Seahorses are fish, yet they look nothing like conventional ones – being upright, horse-headed and equipped with curling tails, it’s little wonder that the Japanese call them “children of the dragon”.
They have also developed commercial value as traditional Chinese medicine, curio objects and aquarium favourites. When seahorses became the first marine fish protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 2004, attention shifted to aquaculture as an alternative to meet global demand. And Portuguese marine biologist Daniel Alexandre, and his team at Ecomare, are proving that aquaculture can become a true alternative to wild capture before natural seahorse populations disappear.
“At the rate of demand that we are experiencing today, it is inevitable that wild populations will not resist and will no longer meet the needs of the Asian market,” warns Alexandre. “After that, either aquaculture supplies the market, or the market ceases to exist. We want aquaculture to become a real alternative.”
Alexandre began working with seahorses in 2009 while completing his master’s thesis, which focused on the cultivation of the juveniles, in Mexico.
“Since getting my degree, my interest has been in marine ornamental species aquaculture,” he says. “Their beautiful colours and the relatively small life support systems they require compared to food aquaculture were crucial in attracting me to this field. I love the challenge of finding easily reproducible technical solutions for the biological needs of each species at different life stages.”
After two years with Lusoreef – Portugal’s first company specialising exclusively in the aquaculture of ornamental marine species – Alexandre launched and managed his own seahorse farming operation for a decade. In 2023, he joined Ecomare as a senior technician. The facility, a joint venture between the University of Aveiro, the Municipality of Ílhavo and Port of Aveiro, focuses on the industrial production of lined seahorses (Hippocampus erectus) for the aquarium trade.
During his previous venture, Alexandre worked primarily with Hippocampus reidi, a species considered more demanding in early cultivation.
“It’s a more difficult species to cultivate because they’re much smaller at birth than H. erectus,” he explains. “That makes the first 15 days challenging – during that period, you can only give rotifers because their mouths aren’t big enough to eat Artemia. It’s a long and demanding process to keep the right concentration of rotifers all day.”
Among seahorses, the lined seahorse is considered one of the more manageable species for aquaculture, though it still presents significant challenges. Seahorses are notoriously reluctant to accept pelleted feed, relying instead on live or freshly frozen prey such as Artemia, mysis shrimp, copepods and amphipods.
© Ecomare
In captivity, they typically live for four to five years and form long-term monogamous pairs. When reproductively active, females deposit eggs into the male’s brood pouch during the early morning hours, where fertilisation occurs. After a gestation period of 10 to 40 days, H. erectus males release 100–400 juveniles, each around 10 mm in length – large enough to begin feeding on Artemia.
“Recent studies indicate that eggs are enveloped in the internal structure of the brood pouch, almost like a placenta. However, until now, no direct fluid exchange between embryos and parent has been demonstrated. The term ‘pregnancy’ is used due to the contraction movements that the male makes when expelling the offspring,” explains Alexandre.
Consistent environmental parameters are critical throughout the production cycle. Ecomare relies on natural seawater sourced directly from the Atlantic to maintain optimal conditions. Feed quality is equally important and must be precisely adapted in terms of both size and nutritional composition – a task that remains complex and species-specific.
Under these controlled and stable conditions, Ecomare recorded 30 consecutive births – 15 from each of two males – each occurring exactly 16 days apart, a consistency that Alexandre describes as remarkable.
“[It’s like] an authentic Swiss clock in action,” jokes Alexandre. “Of course, it would be better if they were only born on Mondays, it would be much more adaptable to our work schedule.”
© Ecomare
Fighting bacterial infections and other challenges
Seahorses are particularly vulnerable to bacterial infections compared to other fish species. Their prehensile tails, which frequently come into contact with tank surfaces and enrichment structures, increase the risk of minor abrasions and bacterial transfer. Frozen feeds can also serve as potential vectors for contamination.
Rearing temperatures between 23°C and 26°C further promote the activity of pathogenic bacteria such as Vibrio, Aeromonas and Mycobacterium – which are all commonly found in marine aquaculture systems.
“The best way to tackle disease is to ensure the best possible water quality, without sudden shifts in temperature and salinity that could increase stress, and to use high-quality feed. It is necessary to be constantly alert to the first signs of disease to quickly isolate infected animals,” explains Alexandre.
Interestingly, the team has found over time that constant disinfection of the tanks provided space for opportunistic bacteria to colonise. The team has adjusted its approach, focusing instead on regular manual cleaning of the tank walls and bottoms by scrubbing to control organic buildup while avoiding full disinfection.
“The main bottleneck to scaling the production is dealing with the daily amount of work, 7 days a week, 365 days a year, maintaining the same quality and criteria in the tasks performed. It is very easy when everything is going well for there to be some negligence, which is costly in this work area. Many times, mistakes cannot be corrected; you must start over,” says Alexandre.
Seahorse culture also presents unique husbandry requirements. The species need environmental enrichment structures to anchor themselves to during rest, particularly at night. Regular size grading, typically after two months, is also essential – not to prevent predation, but to minimise tail-grabbing among individuals of different sizes during feeding, which can cause injury and stress.
© Ecomare
“As I like to say, animal welfare in aquaculture is not an option, or compliance with regulations, it is a basic objective. A seahorse, like any fish, if it is stress-free, well-fed, in optimal water conditions and handled in the least intrusive way possible, is an animal that will grow better and will be less likely to contract diseases and die,” notes Alexandre.
Economic stability, market and demand
According to Alexandre, three key pillars underpin the sustainable culture of seahorses:
- Quality: animals must be healthy, of suitable size, and ideally display colours preferred by the market – usually bright ones such as white, yellow or red.
- Quantity: it’s essential to produce a minimum number of animals per month to be profitable. For seahorse aquaculture, this equates to around 250 individuals per month per technician.
- Consistency: operations must maintain stable, repeatable results across months and years, adjusting production to account for seasonal or biological variability.
China currently leads large-scale seahorse production, primarily driven by demand from traditional Chinese medicine which attributes to seahorses properties such as enhancing fertility and providing antitumor, antifatigue and antiaging benefits. Research institutions such as the East China Sea Fisheries Research Institute, the Chinese Academy of Fisheries Science and Hainan University are publishing much of the latest scientific work in this field.
“I have a friend there that's living there [in China]. A couple of weeks ago, he sent me a links to photographs, and we saw big concrete tanks with a lot of seahorses,” says Alexandre, suggesting that Chinese producers may have achieved higher levels of technical and operational efficiency than those seen in Europe.
© Ecomare
Ecomare currently supplies lined seahorses to several European distributors and occasionally to public aquariums. Prices in Europe vary widely, shaped by factors such as production scale, supply-chain structure and the colouration of individuals. With its current staffing levels, the facility produces about 5,000 seahorses per year, a figure that could rise with additional manpower, as there is capacity for expanded production.
Ongoing research at Ecomare focuses on overcoming the biological and operational challenges associated with industrial-scale production. One current project addresses the “black seahorse” phenomenon, where animals lose their natural colouration, often after transport.
“One of the problems we currently face is that our seahorses turn black so we will begin a study on how seahorse colour can be influenced by the colour of their tanks. Colour behaviour during transportation and colour recovery times are other related topics will be addressed and new solutions will be developed,” says Alexandre.
Despite the operational demands, Alexandre highlights that public engagement – mainly through conference presentations and farm visits – remains an unexpectedly rewarding aspect of his work.
“People's reactions when they see the seahorses, when they watch videos of their birth and the smiles on the women's faces when we explain that it is the male that becomes pregnant, is without a doubt the best part of working with seahorses. For me it is another day, a week, a year seeing these animals, but for 90 percent of people it is the first time they have seen a live seahorse in person,” concludes Alexandre.
© Ecomare
