Author: Jorge Palma, Doctorate Researcher, CCMAR / University of Algarve
About the model organism
Seahorse is the common name for the fish belonging to the genus Hippocampus. Of the 42 presently known species, the long-snout seahorse, Hippocampus guttulatus, and the short-snout seahorse, H. hippocampus, are the only two European species. Seahorses are among the many genera whose life history might render them vulnerable to environmental disruption factors, including habitat degradation and overfishing.
Generally characterised as having low mobility, small home ranges, low fecundity, lengthy parental care and sparse distribution, these life-history characteristics help to explain why 12 seahorse species are presently listed as ‘Vulnerable’, ‘Near Threatened’ or ‘Endangered’ in the 2021 IUCN Red List of Threatened Species, 17 as ‘Data Deficient’, and only 10 as of ‘Least Concern’.
Globally, seahorses inhabit shallow coastal areas including coral reefs, mangroves and coastal lagoons in a close dependence with the local bottom coverage. In the early 2000’s, high densities of H. guttulatus were reported in the Ria Formosa lagoon, South Portugal; however, the situation has changed dramatically, as there has been a 96% drop in population size. Anthropogenic impacts, including illegal catches and habitat degradation have been identified as the main causes for the decrease. As a response to this severe decline, a conservation program was initiated in 2020, under the scientific coordination of the Centre of Marine Sciences (CCMAR), which includes the creation of two marine protected areas, focal habitat restauration, and awareness campaigns targeted at the general public. Captive breeding programmes are equally fundamental for the long-term conservation of these species. They contribute to removing pressure from natural populations, as any research, education or market necessities are supplied with captive-bred specimens.
Relevant fields of research
Seahorses are regarded as candidate species for aquaculture, yet only a small number of species are commercially cultured worldwide. This is due, in part, to insufficient knowledge of seahorse nutrition, including their specific lipid and protein requirements. This information is of vital importance for diet formulation and the establishment of optimised feeding protocols. Seahorses must be fed natural diets, either live or frozen, as their imprinted feeding behaviour means that they only accept and ingest food items that match a recognisable prey shape. Adult seahorses can be fed natural frozen diets, yet juveniles must be fed live natural diets. Live prey enrichment (eg Artemia salina) is mandatory for optimal growth and survival. Gaining in-depth understanding of juvenile seahorse nutrition is currently the most relevant field of research regarding seahorse aquaculture.
Available tools or techniques to study the marine organism & current research
The CCMAR long-term captive breeding programme, initiated more than a decade ago, promotes research on seahorses. Fitted husbandry and feeding protocols have been developed to enable species reproduction in captivity. Captive-bred species can be used in experiments on ecology and seahorse nutrition.
Two research lines are currently being conducted with these species (at CCMAR). Local wild populations are periodically monitored for population trending and a conservation programme is being developed which includes the creation of seahorse marine protected areas and habitat restauration.
Potential impact & commercial application
Seahorses are an aquatic resource under constant demand for the ornamental fish market. Due to the limited number of seahorse species that are internationally produced to supply this market, the individual fish price is normally high, making it a more commodity than most other aquatic products.
Relevant articles / publications
- Palma, J., Magalhães, M., Correia, M., Andrade J.P., 2019. Effects of anthropogenic noise as a source of acoustic stress in wild populations of Hippocampus guttulatus in the Ria Formosa, South Portugal. Aquatic Conservation: Marine and Freshwater Ecosystems. 28(5), 751-759. (https://doi.org/10.1002/aqc.3056)
- Correia, M., Koldewey, H. J., Andrade, J.P., Esteves, E., & Palma, J., 2018. Identifying key environmental variables of two seahorse species (Hippocampus guttulatus and Hippocampus hippocampus) in the Ria Formosa lagoon, South Portugal. Environmental Biology of Fishes. 101(9), 1357-1367. (https://doi.org/10.1007/s10641-018-0782-7)
- Palma, J., Andrade, J.P., Bureau, D.P., 2017. The impact of dietary supplementation with astaxanthin on egg quality and growth of long snout seahorse (Hippocampus guttulatus) juveniles. Aquaculture Nutrition. 23, 304-312. (https://doi.org/10.1111/anu.12394)
- Palma, J., Bureau, D.P., Andrade, J.P. 2014. The effect of diet on ontogenic development of the digestive tract in juvenile reared long snout seahorse Hippocampus guttulatus. Fish Physiology and Biochemistry. 40:739–750. (https://doi.org/10.1007/s10695-013-9881-8)
- Palma, J., Andrade, J.P., Bureau, D.P. 2012. Growth, reproductive performances and brood quality of long snout seahorse, Hippocampus guttulatus fed enriched shrimp diets. Journal of the World Aquaculture Society. 43(6): 802-813. (https://doi.org/10.1111/j.1749-7345.2012.00611.x)
