PYQ – MZOE-003: Aquaculture (Solved Q&A) | MZOE-003 | MSCZOO | M.Sc.Zoology | IGNOU | December 2024

M.Sc. (Zoology) (MSCZOO)
Term-End Examination
December, 2024
MZOE-003 : AQUACULTURE

Time  : 2 Hours | Maximum Marks : 50

Note: Answer any five questions. All questions carry equal marks.

1. (a) Enumerate the different constraining factors for aquaculture development. (5 Marks)

Aquaculture is a rapidly growing sector that holds promise for food security and economic development. However, several constraints affect its sustainable growth. These constraints can be classified into the following categories:

1. Environmental Constraints

Water is the most essential component of aquaculture. But the increasing pollution of natural water bodies, salinity intrusion, water scarcity and eutrophication are major problems. Moreover, climate change leads to unpredictable rainfall, increasing water temperature, and extreme weather events like floods and droughts, all of which disturb aquaculture operations and productivity.

2. Economic Constraints

High cost of fish feed, medicines, quality seed and other inputs make aquaculture expensive. Small farmers often face difficulty in accessing loans, insurance and government subsidies. Market-related issues like price fluctuation, middlemen exploitation, and lack of cold storage and transport facilities also reduce profit margins.

3. Technical Constraints

There is a significant gap in technical knowledge, especially in rural areas. Lack of trained personnel, modern equipment and diagnostic labs for disease detection weakens the system. Poor extension services and limited exposure to scientific farming practices also hamper growth.

4. Social Constraints

Aquaculture projects often face resistance from local communities due to land and water use conflicts. Gender inequality, lack of awareness and poor community participation also affect implementation. In many places, aquaculture is not yet considered a primary livelihood option.

5. Policy and Legal Constraints

Many states lack a clear aquaculture policy. There is often delay in licensing, poor coordination among departments and unclear land ownership rights. Weak enforcement of environmental regulations and poor monitoring lead to overexploitation of resources and discourage long-term investments.

(b) Explain with suitable illustrations the characteristic zone of marine environment. (5 Marks)

The marine environment is divided into five major ecological zones based on depth, distance from shore and light penetration. These zones are: Littoral zone, Neritic zone, Oceanic zone, Pelagic zone and Benthic zone.

1. Littoral Zone:

This is the shallow coastal area between high and low tide marks. It is regularly exposed to air during tides. This zone receives plenty of sunlight and nutrients, supporting rich biodiversity like mollusks, crabs, algae and small fishes. It is also known as the intertidal zone.

2. Neritic Zone:

This zone extends from the low tide line to the edge of the continental shelf. It is relatively shallow (up to 200 meters), receives ample sunlight and has high nutrient availability. Coral reefs, seaweeds and many commercial fish species like sardines and anchovies are found here. It is the most productive marine zone.

3. Oceanic Zone:

Beyond the continental shelf lies the oceanic zone, which is deep and vast. Sunlight penetration is limited to the upper layers. This zone includes both photic (light-receiving) and aphotic (dark) regions. Organisms such as whales, deep-sea fishes and squids are found here.

4. Pelagic Zone:

This refers to the open water column of the ocean, from the surface to the deep sea. It includes both neritic and oceanic waters but excludes the sea floor. Organisms like tuna, plankton and jellyfish float or swim in this zone.

5. Benthic Zone:

This is the ocean floor, extending from shallow coastal areas to deep-sea trenches. It includes sediment-dwelling organisms like starfish, sea cucumbers and benthic bacteria. It plays a key role in nutrient recycling.

2. (a) List out the different fish species in Indian reservoirs. (5 Marks)

Indian reservoirs are man-made freshwater bodies that support a wide range of fish biodiversity. These fishes are important for inland fisheries, local livelihoods and ecological balance. Based on their nature and origin, there are four major categories of fish species commonly found in Indian reservoirs:

1. Indian Major Carps (IMCs)

These are the most important native species, widely cultured due to their fast growth and market demand.

Examples:

• Catla catla (Catla)
• Labeo rohita (Rohu)
• Cirrhinus mrigala (Mrigal)

2. Exotic Carps

These are non-native fishes introduced to increase fish production due to their fast growth and compatibility with Indian species.

Examples:

• Cyprinus carpio (Common carp)
• Hypophthalmichthys molitrix (Silver carp)
• Ctenopharyngodon idella (Grass carp)

3. Catfishes and Murrels

These fishes are bottom dwellers or predatory species that naturally occur or are stocked for ecological balance and diversity.

Examples:

• Wallago attu
• Mystus seenghala
• Ompok bimaculatus
• Channa striata (Murrel)

4. Other Important Species

Some less common but ecologically or commercially significant fishes also exist in reservoirs.

Examples:

• Notopterus notopterus (Featherback)
• Pangasius spp. (when introduced)

[Note: Marine or brackish water fishes are not naturally present in reservoirs since these are freshwater ecosystems, but a few euryhaline species like Pangasius can be cultured under specific conditions.]

(b) Discuss the biology of Pinctada fucata or Holothuria scabra. (5 Marks)

Biology of Pinctada Fucata

Pinctada fucata, commonly known as the Indian pearl oyster, belongs to the family Pteriidae under the class Bivalvia. It is well known for its ability to produce high-quality pearls. This species is mainly found in the coastal waters of India, Japan and the Indo-Pacific region.

The body of Pinctada fucata is enclosed within two calcareous shells joined by a hinge. The outer shell is rough and brownish, while the inner layer is smooth and shiny due to nacre or mother-of-pearl. It has a well-developed adductor muscle that helps in closing the shell tightly. The mantle, a thin tissue under the shell, secretes nacre and is responsible for pearl formation when an irritant or foreign particle gets lodged inside the shell.

Pinctada fucata is a filter feeder, mainly feeding on phytoplankton. It uses its gills not only for respiration but also for food capture. Water enters through the inhalant siphon and exits through the exhalant siphon.

Reproduction in Pinctada fucata is mostly sexual, with external fertilization. It shows separate sexes (dioecious) and spawns seasonally. After fertilization, the larva passes through trochophore and veliger stages before settling on a suitable substrate.

It inhabits shallow waters and is typically found attached to hard substrates like rocks or dead corals. This species is of great economic importance due to its use in cultured pearl industries, particularly in India and Japan.

Biology of Holothuria Scabra

Holothuria scabra, commonly known as the sandfish, is a species of sea cucumber belonging to the family Holothuriidae under the class Holothuroidea. It is widely distributed in shallow coastal waters of the Indo-Pacific region, including India, Sri Lanka, the Philippines and East Africa. It is commercially important due to its high value and is involved in the trade of processed and dried sea cucumbers, known as the beche-de-mer trade.

The body of Holothuria scabra is soft, elongated and cylindrical, with a leathery skin covered by fine papillae. The dorsal surface is often dark grey or brown, while the ventral side is lighter. It has five rows of ambulacral feet (tube feet) used for movement and attachment to the substrate. Around the mouth are 20 feather-like tentacles used for feeding.

It is a deposit feeder, mainly ingesting detritus, organic matter and microorganisms from the sediment. The digestive tract is long and coiled, adapted to extract nutrients efficiently from ingested sand.

Holothuria scabra is gonochoristic, meaning individuals are either male or female. Fertilization is external. After spawning, the fertilized eggs develop into planktonic larvae, including auricularia, doliolaria, and pentactula stages before settling and metamorphosing into juveniles.

It typically inhabits seagrass beds, sandy lagoons and reef flats up to a depth of 20 meters. It plays a vital role in nutrient recycling and maintaining sediment quality in marine ecosystems. Due to overexploitation, the species is under conservation and aquaculture programs in many regions.

3. What is meant by integrated aquaculture ? Give a broad overview of the classification of integrated aquaculture. (10 Marks)

Integrated aquaculture is a sustainable farming practice where aquaculture is combined with other agricultural systems such as crop farming, livestock rearing, horticulture, agroforestry. It focuses on efficient use of resources, recycling of nutrients and minimizing environmental pollution. In this system, the waste or by-products of one component are used as input for another, making the whole system cost-effective and eco-friendly. It increases productivity, ensures food security and provides multiple sources of income for farmers. Integrated aquaculture not only enhances resource use efficiency but also helps in rural development, livelihood improvement and ecological balance.

Classification of Integrated Aquaculture

Integrated aquaculture can be classified into the following broad categories:

1. Fish-Livestock Integrated Farming

This system involves the integration of fish culture with animals like poultry, pigs, ducks or cattle. The animal manure either directly or indirectly enriches pond water, increasing the natural productivity of fish food organisms like phytoplankton and zooplankton. For example, in fish-duck culture, ducks swim in ponds and their droppings serve as manure. In fish-pig culture, pig shelters are constructed near ponds and their waste is washed into the water to fertilize it.

2. Fish-Crop Integrated Farming

This system combines fish culture with crop production. The most common model is rice-fish farming, where fish are raised in flooded paddy fields. Fish help control pests and weeds while their excreta add nutrients to the soil. After the paddy harvest, fish can also be collected. Other crop combinations may include vegetables or cereals grown on pond embankments using pond water rich in nutrients.

3. Fish-Fish Integrated System (Polyculture)

Here, different species of fish are cultured together to utilize all ecological niches of the pond. For example, surface feeders (Catla), column feeders (Rohu) and bottom feeders (Mrigal) are cultured in the same pond. This reduces competition and increases total yield. Prawns or freshwater mussels may also be added to enhance diversity and productivity.

4. Fish-Horticulture and Agroforestry Integration

Fish ponds are combined with horticultural crops or trees along bunds or adjacent fields. Banana, coconut, papaya or timber species like teak may be planted. Pond sludge or nutrient-rich water can be used for irrigation and fertilization, reducing dependence on chemical inputs.

5. Aquaculture Using Treated Wastewater

In urban or peri-urban areas, treated domestic or agro-industrial wastewater is used for aquaculture. The organic matter and nutrient-rich water supports plankton growth which serves as natural food for fish. This method should follow strict health and environmental guidelines to avoid any contamination.

4. (a) Give a broad overview of Bundh Breeding with a schematic diagram. (5 Marks)

Bundh breeding is a traditional method of induced breeding practiced mainly in eastern and central parts of India, especially in West Bengal, Madhya Pradesh and Chhattisgarh. It involves the use of specially constructed or naturally occurring seasonal water bodies known as "bundhs", which are of two types – wet bundhs and dry bundhs.

Wet bundhs are shallow ponds that retain water throughout the year, while dry bundhs remain dry during summer and are filled with rainwater during monsoon. When the first heavy rains occur, these bundhs receive a sudden inflow of water along with a drop in temperature and increased oxygenation. This simulates natural breeding conditions for major carps like Catla catla, Labeo rohita and Cirrhinus mrigala.

Mature brooders (which means the fish whose reproductive organs are fully developed and can reproduce) are released into the bundh just before the rainy season. The flow of fresh rainwater into the bundh acts as a natural signal and helps in starting the spawning process (means the natural process by which fish release their eggs and sperm into water to reproduce). After the fish breed, the fertilized eggs are collected using mosquito nets or clean cloth. These eggs are then shifted to hatcheries or hapas where they can grow further.

Bundh breeding is low-cost and environment-friendly as it utilizes natural stimuli for breeding, but it also depends heavily on seasonal rains, making it unpredictable in years of poor rainfall.

(b) Describe the mechanism of sex reversal as a part of aquaculture practice. (5 Marks)

Sex reversal is a useful tool in aquaculture to produce monosex populations, either all-male or all-female, depending on which sex shows better growth and market value. For example, in species like Nile tilapia (Oreochromis niloticus) and common carp (Cyprinus carpio), males grow faster and more uniformly, so farmers prefer to rear all-male populations. This improves growth rate, avoids unwanted reproduction and helps in efficient management.

The process of sex reversal is done during the early stage of fish development when the gonads are not fully differentiated, typically within the first 21 to 28 days after hatching. The most common method is hormonal treatment, where synthetic hormones are used to influence the sex development of the fish. The hormone 17α-methyltestosterone, which is a male hormone, is often used in species like tilapia. This hormone is mixed with the feed and given daily for a fixed period. During this time, the hormone affects the development of the gonads and causes even genetic females (XX) to develop as functional males (phenotypically male).

In addition to hormonal treatment, in some species, environmental factors like temperature also influence sex differentiation. For example, in some reptiles and a few fish, high temperatures during the larval stage can cause more males to form, while low temperatures may lead to more females. However, this method is less precise and not commonly used in commercial aquaculture.

5. (a) Describe the importance of fish as a major source of dietary protein. (6 Marks)

Fish is one of the most important and affordable sources of high-quality dietary protein, especially in countries like India where a large part of the population depends on low-cost protein foods.

Fish protein is considered of high biological value. It contains all the essential amino acids required by the human body in balanced amounts. These amino acids help in growth, repair of body tissues, enzyme and hormone production, and maintenance of immune functions. This makes fish a complete protein source, similar to eggs and milk.

One of the most important features of fish protein is its high digestibility, often ranging from 90% to 98%. Unlike other meat, fish has less connective tissue, so it cooks easily and it is easier to digest and suitable for people of all age groups, including children, elderly people, and patients recovering from illness.

Fish provides about 18% to 20% protein per 100 grams of edible flesh, depending on the species. Marine fish like tuna and mackerel, and freshwater species like rohu and catla are rich in protein content. Many fish also contain low fat, which makes them ideal for high-protein, low-fat diets.

Fish is also quickly available post-harvest, and can be eaten in many forms like dried, boiled, grilled, or fermented without losing its protein quality. In protein-deficient areas, fish plays a critical role in fighting protein-energy malnutrition.

Because of its affordability, availability, and high nutritional value, fish is considered a vital part of a balanced and protein-rich diet in many parts of the world.

(b) How will you select the major ingredients for formulation of fish feed? (4 Marks)

To formulate an effective and balanced fish feed, it is important to select the major ingredients based on the nutritional needs of the fish, their feeding habits, and also the availability and cost of ingredients. The aim is to promote healthy growth, efficient feed conversion and overall well-being of the fish.

Selection of fish feed ingredients can be done based on five major criteria:

1. Protein Sources

Protein is the most important nutrient in fish feed, especially for carnivorous and fast-growing species. The protein source should be highly digestible and rich in essential amino acids. Common ingredients include:

• Fish meal (high-quality animal protein)
• Soybean meal (rich plant protein)
• Groundnut cake
• Cottonseed meal
• Meat-bone meal

The protein requirement varies by species. Carnivorous fishes like catfish and seabass need higher protein, while omnivorous species like rohu and tilapia need moderate levels.

2. Energy Sources (Carbohydrates and Fats)

Carbohydrates provide energy and help in pellet binding. Wheat bran, rice bran, maize and broken rice are common carbohydrate sources.

Fats or oils provide essential fatty acids. Fish oil, mustard oil and soybean oil are the common fat sources.

3. Vitamins and Minerals

To support immunity and metabolism, vitamin-mineral premixes are added. Vitamin C, vitamin E, calcium, and phosphorus are the  Common supplements.

4. Palatability and Water Stability

The feed ingredients should enhance palatability and maintain water stability, preventing nutrient loss and water pollution.

5. Local Availability and Cost

Ingredients should be easily available, affordable and free from anti-nutritional factors or toxins.

6. Name any three bacterial diseases of fish. List out the symptoms of those diseases and mention the species affected. (10 Marks)

In aquaculture and wild fisheries, bacterial diseases are one of the major causes of fish mortality, and reduced population and  production. These diseases are caused by pathogenic bacteria which enter the fish body mainly through gills, wounds, or digestive tract. They often spread rapidly, especially in crowded, unclean and stressful environments.

Here are three significant bacterial diseases of fish explained with their cause, symptoms and the species they commonly affect.

1. Columnaris Disease

Columnaris disease is caused by Flavobacterium columnare. It mostly affects freshwater fish in warm conditions. This bacterium attacks skin, fins, gills, and mouth areas. This disease spreads through water and direct contact. Poor water quality and high temperature increase the risk.

Symptoms: Infected fish show cotton-like patches near the mouth, gills, or fins. There may be ulcers on the skin, fraying of fins and difficulty in breathing.

Species Affected: This disease commonly affects catfish, tilapia, goldfish and carps.

2. Furunculosis

Furunculosis is caused by Aeromonas salmonicida, a gram-negative bacterium. It is a common disease in temperate freshwater fish, especially in salmonids. It enters the fish body through injuries or skin abrasions. It can be acute or chronic, depending on water conditions and stress.

Symptoms: Fish show red spots on the skin, hemorrhages at fin bases, swollen abdomen, exophthalmia (bulging eyes) and furuncle-like boils filled with pus.

Species Affected: Commonly affects trout, salmon and carp species.

3. Bacterial Gill Disease (BGD)

This disease is caused mainly by Flavobacterium branchiophilum and occurs especially in hatchery-reared fish like salmonids. It spreads in high-density and low-oxygen conditions. The bacteria colonize gill tissues, blocking oxygen exchange.

Symptoms: Fish breathe rapidly, show flared gill covers, pale and swollen gills with excess mucus, and may come near the surface gasping for air.

Species Affected: Primarily affects young salmon, trout and sometimes carps under intensive rearing.

7. Write notes on any two of the following: (5+5 Marks)

(a) Impact of intensive aquaculture on biological resources

Intensive aquaculture refers to the high-density rearing of fish and other aquatic organisms using artificial feeding and controlled conditions. Although it helps increase fish production, it also puts serious pressure on natural biological resources. The high input and output system of intensive aquaculture can disturb natural ecosystems, affect wild species and reduce the quality of aquatic environments.

There are following major types of impacts caused by intensive aquaculture on biological resources:

1. Genetic Pollution

Intensive aquaculture often uses exotic or genetically modified fish. If these fish escape into natural ecosystems, they may interbreed with native species. This leads to the loss of genetic purity and weakens the gene pool of wild populations.

2. Eutrophication and Water Pollution

Excess feed and fish waste in intensive systems increase nitrogen and phosphorus levels in water. This causes algal blooms and reduces dissolved oxygen. It results in poor water quality and can cause mass death of aquatic organisms.

3. Disease Transmission

The dense population of fish in intensive systems creates a high risk of disease outbreaks. Infected fish or water discharge from farms can spread pathogens to nearby wild fish, harming the biodiversity of the surrounding area.

4. Habitat Degradation

Intensive aquaculture sometimes requires clearing of mangroves, wetlands or riverbanks. This destroys breeding and feeding grounds for many aquatic species, especially in ecologically sensitive zones.

(b) Principles of extension education in fisheries

Extension education in fisheries is a branch of applied science that focuses on teaching fish farmers and fishing communities about better production techniques, scientific fish farming and resource conservation. It helps in improving livelihood, food security, and income generation among rural and coastal populations. To ensure effective communication and learning, this process follows certain core principles.

There are the following six principles of extension education in fisheries:

1. Principle of Interest

Learning becomes meaningful when it connects to the actual needs and interests of the target group. Fishermen will actively participate in training if the content matches their problems like disease control or low productivity.

2. Principle of Participation

Involving fish farmers or stakeholders in planning and execution increases acceptance. People learn better when they are directly involved. Extension workers should encourage farmers to share their ideas and experiences to make learning interactive and engaging.

3. Principle of Learning by Doing

Practical experience helps better understanding. Demonstrations, hands-on activities and field training are very effective in teaching new techniques in fisheries.

4. Principle of Cultural Compatibility

Every community has its own customs, language and beliefs. Extension education must respect these differences and design methods that suit the local environment and mindset. Ignoring culture may lead to resistance.

5. Principle of Leadership

Identifying and training local leaders can help spread knowledge faster within the community, as people trust their peers more than outsiders.

6. Principle of Evaluation

Regular monitoring and feedback help understand the success and limitations of extension programs. It allows for continuous improvement and effective planning.

(c) Technical challenges in aquaculture technology

Aquaculture has adopted various modern technologies for improving fish production, but several technical challenges still limit its efficiency and sustainability. These challenges are related to infrastructure, equipment, monitoring systems and digital management tools.

There are the following major technical challenges that affect aquaculture development:

1. Difficulty in Real-time Water Quality Monitoring

Effective aquaculture requires precise control of water parameters like temperature, pH, dissolved oxygen, and ammonia. Affordable and accurate real-time monitoring tools are often missing, especially in rural setups, leading to delayed responses and stress on aquatic organisms.

2. Technical Barriers in Using Recirculating Aquaculture Systems (RAS)

RAS helps in water recycling and maintaining high-density fish culture. But it demands technical expertise, regular monitoring, and system maintenance. Many farmers find it hard to operate due to high complexity and lack of training.

3. Poor Access to Automated Feeding and Monitoring Tools

Technologies like auto-feeders and remote sensors help reduce feed waste and improve growth. However, small-scale farmers often cannot afford them or do not have technical training to operate these systems effectively.

4. Challenges in Disease Surveillance and Control 

Identifying fish diseases in early stages using molecular or advanced diagnostic methods is limited in most farms. Lack of trained technicians and diagnostic infrastructure leads to delayed treatment and higher mortality.

5. Inadequate Skill Development and Technical Training

Adopting new aquaculture technologies needs trained manpower. Many farmers lack access to structured technical education or field training which creates a gap between technology development and its proper field application.