There are 30 to 40 different kinds of seahorses, but only five of these have been seen around the southern African coastline. The Knysna seahorse is the best known, and is the only seahorse that is endangered. Knysna seahorses are found only in the Knysna, Keurbooms and Swartvlei estuaries on the south coast of South Africa. They are green to brown in colour and grow to about 12cm in length. They live at depths of 50cm to 8m, on sandy bottoms or around clumps of plants.
Seahorses have lived in the oceans for about 40 million years. They have a head shaped like that of a horse, a tail like a monkey’s and male seahorses have a ‘pouch’ like female kangaroos! The male seahorse gives birth to offspring – the female lays her eggs in the male’s pouch and when they are ready, the babies hatch out of the pouch into the water! Seahorses are fascinating to watch – you may be lucky to see male and female seahorses in a coy courtship dance or even a male seahorse giving birth!
Seahorses are fish
Seahorses breathe through gills, use their fins to move through the water and hatch from eggs. The largest seahorse measures 35 centimetres from the top of its head to the tip of its tail and the smallest seahorse is only 3 centimetres long!
Eyes like a chameleon
Seahorses swim upright, propelled by their dorsal fin, while their small pectoral fins help to steer them as they glide along. Seahorses feed on small fish and shellfish, which they suck into their mouths. The eyes of a seahorse are like those of a chameleon – they move independently, one looking for food and
the other watching out for predators. Seahorses
are also able to change colour so that they blend into their environment.
The Seahorse on the hunt for food
The seahorse is an ambush predator, it uses it’s tail to anchor itself around the base of the seagrass and will lie in wait of prey. The seahorse is hidden well by its ability to change colour in order to blend into its surroundings. When a prey item swims, crawls or slithers past the waiting (and hungry) seahorse’s snout, the seahorse will suck the unsuspecting prey in through it’s tubular mouth. The sucking mechanism is in fact so strong that a click can be heard when the food is ingested. Seahorses have no stomachs or teeth and are therefore unable to store large meals or chew their food. They therefore need to eat small crustaceans such as shrimp at very regular intervals. Their eating style results in very particular food requirements which would challenge the most dedicated aquarium hobbyist. Seahorses will only eat live food, thus food needs to be caught daily for them. If not given the correct nutrition the seahorse will develop tuberculosis. In the absence of live food they will in fact starve slowly to
death. They would indeed rather die than lower themselves to eat fish flakes.
It is important to note that the Knysna seahorse is protected by law and it is illegal to remove or keep this fish in aquaria.
Urban sprawl threatens Knysna seahorses
The development of nearby towns is threatening the survival of the Knysna seahorses. Houses and shopping centres are being built right on the water’s edge and polluted water flows directly into the estuaries where these seahorses live. Boats and people in the estuaries are also disturbing the unique habitat of these animals.
The Pregnant Male?
Seahorses are the only fish species where the male experiences a true pregnancy. The pregnancy is considered true, as
fertilization is internal and the eggs are held in a pouch consisting of tissues, which contain a capillary network which provides oxygen and placental fluid to the embryos. The pregnancy of the Knysna seahorse lasts up to two or three weeks. The male will then give birth to between 5 and 200 young from one pregnancy and during the male’s pregnancy the female will be busy producing more eggs. This means that just a few hours after the male giving birth, the female will once again pass her now ripe eggs into the male’s pouch. The male will therefore be pregnant throughout the entire breeding season which is usually during the summer months when the water temperature reaches about 20°C.
The seahorses mate monogamously for the entire breeding season. Every day the pair will come together in a ritualistic flirtatious dance to reinforce their connection. While the male is pregnant he will move very little, which for a seahorse means not more than a few centimeters. The male will eat food that happens to be in the area while the female will roam about in search of food. Regardless of this separation however, the female will always come back to the male to perform their daily ritual of entwining their tails and spiraling to the surface. This ritual helps keep the pair synchronized reproductively. If a mate is removed or dies, it will take weeks to find a new mate, that is, if it is able to at all! This is because seahorses live in isolated groups and move very little. It is thus extremely difficult to find another seahorse in the same part of the reproductive cycle. Due to the fact that it is the male that becomes pregnant it was previously believed that it would be the females that competed for the male partners. This however is simply not the case. Like in most species, it is the male that competes with other males to attract and defend his female seahorse. So, it would appear that the male actually wants to be pregnant. The seahorse male is sounding more and more like every woman’s perfect mate!
A costly cure
Every year about 20 million seahorses are caught around the world, for medicine or to be sold as curios. Some people believe that eating dead seahorses will cure asthma, skin problems and even baldness. Another one million seahorses are caught annually for display in home and public aquariums.
We protect our seahorses
Fortunately, there is a law in South Africa that protects
the Knysna seahorses. The law states that one is not allowed to catch these seahorses or disturb them in their natural environment. There are also strict laws about importing seahorses into South
Africa from other parts of the world.
And for those wanting to see these amazing creatures, come and visit us at 34 South. We have a specialised holding tank and permit.
For more information, please contact us on +27 44 382 7331 or visit our webisite www.34south.biz