• Concept of Limiting Amino Acids:
• limiting amino acid is an essential amino acid present in a dietary protein in the lowest amount relative to the animal's nutritional requirement (governed by Liebig's Law of the Minimum).
• Methionine and Lysine:
• When fishmeal is replaced with economical plant protein sources (such as soybean meal, groundnut cake, mustard oil cake, and cereal by-products):
• Lysine is deficient in cereal grains and corn gluten meal.
• Methionine is severely deficient in oilseed meals and pulses (e.g., soybean meal).
• Hence, Methionine and Lysine are recognized globally as the first two most limiting essential amino acids in commercial fish feeds.
• nalysis:
• (Methionine and Lysine): Correct.
• Options 1, 3, 4: Do not represent the universally limiting pair in plant-based aquafeeds.

Correct option: (2) Methionine and Lysine