WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2023 49 The Pacific seahorse Hippocampus ingens is the sole species found on the eastern Pacific coast with a distribution extending from California to southern Peru, mostly associated with algae, rocks, soft corals, and coral reefs. It can be found at 1-20 m depth clinging to seagrass, macroalgae and coral reefs. The maximum adult height reported for this species is 31 cm (Lourie et al. 2004) (Figure 1). As with all other Hippocampus species, H. ingens is listed in Appendix II of CITES and classified as Vulnerable by IUCN. In Mexico, it is cataloged as a species subject to special protection by the NOM-059SEMARNAT-2001 allowing only the commercialization of incidentally caught specimens and those produced in cultured conditions. Therefore, aquaculture stands as a promising alternative to address the unsustainable exploitation of seahorse populations. However, the lack of basic information regarding growth and development hinders advances in establishing optimal and sustainable culture protocols. Although some culture trials with H. ingens have been reported where length at birth (0.69-0.70 mm), growth rate and survival during the first months of development were evaluated (Téllez-Mohedano et al. 1997, Reyes-Bustamante and Ortega-Salas 1999, Ortega-Salas and Reyes-Bustamante 2006), no clear description of juvenile development or morphological changes during early development has been reported. (CONTINUED ON PAGE 50) Seahorses are a special type of fish, along with the pipefishes and sea dragons they belong to the family Syngnathidae. Currently, there are 46 described species of seahorses, and all are grouped in the genus Hippocampus. They are fishes with unique morphological and ecological characteristics. For instance, their heads are at right angles to the body, they have curved trunks, and they possess a prehensile tail instead of a caudal fin. The body presents a series of bony plates visible as rings around the trunk and tail and the ring number is a consistent character used during species identification. The males are responsible for egg incubation in a brood pouch and the birth of the juveniles. They are slow swimmers and rely on their capacity for camouflage to avoid predators, which is achieved by their ability to change color. They have low population densities, small home ranges and high site fidelity for their distribution areas. These characteristics make them particularly susceptible to overfishing, bycatch, and anthropogenic disturbances, which are the main factors affecting their natural populations. Seahorses are traded live or dried for the ornamental industry or traditional medicine (mostly in Asian countries), respectively. The impacts of these activities on their natural populations have been increasing. Therefore, the red list of the International Union for Conservation of Nature (IUCN) recognizes some of the seahorse species as vulnerable and one as endangered. Additionally, in 2002, the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) included all the species in Appendix II in a multinational effort to oversee and regulate the international trade of seahorses. Growth Patterns and Early Development of Pacific Seahorse Hippocampus ingens Under Culture Conditions Renato Peña and Eliezer Zúñiga-Villarreal FIGURE 1. Juvenile Pacific seahorse Hippocampus ingens at INGENS Cultivos Marinos in Mazatlán, Mexico. Photo by E. Z. V. FIGURE 2. Broodstock and juvenile seahorses at INGENS Cultivos Marinos, in Mazatlán, Mexico. Photo by E. Z. V.