Aquaculture Systems(Biofloc, pen, Cage, Raceway, RAS systems....... )

 

Aquaculture Systems

Clarius Batrachus and Crustacean Culture

• Species:
• Clarius batrachus (Catfish)
• Penaeus spp (Shrimp)
• Macrobrachium spp (Prawn)

Culture Operations

1. Seed Procurement: Collecting young fish or crustaceans for farming.
2. Cleaning Nursery and Fattening Pens: Ensuring pens are free from contaminants.
3. Stocking:
• Nursery pens: For young fish.
• Fattening (grow-out) pens: For larger fish.
4. Fertilization and Feeding: Providing nutrients for growth.
5. Maintenance of Pens: Regular checks and cleaning.

Advantages of Pen Culture

• Assured production in limited space with rich food and oxygen.
• Continuous water supply ensures a non-stop process.
• Maximum growth due to energy savings in movement and feeding.
• Reduced risk of mass mortality from toxic waste.
• Generates employment for local fisher-folk.
• Low capital investment and simple technology required.

Disadvantages of Pen Culture

• Vulnerable to unfavorable climatic conditions.
• Limited to still water bodies (lentic).
• High oxygen and water flow demand.
• Dependence on artificial feed.
• Risk of food losses and pollution.
• Rapid disease spread and theft risks.
• Conflicts with other water uses.

Aquaponics System

Introduction

• Definition: An eco-friendly food production system combining aquaculture (fish farming) and hydroponics (growing plants without soil).
• Cycle: Fish waste (ammonia) is converted by bacteria into nitrates, which plants use for growth, and the cleaned water is returned to the fish.

How Aquaponics Works

1. Fish are raised in a tank.
2. Water from the fish tank is pumped to the plants.
3. Bacteria convert ammonia and nitrite to nitrate.
4. Plants absorb nutrient-rich water.
5. Filtered water returns to the fish tank.

Advantages of Aquaponics

• Plants utilize nutrients from fish waste.
• Hydroponic plants act as biofilters.
• Integrated systems conserve water (up to 98% less than conventional farming).

Disadvantages of Aquaponics

• Requires knowledge of fish and plant care.
• Needs a reliable fish diet and energy source.
• Moderate initial capital costs for setup.

Recirculating Aquaculture Systems (RAS)

How RAS Works

• Definition: A technology that recycles water after filtration to maintain a controlled environment for high-density fish culture.
• Process: Water is filtered and cleaned, then reused in fish tanks, with minimal new water added.

Components of RAS

• Insulated building for fish farming.
• Grow-out tanks (circular cement or FRP).
• Settling tanks for sludge.
• Mechanical filters (drum filters, glass wool).
• Pumps, motors, and power generators.
• Biofilters and aeration systems.
• Water testing kits and supply systems.

Species Suitable for RAS

• Baramundi (Lates calcarifer)
• Cobia (Rachycentron canadum)
• Silver Pompano (Trachinotus spp)
• Tilapia (Oreochromis niloticus)
• Pearl Spot (Etroplus suratensis)
• Pangasius (Pangasianodon hypophthalmus)
• Rainbow Trout (Oncorhynchus mykiss)

Advantages of RAS

• Extended durability of tanks and equipment.
• Reduced dependency on antibiotics.
• Lower operational costs related to feed and predator control.
• Flexibility in farming location and market proximity.
• Enhanced feed management and monitoring.

Cage Culture and Pen Culture in Aquaculture

Cage Culture

• Definition: Rearing fish from juvenile to commercial size in a water volume enclosed on all sides, allowing free water circulation.
• Adaptability: Suitable for lakes, reservoirs, and riverine pools that cannot be drained.
• Countries: Popular in Japan, South Korea, China, Philippines, Thailand, Malaysia, Germany, Norway, and the USA.
• Cultivable Species: Includes carps, tilapia, trout, catfish, etc.

Types of Cages

1. Fixed Cages
2. Floating Cages
3. Submersible Cages
4. Submerged Cages

Site Selection for Cage Culture

• Materials Used:
• Frame: Bamboo, Wood, HDPE, Steel
• Netting Materials:
• Flexible: PA, PES, PE, PP
• Rigid: Netlon (HDPE)
• Lids: Plywood, Masonite, Steel
• Collar: Work platform
• Sinkers: Stones (3-4 Kg)
• Anchors: Stones (40-50 Kg)

Cage Specifications

• Volume: Typically between 100 and 500 cubic meters; smaller cages range from 1 to 36 square meters.
• Ideal Depth: 0.9 to 1.6 m
• Mesh Size:
• Fry: 4 to  6 mm
• Growout: 16 to 20   mm

Suitable Species for Cage Culture

• Tilapia
• Common Carp
• Trout
• Pangasius
• White Fish

Advantages of Cage Culture

• Utilizes various water resources (ponds, lakes, rivers).
• Requires relatively small financial investment.
• Simple feeding, sampling, observation, and harvesting.
• Water resource can be used for other activities.

Disadvantages of Cage Culture

• Crowded conditions can lead to disease spread.
• Potential for localized poor water quality.
• Caged fish require a complete diet as they lack access to natural food.
• Vulnerable to predators, vandals, and poachers.

Problems in Cage Fish Culture

• Acidification of freshwater bodies
• Currents
• Disease
• Drifting objects
• Fouling
• Oxygen depletion
• Predators
• Wastes
• Poaching and vandalism

Pen Culture (Enclosure Culture)

• Definition: Raising fish in a volume of water enclosed on all sides except the bottom, allowing free water circulation from at least one side.
• Hybrid System: Combines aspects of pond culture and cage culture.
• Location: Typically in shallow regions along shores and banks of lakes and reservoirs.

Characteristics of Pens

• Depth: 3-5 m in shallow waters (<10 m).
• Size: 2-7 hectares.
• Bottom Conditions: Prefer muddy, clayey, or sandy mud with detritus; avoid areas with excessive silt.

Shape, Size, and Design of Pens

• Shapes: Circular, square, or rectangular based on harvesting needs.
• Height: At least 50 cm, with 30 cm fixed into the bottom for stability.

Materials Used for Pen Culture

• Bamboo stakes
• Netting placed outside bamboo stakes

Advantages of Pen Culture

• Intensive space utilization.
• Safety from predators.
• Suitable for various species.
• Easy harvesting.
• Flexibility in size and economy.
• Availability of natural bottom and material exchange.

Environmental Impact of Pen Culture

• Space utilization
• Water flow and currents
• Predation
• Wild fish populations
• Toxic substances
• Eutrophication

Types of Pens

• Bamboo screen pens
• Monofilament cloth fencing pens
• Single-layered nylon webbing
• Double-layered pens

Criteria for Selection of Species for Pen Culture

1. Value of fish and market demand
2. Hardiness (ability to adjust to high density, disease, and handling)
3. Availability of fish seed or juvenile fish
4. Fast growth in confined waters
5. Availability of suitable feeds

Suitable Species for Pen Culture

• Milk Fish
• Chinese Carps
• Indian Carps
• Mullets
• Eels
• Catfish
• Tilapia
• Species that require supplementary feeding in low productivity habitats (e.g., Pangasius).

Aquaculture Systems

RAS (Recirculating Aquaculture Systems)

• Definition: RAS is a method of fish farming that recycles water to maintain a controlled environment.
• Advantages:
• Enables secure production of non-endemic species.
• Judicial use of water and land areas.
• Disadvantages:
• Requires constant, uninterrupted power supply; backup is necessary if power fails.
• High capital cost compared to ponds and raceways.

Raceway Systems

Introduction

• Definition: Raceway culture involves raising fish in running water, allowing for higher stocking densities.
• Design: Provides a flow-through system for rearing fish.

Types of Raceways

1. Earthen Flow-Through Ponds:
• Inexpensive to build.
• No need for supplemental oxygenation.
• Water flow must be maintained at low velocities to minimize erosion.
2. Concrete Raceways:
• Most modern raceways are constructed of concrete.
• Can increase production by 25% to 40% using the same amount of water.
• Typically consist of rectangular tanks with water flowing along the long axis.

Arrangement of Raceways

• Linear Type:
• Ponds arranged in sequence.
• Higher risk of disease transfer between ponds.
• Lateral Type:
• Ponds laid out in parallel.
• Fresh water supply ensures no disease transfer.

Site Characteristics

• Requires:
• Inexpensive and reliable supply of flowing water.
• Sufficient slope for gravity flow.
• Culture species that can tolerate high density.

Raceway Characteristics

• Individual raceways are long, narrow, shallow troughs.
• Common length to width ratio is 10:1
• Recommended length:width:depth ratio is 30:3:1.

Advantages of Raceways

• Higher production per unit of space compared to ponds.
• Easier observation of fish, leading to efficient feeding and early disease detection.
• Better monitoring of growth and mortality.
• Easier harvesting and size grading.

Disadvantages of Raceways

• Need for a large, consistent flow of high-quality water.
• Securing a proper water supply is crucial.
• Requires suitable topography for gravity flow.
• High volume of effluent released.

Biofloc Technology (BFT)

Introduction

• Definition: BFT is an aquaculture technique that recycles nutrients with minimal or zero water exchange.
• Composition: Biofloc consists of aggregates of living and dead organic matter, phytoplankton, bacteria, and grazers.

How BFT Works

• Maintains a high carbon-to-nitrogen (C-N) ratio by adding carbohydrate sources.
• Improves water quality through the production of high-quality microbial protein.
• Heterotrophic microbial growth assimilates nitrogenous waste, providing feed for cultured species.

Composition and Nutritional Value of Biofloc

• Composed of bacteria, algae, fungi, invertebrates, and detritus.
• Protein content ranges from  25%  to 50%  fat from 0.5% to 15%.
• Good source of vitamins and minerals, particularly phosphorus.
• Acts similarly to probiotics in promoting health.

Summary

• RAS and raceway systems are efficient aquaculture methods with distinct advantages and challenges.
• Biofloc technology offers an innovative approach to nutrient recycling and water quality management in aquaculture.

Biofloc and Pond Aquaculture

Biofloc Preparation

Method I

1. Water Preparation
• Use 150 Litres of clean water in a tub/can.
• Ensure vigorous aeration.
2. Add Ingredients
• 3 Kg of pond soil
• 1.5 gm of Ammonium sulphate or Urea
• 30 gm of carbon source (e.g., Jaggery, Wheat flour, Tapioca flour)
3. Mix and Aerate
• Mix well and continue aeration.
4. Inoculum Readiness
• The inoculum will be ready in 24-48 hours for transfer to the main tank.

Method II

1. Water Preparation
• Use 130 Litres of clean water in a tub/can.
• Ensure vigorous aeration.
2. Add Ingredients
• 20 Litres of pond water or RAS water (before filtration)
• 30 gm of carbon source (e.g., Jaggery, Wheat flour, Tapioca flour)
• 10 gm of probiotic (with Bacillus Sp., Aspergillus Sp., etc., at a concentration of  10 ^9  CFU/gm)
3. Follow Remaining Steps
• Continue with the same steps as in Method I.

Notes

• A well-developed inoculum appears turbid with foam on the surface.
• Ideal floc volume in Imhoff cone:
• Shrimp:  10-15    ml/L
• Fish:  25-35  ml/L

Carbon Source Addition

• Daily addition of carbon is required.
• For every 1 kg of feed (with 25% crude protein), add 600 gm of carbon source to maintain a C:N ratio of  10:1
• Once floc volume reaches  15-20   ml further carbon addition is not needed.

Suitable Species for Biofloc Culture

• Air-breathing Fish:
• Singhi  Heteropneustes fossilis
• Magur  Clarias batrachus
• Pabda  Ompok pabda
• Anabas  Anabas testudineus
• Pangasius  Pangasianodon hypophthalmus
• Non Air-breathing Fish:
• Common Carp  Cyprinus carpio
• Rohu  Labeo rohita
• Tilapia  Oreochromis niloticus
• Milkfish  Chanos chanos
• Shellfish:
• Vannamei  Litopenaeus vannamei
• Tiger Shrimp  Penaeus monodon

Benefits of Biofloc System

• Eco-friendly culture system.
• Reduces environmental impact.
• Improves land and water use efficiency.
• Limited or zero water exchange.
• Higher productivity (enhanced survival, growth, and feed conversion).
• Higher biosecurity.
• Reduces water pollution and pathogen spread.
• Cost-effective feed production.

Disadvantages of Biofloc System

• Increased energy requirement for mixing and aeration.
• Reduced response time due to elevated respiration rates.
• Start-up period required.
• Alkalinity supplementation needed.
• Increased pollution potential from nitrate accumulation.
• Inconsistent performance in sunlight-exposed systems.

Pond Aquaculture

Introduction

• Ponds are small, confined bodies of standing water used for growing fish or crustaceans in commercial aquaculture.

Structure

• Types of Ponds:
• Embankment ponds (most common)
• Excavated ponds
• Watershed ponds

Water Use

• Pond aquaculture uses large volumes of water, with sources including:
• Precipitation
• Runoff from watersheds
• Groundwater

Construction Steps

1. Prepare the site (remove trees, bushes, rocks).
2. Construct a clay core for a leak-free dyke.
3. Dig the pond and build the dyke over the clay core.
4. Construct inlet and outlet.
5. Protect the dyke with soil and plant grass (e.g., Rhodes grass, Star grass).
6. Fence the pond to protect against theft and predators.

Design Considerations

• Various ponds (nursery, rearing, stocking, treatment) are required.
• Ideal pond shape: rectangular (3:1 length to breadth ratio).
• Maximum breadth: 30-50 m.

Pond Area Allocation

• Nursery pond: 5% of total area
• Rearing pond: 20% of total area
• Stocking pond: 70% of total area
• Bio pond/Treatment pond: 5% of total area

Pre-stocking Management

• Eradicate undesirable fish and weeds.
• Lime the pond.
• Fill with water and apply basal manuring and fertilization.
• Prepare the pond (drying, desilting, reconstruction).

Post-stocking Management

• Manuring and fertilizing.
• Supplementary feeding.
• Regular fish sampling.
• Harvesting.

Criteria for Species Selection

• Fast growth rate.
• Short food chain.
• Climate adaptation.
• Consumer preference.
• Tolerance to water condition fluctuations.
• Resistance to diseases and parasites.
• Easy reproduction under controlled conditions.
• Compatibility with other species.

Cultivable Species

• Indian major carps: Catla, Rohu, Mrigal.
• Exotic carps: Grass carp, Common carp, Minor carp.
• Tilapia.
• Seabass  Lates calcarifer .

Advantages of Pond Aquaculture

• Can be a low-tech method of fish culture.

Fish Production Ponds

Advantages

• Minimal Labor:
• A small amount of labor can effectively manage large areas of pond acreage.
• Compatibility with Crop Operations:
• Pond culture can be integrated with other farming activities, allowing for diversified farming practices.

Disadvantages

1. Land Costs/Availability:
• The cost and availability of suitable land can be a significant barrier.
2. Land Intensive Practice:
• Requires a considerable amount of land for effective fish production.
3. Construction Costs:
• Initial setup and construction of ponds can be expensive.
4. Renovation Needs:
• Ponds may require renovation every 8 to 10 years to maintain productivity.
5. Predators and Pathogens:
• Fish ponds are vulnerable to threats from predators and diseases.
6. Environmental Management:
• Must manage various factors such as:
• Weather events
• Temperature fluctuations
• Water quality
• Algal blooms

These factors can complicate fish management and affect production outcomes.