Food matters for seahorses
Science Centres: Fisheries
Culturing seahorses for aquaria or for the dried medicines trade is still a young and largely unproven industry in New Zealand. The supply of sufficient nutritionally adequate food for the seahorses, which are voracious feeders, is a major bottleneck.
Food for seahorse food
Many commercial culturists still rely to various degrees on culturing live prey, such as brine shrimp and copepods, to feed their seahorses. What the brine shrimp and copepods are themselves fed on critically influences their nutritional value, and therefore affects seahorse growth, survival, coloration, and health. Numerous commercial feed and enrichment products are available for growing these live prey, costing from as little as $4/kg to over $200/kg. The obvious question for most culturists is, “Which is the most cost effective for culturing seahorses?” We recently tested a range of enrichment products for their effects on brine shrimp nutritional value, and on seahorse growth and survival when fed on these variously enriched brine shrimp.
Food for seahorses
Weaning seahorses off live foods on to artificial foods is highly desirable to reduce culture costs and guarantee feed quality and supply. To date, this has proved difficult in large-scale commercial culture, although we have had some success experimentally at NIWA’s Mahanga Bay research facility (with our results soon to be published in Aquaculture). More readily achievable is the weaning of seahorses off live food on to frozen natural products, such as mysid shrimp and copepods. Home aquarists often have reasonable success doing just this. The ability to wean seahorses on to frozen food is critically important to culturists targeting the aquarium market because many aquarium wholesalers, retailers, and customers use frozen foods, and the seahorses need to be adapted to frozen food if they are not to be poorly fed or stressed between initial sale and final purchase. Non-weaned seahorses, and in particular wild-captured seahorses, have a lower survival rate during trading. We tested the ability of Hippocampus abdominalis to be weaned on to frozen mysids, and compared the growth and survival of seahorses fed on frozen mysids with seahorses fed enriched live brine shrimp.
Food for thought
Some of the results of our enrichment product testing were surprising, and have potential cost-saving implications for commercial seahorse culture. For example, an $11/kg rice bran and Spirulina product gave better growth than a commonly used $270/kg fish oil enrichment.
In our weaning test, growth and survival were the same for seahorses fed on frozen mysids and on live brine shrimp, but, more importantly, the weaning of H. abdominalis proved very easy. This bodes well for improving the economic efficiency of commercial culture of this species, because it reduces the need to culture larger live prey for the seahorses as they grow bigger.