Animal Keeper's Association of Africa

NUTRITION

ENRICHMENT

Suggestions for enrichment could go as follows, remembering that each animal and its environment is unique:

1. slightly changing water temperature as part of environmental change?
2. change the water flow, to engage the animals in changing their 'normal' tendencies.
3. light - how can you create a day night effect using the current lighting.
4. discover what the animals can see (from behind the glass)either change it or try change the possible 'reflections' that the animals perceive.

TRAINING TECHNIQUES

ENCLOSURE NEEDS

NATURAL HISTORY

VETERINARY NEEDS

Knysna seahorses (Hippocampus capensis)

NOTES BY STEVE WARREN

Distribution: Knysna estuary, Keurbooms estuary, Mossel Bay and Plettenberg Bay.
Diet: Mysis shrimp, fish larvae, small shrimp and small invertebrates.

In the wild

These are protected in the wild and it is illegal to collect seahorses and pipefish unless you have a special permit from Marine and Coastal Management. If they are in a National Park then a permit from the National Parks Board would also be required.

The expected maximum length in the wild is 7cm although larger ones are occasionally seen (up to 13cm). They live for approximately 2 years and will be subjected to various conditions due to living in an estuarine environment where changes in salinity, temperature and pH, among other parameters can be expected. These changes will obviously result in the death of many seahorses if they are too severe and they will also affect the availability of food. Various organisms prey on seahorses including octopus, fish and crabs; animals such as sea urchins and starfish will also eat the juveniles.

In both seahorses and pipefish the female places the fertilised eggs in a pouch on the male where they are incubated for two to three weeks. With Knysna seahorses the water needs to be at least 50cm deep for mating to facilitate the successful transfer of the eggs from the female into the males pouch and if it is shallower they will end up being scattered in the water and on the substrate. The babies are born live and are ejected from the pouch quite forcibly in an action reminiscent of coughing. Up to just over 80 babies may be produced but there would usually be less than 20. Most of these would generally die from natural causes such as natural predation including predation by adult seahorses.

In captivity

As mentioned they are a protected species and it is illegal to collect and keep Knysna seahorses and it is also illegal to buy and sell them. Those that are displayed in South African public aquaria are captive bred and distributed from one aquarium to the other when breeding is successful. At Bayworld we received our seahorses from a Marlene Gunter who is breeding them at a Perlemoen farm in Port Nolloth. She received hers from Jacqueline Lockyear who was studying them at Rhodes University. We also received juveniles from Two Oceans Aquarium in Cape Town.

We feed our adult seahorse’s mysis shrimps and small invertebrates that are collected across the road on a sandy beach and also collected in rock pools by shaking small rocks and seaweed in a bucket of seawater. Recently we have also begun culturing various small invertebrates to use when the weather is not suitable for collecting across the road. An old plastic garden pond with ledges has been utilized as a culture container and water from our large predator tank is allowed to flow through it and overflow back into the display, algae is allowed to grow in the pond and rocks are placed on the ledges. It has been seeded with invertebrates and algae from liverock and these have been allowed to reproduce and grow. The baby seahorses are sometimes fed newly hatched brine shrimp as a first food but we try to wean them onto small invertebrates as soon as possible as they have a much higher food value.

Our largest male Knysna seahorse is at least 16cm long and the most baby seahorses that we have had from one male is 109. We attribute this to regular feeding and a longer lifespan in captivity. We have previously kept Knysna seahorses for over 4 years.

Due to our collecting of live food from the sea we introduce large quantities of small animals which remain alive and breed in our seahorse display tank. These provide food for a small quantity of baby seahorses, which are kept in the tank, but most of our babies were sent to Seaworld in Durban where they are being grown to a larger size in preparation for their seahorse display. As they already breed clownfish they have suitable quantities of newly hatched brine shrimp available to enable them to feed large numbers of juvenile seahorses.

We now also just take the babies and place them in the invertebrate culture tank where survival is left to a process of natural selection and although only a small number can be expected to survive the ones that have been seen so far have grown at a faster rate than those fed on newly hatched brine shrimp. We are not allowed to sell the seahorses to private individuals or companies and the public aquariums in South Africa basically have enough specimens to supply there own collections at present.

We are also not allowed to release captive bred specimens into the wild as the risk of introducing a disease from an aquarium to a wild population where the seahorses may not have a resistance to the disease is too great. There is also the risk of genetic contamination, as seahorse species can be hybridized quite readily. If the captive population were ever in doubt as to the purity of the strain then it would be immoral if those doubts were carried over to a wild population.

Many of the methods we use for keeping our Knysna seahorses would also work or could be adapted to successfully keep imported seahorses such as the Yellow seahorse (Hippocampus kuda). The offspring of captive bred Yellow seahorse can however be sold to aquarists and aquarium shops.

OTHER