The seahorse Hippocampus reidi is a high-value ornamental species listed as ‘Vulnerable’ on the IUCN Red List of Threatened Species. Aquaculture offers a potential solution for reducing pressure on wild populations by providing a sustainable source of seahorses for the aquarium trade. However, seahorse aquaculture still presents some challenges, especially in the larviculture phase, related to nutrition during the early development of fish.
This study evaluated the effect of two marine microalgae tested in green water technique on the fatty acid composition of H. reidi larvae over 15 days, 20 oC, 30 ppt salinity. Four treatments were tested: TSM -no microalgae; TISO - Tisochrysis lutea; TCHO - Chaetoceros muelleri; and TIC - a combination of both (1:1). Larvae were reared in a recirculating system and fed rotifers enriched with Red Pepper® (10 ind/mL), followed by Artemia nauplii (2 ind/mL) from day 8 onward. Microalgae were added daily at 200,000 cells/mL per species.
The TIC treatment yielded the highest concentration of docosahexaenoic acid (DHA) in larvae (4.45 mg/g), demonstrating the nutritional advantage of combining T. lutea and C. muelleri in green-water systems (Fig.1). Compared with single-species or treatment with no microalgae, the mixed culture promoted greater DHA transfer and retention in larval tissues, indicating a synergistic effect that enhanced DHA availability and assimilation during early development. Given the limited digestive capacity of seahorses, readily assimilable DHA sources are essential for supporting optimal neural and visual development, membrane function, and overall survival and growth.
Acknowledgments: Acknowledgments: This research was partially funded by the Coordination for the Improvement of Higher Education Personnel (CAPES, Brazil) – Finance Code 001, and by the Brazilian National Council for Scientific and Technological Development (CNPq, Brazil), which provided a grant to M.Y. Tsuzuki (310843/2021-9) and financial support for the research (Process 407610/2021-9