Which organism serves as a vital food source for all fish fry?

• A. Phytoplankton
• B. Rotifer
• C. Phytoplankton
• D. Aquifer

Answer: (B)

Rotifers are a perfect first live feed for many fish larvae because they are the right size, mobile, and nutritionally rich. Their small size—large enough to be easy for fry to capture but not so large as to require advanced mouthparts—fits the early feeding stage for a wide range of species. They provide essential nutrients, including fatty acids and amino acids, supporting healthy growth during the critical early life period. In hatcheries, rotifers can be cultured in large numbers and enriched with microalgae to boost their nutritional value, giving growers a reliable, controllable food source. While phytoplankton forms the base of the aquatic food web and is important for supporting overall culture health, it isn’t universally suitable as the primary food for all fry because many larvae cannot efficiently feed on undigested phytoplankton, making rotifers the more universally vital live feed. An aquifer is not an organism and has no role as a fry food source.