculture Techniques: A Comprehensive Guide to Fish and Oyster Farming

Posted on May 26, 2024 in Biology

Culture Facilities

Fish Farming

Ponds

Enclosures designed to store and circulate water, enabling the confinement and rearing of fish. Ponds serve as artificial habitats that mimic natural environments, requiring farmers to manage feeding and health for optimal production.

Types of Ponds:
  1. Semi-natural: Existing bodies of water, often on clay soil to prevent leakage, modified for fish farming.
  2. Artificial: Purpose-built structures, either open pits or constructed with reinforced concrete (cement, brick, stone).
  3. Dam or Interception: Located at the bottom of valleys, utilizing a transverse wall to create a small dam. Water sources typically include springs or streams.
  4. Branch: Utilize land topography to channel water from rivers, streams, or springs.
    • Rosary or Series: Arranged sequentially, connected by a single channel where water flows from one pond to the next.
    • Parallel: Constructed alongside each other, each with separate water supply and drainage for easy cleaning.
    • Mixed: Combine elements of both parallel and continuous pond designs.
Shape and Size:

Rectangular or circular shapes are common, with size determined by topography and fish growth stages. Smaller ponds are used for nurseries, medium for juveniles, and larger ones for adults. Earthen ponds offer flexibility in size but should be manageable, often around 30 meters long and 10 meters wide.

Key considerations for pond design include water resources, land use, pond type, shape, size, water inlets and outlets, and water levels.

Cages

Floating structures placed in ponds, reservoirs, or dams. They consist of a floating platform supporting a mesh”ba” or”cag” that confines the fish. Cages can be solitary or interconnected, depending on the farming intensity and site characteristics.

Advantages of cages include utilizing large water bodies, even in areas where pumping water is impractical or expensive. Modern cage designs and materials simplify handling, while cost-effective craft facilities remain viable.

Feeding Guidelines

  • Prioritize daily feeding and fish care.
  • Implement a consistent feeding schedule, 7 days a week.
  • Avoid feeding near outflow gates to prevent food loss.
  • Gradually increase food rations every 3 days.
  • Regularly sample fish to monitor growth rates and adjust feeding accordingly.
  • Fast fish for 24 hours before selection, handling, or transport.
  • Maintain detailed records of tank numbers, conversions, growth percentages, water flow, dissolved oxygen levels, and mortality rates.

Fish Reproduction

Natural Reproduction

Trout, like other salmonids, reach sexual maturity after two years. They return to freshwater streams to spawn, seeking shallow areas with sand and gravel. Females create nests with their tails and lay eggs, which males fertilize.

Visible signs of the reproductive period in females include a swollen belly due to eggs and a plump, rosy genital pore. Males exhibit a more elongated body and a slightly white-tinted first dorsal fin.

Artificial Reproduction

Requirements:
  1. Broodstock: A dedicated group of adult male and female trout for egg production. Separating males and females before spawning is recommended.
  2. Hatchery: A controlled environment for egg incubation, ideally dark and sized according to the number of eggs. Clean, clear water is crucial.
Spawning and Fertilization:

Involves the artificial expulsion of eggs from females and sperm from males. Two primary methods exist:

  • Dry Method (not recommended): Eggs in contact with water undergo micropyle closure, hindering fertilization.
  • Wet Method (recommended): Ensures micropyle remains open for successful fertilization.
Incubation:

Eggs are placed in incubation trays, either vertically or horizontally. Incubation typically lasts around 30 days, depending on water temperature.

Factors Affecting Production

  1. Fish-Related: Behavior, life stage, nutritional needs, environmental requirements, growth rate, food assimilation, health history, condition factor, cannibalism, oxygen uptake, waste production, stress tolerance, and adaptation to high stocking densities.
  2. Water-Related: Dissolved oxygen, nitrite, nitrate, alkalinity, pH, flow rate, ammonia, suspended and settled solids, temperature, transparency, pollutants, biological oxygen demand (BOD), and viscosity.
  3. Confinement-Related: Water volume, velocity, depth, exchange rate, pond design, and outlet configuration.
  4. Nutrition-Related: Feeding frequency, food type, nutritional quality, and storage conditions.
  5. Management-Related: Sampling techniques, sampling frequency, feeding methods, stocking density, pond maintenance, cleaning routines, size grading, handling, breeding practices, and production planning.

Oyster Hatchery

Broodstock Conditioning and Selection

  • Select oysters based on size, weight, and yield.
  • A medium-sized hatchery requires 40-50 broodstock oysters.
  • Condition oysters in 1,000-liter tanks with temperatures ranging from 20-23°C for 4-5 weeks.

Spawning

  • Induce spawning by raising the temperature from 20°C to 28°C.
  • Oysters release eggs (58-60μm in size), producing approximately 100 million eggs.

Fertilization

  • Maintain a sperm-to-egg ratio of 10:1 to prevent self-fertilization.

Post-Settlement Larval Culture

  • Cultivate larvae on 300μm particles until they reach 270μm.
  • Each larva attaches to a particle and grows independently.

Oyster Market Options

  1. Oysters for Meat: Cultivated on whole mollusk shells, with mass fixation in large groups, prioritizing meat production over shell appearance.
  2. Oyster Shells: Cultivated on substrates like sand or crushed shells, allowing individual oysters to attach and develop desirable shell shapes.

Pearl Net Pre-Culture

  • Employ a suspended pyramid-shaped net system with a square base.
  • Culture oysters for 3-4 months until they reach 2-2.5 cm in size.

Final Culture or Fattening

  • Duration varies depending on the desired market size.
  • Utilize either bottom or suspended culture systems.

Major Oyster Markets

Japan, Korea, Canada, USA, China, France, Germany.

ina, France, Germany.