Feed is where most aquaculture exams — and most fish farms — are won or lost. A farmer who feeds the right ration, at the right size, at the right frequency, converts feed into growth instead of waste. A student who understands protein, amino acids, lipids and feeding practice can answer almost any feed question an examiner sets. This set of 20 multiple-choice questions covers exactly that ground: Indian major carp nutrition, feed formulation, feed types and on-farm feeding practice.
Try every question before you look at the answer. The explanation after each answer is the revision point — read it even when you get the question right, because examiners love to test the reason, not just the fact. The images in this post are illustrations.
First, the five facts examiners repeat
Fish do not have a requirement for protein as such — they need a balanced supply of amino acids. Ten amino acids are essential for fish, meaning the fish cannot make them and must get them from feed. In plant-protein diets, lysine and the sulphur amino acids (methionine + cystine) are usually the first to run short, which is why fishmeal, with its balanced essential amino acid profile, has traditionally been so valued, and why plant-based diets often need amino acid supplementation.
Protein need falls as a carp grows. The textbook values for Indian major carps are about 40% dietary protein for fry, 35% for fingerlings and 30% for adults — while the Bureau of Indian Standards values quoted in ICAR-CIFA’s feed training manual put spawn/fry feed at 35% and grow-out/broodstock feed at 25%. The difference is a useful exam lesson in itself: exact percentages vary with the diet, the species and the study, so questions normally test the pattern (young fish need more protein than adults) and the widely quoted textbook set, not a single universal number.
| Indian major carp stage | Textbook dietary protein (approx.) | What to remember |
|---|---|---|
| Fry | ~40% | Highest protein need; small, frequent meals |
| Fingerling | ~35% | Still high; growth is rapid |
| Adult / grow-out | ~30% | Lower protein need; energy can spare protein |
ICAR-CIFA’s commercial grow-out feed, CIFA-Carp Grower, illustrates the practical end of the same science: 28% crude protein and 4% crude fat, fed as a floating feed. In CIFA’s own trial, rohu fingerlings averaging 105 g reached 1,088 g in 10 months on it, with a feed conversion ratio (FCR) of 1.290 — feed fed divided by weight gained, where a lower number means better conversion.
| Fish size (CIFA-Carp Grower guide) | Daily feeding rate |
|---|---|
| Up to 100 g | 3% of body weight |
| 100–200 g | 2.5% of body weight |
| 200–300 g | 1.5% of body weight |
That table shows the second great pattern in fish feeding: the ration, as a percentage of body weight, falls as the fish grows. Fry may be fed 10% of body weight or more, split over several meals; a large grow-out fish needs only a small percentage. Overfeeding does not speed growth — it wastes feed, fouls water and raises ammonia.
20 MCQs: Fish Feed & Nutrition
Q1. The textbook dietary protein requirement for Indian major carp fry is about
(a) 20% (b) 30% (c) 40% (d) 50%
Answer: (c) 40%. Fingerlings need about 35% and adults about 30% — protein need falls with age.
Q2. How many amino acids are essential (indispensable) in fish diets?
(a) 5 (b) 8 (c) 10 (d) 15
Answer: (c) 10. Arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine must come from the diet.
Q3. Which amino acids are most often the first limiting amino acids in plant-protein fish diets?
(a) Arginine and histidine (b) Lysine and methionine (c) Leucine and valine (d) Tryptophan and phenylalanine
Answer: (b) Lysine and methionine. Plant proteins are typically short of lysine and the sulphur amino acids; that is why supplementation, or a little animal protein, improves a plant-based diet so much.
Q4. The “protein-sparing effect” in fish nutrition means
(a) Protein is stored in the liver (b) Adequate dietary lipid and carbohydrate let protein be used for growth instead of energy (c) Fish eat less protein in winter (d) Protein is replaced by vitamins
Answer: (b). When non-protein energy is sufficient, ingested protein goes to tissue building rather than being burned for energy.
Q5. Feed conversion ratio (FCR) is calculated as
(a) Weight gain ÷ feed fed (b) Feed fed ÷ weight gain (c) Feed fed × weight gain (d) Protein fed ÷ weight gain
Answer: (b) Feed fed ÷ weight gain. Lower is better: CIFA-Carp Grower’s trial FCR of 1.290 means 1.29 kg of feed per kg of growth.
Q6. ICAR-CIFA’s CIFA-Carp Grower floating feed contains
(a) 20% crude protein, 2% fat (b) 28% crude protein, 4% crude fat (c) 35% crude protein, 8% fat (d) 40% crude protein, 10% fat
Answer: (b) 28% crude protein, 4% crude fat. It is a grow-out feed, not a fry feed — which is why its protein level sits below the fry requirement.
Q7. The gross lipid requirement of Indian major carps is about
(a) 2–3% (b) 7–8% (c) 15–18% (d) 25–30%
Answer: (b) 7–8%. Lipids supply energy and essential fatty acids; excess lipid, however, deposits as body fat and can harm feed efficiency.
Q8. Why is fishmeal traditionally valued in aquafeeds?
(a) It is the cheapest ingredient (b) It has a balanced essential amino acid profile and high digestibility (c) It floats on water (d) It contains no protein
Answer: (b). Even small amounts of fishmeal can lift the amino acid balance of a whole diet — the reason replacing it entirely is a formulation challenge.
Q9. Vitamin C (ascorbic acid) deficiency in fish is classically associated with
(a) Fin rot only (b) Skeletal deformities such as scoliosis and poor wound healing (c) Loss of scales only (d) Blindness only
Answer: (b). Vitamin C is needed for collagen formation; deficiency weakens connective tissue and bone, producing bent spines and slow healing.
Q10. The standard first live feeds for most marine fish larvae are
(a) Chopped trash fish (b) Rotifers followed by Artemia nauplii (c) Dry pellets only (d) Rice bran
Answer: (b) Rotifers followed by Artemia nauplii. Larvae need tiny, moving, digestible prey; formulated feeds come later, once the gut and mouth are ready.
Q11. Marine fish particularly need which fatty acids in the diet?
(a) Only saturated fats (b) EPA and DHA, the long-chain omega-3 highly unsaturated fatty acids (c) Only short-chain fats (d) No dietary fat at all
Answer: (b) EPA and DHA. Marine species have limited ability to make these from shorter-chain precursors, so they must be supplied ready-made.
Q12. As a fish grows, its daily feeding rate as a percentage of body weight
(a) Increases steadily (b) Stays the same (c) Decreases (d) Doubles every month
Answer: (c) Decreases. Compare the CIFA-Carp Grower guide above: 3% at up to 100 g, falling to 1.5% at 200–300 g.
Q13. A major practical advantage of floating feed over sinking feed is that
(a) It is always cheaper (b) The farmer can watch feeding and adjust the ration, reducing waste (c) It never breaks up (d) It needs no protein
Answer: (b). Visible feeding lets the farmer stop when fish lose interest — uneaten sinking feed is invisible waste that decays on the pond bottom.
Q14. The main anti-nutritional factor in raw soybean meal is
(a) Gossypol (b) Trypsin inhibitor (c) Phytic acid only (d) Tannin only
Answer: (b) Trypsin inhibitor. It blocks protein digestion; proper heat treatment destroys it. Gossypol is the classic problem of cottonseed meal, and phytic acid binds minerals — both are good distractors in exams.
Q15. Which statement about carbohydrate use in fish is correct?
(a) Carnivorous fish use carbohydrate as well as herbivores do (b) Carnivores use carbohydrate poorly; omnivorous carps use it much better (c) Fish cannot use carbohydrate at all (d) Carbohydrate replaces all protein
Answer: (b). This is why carp diets can carry more carbohydrate than a salmon or seabass diet, and why carbohydrate helps spare protein in carp feeds.
Q16. The crude fibre level quoted for carp grow-out and broodstock feed (BIS, in ICAR-CIFA’s manual) is
(a) 2% (b) 4% (c) 8% (d) 15%
Answer: (c) 8%. Spawn feed is quoted at 6% and fry, grow-out and broodstock feeds at 8% — fibre is bulk, not nutrition, and too much of it dilutes the diet.
Q17. Why is water stability important in a pelleted fish feed?
(a) It makes pellets float forever (b) It limits nutrient leaching into the water before the fish eats the pellet (c) It changes the colour (d) It adds protein
Answer: (b). A pellet that disintegrates in minutes loses water-soluble vitamins and amino acids to the pond instead of delivering them to the fish.
Q18. Fry and early fingerlings should be fed
(a) Once a week (b) One large meal a day (c) Small meals several times a day (d) Only at night
Answer: (c) Small meals several times a day. Small stomachs, fast metabolism and high growth rates all point the same way: little and often.
Q19. Poor feed storage — damp, warm conditions — most directly risks
(a) Higher protein content (b) Mould growth, mycotoxins and rancidity of fats (c) Larger pellet size (d) Better palatability
Answer: (b). Moisture invites mould and mycotoxins, while heat and air oxidise lipids; both destroy nutrients and can harm fish. Store feed dry, cool and off the floor.
Q20. A farmer switches from a 40% protein fry feed to a 28% protein grow-out feed as fish grow. This is correct because
(a) Older fish cannot digest protein (b) Protein requirement falls with age, and the grow-out feed still meets the adult requirement while cutting cost (c) Protein is toxic to adults (d) Grow-out feeds contain no amino acids
Answer: (b). Matching the feed to the stage is the whole point of stage feeding: it protects growth and stops the farmer paying for protein the fish no longer needs.
How to revise from this set
Score yourself out of 20, then re-read only the explanations you got wrong — and write each one out in your own words. The patterns worth memorising for any fisheries exam are: protein need falls with age; the feeding rate as a percentage of body weight falls with age; lysine and methionine limit plant diets; FCR is feed divided by gain; and floating feed exists so the farmer can see what is eaten. Almost every feed question is a variation on one of those five ideas.
For the science behind these questions, see ICAR-CIFA’s training manual on application and practices of fish feed in aquaculture, FAO’s feed ingredient survey and formulated feeds for aquaculture in the tropics, and ICAR’s published trial of CIFA-Carp Grower in rohu. Links are in the sources below.
Frequently asked questions
Do all fish need the same protein percentage? No. Carnivorous species need more protein than omnivorous carps, and young fish need more than adults. Always match the feed to the species and the stage.
Is a lower FCR always better? Yes, as a measure of conversion — but it must be read with growth rate, survival and cost. A very low FCR with slow growth or high mortality is not a good result.
Can plant proteins fully replace fishmeal? They can come close when amino acids are balanced and anti-nutritional factors are treated, but the amino acid profile — especially lysine and methionine — must be checked, not assumed.
Related reading on Fisheries India
- Catla vs Rohu vs Mrigal: 20 MCQs Fisheries Exams Love
- Shrimp Farming in India: 20 MCQs Every Aspirant Must Try
- Water Quality MCQs: 20 Questions Every Fisher Must Ace
- Biofloc MCQs: 20 Questions Every Aspirant Must Ace
Sources
- ICAR-CIFA Training Manual No. 65, Application and Practices of Fish Feed in Aquaculture (2017) — carp protein values, BIS fibre values, lysine requirement notes: CIFA feed training manual (PDF)
- ICAR, CIFA-Carp Grower trial in rohu (28% crude protein, 4% crude fat, 105 g to 1,088 g in 10 months, FCR 1.290): ICAR e-publication
- FAO, Feed Ingredient Survey — animal proteins rich in lysine and methionine, limiting in plant proteins: FAO feed ingredient survey
- FAO, Marine Finfish Netcage Culture training manual — 10 essential amino acids and dietary protein requirements: FAO marine finfish nutrition