A Promising Alternative: Amphipods as Sustainable Live Feed for Juvenile Seahorses

Ornamental aquaculture has shown significant growth, contributing to species conservation and reducing the pressure of wild harvesting on natural stocks. In Brazil, populations of the seahorse Hippocampus reidi are in decline due to environmental degradation and capture for trade. Cultivation of this species has emerged as an alternative to reconcile conservation and commercial interests, but feeding remains a major challenge. Seahorses naturally prey on amphipods, which offer good nutritional quality, low production cost, and potential as an alternative live feed. In this study, two amphipod species (Cymadusa filosa and Parhyale hawaiensis) were tested as a monospecific diet for H. reidi, in comparison to Artemia (Artemia salina). Additionally, C. filosa was cultivated with either algae (Sargassum filipendula) or formulated feed to assess the influence of diet on its nutritional quality and the resulting performance of seahorses. Results showed that amphipods, even when consumed in smaller quantities, promoted greater weight gain, specific growth rate, and feed efficiency compared to Artemia. The observed benefits may be related to the superior nutritional composition of amphipods, especially in terms of essential fatty acids. No significant differences were found between the tested amphipod species or between the diets offered to C. filose, suggesting both factors are suitable and promote similar growth and efficiency. However, C. filosa stands out due to its higher fecundity, lower mobility and ease of culture with formulated feed, favoring its application in ornamental aquaculture. This study indicates that the use of amphipods, especially C. filosa reared on formulated feed, represents a viable, efficient, and sustainable alternative for feeding H. reidi, contributing to the development of cultivation protocols for the conservation of the species.