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Odisha CHSE +2 Vocational Inland Fisheries study materials
Odisha CHSE +2 Vocational Inland Fisheries study resources

Odisha CHSE +2 Vocational Inland Fisheries practice questions

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Question 1General Foundation Science and Mathematics for Fisheries

In an inland fish pond, dissolved oxygen is mainly replenished during daylight hours by which process?

  1. Respiration by fish
  2. Photosynthesis by phytoplankton Correct answer.
  3. Decomposition by bacteria
  4. Nitrogen fixation in sediments

Explanation

Phytoplankton and other aquatic plants use sunlight to photosynthesise, releasing oxygen into the pond water. This is why dissolved oxygen typically peaks in the afternoon and falls to its lowest just before dawn. Respiration and decomposition consume oxygen rather than add it.

Question 2General Foundation Science and Mathematics for Fisheries

A fish farmer records the pH of pond water as 5.2. Which corrective measure is most appropriate?

  1. Increase stocking density
  2. Add agricultural lime to raise alkalinity Correct answer.
  3. Aerate the pond at night only
  4. Add urea to boost plankton growth

Explanation

A pH of 5.2 indicates acidic water, which reduces fish growth and makes nutrients less available. Agricultural lime (calcium carbonate) neutralises acidity and raises total alkalinity, buffering the pond. Adding fertiliser or fish would worsen the problem in acidic water.

Question 3General Foundation Science and Mathematics for Fisheries

Which unit expresses the concentration of dissolved oxygen in pond water as commonly used in Indian aquaculture practice?

  1. Milligrams per litre (mg/L) Correct answer.
  2. Centimetres of water column
  3. Parts per thousand (ppt)
  4. Kilograms per hectare

Explanation

Dissolved oxygen is a concentration in water and is conventionally reported as milligrams per litre, which is numerically equal to parts per million. Kilograms per hectare measures mass per area, ppt is used for salinity, and a water-column height measures depth.

Question 4General Foundation Science and Mathematics for Fisheries

A farmer stocks 4,000 fingerlings in a pond of 0.5 hectare. What is the stocking density?

  1. 20,000 fingerlings per hectare
  2. 8,000 fingerlings per hectare Correct answer.
  3. 2,000 fingerlings per hectare
  4. 4,000 fingerlings per hectare

Explanation

Stocking density equals the number of fish divided by the pond area. Dividing 4,000 by 0.5 hectare gives 8,000 fingerlings per hectare. This figure is then compared with recommended densities for the species and culture system.

Question 5General Foundation Science and Mathematics for Fisheries

Which fish is a native Indian major carp commonly cultured in Odisha ponds?

  1. Cyprinus carpio
  2. Clarias batrachus
  3. Catla catla Correct answer.
  4. Oreochromis niloticus

Explanation

Catla catla, the catla, is one of the three Indian major carps along with rohu and mrigal and is a mainstay of composite carp culture in Odisha. Common carp, tilapia and magur are introduced or different groups.

Question 6General Foundation Science and Mathematics for Fisheries

In composite fish culture, which combination best describes the three Indian major carps?

  1. Rohu, common carp and grass carp
  2. Silver carp, grass carp and mrigal
  3. Catla, tilapia and magur
  4. Catla, rohu and mrigal Correct answer.

Explanation

The Indian major carps are catla (surface feeder), rohu (column feeder) and mrigal (bottom feeder). Their different feeding zones allow them to share a pond without competing strongly. Silver carp, grass carp and common carp are the exotic carps used in a separate combination.

Question 7General Foundation Science and Mathematics for Fisheries

A pond is treated with lime at 200 kg per hectare. How much lime is needed for a 0.25 hectare pond?

  1. 80 kg
  2. 50 kg Correct answer.
  3. 800 kg
  4. 25 kg

Explanation

The required mass is the dose multiplied by the pond area. Multiplying 200 kg per hectare by 0.25 hectare gives 50 kg. This calculation prevents over- or under-application of lime.

Question 8General Foundation Science and Mathematics for Fisheries

Water in a pond has a total alkalinity of 40 mg/L as CaCO3. What does this value most directly indicate?

  1. A high salinity unsuitable for carp
  2. A high level of organic pollution
  3. A low buffering capacity that needs liming Correct answer.
  4. An excess of dissolved oxygen

Explanation

Total alkalinity measures the water's capacity to neutralise acid and buffer pH changes. A value near 40 mg/L as CaCO3 is on the low side for carp ponds, where 75 to 200 mg/L is generally preferred, so liming is often advised. Alkalinity is not a measure of salinity, oxygen or organic load.

Question 9General Foundation Science and Mathematics for Fisheries

A pond shows a dense green surface scum in the afternoon, pH rising above 9.5, and very low oxygen before dawn. Which explanation fits best?

  1. An algal bloom causing wide day-night oxygen and pH swings Correct answer.
  2. A sudden drop in total alkalinity
  3. An overdose of agricultural lime
  4. Heavy silt deposition on the pond bottom

Explanation

Dense phytoplankton photosynthesise strongly in daylight, raising pH and oxygen, then respire at night and can crash oxygen levels before dawn. This day-night cycle is characteristic of an algal bloom. Liming raises pH but does not produce the dawn oxygen drop.

Question 10General Foundation Science and Mathematics for Fisheries

Which feeding habit is correctly matched with its carp?

  1. Grass carp feeds mainly on aquatic macrophytes Correct answer.
  2. Mrigal feeds mainly on surface plankton
  3. Rohu feeds mainly on molluscs
  4. Catla feeds mainly on benthic detritus

Explanation

Grass carp have pharyngeal teeth suited to shredding aquatic weeds such as Hydrilla and are used for weed control. Catla is a surface plankton feeder, mrigal feeds on bottom detritus, and rohu is a column feeder taking plankton and plant material.

Question 11General Foundation Science and Mathematics for Fisheries

A farmer wants to estimate the mean weight of harvested rohu. Which procedure gives the most reliable estimate?

  1. Weigh one fish chosen at the pond gate
  2. Estimate from the total harvest weight without counting fish
  3. Weigh only the largest fish caught
  4. Weigh a random sample of fish and divide total weight by the number weighed Correct answer.

Explanation

A random sample gives an unbiased estimate, and mean weight is the total sample weight divided by the number of fish in the sample. Choosing only large fish or a single fish introduces bias. Total weight without a count cannot give a per-fish mean.

Question 12General Foundation Science and Mathematics for Fisheries

The relationship between fish growth rate and water temperature in a carp pond is best described as which type of relationship over the normal culture range?

  1. Growth is completely independent of temperature
  2. Growth is highest at the lowest temperature
  3. Growth rises steadily and without limit as temperature rises
  4. Growth increases with temperature up to an optimum, then declines Correct answer.

Explanation

Fish are ectotherms, so metabolic rate and growth rise with temperature up to a species-specific optimum and then fall as oxygen demand and stress increase. For most cultured carps the optimum lies roughly between 25 and 32 degrees Celsius. Growth is therefore neither unlimited nor independent of temperature.

Question 13General Foundation Science and Mathematics for Fisheries

A pond receives 30 kg of feed per day. If the feed contains 30 percent crude protein, how much crude protein is supplied daily?

  1. 30 kg
  2. 3 kg
  3. 9 kg Correct answer.
  4. 90 kg

Explanation

The protein supplied equals feed mass multiplied by the protein fraction. Thirty kilograms multiplied by 0.30 gives 9 kg of crude protein per day. This figure is used to check whether protein input matches the standing biomass.

Question 14General Foundation Science and Mathematics for Fisheries

Which measurement best indicates the amount of suspended plankton in a pond for feeding purposes?

  1. Total hardness
  2. Chloride concentration
  3. Bottom soil pH
  4. Secchi disc transparency Correct answer.

Explanation

Secchi disc transparency estimates water clarity, and a reading in roughly the 30 to 40 cm range usually indicates a healthy plankton bloom. Low transparency suggests dense plankton or turbidity, while high transparency suggests poor plankton growth. Hardness, chloride and soil pH measure different properties.

Question 15General Foundation Science and Mathematics for Fisheries

In a pond, ammonia is present mainly as un-ionised ammonia (NH3) and ammonium (NH4+). Which condition shifts the balance toward the more toxic un-ionised form?

  1. Low pH and low temperature
  2. High alkalinity and low temperature
  3. Low pH and high temperature
  4. High pH and high temperature Correct answer.

Explanation

The equilibrium between ammonium and un-ionised ammonia shifts toward NH3 as pH rises, and the proportion of NH3 also increases with temperature. High pH combined with warm water therefore makes ammonia more toxic. Lower pH favours the less toxic ammonium ion.

Question 16General Foundation Science and Mathematics for Fisheries

A farmer plans to harvest 1,200 kg of fish from a 0.6 hectare pond. What yield does this represent per hectare?

  1. 720 kg per hectare
  2. 2,000 kg per hectare Correct answer.
  3. 1,200 kg per hectare
  4. 200 kg per hectare

Explanation

Yield per hectare is total harvest divided by pond area. Dividing 1,200 kg by 0.6 hectare gives 2,000 kg per hectare, a figure used to compare productivity with regional benchmarks.

Question 17General Foundation Science and Mathematics for Fisheries

A pond manager observes that oxygen is adequate at dusk but falls below 2 mg/L by dawn, with no algal scum. Which management measure addresses the root cause most directly?

  1. Add lime to raise pH above 9
  2. Increase stocking with surface-feeding catla
  3. Reduce the organic load and aerate during the night Correct answer.
  4. Apply more organic manure to feed plankton

Explanation

The overnight oxygen decline reflects respiration and decomposition exceeding photosynthesis in darkness, so cutting the organic load reduces oxygen demand. Night aeration directly supplies oxygen during the critical hours. Adding manure or fish increases demand, and raising pH does not add oxygen.

Question 18General Foundation Science and Mathematics for Fisheries

Two ponds have equal total alkalinity of 120 mg/L as CaCO3, but pond A has a total hardness of 40 mg/L and pond B has 150 mg/L. What is the most likely interpretation?

  1. Both ponds have identical calcium supply
  2. Pond A has higher salinity than pond B
  3. Pond B is soft water and needs liming
  4. Pond A is soft water and may need calcium supplementation Correct answer.

Explanation

Hardness reflects dissolved calcium and magnesium, so pond A with 40 mg/L is soft despite adequate alkalinity, which may come mainly from sodium or potassium bicarbonate. Soft water can limit calcium availability for shell and bone formation, so calcium supplementation may help. Pond B is comparatively hard.

Question 19General Foundation Science and Mathematics for Fisheries

A farmer applies urea to a pond and within days the pH rises above 9.5 with a heavy phytoplankton bloom. Which sequence best explains the observation?

  1. Urea increases hardness, which raises pH
  2. Nitrogen kills zooplankton, releasing alkaline compounds
  3. Nitrogen stimulates phytoplankton growth, whose photosynthesis consumes carbon dioxide and raises pH Correct answer.
  4. Urea directly neutralises acidity and raises pH chemically

Explanation

Nitrogen from urea promotes rapid phytoplankton growth, and their photosynthesis removes dissolved carbon dioxide from the water. This shifts the carbonate equilibrium and raises pH, often sharply on sunny afternoons. The effect is biological and indirect rather than a direct chemical neutralisation.

Question 20General Foundation Science and Mathematics for Fisheries

A pond has a standing crop of 3,000 kg of fish and receives 90 kg of feed per day at 30 percent protein. If the fish are fed 3 percent of body weight daily, what is the daily ration and is the feed allocation consistent?

  1. 300 kg per day, inconsistent and too high
  2. 90 kg per day, consistent with 3 percent of 3,000 kg Correct answer.
  3. 9 kg per day, inconsistent and too low
  4. 30 kg per day, inconsistent and too low

Explanation

Three percent of a 3,000 kg standing crop is 90 kg per day, which matches the amount actually allocated. This check confirms the ration is consistent with the biomass and feeding rate. It also shows how feeding rate, biomass and feed quantity are linked.

Question 21Introduction to Inland Fisheries and Aquaculture Systems

In inland fisheries terminology, which water body is classified as a lentic system?

  1. A fast-flowing hill stream
  2. A tidal estuary mouth
  3. A seasonal rain-fed rivulet
  4. A pond or lake with standing water Correct answer.

Explanation

Lentic systems are standing or still-water bodies such as ponds, lakes and reservoirs, where water movement is minimal. Lotic systems, by contrast, are flowing waters like streams and rivers. The distinction governs stocking density, oxygen dynamics and management practice.

Question 22Introduction to Inland Fisheries and Aquaculture Systems

Which term describes the practice of raising fish in enclosed ponds where the stock is owned and fed by the farmer?

  1. Open-water ranching
  2. Aquaculture Correct answer.
  3. Subsistence gleaning
  4. Capture fishery

Explanation

Aquaculture is the controlled rearing of aquatic organisms under ownership, with interventions such as stocking, feeding and predator control. Capture fishery relies on harvesting naturally recruited stocks without such ownership. The ownership and intervention criteria separate the two clearly.

Question 23Introduction to Inland Fisheries and Aquaculture Systems

A composite fish culture pond in Odisha is stocked with surface, column and bottom feeders together. What is the main purpose of this polyculture design?

  1. To ensure that only one species dominates the harvest
  2. To use the whole water column and available natural food without competition Correct answer.
  3. To eliminate the need for any pond manuring
  4. To reduce the number of species a farmer must market

Explanation

Polyculture combines species with different feeding niches - for example surface feeders such as catla, column feeders such as rohu and bottom feeders such as mrigal - so that natural food at each level is used. This raises total yield per unit area compared with monoculture. Competition is minimised because the species do not target the same food.

Question 24Introduction to Inland Fisheries and Aquaculture Systems

Which pond zone is the primary site of photosynthetic oxygen production in a fertilised fish pond?

  1. The benthic mud layer
  2. The deepest hypolimnion
  3. The pond dyke soil
  4. The euphotic upper water layer Correct answer.

Explanation

Photosynthesis by phytoplankton occurs where light penetrates, that is the euphotic upper layer of the water column. This layer supplies most of the dissolved oxygen during daylight. Deeper zones and sediments mainly consume oxygen through decomposition.

Question 25Introduction to Inland Fisheries and Aquaculture Systems

A farmer notices that dissolved oxygen in a stocked pond falls sharply just before dawn. Which explanation is most accurate?

  1. Fish stop feeding and therefore stop consuming oxygen
  2. Water temperature falls and oxygen becomes insoluble
  3. Sunlight at night accelerates algal photosynthesis
  4. Photosynthesis stops at night while respiration by all pond organisms continues Correct answer.

Explanation

At night there is no light for photosynthesis, so phytoplankton cease producing oxygen, yet plants, plankton, fish and bacteria continue respiring. Oxygen therefore declines through the night and reaches its lowest level near dawn. This diurnal cycle is a standard feature of pond management.

Question 26Introduction to Inland Fisheries and Aquaculture Systems

Which characteristic best distinguishes a reservoir from a natural lake in inland fisheries management?

  1. It is created by damming a river and shows riverine-to-lacustrine gradients Correct answer.
  2. It always has a constant water level
  3. It never supports plankton growth
  4. It contains only exotic fish species

Explanation

Reservoirs are man-made impoundments formed by damming a river, and they typically show a gradient from flowing riverine conditions at the inflow to still lacustrine conditions near the dam. Natural lakes lack this engineered origin and longitudinal gradient. Water levels in reservoirs usually fluctuate with irrigation and power demand.

Question 27Introduction to Inland Fisheries and Aquaculture Systems

In composite fish culture, which species is classically described as a surface feeder that takes zooplankton?

  1. Catla catla Correct answer.
  2. Labeo rohita
  3. Heteropneustes fossilis
  4. Cirrhinus mrigala

Explanation

Catla catla is the surface-feeding component of the classic three-species Indian major carp combination, feeding largely on zooplankton in the upper water layer. Rohu is a column feeder and mrigal a bottom feeder. This niche separation is the basis of carp polyculture.

Question 28Introduction to Inland Fisheries and Aquaculture Systems

Which practice is the most direct method of correcting low dissolved oxygen in a stocked pond during an emergency?

  1. Applying raw cow dung
  2. Adding lime to raise alkalinity
  3. Increasing the stocking density
  4. Running an aerator or splashing water to increase gas exchange Correct answer.

Explanation

Mechanical aeration or splashing water increases the air-water interface and drives oxygen into solution quickly. Liming affects pH and alkalinity rather than immediate oxygen levels. Organic manures actually consume oxygen as they decompose.

Question 29Introduction to Inland Fisheries and Aquaculture Systems

A pond manager applies cow dung and chemical fertiliser to a pond before stocking. What is the primary intended effect?

  1. Stimulation of natural plankton production as live food Correct answer.
  2. Reduction of water alkalinity to zero
  3. Direct feeding of fingerlings with organic matter
  4. Sterilisation of the pond bottom

Explanation

Manuring and fertilisation supply nutrients, chiefly nitrogen and phosphorus, that promote phytoplankton and zooplankton growth. These plankton then serve as natural food for stocked fish, particularly in carp culture. The organic matter is not eaten directly by most carp fingerlings.

Question 30Introduction to Inland Fisheries and Aquaculture Systems

Which water quality parameter is most directly measured to express the pond's capacity to resist a fall in pH after acid addition?

  1. Turbidity
  2. Specific conductance
  3. Total alkalinity Correct answer.
  4. Dissolved oxygen

Explanation

Total alkalinity reflects the concentration of bicarbonate and carbonate buffers that neutralise added acid and stabilise pH. Ponds with low alkalinity are prone to wide pH swings. Turbidity, conductance and oxygen measure different properties and do not express buffering capacity.

Question 31Introduction to Inland Fisheries and Aquaculture Systems

A farmer wants to control excessive aquatic weeds that interfere with netting and deplete oxygen at night. Which approach is the most sound first step in pond management?

  1. Increasing water depth to double the pond volume
  2. Stocking more bottom-feeding fish immediately
  3. Adding more organic manure to shade the weeds
  4. Manual or mechanical removal combined with preventing nutrient inflow Correct answer.

Explanation

Excess weed growth is usually driven by high nutrient loading, so removal must be paired with reducing the nutrient input that fuels it. Manual or mechanical clearing restores access and reduces night-time oxygen consumption by weeds. Simply adding manure or fish worsens the underlying nutrient problem.

Question 32Introduction to Inland Fisheries and Aquaculture Systems

Which statement correctly describes the difference between a hatchery and a nursery in carp seed production?

  1. A hatchery cultures plankton, while a nursery harvests weeds
  2. A hatchery produces spawn from brood fish, while a nursery rears spawn to fry and fingerlings Correct answer.
  3. A hatchery rears fingerlings to market size, while a nursery breeds brood stock
  4. A hatchery stores harvested fish, while a nursery transports them

Explanation

The hatchery is where induced breeding of brood fish yields eggs and spawn. Nursery and rearing ponds then grow that spawn through fry to fingerling stages before stocking. Confusing the two stages disrupts the seed production chain.

Question 33Introduction to Inland Fisheries and Aquaculture Systems

Which hormone-based technique is commonly used to induce spawning in Indian major carps in a hatchery?

  1. Exposure to continuous bright light
  2. Immersion in potassium permanganate solution
  3. Injection of pituitary gland extract or synthetic gonadotropin-releasing hormone Correct answer.
  4. Oral administration of antibiotics

Explanation

Induced breeding in carps relies on injecting pituitary gland extract or synthetic GnRH analogues, often with a dopamine antagonist, to trigger ovulation and spermiation. Antibiotics, permanganate and light exposure do not act on the reproductive endocrine axis. This technique allows seed production independent of riverine spawning cues.

Question 34Introduction to Inland Fisheries and Aquaculture Systems

A pond has a pH of 5.2 and low total alkalinity. Which management action is most appropriate before stocking?

  1. Stock the pond immediately at high density
  2. Apply agricultural lime to raise pH and alkalinity Correct answer.
  3. Drain the pond and leave it dry indefinitely
  4. Add ammonium sulphate to increase nitrogen

Explanation

Acidic ponds with low alkalinity are corrected by liming, which raises pH and increases bicarbonate buffering. This improves nutrient availability and fish welfare. Acidifying fertilisers would lower pH further, and high stocking in such water risks mortality.

Question 35Introduction to Inland Fisheries and Aquaculture Systems

Which of the following is a primary producer in the food web of an inland fish pond?

  1. Tilapia fry
  2. Zooplankton
  3. Benthic bacteria
  4. Phytoplankton Correct answer.

Explanation

Phytoplankton are photosynthetic organisms that fix light energy into organic matter, making them the base of the pond food web. Zooplankton and fish fry are consumers, and bacteria are decomposers. This trophic ordering underpins pond fertilisation strategy.

Question 36Introduction to Inland Fisheries and Aquaculture Systems

In pond aquaculture, which combination of measurements best indicates that organic loading has exceeded the pond's assimilative capacity?

  1. Low dawn oxygen, high biochemical oxygen demand, turbid green water Correct answer.
  2. High dawn oxygen, low biochemical oxygen demand, clear water
  3. High alkalinity, low plankton density, cool water
  4. Stable pH, low ammonia, high transparency

Explanation

Excess organic loading raises biochemical oxygen demand as bacteria decompose the material, which drives dawn oxygen low and often produces dense turbid algal blooms. Together these signals indicate that the pond is overloaded. Clear, well-oxygenated water with low BOD indicates a balanced pond.

Question 37Introduction to Inland Fisheries and Aquaculture Systems

Why is a fertilised pond with dense phytoplankton likely to show a very wide daily swing in dissolved oxygen?

  1. Plankton respire only during daylight hours
  2. Fish switch to anaerobic respiration in daylight
  3. Oxygen is chemically destroyed by alkalinity at noon
  4. Photosynthesis adds oxygen by day, while respiration by the whole community removes it at night Correct answer.

Explanation

Dense phytoplankton produce large oxygen surpluses during photosynthesis in daylight but consume oxygen through respiration after dark, when no production occurs. The result is a high afternoon peak and a low pre-dawn trough. Sparse plankton communities show much smaller swings.

Question 38Introduction to Inland Fisheries and Aquaculture Systems

A manager must choose between stocking a seasonal tank that dries annually and a perennial pond. Which strategy is most defensible for the seasonal tank?

  1. Stock only air-breathing snails
  2. Stock slow-growing brood stock that requires several years to mature
  3. Stock fast-growing species and harvest before the water recedes Correct answer.
  4. Stock at maximum density and never harvest

Explanation

In a water body that dries predictably, the production cycle must fit within the period of water availability. Fast-growing species stocked and harvested within that window avoid total loss at drying. Slow-maturing stock or very high unharvested densities would result in mortality or stunted crops.

Question 39Introduction to Inland Fisheries and Aquaculture Systems

Which factor most directly limits primary productivity in a clear, nutrient-poor upland pond?

  1. Excess dissolved oxygen
  2. Absence of fish predators
  3. Presence of clay dykes
  4. Availability of dissolved nitrogen and phosphorus Correct answer.

Explanation

In clear water where light penetrates adequately, phytoplankton growth is limited chiefly by the supply of dissolved nutrients, especially nitrogen and phosphorus. Adding these through fertilisation raises productivity. Oxygen, dyke material and predator absence are not the primary limiting factors here.

Question 40Introduction to Inland Fisheries and Aquaculture Systems

Which statement about air-breathing fishes in inland aquaculture is correct?

  1. They cannot survive in low-oxygen water under any condition
  2. They can tolerate low dissolved oxygen by gulping atmospheric air Correct answer.
  3. They are obligate marine species
  4. They require higher dissolved oxygen than carps

Explanation

Air-breathing fishes such as Clarias, Heteropneustes and Anabas possess accessory respiratory organs that let them use atmospheric oxygen. This allows them to survive in stagnant, low-oxygen ponds and even in wet soil for periods. Carps generally require higher dissolved oxygen than these species.

Question 41Fish Biology, Taxonomy and Anatomy

In the classification of fishes, the class Chondrichthyes is characterised by which type of skeleton?

  1. Notochord without vertebrae
  2. Exoskeleton of scales only
  3. Bony skeleton
  4. Cartilaginous skeleton Correct answer.

Explanation

Chondrichthyes (sharks, rays, skates) have a skeleton made mainly of cartilage rather than bone, and the vertebral column lacks true ossification. This cartilaginous condition is the defining feature separating them from the bony fishes.

Question 42Fish Biology, Taxonomy and Anatomy

The type of scales found on the skin of a shark such as Scoliodon is:

  1. Ctenoid scales
  2. Cycloid scales
  3. Placoid scales Correct answer.
  4. Ganoid scales

Explanation

Placoid scales are tooth-like structures with a basal plate and a spine, found in elasmobranchs including sharks and rays. They are also called dermal denticles because of their structure.

Question 43Fish Biology, Taxonomy and Anatomy

Which of the following is a cyclostome with a sucking, jawless mouth?

  1. Catla
  2. Petromyzon Correct answer.
  3. Heteropneustes
  4. Mystus

Explanation

Petromyzon (lamprey) belongs to the jawless cyclostomes, whose mouth is a circular suctorial disc without jaws. Catla, Heteropneustes and Mystus are all jawed bony fishes.

Question 44Fish Biology, Taxonomy and Anatomy

The air-breathing organ of the Indian catfish Heteropneustes fossilis is:

  1. A pair of lung-like air sacs Correct answer.
  2. Gill rakers modified for air intake
  3. A swim bladder used only for buoyancy
  4. A labyrinthine organ in the pharynx

Explanation

Heteropneustes (the stinging catfish) possesses a pair of elongated, tubular air sacs extending backward from the gill chamber that function as accessory respiratory organs. This adaptation lets it survive in oxygen-poor, stagnant water.

Question 45Fish Biology, Taxonomy and Anatomy

The lateral line system in fishes primarily serves which function?

  1. Excreting nitrogenous wastes
  2. Detecting water currents and pressure changes Correct answer.
  3. Maintaining buoyancy
  4. Producing sound for communication

Explanation

The lateral line system consists of neuromast receptors in canals along the body that detect water movements, pressure gradients and low-frequency vibrations. It is a mechanosensory system important for schooling, prey detection and predator avoidance.

Question 46Fish Biology, Taxonomy and Anatomy

Which type of caudal fin is found in sharks such as Scoliodon?

  1. Diphycercal
  2. Homocercal
  3. Hypocercal
  4. Heterocercal Correct answer.

Explanation

In a heterocercal tail the vertebral column bends upward into the larger upper lobe, so the two lobes are unequal. Sharks show this condition, which provides lift during swimming.

Question 47Fish Biology, Taxonomy and Anatomy

The Weberian apparatus of a major carp connects the swim bladder to which structure?

  1. The heart
  2. The liver
  3. The kidney
  4. The inner ear Correct answer.

Explanation

The Weberian apparatus is a chain of small bones (ossicles) derived from vertebrae that transmits sound vibrations from the swim bladder to the inner ear. This gives cyprinids an enhanced sense of hearing.

Question 48Fish Biology, Taxonomy and Anatomy

The characteristic feature of the order Siluriformes (catfishes) is the presence of:

  1. Scales covering the whole body
  2. A single dorsal fin with spines only
  3. Barbels around the mouth Correct answer.
  4. Absence of a swim bladder

Explanation

Catfishes are recognised by their prominent barbels, which are fleshy sensory appendages around the mouth used for locating food in turbid water. Their bodies are typically scaleless.

Question 49Fish Biology, Taxonomy and Anatomy

In fishes, the gill lamellae are arranged so that blood flows through them in the opposite direction to the water current. This arrangement is called:

  1. Concurrent circulation
  2. Counter-current exchange Correct answer.
  3. Closed-loop circulation
  4. Parallel flow

Explanation

Counter-current exchange means blood in the secondary lamellae flows opposite to the water passing over the gills, maintaining a gradient that maximises oxygen uptake. It allows fishes to extract a high percentage of dissolved oxygen.

Question 50Fish Biology, Taxonomy and Anatomy

The swim bladder of a physostomous fish differs from that of a physoclistous fish in that it:

  1. Contains no gas at all
  2. Remains connected to the gut by a pneumatic duct Correct answer.
  3. Has no connection to the gut at any stage
  4. Is found only in cartilaginous fishes

Explanation

Physostomous fishes retain a pneumatic duct linking the swim bladder to the oesophagus, so gas can be added or released through the gut. Physoclistous fishes lack this duct and regulate gas by a rete mirabile and oval body.