Animal Husbandry – Fish Production – Long Answer Questions
Medium Level (Application & Explanation)
Q1. Explain the difference between capture fishing and culture fishery. Give examples, and state one advantage and one disadvantage of each.
Answer:
Capture fishing means catching fish from natural waters like seas, rivers, reservoirs and lakes. Examples include catching mackerel, tuna from the sea or local river fish.
Advantage: It uses natural fish populations and can be low-cost for fishers.
Disadvantage: It depends on wild stocks and can lead to overfishing and unpredictable catches.
Culture fishery (fish farming) is raising fish in controlled ponds, tanks or cages. Examples include pond culture of carps or prawn farms.
Advantage: It gives a steady and predictable supply of fish and helps meet demand.
Disadvantage: It needs investment, management, and may cause water pollution if not managed well.
In short, capture fishing relies on nature; culture fishery relies on human management.
Q2. Describe composite fish culture. Why are certain species chosen to be grown together? Mention the main benefits.
Answer:
Composite fish culture means growing five or six different species together in the same pond. The species are chosen so they do not compete for the same food and occupy different layers of the pond.
For example, Catla (surface feeder), Rohu (middle feeder), Mrigal and Common Carp (bottom feeders), and Grass Carp (weed eater) can share a pond.
Benefits:
It uses the entire food resources of the pond (surface, middle, bottom, weeds).
This increases total yield per unit area without increasing pond size.
It reduces waste because each species consumes a different food niche.
Thus, composite culture improves productivity and efficiency by smart species selection.
Q3. What is mariculture? Explain why mariculture is becoming important in India and list two challenges faced in practising mariculture.
Answer:
Mariculture is the farming of aquatic organisms in seawater — for example, farming prawns, oysters, mussels, seaweeds, mullets and bhetki in coastal areas.
It is becoming important in India because marine fish stocks are declining due to heavy fishing. Mariculture helps meet the increasing demand for fish and adds economic value through high-value species like prawns and oysters (pearls).
Two challenges:
Environmental risks such as coastal pollution, disease outbreaks, and habitat damage from poorly managed farms.
Technical and investment needs, including infrastructure, hatcheries for seeds, and skilled management.
Mariculture can help food security and livelihoods if practiced sustainably and responsibly.
Q4. Explain how satellites and echo-sounders help in modern marine fishing. What are the advantages of using this technology?
Answer:
Satellites provide large-scale information on sea surface temperature, currents and plankton blooms. Fish often gather where conditions are favourable, so satellite data help identify these areas.
Echo-sounders use sound waves to detect schools of fish under boats. They show depth and density of fish below the vessel.
Advantages:
Fishermen can locate schools quickly, reducing time and fuel costs.
They increase catch efficiency and help plan safer navigation.
These tools aid in sustainable fishing by targeting specific areas and avoiding random over-exploitation.
Overall, technology makes marine fishing more precise, economical, and data-driven.
Q5. Describe how fish farming can be integrated with rice cultivation. State two benefits and two precautions a farmer should take.
Answer:
Fish can be grown in the flooded fields of paddy (rice) cultivation during the cropping season. Small fish are introduced into the paddy water where they feed on insects, weeds and leftover organic matter, while rice plants grow above.
Benefits:
Provides additional income and a source of animal protein for the farmer.
Fish help control pests and weeds, reducing the need for chemical pesticides and increasing rice yields.
Precautions:
Ensure fish species are compatible with paddy water depth and do not damage rice roots.
Maintain good water quality and proper drainage so both rice and fish get required conditions.
Integrated farming improves resource use and sustainability when managed well.
High Complexity (Analytical & Scenario-Based)
Q6. A small farmer has one pond (0.1 hectare) and wants to maximize yield sustainably using composite fish culture. Propose a practical plan including species selection, stocking density, feeding, and basic water management.
Answer:
Species selection: Use a mix of surface, column, bottom feeders and a weed eater — for example Catla (surface), Rohu (column), Mrigal or Common Carp (bottom), and Grass Carp (weed control). This reduces food competition.
Stocking density: For 0.1 ha, keep moderate density—about 1000–1500 fingerlings total, proportioned by species (e.g., 25% Catla, 25% Rohu, 30% Mirgal/Carp, 20% Grass Carp). Avoid overcrowding to prevent oxygen stress.
Feeding: Provide balanced supplementary feed (home-made or commercial) based on species needs; feed twice daily and avoid overfeeding to reduce pollution.
Water management: Maintain dissolved oxygen (aerate if needed), remove excess weeds, monitor pH (6.5–8), and exchange partial water when quality declines.
Seed quality: Use disease-free certified seeds. Regularly check fish health and harvest progressively to ensure steady income.
Q7. Analyze reasons for declining marine fish stocks. How can mariculture and inland aquaculture together reduce pressure on wild fish and support livelihoods?
Answer:
Reasons for decline: Overfishing, use of destructive gear, habitat loss (mangrove cutting, coastal pollution), and climate change affecting fish distribution. High demand increases pressure on wild populations.
Role of mariculture and inland aquaculture:
Mariculture farms high-value marine species (prawns, oysters, seaweed), reducing dependence on wild catches and providing alternative incomes for coastal communities.
Inland aquaculture (ponds, reservoirs) increases freshwater fish production, supplying local markets and reducing market demand for marine stocks.
Combined benefits:
They provide stable employment and income, diversify rural livelihoods, and improve food security.
With proper regulation and sustainable practices, aquaculture can relieve fishing pressure, allow wild stocks to recover, and promote ecosystem conservation.
Therefore, both forms complement capture fisheries and help balance resource use and livelihoods.
Q8. Many farmers face the problem of mixed or poor-quality fish seeds. Explain how a hatchery can produce pure and good-quality seeds using hormonal stimulation and broodstock management.
Answer:
Broodstock selection: Choose healthy, genetically good adult fish kept in clean conditions. Maintain separate tanks to avoid unwanted mixing of species. Proper nutrition and quarantine reduce disease.
Hormonal stimulation: Some species breed only in monsoon; hatcheries use hormonal injections (under expert guidance) to induce timed spawning in ponds or tanks. This helps to produce seeds out of season and ensures synchronized spawning.
Controlled spawning: Eggs and milt are collected and fertilized in controlled conditions. Use suitable incubation and protect hatchlings from predators.
Quality control: Monitor water quality, temperature and feed larvae appropriate food. Label and record seed batches to maintain traceability.
Result: Hatcheries produce pure, healthy, disease-free seeds year-round, helping farmers get reliable stock and higher yields.
Q9. Discuss the environmental impacts of intensive aquaculture and list at least four strategies to mitigate these impacts while keeping production efficient.
Answer:
Environmental impacts: Intensive aquaculture can cause water pollution from uneaten feed and faeces, eutrophication, disease spread to wild populations, genetic mixing with wild fish, and habitat changes (mangrove loss for ponds). It can also lead to antibiotic resistance if drugs are misused.
Mitigation strategies:
Use balanced feeding and proper feed management to reduce waste and nutrient loading.
Apply regular water exchange and filtration systems, and use biofilters or wetlands to treat effluents before discharge.
Practice integrated multi-trophic aquaculture (IMTA) — combine species like seaweed and shellfish that absorb waste nutrients.
Maintain hygiene, vaccination and reduced antibiotic use, and implement strict biosecurity to prevent disease.
These steps help reduce environmental harm while sustaining productive aquaculture.
Q10. Design an integrated coastal aquaculture system that includes oysters, seaweed, and prawns. Explain the ecological interactions, economic benefits, and one major management challenge.
Answer:
Design overview: Use coastal plots or cages where prawns are farmed in sheltered ponds or enclosures, oyster racks are placed in intertidal zones, and seaweed lines are grown nearby. The layout allows water flow so nutrients move between units.
Ecological interactions: Seaweeds absorb dissolved nutrients (nitrogen, phosphorus) from prawn effluents, reducing eutrophication. Oysters filter suspended particles, improving water clarity. Together they recycle waste and create a balanced system.
Economic benefits: Multiple products (prawns, oysters/pearls, seaweed) give diverse income streams, reduce risk, and increase tota...
