Seahorses on your doorstep: an update on what we found!

A female Knysna seahorse

Codium tenue, an aquatic plant, has been found to be a suitable habitat for the Knysna seahorse within Thesen Islands Marina. This project aimed to assess and compare the density and sex structure of the Knysna seahorse within this habitat. Results were also compared to the 2016 assessment of this population. The study ran from March to August 2017 (6 months) at three sites within the marina and the density of seahorses was found to be similar across sites as well as over the six-month period. The overall average density of Hippocampus capensis was found to be 0.32 ± 0.02 seahorses per kilogram of Codium tenue. This density was found to be similar to surveys from 2016. (more…)

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Mediterranean Mussel

Mediterranean mussel (Mytilus galloprovincialis)

My name is James Radloff and I am currently doing my MSc in Marine Biology at Rhodes University. I am working on one of the most alien invasive marine species along the South African coastline, the Mediterranean mussel - Mytilus galloprovincialis. The Mediterranean mussel has the characteristics of a successful invasive species, having a high tolerance to salinity and desiccation, fast growth rate, high reproductive output, they are better competitors than native mussel species and have relatively few predators. Because of these successful characteristics this species has been able to spread extensively along the coasts of South Africa. (more…)

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Jaap Se Bay

Jaap Se Bay at Brenton on Sea is a ‘secret’ cove – around the corner from Castle Rock but tricky to find and a long climb down. But a climb well worth doing as Frances and Peter Smith found when they were introduced to it by Dave and Hannah Edge (Brenton Blue butterfly). At low tide there are rocks after rocks covered in huge brown mussels (Perna perna) and others closely packed with redbait (Pyura stolonifera ) – amazing sights. Sheltering in with the redbait were brightly coloured sponges and sea squirts. Around the bases of the rocks were large sandy anemones that close up into sand covered doughnuts and multi-coloured sea anemones including the striking purple knobbly anemone (Bunodosoma...

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The Truncated Mangrove Snail

The Truncated Mangrove Snail

Each month we feature a new species. This month we discuss Cerithidea decollata (Linnaeus, 1767) (text and photograph by Alan Hodgson). This marine snail is commonly known as the Truncated Mangrove Snail. It has a wide subtropical to tropical distribution in the West Indian Ocean, but in South Africa extends south into the Western Cape. As its common name suggests it mainly lives in mangroves, but south of East London it can be found in the salt marshes of estuaries. (more…)

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An Artful Waste Challenge

Artful Waste Challenge by Knysna Basin Project

The Knysna Basin Project launched the Artful Waste Challenge during last year’s Knysna Oyster Festival. What does this challenge entail, you might ask? First, an estuary clean-up takes place, where teams walk along the Knysna estuary and collect litter (or shall I say art materials) lying around. Once this is done, teams use the litter collected to find their artistic side and create pieces of art with an environmental message. The teams with the best artworks are then rewarded with awesome prizes from our sponsors (Metelerkamps, Ocean Odyssey and Knysna Elephant Park). (more…)

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Starfish Sundays

Spiny starfish by Knysna Basin Project

I am a student at Rhodes University currently doing my honours in Marine Biology. I completed my undergrad at UJ in Zoology and Human Physiology and I must say, Marine Biology is possibly one of the most soul filling subjects you could ever do in my opinion. I am working with the size, biomass, consumption rates and population distribution of the spiny starfish (Marthasterias glacialis). Not to mention that we are also looking if a relationship exists among M. glacialis and the invasive Mediterranean mussel species (Mytilus galloprovicialis). A mouthful I know, but it is one heck of an experience. (more…)

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A Shaggy Tale

The shaggy sea hare by Knysna Basin Project

It’s coming into low tide and in the clear water it’s easy to see the fascinating creatures that live in this Eden under the water. A strange brownish-red ball of shaggy tassels can be found sitting on clumps of Codium tenue, a macroaglae species, the shaggy sea hare (Bursatella leachii).  These odd gastropods have no shell and are named for the two extended ear-like structures on their heads, making them look like the terrestrial hares. They are about 10cm in length and munch on alga or decaying matter. If disturbed they will produce a bright purple ink to deter any predator from eating them. As they prefer low intensity water flow, the canals of Thesen Islands Marina provide a perfect...

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The Green Bubble Shell

Green Bubble Shell

Each month we feature a new species. This month we discuss Haminoea alfredensis Bartsch, 1915 (text by Alan Hodgson, photograph by Peter Smith). This opisthobranch gastropod mollusc (Order Cephalaspidea) is commonly known as the Green Bubble Shell and is endemic to South Africa. It is found all around the South African coastline and is very common in estuaries especially on sea grasses such as the eelgrass Zostera capensis (as shown in the image). (more…)

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Seahorses on your doorstep

Seahorse research by Knysna Basin Project

A curious, ancient looking creature grasps to its Codium anchor as sampling begins every month at low tide in the canals of Thesen Island Marina. This brownish-green resident is the Knysna seahorse (Hippocampus capensis), the only endangered seahorse in the world. This means as a student, and full-time ocean-lover, it is such an amazing experience to study these animals. We set off just before low tide hits in the Knysna Basin Project boat armed with a pool scoop-net, a scale and calipers. Spending around an hour sifting through scoops of Codium tenue (the free floating green-black macroaglae all over the canals) we eventually find a couple of shy individuals. Transferring the surprised animals into a container of water is step...

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Proper identification of the Moonshine worm in the Knysna Estuary

Knysna moonshine worm

In the week of the 27th of February, I had the privilege of working in the Knysna Estuary and connecting with the people involved in the Knysna Basin Project. As part of my M.Sc degree I look at the proper identification of the Moonshine worm in the Knysna Estuary. On-going interviews with local fishermen and published data suggest that polychaete worms are increasingly being harvested and utilized as baiting species in the Knysna Estuary. It is, however, not known whether harvesting of polychaetes is sustainable or how the apparent increase in utilization by recreational and subsistence fishermen may affect stocks. These problems are compounded by widespread confusion over proper identification of some species. (more…)

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