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Maharashtra HSC Vocational Fisheries Technology study materials
Maharashtra HSC Vocational Fisheries Technology study resources

Maharashtra HSC Vocational Fisheries Technology practice questions

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Question 1Aquaculture and Fish Farming

Which pond treatment is most directly used to kill unwanted wild fish and predatory fish before stocking a nursery pond with carp spawn?

  1. Application of lime only
  2. Application of urea
  3. Application of mahua oil cake Correct answer.
  4. Application of single super phosphate

Explanation

Mahua oil cake contains saponin, which is toxic to fish and is a traditional Indian pond poison used for eradicating unwanted and predatory fish before stocking. Fertilizers and lime are used for nutrient and pH management, not for fish eradication.

Question 2Aquaculture and Fish Farming

In composite fish culture, which species combination is correctly described as a surface feeder paired with a column feeder?

  1. Catla as surface feeder and rohu as column feeder Correct answer.
  2. Rohu as surface feeder and mrigal as bottom feeder
  3. Mrigal as surface feeder and catla as column feeder
  4. Grass carp as surface feeder and silver carp as bottom feeder

Explanation

Catla feeds mainly in the upper water layer, while rohu feeds in the middle column, so together they exploit different niches of the pond. This niche separation is the basis of composite fish culture, which raises several species together without serious competition for food.

Question 3Aquaculture and Fish Farming

Which instrument is used to measure the dissolved oxygen content of pond water in a fish farm?

  1. Winkler titration set Correct answer.
  2. Secchi disc
  3. Salinometer
  4. Turbidity tube

Explanation

Dissolved oxygen is estimated by the Winkler iodometric titration method, in which fixed oxygen reacts with manganese and iodide and the liberated iodine is titrated. It is the standard field and laboratory method for pond oxygen estimation.

Question 4Aquaculture and Fish Farming

Which carp is deliberately stocked in a pond mainly to control excessive growth of submerged and floating aquatic weeds?

  1. Mrigal
  2. Grass carp Correct answer.
  3. Common carp
  4. Silver carp

Explanation

Grass carp is a herbivorous fish that consumes aquatic macrophytes such as Hydrilla and Vallisneria, so it is stocked as a biological weed control agent. Silver carp filters phytoplankton and does not graze on weeds.

Question 5Aquaculture and Fish Farming

Which hatchery practice is used to induce breeding in Indian major carps by injecting pituitary gland extract?

  1. Acclimatization
  2. Hypophysation Correct answer.
  3. Grading
  4. Conditioning

Explanation

Hypophysation is the technique of injecting pituitary gland extract, usually along with a synthetic hormone, to induce ovulation and spawning in carps that do not breed naturally in confined ponds. Grading, conditioning and acclimatization are handling practices, not hormone induction.

Question 6Aquaculture and Fish Farming

A fish farmer wants to raise fry to fingerling size in small, well-managed earthen ponds before releasing them into a large grow-out pond. Which practice is described?

  1. Cage culture
  2. Nursery rearing Correct answer.
  3. Grow-out culture
  4. Brood stock maintenance

Explanation

Nursery rearing is the stage in which delicate fry are kept at high density in small, well-prepared ponds and fed intensively until they reach fingerling size. Grow-out culture follows this stage in larger ponds.

Question 7Aquaculture and Fish Farming

Which feed ingredient is generally used as the main energy-rich component in a supplementary carp feed mixture?

  1. Rice bran Correct answer.
  2. Fish meal
  3. Bone meal
  4. Common salt

Explanation

Rice bran is a cheap, energy-rich agricultural by-product widely used as the base of supplementary carp feeds, usually mixed with oil cakes. Fish meal and bone meal are protein and mineral sources, and salt is a minor additive.

Question 8Aquaculture and Fish Farming

Which disease of freshwater fish is characterised by white cotton-like patches on the skin and fins caused by a fungus?

  1. Epizootic ulcerative syndrome
  2. Argulosis
  3. Fin rot caused by bacteria
  4. Saprolegniasis Correct answer.

Explanation

Saprolegniasis is a fungal infection producing cotton-wool-like white growth on skin, fins and eggs, often after injury or handling stress. It is treated with salt or formalin baths and improved hygiene.

Question 9Aquaculture and Fish Farming

A pond shows a dense, dark green surface scum of blue-green algae with a very high plankton density. Which management measure is most appropriate?

  1. Exchange part of the water and reduce fertilizer application Correct answer.
  2. Apply lime heavily to raise pH
  3. Increase urea application to boost plankton further
  4. Stock more silver carp without any water exchange

Explanation

Dense blue-green algal blooms indicate over-fertilization and risk of oxygen depletion and off-flavour in fish. Partial water exchange and reduced fertilizer input lower nutrient loading and break the bloom.

Question 10Aquaculture and Fish Farming

In a composite carp culture pond, the stocking ratio is planned so that catla and silver carp together occupy about 3 to 4 parts, rohu about 3 parts and mrigal about 2 parts per 10 fish. What is the main reason for this ratio?

  1. To balance surface, column and bottom feeding niches and avoid food competition Correct answer.
  2. To ensure that only one species dominates the harvest
  3. To keep the total stocking density below one fish per square metre
  4. To ensure that all stocked fish mature and breed in the same pond

Explanation

The ratio is designed so that surface feeders, column feeders and bottom feeders share the available natural food without serious overlap, which raises total yield per pond. It is not intended to trigger natural breeding in the pond.

Question 11Aquaculture and Fish Farming

A farmer's pond has a Secchi disc visibility of about 20 cm in the afternoon. What does this observation most likely indicate?

  1. Correct transparency for carp culture
  2. High salinity of pond water
  3. Very low plankton density requiring immediate manuring
  4. Very dense plankton and a risk of oxygen depletion at night Correct answer.

Explanation

Secchi visibility of about 20 cm means the water is highly turbid from dense plankton. Such heavy blooms produce oxygen by day but consume it heavily at night, so night-time oxygen depletion and fish kills are a real risk.

Question 12Aquaculture and Fish Farming

Why is cow dung or poultry manure usually composted or allowed to decompose before being applied to a fish pond?

  1. To kill all plankton present in the pond
  2. To convert it into a direct fish feed
  3. To reduce the oxygen demand it would otherwise create in the pond Correct answer.
  4. To increase its nitrogen content by microbial fixation

Explanation

Fresh organic manure decomposes in the pond and consumes dissolved oxygen, which can suffocate fish. Composting allows much of the decomposition to occur before application, reducing oxygen demand and the risk of oxygen depletion.

Question 13Aquaculture and Fish Farming

A hatchery operator needs to determine the correct dose of pituitary extract for a female catla brood fish. Which factor is most important in deciding the dose?

  1. Colour of the pond water
  2. Size of the hatchery building
  3. Body weight of the brood fish Correct answer.
  4. Number of ponds on the farm

Explanation

Hormone dose in hypophysation is expressed per unit body weight of the brood fish, so the fish's weight must be measured to calculate the injection volume. Water colour and farm infrastructure do not determine the dose.

Question 14Aquaculture and Fish Farming

Which practice best reduces the risk of cannibalism and size variation among fry during nursery rearing?

  1. Periodic grading and sorting by size Correct answer.
  2. Stopping supplementary feeding after one week
  3. Increasing stocking density without limit
  4. Keeping the pond completely free of plankton

Explanation

Grading separates larger, faster-growing fry that would otherwise prey on or outcompete smaller ones, giving more uniform survival and growth. Unlimited density and feed restriction increase competition and mortality.

Question 15Aquaculture and Fish Farming

A carp farmer notices that fish are gasping at the surface at dawn, and the dissolved oxygen reading is 2 mg/L. Which immediate action is most appropriate?

  1. Increase the stocking density
  2. Stop all fertilization and aerate or exchange water Correct answer.
  3. Add fresh cow dung to enrich the pond
  4. Apply mahua oil cake to the pond

Explanation

Surface gasping at dawn with dissolved oxygen near 2 mg/L indicates hypoxia caused by night-time respiration of a heavy plankton bloom. Stopping fertilization and adding aeration or fresh water raises oxygen quickly and removes the cause.

Question 16Aquaculture and Fish Farming

Which of the following is the most appropriate reason for applying agricultural lime to a fish pond with acidic soil and low alkalinity?

  1. To increase the dissolved oxygen content directly
  2. To supply nitrogen directly to the phytoplankton
  3. To raise pH and alkalinity and improve phosphorus availability Correct answer.
  4. To act as a piscicide against unwanted fish

Explanation

Lime neutralizes soil and water acidity, raising pH and alkalinity, which improves the availability of phosphorus and the efficiency of fertilizers. It does not supply nitrogen or oxygen directly.

Question 17Aquaculture and Fish Farming

Which of the following best explains why rohu and mrigal can be stocked together in the same pond without serious competition?

  1. They breed naturally in the pond at the same time
  2. They both require exactly the same natural food
  3. They feed at different depths and on different food items Correct answer.
  4. They both graze only on aquatic weeds

Explanation

Rohu feeds in the mid-water column on plankton and decaying matter, while mrigal feeds near the bottom on detritus and benthic organisms. This separation of feeding niches allows coexistence without heavy competition.

Question 18Aquaculture and Fish Farming

Which method of fish preservation relies on lowering the water activity of fish flesh by osmotic removal of moisture?

  1. Vacuum packing
  2. Chilling in ice
  3. Dry salting Correct answer.
  4. Freezing at minus 20 degrees Celsius

Explanation

Dry salting draws water out of fish tissue by osmosis, lowering water activity and inhibiting spoilage bacteria. Chilling and freezing reduce temperature, and vacuum packing limits oxygen, but none of these lowers water activity by osmosis.

Question 19Aquaculture and Fish Farming

A farmer mixes rice bran, groundnut oil cake and fish meal to prepare a supplementary feed for carp. Which change would most improve the protein content of the mixture?

  1. Increasing the proportion of fish meal Correct answer.
  2. Adding more common salt
  3. Adding more tapioca flour
  4. Increasing the proportion of rice bran

Explanation

Fish meal is the richest protein ingredient in such mixtures, so raising its share raises the overall crude protein level. Rice bran and tapioca flour are mainly energy sources, and salt is a minor mineral additive.

Question 20Aquaculture and Fish Farming

Which of the following is a viral disease of cultured fish that causes high mortality and has no specific chemotherapeutic cure, so control depends on biosecurity?

  1. Argulosis
  2. Koi herpesvirus disease Correct answer.
  3. Saprolegniasis
  4. Columnaris disease

Explanation

Koi herpesvirus disease is a viral infection of common carp and koi with high mortality and no specific drug treatment, so prevention through biosecurity and movement control is essential. The other options are fungal, bacterial and parasitic conditions.

Question 21Aquaculture and Fish Farming

A pond manager calculates that 4000 fingerlings will be stocked in a 0.4 hectare pond. What is the stocking density per hectare?

  1. 1600 per hectare
  2. 10000 per hectare Correct answer.
  3. 40000 per hectare
  4. 400 per hectare

Explanation

Stocking density is the number of fish divided by pond area in hectares, so 4000 divided by 0.4 gives 10000 fingerlings per hectare. Expressing density per hectare allows comparison between ponds of different sizes.

Question 22Aquaculture and Fish Farming

Which change in pond water is most likely when a heavy phytoplankton bloom collapses suddenly after a cloudy spell?

  1. A sharp fall in dissolved oxygen with a rise in carbon dioxide Correct answer.
  2. A permanent rise in pH above 10
  3. A sharp rise in dissolved oxygen at night
  4. Complete disappearance of carbon dioxide

Explanation

When a bloom collapses, photosynthesis stops while dead algae are decomposed by bacteria that consume oxygen and release carbon dioxide. The result is a sudden oxygen drop that can cause fish mortality, especially at night and early morning.

Question 23Aquaculture and Fish Farming

A hatchery produces spawn from induced breeding. Which sequence correctly describes the handling steps from stripped eggs to free-swimming spawn?

  1. Fertilization, incubation, hatching, yolk-sac absorption, spawn stage Correct answer.
  2. Incubation, fertilization, yolk-sac absorption, hatching, spawn stage
  3. Hatching, fertilization, incubation, spawn stage, yolk-sac absorption
  4. Yolk-sac absorption, fertilization, hatching, incubation, spawn stage

Explanation

Stripped eggs and milt are mixed for fertilization, then incubated in hatchery jars or tanks where embryos develop and hatch. The hatchlings absorb the yolk sac and then begin exogenous feeding as spawn.

Question 24Aquaculture and Fish Farming

In a polyculture pond, grass carp are stocked at low density along with Indian major carps. What is the main risk if grass carp density is raised too high?

  1. Sudden increase in dissolved oxygen above saturation
  2. Prevention of rohu from feeding in the mid-water column
  3. Complete elimination of phytoplankton by filter feeding
  4. Depletion of aquatic weeds and increased competition for supplementary feed Correct answer.

Explanation

Grass carp consume large quantities of macrophytes, so excessive stocking removes weed cover and forces the fish to compete for supplementary feed. It also produces heavy fecal loads that can degrade water quality.

Question 25Aquaculture and Fish Farming

A farmer applies urea and single super phosphate to a pond and observes no increase in plankton growth over two weeks. Which pond condition most plausibly explains the poor fertilizer response?

  1. Low water alkalinity causing rapid phosphorus precipitation and loss Correct answer.
  2. Presence of rohu in the pond
  3. A Secchi visibility of 35 cm
  4. Water temperature of 28 degrees Celsius

Explanation

In low-alkalinity, acidic ponds, applied phosphate is rapidly bound and precipitated, so it is unavailable to phytoplankton. Liming to raise alkalinity is needed before fertilizers give a response. Warm temperature and moderate transparency favour plankton, not prevent it.

Question 26Aquaculture and Fish Farming

A farmer wants to control excessive aquatic weeds in a carp pond without using chemicals. Which biological control measure is most appropriate for dense submerged vegetation?

  1. Introducing water hyacinth for shade
  2. Stocking silver carp at an appropriate density
  3. Stocking grass carp at an appropriate density Correct answer.
  4. Adding more cow dung to increase turbidity

Explanation

Grass carp are herbivorous fish that feed on submerged aquatic vegetation and can significantly reduce weed biomass when stocked at suitable densities. Silver carp are planktivorous and do not consume macrophytes, while adding manure or water hyacinth would worsen weed and water quality problems.

Question 27Aquaculture and Fish Farming

In composite fish culture, which combination of species is most suitable for utilizing both surface and bottom food niches in a pond?

  1. Mrigal and grass carp only
  2. Silver carp and catla only
  3. Catla, rohu and mrigal Correct answer.
  4. Grass carp and common carp only

Explanation

Catla is a surface feeder, rohu is a column feeder, and mrigal is a bottom feeder, so together they exploit different zones of the pond and reduce competition. The other combinations either omit a major niche or pair species with overlapping feeding habits.

Question 28Aquaculture and Fish Farming

Which water quality parameter is most directly affected by the addition of high doses of agricultural lime to a fish pond?

  1. Water temperature
  2. Salinity
  3. Dissolved oxygen only
  4. pH and total alkalinity Correct answer.

Explanation

Lime raises pH and increases total alkalinity by neutralizing acidity and adding calcium and bicarbonate ions. It does not directly control temperature or salinity, and its effect on dissolved oxygen is indirect through improved plankton growth.

Question 29Aquaculture and Fish Farming

A hatchery manager observes that newly hatched carp larvae are dying in large numbers within the first three days. Which factor is most likely responsible?

  1. Presence of adult brood fish in the same tank
  2. High calcium hardness above 200 mg/L
  3. Excessive water depth in the rearing tank
  4. Inadequate initial live food such as rotifers Correct answer.

Explanation

Carp larvae have a small mouth and require live food, especially rotifers, during the first few days after yolk absorption. Without suitable prey they starve and mortality rises sharply. Water depth, brood stock presence, and moderate hardness are less critical at this stage.

Question 30Aquaculture and Fish Farming

Which method of induced breeding is commonly used for Indian major carps in commercial hatcheries?

  1. Use of only environmental manipulation such as rain simulation
  2. Stripping without any hormonal stimulation
  3. Artificial insemination after natural spawning
  4. Hypophysation using pituitary gland extract Correct answer.

Explanation

Indian major carps do not normally spawn in confined ponds, so hatcheries use hypophysation, injecting pituitary gland extract to induce ovulation and spermiation. Environmental manipulation alone is unreliable, and stripping without hormonal priming usually fails.

Question 31Aquaculture and Fish Farming

A farmer notices that the pond water has turned turbid with suspended clay particles after heavy rain. Which management measure is most appropriate to clarify the water?

  1. Add fresh cow dung to settle the clay
  2. Apply gypsum or alum to flocculate suspended particles Correct answer.
  3. Increase stocking density of bottom feeders
  4. Stop all water exchange and wait for evaporation

Explanation

Gypsum or alum causes clay particles to coagulate and settle, clearing turbidity that blocks light and reduces plankton growth. Adding manure worsens turbidity, and bottom feeders do not remove suspended clay.

Question 32Aquaculture and Fish Farming

Which of the following is the most important reason for testing the viability of fish eggs before stocking them in a hatchery?

  1. To count the number of brood fish in the pond
  2. To determine the exact colour of the eggs
  3. To measure the egg diameter for feed selection
  4. To estimate the proportion of fertilized and developing eggs Correct answer.

Explanation

Viability testing helps estimate fertilization and hatching rates, allowing the hatchery to plan larval rearing and avoid wasting resources on dead eggs. Colour, diameter, and brood stock counts are not the purpose of viability assessment.

Question 33Aquaculture and Fish Farming

In a fish pond, a sudden algal bloom collapse is often followed by a drop in dissolved oxygen. Which process best explains this?

  1. Algae release oxygen when they die
  2. The pond water becomes colder and holds more oxygen
  3. Dead algae sink and stop all respiration
  4. Bacterial decomposition of dead algae consumes oxygen Correct answer.

Explanation

When algae die, bacteria decompose the organic matter and consume large amounts of dissolved oxygen, often causing oxygen depletion. Dead algae do not release oxygen, and decomposition increases rather than stops respiration.

Question 34Aquaculture and Fish Farming

Which type of pond is specifically designed for the rearing of fry to fingerling stage before they are released into grow-out ponds?

  1. Breeding pond
  2. Nursery pond Correct answer.
  3. Stocking pond
  4. Harvesting pond

Explanation

A nursery pond is a small, well-managed pond used to raise fry to fingerling size. Breeding ponds are for spawning, and stocking and harvesting ponds are not standard terms for this stage.

Question 35Aquaculture and Fish Farming

A farmer wants to reduce the cost of supplementary feed while maintaining protein content. Which combination is most suitable?

  1. Only fish meal
  2. Only rice bran
  3. Rice bran and groundnut oil cake in appropriate proportions Correct answer.
  4. Only maize flour

Explanation

Rice bran provides energy and groundnut oil cake provides protein, so combining them gives a balanced feed at lower cost than fish meal alone. Single ingredients are deficient in one or more nutrients.

Question 36Aquaculture and Fish Farming

Which disease of fish is caused by a bacterium and is characterized by red ulcers on the body surface?

  1. Motile Aeromonas septicaemia Correct answer.
  2. White spot disease
  3. Epizootic ulcerative syndrome
  4. Saprolegniasis

Explanation

Motile Aeromonas septicaemia is a bacterial infection that produces red ulcers and haemorrhages. White spot disease is viral, epizootic ulcerative syndrome is fungal, and saprolegniasis is a fungal infection with cotton-like growth.

Question 37Aquaculture and Fish Farming

A pond has a high density of phytoplankton but very low dissolved oxygen at dawn. Which management action is most appropriate?

  1. Stop aeration to avoid disturbing the pond
  2. Reduce nutrient input and increase water exchange Correct answer.
  3. Increase stocking density to consume algae
  4. Add more fertilizer to boost phytoplankton

Explanation

High phytoplankton density causes low oxygen at dawn because respiration exceeds photosynthesis at night. Reducing nutrient input and improving water exchange helps balance the bloom and prevent oxygen depletion. Adding fertilizer or stopping aeration would worsen the problem.

Question 38Aquaculture and Fish Farming

Which factor is most critical for the successful storage of fish feed ingredients to prevent spoilage?

  1. Mixing them with water before storage
  2. Keeping them dry and cool Correct answer.
  3. Exposing them to direct sunlight
  4. Storing them in open containers

Explanation

Feed ingredients should be stored in a dry, cool place to prevent mould growth and insect infestation. Sunlight, open containers, and moisture promote spoilage and reduce feed quality.

Question 39Aquaculture and Fish Farming

In a polyculture pond, high densities of silver carp are stocked along with catla. Which interaction is most likely to occur?

  1. Competition for phytoplankton Correct answer.
  2. Mutualism through waste exchange
  3. Predation by silver carp on catla fry
  4. No interaction because they occupy different niches

Explanation

Both silver carp and catla are primarily planktivorous and feed on phytoplankton, so high densities can lead to competition for food. They do not exhibit predation on each other's fry, and their niches overlap significantly.

Question 40Aquaculture and Fish Farming

A farmer wants to improve the survival of fish during transport from hatchery to pond. Which practice is most effective?

  1. Increase water temperature in transport bags
  2. Feed heavily just before transport
  3. Transport fish in dense crowding without aeration
  4. Reduce feeding before transport and maintain adequate oxygen Correct answer.

Explanation

Withholding feed before transport reduces metabolic waste and oxygen demand, while maintaining oxygen levels prevents stress and mortality. Heavy feeding, higher temperature, and crowding without aeration all increase stress and oxygen consumption.

Question 41Fish Biology, Anatomy and Physiology

किस प्रकार की मछली में श्वसन के लिए गिल स्लिट के साथ-साथ फुफ्फुस (lung) भी पाया जाता है?

  1. कतला (Catla)
  2. रोहू (Rohu)
  3. क्लेरियस (Clarias) Correct answer.
  4. सुरमई (Mackerel)

Explanation

क्लेरियस एक एयर-ब्रीदिंग कैटफिश है जिसमें गिल के अतिरिक्त एक सहायक श्वसन अंग होता है जो वायुमंडलीय ऑक्सीजन लेने में सक्षम है। यह अंग इसे कम ऑक्सीजन वाले दलदली जल में भी जीवित रहने देता है। रोहू और कतला केवल गिलों से श्वसन करते हैं।

Question 42Fish Biology, Anatomy and Physiology

मछली के हृदय में कितने कक्ष होते हैं और रक्त का प्रवाह किस प्रकार होता है?

  1. तीन कक्ष, दोहरा परिसंचरण
  2. चार कक्ष, दोहरा परिसंचरण
  3. दो कक्ष, एकल परिसंचरण Correct answer.
  4. एक कक्ष, खुला परिसंचरण

Explanation

मछली का हृदय दो कक्षों (एक अलिंद और एक निलय) वाला होता है और इसमें केवल शिरापरक रक्त प्रवाहित होता है। हृदय से रक्त गिलों में जाता है और ऑक्सीजनित होकर शरीर में बहता है, इसलिए इसे एकल परिसंचरण कहते हैं।

Question 43Fish Biology, Anatomy and Physiology

मछली की त्वचा पर स्थित श्लेष्मा (mucus) की परत का मुख्य कार्य क्या है?

  1. पाचन एंजाइम स्रावित करना
  2. घर्षण कम करना और रोगाणुओं से रक्षा करना Correct answer.
  3. शरीर का तापमान बढ़ाना
  4. जल में ऑक्सीजन का संचय करना

Explanation

श्लेष्मा की परत त्वचा को चिकना बनाकर तैरने में घर्षण घटाती है और साथ ही जीवाणुओं तथा परजीवियों के प्रवेश को रोककर सुरक्षा देती है। यह परत शरीर से जल के नुकसान को भी सीमित करती है।

Question 44Fish Biology, Anatomy and Physiology

मछली के शरीर में पाई जाने वाली पार्श्व रेखा (lateral line) किस प्रकार की संवेदी भूमिका निभाती है?

  1. गंध का पहचानना
  2. प्रकाश की तीव्रता का मापन
  3. जल का तापमान मापना
  4. जल के दाब और कंपन का संवेदन Correct answer.

Explanation

पार्श्व रेखा में न्यूरोमास्ट कोशिकाएँ होती हैं जो जल के कंपन और दाब परिवर्तन को ग्रहण करती हैं। इससे मछली को शिकारी, बाधा तथा झुंड के सदस्यों की स्थिति का पता चलता है।

Question 45Fish Biology, Anatomy and Physiology

मछली में पित्ताशय (gall bladder) से स्रावित पित्त का पाचन में क्या योगदान है?

  1. विटामिन का संश्लेषण
  2. प्रोटीन का अमीनो अम्ल में विघटन
  3. वसा का पायसीकरण (emulsification) Correct answer.
  4. स्टार्च का ग्लूकोज में विघटन

Explanation

पित्त में पित्त लवण होते हैं जो वसा को छोटी बूँदों में तोड़कर उसका पायसीकरण करते हैं। इससे लाइपेज एंजाइम की क्रिया का क्षेत्र बढ़ जाता है और वसा का पाचन सुगम होता है।

Question 46Fish Biology, Anatomy and Physiology

मछली के गिल्स में जल के प्रवाह की दिशा और रक्त के प्रवाह की दिशा के संबंध को क्या कहते हैं?

  1. समांतर प्रवाह
  2. व्युत्क्रम दाब
  3. प्रतिप्रवाह (counter-current) Correct answer.
  4. विसरण प्रवाह

Explanation

गिल्स में जल एक दिशा में और रक्त विपरीत दिशा में बहता है, जिसे प्रतिप्रवाह प्रणाली कहते हैं। इससे गिल पटलिकाओं के साथ गैस विनिमय के दौरान ऑक्सीजन का अधिकतम अवशोषण होता है।

Question 47Fish Biology, Anatomy and Physiology

रोहू मछली के मुख गुहा में पाई जाने वाली ग्रसनी दंत पट्टिकाएँ (pharyngeal teeth) मुख्यतः किस कार्य में सहायक होती हैं?

  1. भोजन को पकड़कर पीसना Correct answer.
  2. शिकार को पकड़ना
  3. गंध का संवेदन
  4. जल को छानना

Explanation

कार्प परिवार की मछलियों में ग्रसनी दंत पट्टिकाएँ ग्रसनी में स्थित होती हैं और भोजन को पकड़कर चबाने तथा पीसने का कार्य करती हैं। ये मुख्य दंत नहीं होतीं क्योंकि इन मछलियों में जबड़े के दाँत अनुपस्थित होते हैं।

Question 48Fish Biology, Anatomy and Physiology

मछली के शरीर में वायु पुटिका (swim bladder) का मुख्य कार्य क्या है?

  1. रक्त को शुद्ध करना
  2. पाचन में सहायता करना
  3. जल में उत्प्लावन (buoyancy) नियंत्रित करना Correct answer.
  4. मूत्र का संचय करना

Explanation

वायु पुटिका में गैस की मात्रा बदलकर मछली अपने शरीर का घनत्व जल के बराबर रखती है। इससे उसे तैरने में कम ऊर्जा खर्च करनी पड़ती है और वह विभिन्न गहराइयों पर स्थिर रह सकती है।

Question 49Fish Biology, Anatomy and Physiology

टेलीओस्ट मछली के हृदय से निकलने वाला रक्त सबसे पहले किस अंग में पहुँचता है?

  1. मस्तिष्क
  2. यकृत
  3. गिल्स Correct answer.
  4. गुर्दे

Explanation

टेलीओस्ट में हृदय से शिरापरक रक्त वेंट्रल एओर्टा से होकर सीधे गिल्स में जाता है। गिल्स में ऑक्सीजन ग्रहण करने के बाद यह रक्त डोर्सल एओर्टा द्वारा शरीर के अन्य अंगों में पहुँचता है।

Question 50Fish Biology, Anatomy and Physiology

मछली की आँख में लेंस की आकृति और उसका समायोजन किस प्रकार होता है?

  1. गोलाकार लेंस, कॉर्निया मोड़कर
  2. चपटा लेंस, दृष्टि क्षेत्र बदलकर
  3. बेलनाकार लेंस, पुतली बदलकर
  4. गोलाकार लेंस, लेंस को आगे-पीछे खिसकाकर Correct answer.

Explanation

मछली की आँख में लेंस लगभग गोलाकार होता है और इसकी फोकस दूरी बदलने के लिए लेंस को रेटिना के सापेक्ष आगे-पीछे खिसकाया जाता है। स्तनधारियों की तरह लेंस की आकृति बदलकर समायोजन नहीं होता।