Seahorses

There is something mystical about seahorses. They are very cute and shy looking. Have you ever noticed that when you find one underwater, they look at you and then look away as if they are too shy to look at you for more than a second. I love finding seahorses while diving. It gives me a buzz that I have been able to find something so magnificent and so well camouflaged.

I’m no expert in differentiating the different species of Seahorses but here on many of the dives we do in Sydney we can see three main types of seahorses. They are the Big Bellied Seahorses (Hippocampus abdominalis), Short-headed Seahorse (Hippocampus breviceps) and White’s Seahorse (Hippocampus whitei). There is also a species or pygmy seahorses that can be seen on one of our regular night dives, but I am not sure of its scientific name or if it has one.

Habitat
Most of the fish books list habitat as sheltered to moderately exposed reef, seagrass, algae, 0-20m. Most seahorses I have seen in Sydney are wrapped around pieces of sponge, bits of seaweed or seagrass.

Appearance
Everyone knows what a seahorse looks like. Their body is protected by bony plates, which are arranged in rings. They have a long tubular snout with a toothless small mouth located at the end of the tub. They are slow moving, as they do not have any large fins. The seahorse has a tail, like that of a possum; it can wrap its tail around sponges and seaweed and cling there. Most seahorses use camouflage and their body armour as their main means of defence.

Food
Seahorses live on a diet of small crustaceans, shrimp, crabs and mysids. Like the Weedy Seadragon they suck their prey up through their long snout.

Reproduction
Seahorses have the most interesting sex lives. According to Rudie Kuiter in Under Southern Seas, seahorses breed in early spring and may produce multiple broods in a seasons. Several species form pairs and they have been known to stay together for the entire breeding season. Most of the time the pairs stay within sight of each other. The male is more likely to stay within a small area and the female moves around more.

The female usually indicates that she is ready to reproduce by lifting her snout upwards, the male responds in the same way. Now this is the interesting part, the female places her ovipositor (I think this is a tube that the female uses to transport the eggs) into the male’s pouch opening and the eggs are transformed. The eggs have to be attached to the membrane inside the male’s pouch so that they can become fertilised. The male sometimes has to move from side to side to make sure the eggs are attached. The male keeps the eggs in his pouch for 3-4 weeks and then he ‘gives birth’ to the young! The video “Beneath the Blue” has some excellent information and footage of seahorses reproducing and the male giving birth. After the male gives birth the baby seahorses float off to start their life. While night diving one night at Camp Cove in Sydney harbour, my buddy actually witnessed a seahorse giving birth! He said it was amazing. My eyesight must not have been too good that night as I missed it.

After the male gives birth he displays his empty pouch to his partner and the female seahorses will usually deposit another batch of eggs with in a few days.

Threats & Protective status
As with Weedy seadragons the main threats to seahorses is habitat destruction, the aquarium trade and as use in traditional Asian medicines. Apparently special licences are now required to export seahorses from Australia. Organizations such as Dragon Search also look at Seahorse populations and investigate the species of seahorses on sale in traditional Asian medicine shops to make sure that Australian species are not being sold illegally.

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References and for more information check out these sources: -
Australian Marine Life the plants and animals of temperate waters, by Graham J Edgar, Reed Books, 1997
Under Southern Seas The ecology of Australia's rocky reefs, edited by Neil Andrew, UNSW Press, 1999 section written by Rudie Kuiter on Seahorses and Pipefish
Guide to Sea Fishes of Australia, By Rudie H. Huiter, 1996, New Holland Publishers

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