ICAR AIEEA PG Fisheries Science 14 July 2023 Shift-1 Paper

Assertion (A) is true: In naval architecture, maritime tonnage measures capacity either by enclosed volume (Gross Tonnage and Net Tonnage, where 1 register ton equals $100\text{ cubic feet}$ or $2.83\text{ m}^3$) or by actual gravitational weight (Deadweight Tonnage and Displacement Tonnage in metric tons). Reason (R) is true: Displacement tonnage measures the true physical weight of the entire vessel, calculated by Archimedes' principle as the weight of the water displaced by the hull ($1\text{ metric ton} = 1000\text{ kg}$, corresponding to $1.0\text{ m}^3$ of freshwater with density $1.0\text{ t/m}^3$ and approx. $0.975$ to $0.99\text{ m}^3$ of seawater with density $1.025\text{ t/m}^3$). This directly illustrates how tonnage is defined through physical weight.

Option analysis:

• Both (A) and (R) are true and (R) is the correct explanation of (A): Correct, (R) provides the exact technical and physical basis for weight-based tonnage stated in (A).
• Both true but not explanation: Incorrect, (R) explains the weight aspect of (A).
• is true but (R) is false: Incorrect, (R) is true.
• is false: Incorrect, (A) is true.

Statement (I) is correct: The hydroacoustic echo sounder (fish finder) is universally the most common, indispensable acoustic instrument utilized worldwide for detecting underwater fish shoals, seabed depth, and obstacles. Statement (II) is incorrect: An echo sounder fundamentally consists of four essential major units, not just two: (1) Transmitter (generates high-frequency electrical pulses), (2) Transducer (converts electrical energy to ultrasonic acoustic pulses and vice versa), (3) Receiver/Amplifier (amplifies weak returned echo signals), and (4) Display/Recorder unit (echogram display).

Option analysis:

• Both correct: Incorrect because Statement II is false.
• Both incorrect: Incorrect because Statement I is true.
• Statement (I) is correct but Statement (II) is incorrect: Correct assessment.
• Statement (I) is incorrect: Incorrect because Statement I is true.

The 'mushy' or 'jellied' flesh condition in marine fishes (such as Pacific hake, flounder, and swordfish) and canned fish is caused by infection with histozoic myxosporean/myxozoan Protozoa (principally species of Kudoa, Chloromyxum, and Henneguya). These protozoans release potent, heat-stable proteolytic enzymes that extensively liquefy myofibrillar proteins during heating and cooking, reducing firm muscle to a soft, mushy, unmarketable paste.

Option analysis:

• Protozoa: Correct, Myxozoan parasites (e.g. Kudoa/Chloromyxum) cause mushy/jellied flesh defect.
• Fungus: Causes external mold growth on dried fish, not canned mush.
• Bacteria: Cause spoilage odors and gas blowing, not myxosporean mush.
• Salt: Dehydrates and firms flesh, does not cause enzymatic liquefaction.