Diet Size Preference of Zebrafish (Danio rerio) Larvae Fed on Cross-Linked Protein-Walled Capsules

To optimize diet particle size for ingestion by zebrafish larvae, Danio rerio, a series of diet selection experiments were carried out using two different length classes: 5-day-old, first feeding larvae with a mean standard length (MLs) of 3.8 mm and 15-day-old larvae with MLs of 5.2 mm. For this purpose, crosslinked protein-walled capsules with five different size classes (≤20, 21-45, 46-75, 76-106, and 107-212 μm) were used in selection experiments. A particle size selection model was then developed after accounting for both rate of loss of capsules in the water column and their ingestion by larvae. Results indicated that concentration of larger particles in the water column decreased rapidly and less than 20% of capsules larger than 75 μm were available for the larvae after 30 min. Zebrafish larvae accepted a wide range of particle sizes, but larvae preferred particles much smaller than the maximum size they could ingest. While first feeding larvae preferred 21-45 μm capsules, 15-day-old larvae preferred capsules in the 47-75 μm size range. A better understanding of the behavior of small-sized food particles in the water column and their acquisition by fish larvae is important to optimize feeding protocols in successful larvae culture.