Composite Fish Culture – Definition, Steps, Advantages

What is Composite Fish Culture?

• Composite fish culture refers to a sophisticated aquaculture technique that involves the simultaneous cultivation of compatible fish species within a single aquatic environment. This method strategically utilizes various feeding zones within a pond, allowing for a more efficient exploitation of available natural resources. The primary objective of composite fish culture is to maximize the total fish yield per unit area of water by ensuring that different species occupy distinct ecological niches and thus minimize competition for food and space.
• In essence, composite fish culture promotes the diversification of fish species in aquaculture practices, typically focusing on species that are compatible in terms of feeding habits and growth rates. By integrating multiple species, fish farmers can take full advantage of the biological productivity of the pond, leading to increased fish production. This approach allows for optimal utilization of available fish feed, both natural and supplemental, which is crucial in enhancing the overall output of the system.
• Carp culture, particularly, has gained prominence within the realm of composite fish culture. This practice not only proves to be economically viable but also provides significant returns on investment, making it an attractive option for fish farmers, especially those operating with limited financial resources. Compared to traditional fish farming methods, composite fish culture offers a more accessible entry point for farmers, enabling them to achieve higher production levels and, consequently, improved income.
• Historically, fish has served as a critical source of animal protein for human consumption. However, factors such as overexploitation of natural water bodies and environmental pollution have led to a significant decline in fish availability. To address these challenges, scientists and aquaculturists have developed various strategies, including composite fish culture, to enhance fish production sustainably. This method facilitates fish farming in diverse environments, such as village ponds and tanks, empowering farmers to improve their economic circumstances while contributing to local food security.
• The practical application of composite fish culture can extend to various water bodies, including perennial freshwater ponds and tanks, provided that they maintain a minimum water depth of two meters, although depths should not fall below one meter. Additionally, even seasonal ponds can be utilized for short-duration fish culture, further expanding the opportunities for fish farming.

Steps in Composite Fish Culture

1. Site selection

Site selection is a critical aspect of aquaculture that significantly influences the success of fish farming operations. Choosing an appropriate site requires a comprehensive evaluation of various factors that can affect fish health, growth, and overall productivity. The process can be categorized into three main areas: ecological, biological, and economic-social considerations.

• Ecological Factors: The site should be evaluated based on its environmental characteristics. Key elements include:
  • Location: The geographical area must be suitable for aquaculture and must support the desired species.
  • Topography: The landscape should facilitate water flow and management.
  • Soil Suitability: Soil types should be conducive to pond construction and maintenance. Clayey loam soil is ideal due to its low permeability and high fertility. Its composition typically includes:
    • Sand: 20-45%
    • Silt: 15-23%
    • Clay: 27-40%
  • Water Quality and Quantity: Essential water quality parameters include:
    • pH: An optimal range is between 7.5 and 8.5.
    • Dissolved Oxygen (DO): Levels should exceed 5 ppm to support healthy fish growth.
    • Salinity: Should remain below 2 ppt to prevent stress on freshwater species.
  • Hydrological Factors: The site should have adequate water availability and hydrological conditions to ensure consistent water levels.
  • Meteorological Factors: Weather patterns and seasonal variations can impact fish growth and health.
• Biological Factors: Successful fish culture relies on understanding the biological interactions within the aquaculture system. This includes:
  • Species Selection: The chosen species must be compatible and suited for the environment.
  • Predator Control: Measures should be in place to manage natural predators that may threaten fish stocks.
  • Disease Control: Effective management practices must be established to mitigate disease outbreaks.
• Economic and Social Factors: These considerations are essential for the sustainability and viability of the fish farming operation. Factors to consider include:
  • Type of Facility: The design and structure of the fish farming setup must align with the operational goals and budget.
  • Marketing: Understanding market access and demand for the selected species is vital.
  • Safety and Security: Measures should be taken to protect the facility and fish stocks from theft or environmental hazards.
  • Social Considerations: The impact on local communities and engagement with stakeholders should be evaluated.
• Pond Characteristics: Specific physical attributes of the pond are critical for effective fish culture:
  • Pond Area: An ideal size ranges from 0.5 to 2 hectares; however, ponds as small as 0.02 hectares can be utilized.
  • Depth: A depth of 1.5 to 2 meters is recommended to maintain stable conditions and support aquatic life.
• Additional Construction and Management Considerations:
  • Desilting: Regular removal of sediment from existing ponds to maintain water quality.
  • Deepening Shallow Ponds: Enhancing water depth for better habitat conditions.
  • Excavation of New Ponds: Creating new sites for fish farming to expand production capacity.
  • Impoundment of Marginal Areas: Utilizing underused water bodies for aquaculture.
  • Construction and Repairs: This includes embankments, inlets, and outlets to control water flow and maintain pond integrity.
  • Infrastructure Needs: Facilities for water supply, electricity, and any necessary civil structures, including watchmen’s sheds, should be planned based on the project requirements.

2. Pond Management

Pond Management plays a very important role in fish farming before and after the stocking of fish seed.

A. Prestocking

Prestocking operations are essential for preparing a pond for fish farming, particularly in new ponds or existing ponds that require enhancement. These operations aim to create an optimal environment for fish growth by addressing various ecological and chemical factors before introducing fish. A series of systematic steps must be followed to ensure that the pond is conducive to supporting aquatic life.

• Liming and Water Filling: For new ponds, the initial step involves applying lime to the pond and subsequently filling it with water. This process helps in adjusting the pond’s pH and enhancing overall productivity.
• Clearing Unwanted Vegetation and Fish: Prior to stocking, it is crucial to eliminate undesirable weeds and fish. This can be accomplished through various methods:
  • Weed Removal: Techniques include:
    • Manual or Mechanical: Hand-pulling or using tools to physically remove weeds.
    • Chemical: Applying herbicides such as 2,4-D (2,4-dichlorophenoxyacetic acid), paraquat, aqueous ammonia, or Diuron/Karmex to kill unwanted vegetation.
    • Biological: Introducing species such as grass carp, tilapia, common carp, pearl spot, or giant gourami that consume unwanted weeds.
  • Removal of Unwanted Fish: This involves using methods such as:
    • Netting: Repeatedly using nets to catch and remove unwanted or predatory fish.
    • Toxicants: Employing mahua oil cake at a dosage of 2500 kg/ha, tea seed cake at 15 ppm for low salinity, or tamarind seed powder at 175-200 ppm.
• Liming: The application of lime is essential for adjusting the pH of acidic soils, which are typically less productive than alkaline ones. The benefits of liming include:
  • Increasing the pH to a desirable level.
  • Acting as a buffer to stabilize pH fluctuations.
  • Enhancing soil resistance to parasites.
  • Killing harmful parasites through its toxic effects.
  • Accelerating organic decomposition within the pond.
  The recommended lime application rates vary based on soil pH:
  • Soil pH of 4.0-4.5: Highly acidic (1000 kg/ha)
  • Soil pH of 4.5-5.5: Medium acidic (700 kg/ha)
  • Soil pH of 5.5-6.5: Slightly acidic (500 kg/ha)
  • Soil pH of 6.5-7.5: Near acidic (200 kg/ha)
  • Soil pH of 7.5-8.5: Alkaline (no lime required)
  Common liming materials include calcium carbonate, calcium oxide, and calcium hydroxide.
• Fertilization/Manuring: Fertilization is a vital practice to enhance the natural productivity of the pond and support fish growth. The fertilization schedule should be tailored to the specific conditions of the pond and may include:
  • Organic Fertilizers:
    • Farm yard manure (FYM) such as cow dung (approximately 5000 kg/ha).
    • Other organic sources like poultry or sheep manure and crop byproducts, including cottonseed meal and mustard oil cake.
  • Inorganic Fertilizers: These should be applied approximately 15 days after organic manuring. The requirements for nitrogenous and phosphate fertilizers vary based on soil fertility:
    • Nitrogen Fertilization:
      • High fertility (51-75 mg/100 g soil): Ammonium sulfate 70 kg/ha/month or urea 30 kg/ha/month.
      • Medium fertility (26-50 mg/100 g soil): Ammonium sulfate 90 kg/ha/month or urea 40 kg/ha/month.
      • Low fertility (up to 25 mg/100 g soil): Ammonium sulfate 140 kg/ha/month or urea 60 kg/ha/month.
    • Phosphorus Fertilization:
      • High fertility (7-12 mg/100 g soil): Single super phosphate 40 kg/ha/month or triple super phosphate 15 kg/ha/month.
      • Medium fertility (4-6 mg/100 g soil): Single super phosphate 50 kg/ha/month or triple super phosphate 20 kg/ha/month.
      • Low fertility (up to 3 mg/100 g soil): Single super phosphate 70 kg/ha/month or triple super phosphate 30 kg/ha/month.

B. Stocking

Stocking is a critical phase in fish culture, where the prepared pond is populated with fish fingerlings. This step is essential for establishing a thriving aquatic ecosystem that maximizes productivity and sustainability. The timing and methodology of stocking influence the growth rates and survival of the fish, thereby directly affecting overall yield.

• Timing for Stocking: The pond is deemed ready for stocking approximately 15 days after the application of fertilizers. This waiting period allows for the establishment of a favorable environment, promoting the growth of natural food sources.
• Size and Quantity of Fingerlings: Fish fingerlings of size 50-100 grams are recommended for stocking. The stocking density typically ranges from 5,000 to 8,000 fingerlings per hectare. However, if smaller fingerlings are used, it is advisable to adjust the stocking density to account for potential mortality.
• Duration of Rearing: The model suggests rearing the stocked fingerlings for a period of 10 to 12 months. This duration enables the fish to grow to marketable sizes, thus enhancing profitability.
• Species Selection and Combination: The selection of fish species is vital in composite fish culture. A mixture of Indian and exotic fish varieties is often utilized based on their compatibility and feeding habits. The combinations can vary based on market conditions and the availability of seeds, commonly involving 3, 4, or 6 species. The recommended ratios for species combinations include:
  • Three-Species Combination:
    • Catla: 4.0
    • Rohu: 3.0
    • Mrigal: 3.0
  • Four-Species Combination:
    • Catla: 3.0
    • Rohu: 3.0
    • Mrigal: 2.0
    • Common Carp: 2.0
  • Six-Species Combination:
    • Catla: 1.5
    • Rohu: 2.0
    • Mrigal: 1.5
    • Silver Carp: 1.5
    • Grass Carp: 1.5
    • Common Carp: 2.0
• Feeding Groups and Habits: Understanding the feeding habits of each species is crucial for effective management and growth optimization. The species are categorized based on their feeding zones:
  • Surface Feeders (40% of total stock):
    • Catla (25%)
    • Silver Carp (15%)
  • Column Feeders (20% of total stock):
    • Rohu (20%)
  • Bottom Feeders (30% of total stock):
    • Mrigal (15%)
    • Common Carp (15%)
  • Macrovegetation Feeders (10% of total stock):
    • Grass Carp (10%)
• Water Quality Parameters: Maintaining optimal water quality is crucial for the successful stocking and growth of fish. The safe limits for various water quality parameters include:
  • Turbidity: 30-45 cm
  • Salinity: Less than 0.5 ppt
  • Dissolved Oxygen: Minimum of 5 ppm
  • Un-ionized Ammonia: Less than 0.05 ppm
  • Nitrite: Less than 0.1 ppm
  • Nitrate: 50-150 ppm
  • Carbon Dioxide: Less than 8 ppm
  • Iron: Less than 0.5 ppm
  • Total Alkalinity: 20-150 ppm
  • Total Hardness: 20-200 ppm
  • Hydrogen Sulfide: Less than 0.002 ppm

C. Post stocking

Post-stocking management is a crucial phase in fish culture that directly influences the health and growth of the stocked fish. Proper care and maintenance strategies must be implemented to ensure optimal conditions for the fish to thrive, which includes supplementary feeding and manuring.

• Supplementary Feeding: Fish often require more nutrition than what is available naturally within the pond environment.
  • A balanced diet can be provided by a mixture of rice bran and oilcakes in a ratio of 4:1.
  • Given the high cost of Groundnut Oil Cake (GOC), alternative sources such as Cotton Seed Oil Cake are recommended. The latter is more cost-effective and can be mixed with GOC in equal proportions to maintain similar growth rates.
  • Feeding can be performed by placing the mixture in feeding trays or bags, which can be lowered to the pond bottom or scattered at the corners. This method encourages fish to gather in specific areas, enhancing feeding efficiency and minimizing feed waste.
  • Initially, the recommended feeding rate is approximately 5-6% of the fish’s body weight for fish weighing up to 500 grams. Once fish grow larger, from 500 to 1000 grams, the feeding rate should be reduced to 3.5% of body weight.
  • It is important to note that this feeding is supplementary, meaning it is intended to enhance the natural food available rather than replace it.
• Manuring: Manuring is another essential practice that supports fish growth by increasing the natural productivity of the pond.
  • Organic manuring should be conducted in monthly installments at a rate of about 1,000 kg per hectare. This practice enriches the pond environment with nutrients that promote the growth of phytoplankton and other natural food sources.
  • Inorganic fertilization should also be applied at monthly intervals, alternating with organic manuring. The rates of fertilization depend on several factors, including the productivity of the pond and the growth rates of the fish.
  • Care must be taken to avoid over-fertilization, as this can lead to eutrophication, a process characterized by excessive nutrient enrichment that can deplete oxygen levels and harm aquatic life.

D. Harvesting

Harvesting represents a critical phase in aquaculture, marking the culmination of the growth cycle and directly impacting the overall productivity and profitability of fish farming. This process is primarily executed at the end of the first year when the fish reach an average weight between 800 grams and 1.25 kilograms. Proper management practices can facilitate a production yield of approximately 4 to 5 tons per hectare within this timeframe.

• Timing of Harvesting: The timing of the harvest is crucial. Fish are typically harvested once they reach the desired weight. Careful monitoring of growth rates ensures that harvesting occurs at optimal times, maximizing yield while maintaining quality.
• Methods of Harvesting: Various techniques can be employed to harvest fish, each with distinct advantages depending on the operational scale and specific circumstances.
  • Partial Dewatering and Netting: This method involves lowering the water level in the pond and utilizing nets to capture the fish. It allows for the harvesting of a significant number of fish while leaving others in the pond to continue growing. This technique can be particularly beneficial if market demand fluctuates or if conditions in the pond remain favorable for further growth.
  • Complete Dewatering: In some cases, complete dewatering of the pond may be necessary. This approach facilitates a thorough collection of all fish present in the pond, ensuring no fish are left behind. However, this method can stress the remaining aquatic ecosystem, requiring careful management to minimize negative impacts.
  • Partial Harvesting: Some farmers may choose to engage in partial harvesting, which involves selectively removing fish based on size, market demand, or other criteria. This strategy helps maintain a stable fish population in the pond and can align better with market needs.
• Post-Harvest Considerations: After harvesting, it is vital to consider the health of the pond environment and the remaining fish.
  • Stock Management: If partial harvesting occurs, careful stock management is necessary to ensure that the remaining fish have adequate resources to thrive.
  • Water Quality: Monitoring and maintaining water quality parameters is essential post-harvest to prevent any negative impacts on the remaining fish population and overall pond health.

Advantages of composite fish culture

The advantages of composite fish culture are multifaceted, leading to improved yields and economic benefits for fish farmers.

• Enhanced Productivity: One of the primary benefits of composite fish culture is its potential for high production rates. By integrating various species with different feeding habits and ecological niches, this method maximizes the utilization of available feed and resources within the pond. Therefore, a balanced ecosystem is created, leading to improved growth rates among the cultivated species.
• Diverse Market Offerings: Farmers can strategically choose species based on market demand, allowing for flexibility in production. This adaptability helps mitigate the risks associated with market fluctuations by enabling farmers to adjust their stock composition to align with consumer preferences.
• Efficient Resource Use: Composite fish culture promotes the efficient use of space and food resources. By selecting species that occupy different layers of the water column (e.g., surface, column, and bottom feeders), competition for food and space is minimized. This vertical stratification leads to better growth performance across species, as they exploit different resources without significant overlap.
• Sustainability: This method contributes to sustainable aquaculture practices by fostering a balanced aquatic ecosystem. The interaction between different species can enhance nutrient cycling, thereby improving water quality and reducing the need for chemical inputs. The inclusion of herbivorous and detritivorous species helps manage organic matter and supports a healthier environment for all fish.
• Reduced Risk of Disease: The diversity in species can potentially lower the risk of disease outbreaks. When different species are cultured together, the spread of pathogens may be limited, as the varied immune responses of different species can create a buffer against disease proliferation.
• Higher Economic Returns: Due to increased productivity and the ability to respond to market demands, composite fish culture often results in higher economic returns for farmers. The combined benefits of efficient feed utilization, diverse product offerings, and sustainable practices contribute to improved profitability.
• Educational Opportunities: The complexity of managing a diverse ecosystem allows for enhanced learning and innovation among aquaculture practitioners. Farmers can gain valuable insights into ecological relationships, fish behavior, and sustainable practices, thereby fostering a culture of continuous improvement within the aquaculture industry.