ICAR AIEEA (PG): Master's entrance, Veterinary Science and Animal Sciences · India · NTA for ICAR
Original practice questions written to the published syllabus · not past papersDiseases of fish and crustaceans, the role of water quality, aquaculture biosecurity, and the residue rules for therapeutants used in food fish.
In the exams: NAVLE aquatics 1%; China runs a separate aquatic-animal category of its national exam
ICAR AIEEA (PG) and AICE-JRF/SRF; ASRB NET/ARS (India)
Recall of causal agents and families, WOAH-listed diseases, EUS and white spot disease in the Indian context, myxozoan and crustacean parasites, un-ionised ammonia and DO chemistry, oomycete versus fungus, banned residues under FSSAI, and pathogenesis-level questions (PirA/PirB toxins, vertical transmission of Renibacterium, latency in koi herpesvirus).
How our questions for ICAR AIEEA spread across the units of Aquatic Animal Diseases, Health Care & Management. Difficulty: 20 easy, 25 medium, 12 hard.
| Diagnosis of aquatic animal disease | 9 | |
| Bacterial diseases of fish and shrimp | 7 | |
| Parasitic diseases of fish and shrimp | 7 | |
| Water-quality diseases | 6 | |
| Viral diseases of fish and shrimp | 6 | |
| Fungal diseases of fish | 5 | |
| Therapeutants and residues | 5 | |
| WOAH-listed aquatic animal diseases | 4 | |
| Biosecurity in aquaculture | 4 | |
| Degree-day withdrawal periods | 4 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
At a constant 25 °C (pKa 9.25), by roughly what factor does the un-ionised fraction of total ammonia increase when pH rises from 7.0 to 9.0?
C. About 64-fold
f(pH 7) = 1/(1 + 10^2.25) = 0.56%; f(pH 9) = 1/(1 + 10^0.25) = 36%. 36/0.56 ≈ 64. The tempting answer of exactly 100 (two pH units, 10 × 10) ignores that at pH 9 a large share is already un-ionised, so the fraction cannot keep rising tenfold; at low pH each unit is close to tenfold.
Further reading: Boyd & Tucker, Pond Aquaculture Water Quality Management; Emerson et al. (1975)
A laboratory reports un-ionised ammonia as 0.30 mg/L NH3-N. The permitted limit in the farm's standard is written as mg/L NH3 (as the whole molecule). What is the result on the standard's basis?
B. 0.36 mg/L NH3
NH3 = NH3-N × 17/14 = 0.30 × 1.214 = 0.36 mg/L. Multiplying by 14/17 (0.25) reverses the conversion, dividing by 17 alone gives 0.017, and leaving the figure unchanged ignores the different basis. The molecular mass of NH3 is 17 and of N is 14.
Further reading: Boyd & Tucker, Pond Aquaculture Water Quality Management; Emerson et al. (1975)
Which condition makes hydrogen sulphide in pond-bottom water more toxic?
B. A fall in pH
H2S is the toxic un-ionised form and dominates at lower pH, the opposite of ammonia, which becomes more toxic at higher pH. Higher DO oxidises sulphide, and alkalinity is not the determining factor.
Further reading: Boyd & Tucker, Pond Aquaculture Water Quality Management; Emerson et al. (1975)
A laboratory needs to culture bacteria from a septicaemic rainbow trout. Which approach is appropriate?
A. Sample kidney aseptically and incubate general media at about 20–25 °C
In septicaemia, bacteria are found in the highly vascular kidney; fish pathogens grow best at about 20–25 °C and many fail at 37 °C. Skin and gut are heavily contaminated, and anaerobic culture of the swim bladder is not a standard method.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
Survivors of Taura syndrome in P. vannamei typically show:
B. Multiple irregular melanised lesions in the cuticle
The recovery phase of Taura syndrome shows black melanised cuticular lesions; the acute phase has a red tail fan and soft shell. White opaque muscle suggests infectious myonecrosis; white spots suggest WSSV; bent rostrum suggests IHHNV.
Further reading: Lightner (ed.), A Handbook of Shrimp Pathology and Diagnostic Procedures
Acute hepatopancreatic necrosis disease (AHPND) of shrimp is caused by:
A. Vibrio parahaemolyticus strains carrying a plasmid encoding PirA and PirB toxins
AHPND is caused by vibrios carrying the pVA1-type plasmid with binary PirA/PirB toxins. EHP is a microsporidian causing slow growth; Hepatobacter penaei causes necrotising hepatopancreatitis; WSSV is a virus.
Further reading: Lightner (ed.), A Handbook of Shrimp Pathology and Diagnostic Procedures
The salmon louse of sea-farmed Atlantic salmon is:
C. Lepeophtheirus salmonis
L. salmonis (with Caligus species) is the sea louse of salmon farming. Argulus and Lernaea are mainly freshwater parasites; Ichthyobodo is a flagellate.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
Which of these mollusc pathogens is WOAH-listed?
A. Bonamia ostreae
Infection with Bonamia ostreae (a haplosporidian of flat oysters) is listed, as are Marteilia refringens and Perkinsus marinus. The others are not mollusc pathogens on the list.
Further reading: WOAH Aquatic Animal Health Code, chapter 1.3; WOAH Manual of Diagnostic Tests for Aquatic Animals
What does 'SPF' mean when applied to shrimp broodstock?
D. Free of specified pathogens, as shown by a defined surveillance programme
Specific-pathogen-free refers to documented freedom from named pathogens; it says nothing about resistance, which is what SPR (specific-pathogen-resistant) lines are selected for. Shrimp cannot be conventionally vaccinated.
Further reading: Lightner (ed.), A Handbook of Shrimp Pathology and Diagnostic Procedures
A cage was fed 1,500 kg of feed; biomass rose from 200 kg to 1,400 kg at harvest, and 100 kg of fish died and were removed during the cycle. What is the biological FCR (counting the weight of dead fish as gain)?
A. 1.15
Biological FCR = 1,500 ÷ (1,200 + 100) = 1,500 ÷ 1,300 = 1.15. The economic FCR, using harvested gain only, is 1.25. Subtracting the dead fish from the gain (1,500/1,100 = 1.36) is the wrong direction; 0.87 is the inverse.
Further reading: Standard aquaculture arithmetic
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