Exploring New Feeding Methods For Hippocampus Erectus, The Lined Seahorse

The great popularity of seahorses worldwide in traditional medicine, curio, and aquarium markets has raised many concerns over their long-term viability in nature.

Any seahorse use is, therefore, under strict commercial and management regulations, including the Red List of the International Union for Conservation of Nature (IUCN) and the Appendix II list of endangered species by the Convention for the International Trade in Endangered Species (CITES). Advances in breeding marine ornamental fish now make their ex-situ production possible, representing a viable alternative to wild-borne collections.

One of the main challenges of seahorse aquaculture is reducing the high mortality rate of juveniles, which results from inappropriate feeding protocols. The natural preys of seahorses consist of a great variety of benthonic crustaceans; however, in captivity, they are fed on preys that are not included in their natural diet, do not meet their nutritional requirements, and hardly ever stimulate their feeding behavior.

This study explored the possibility of using (frozen) amphipods, the main natural prey of the lined seahorse (Hippocampus erectus). Since no previous information was available on its use as feed in aquaculture, basic zootechnical information was assessed. The amphipod size in relation to the seahorse size, the feed ration, and the appropriate duration of feeding was studied.

Results revealed that newborn and early juveniles rejected eating amphipods, while fish > 50 mm readily fed on them. Ingestion rate analysis showed that seahorses fed on amphipods almost 10 times faster than the commonly-used prey Artemia salina. This was not surprising, considering that amphipod size played an important role in seahorse feeding behavior.

Furthermore, Artemia is not a natural prey of H. erectus and does not meet the nutritional requirements of seahorses, particularly of highly unsaturated fatty acids (HUFAs), but also of other nutrients such as phospholipids and vitamins A and C, which may play an important role in prey selection and feeding behaviour as well as in growth and development. Better culture practices with enhanced animal production and the use of a new alternative frozen feed are now available for the rearing of seahorse aquaculture together with many other marine species.

How this impacts the broader society

Aquaculture is commonly considered as a potential way of alleviating fishing pressure. Today, less than 10 %of marine aquarium fish are captive-bred, as opposed to more than 90 % of the freshwater species. Ornamental aquaculture of marine species faces several problems related to broodstock management, spawning induction, embryo development, hatching, and the development of efficient grow-out diets. The present study shows promising results on the use of non-traditional feeds that could help to overcome some of the problems on efficient grow-out diets, thus indirectly promoting species conservation.

Future work

Amphipods as an alternative natural prey constitute a novel object of aquaculture research. As described above, the present study allows the use of amphipods for seahorse feeding, but many aspects for this practice to be used extensively still need to be investigated.

Some of these aspects should be directed to increase knowledge of amphipod biology and ecology, with special emphasis on reproduction; assess the nutritional profile of amphipods under different culture media, including the emerging biofloc technology; optimize the performance of  different amphipod culture techniques in terms of, for example, temperature and salinity; identify amphipod species with potential in aquaculture; and assess the use of amphipods on fish grow and reproduction on a variety of fish species for ornamental purposes or otherwise.

These findings are described in the article entitled Feeding the lined seahorse Hippocampus erectus with frozen amphipods, recently published in the journal Aquaculture. This work was conducted by Jorge Arturo Vargas-Abúndez, Nuno Simões, and Maite Mascaró from the Universidad Nacional Autónoma de México.