Blog

Have you seen the horses under the sea?

Knysna Seahorse Project

Sometimes, we don’t realise the curiosities that could be found right at our doorstep, all you must do is look. If you ever find yourself around the Thesen Island Marina in Knysna, be sure to look out for a little boat chugging along with a couple of students and a pool net on board. They’re not there to scoop leaves out of the Marina, I’m afraid, but rather to look for an illusive little fish known as the Knysna seahorse (Hippocampus capensis). (more…)

Read More

Keurbooms Seahorse Research Project

Keurbooms Seahorse Research Project

My past twenty years of research work at sea involved taking along bins of equipment -glassware, chemicals, oceanographic instruments, batteries and spares for everything. So, walking down to the Keurbooms Estuary for this month’s seahorse survey with all my sampling gear inside a small rucksack, feels minimalistic to say the least. The 50m Research vessel has now been replaced by a canoe, and with my family as crew we set off on an ebbing tide to search for Knysna seahorses, albeit in the Keurbooms Estuary. This is one of the few localities other than Knysna, that this endangered species calls home. (more…)

Read More

What lies beneath

What lies beneath by Johan Wasserman

Beneath the surface of the Knysna Estuary lies a rich diversity of plant and animal life which, until now, has been largely unexplored. Due to recent developments in Remote Operated Underwater Vehicle (ROV) technology, we can now discover what lies beneath our estuary. Using an ROV and Geographic Information System (GIS) software, we plan on creating a map that depicts the subtidal habitats of the Knysna Estuary. Estuarine habitats act as nursery areas for many important fish and invertebrate species, providing them with food and shelter for at least a part of their life cycle. As such, the subtidal habitats of estuaries often host diverse communities. It is important to study the distribution of these habitats for conserving and managing...

Read More

What effect has the blanket of Ulva had on the animals of Leisure Island’s Steenbok Channel shoreline?

What effect has the blanket of Ulva had on the animals of Leisure Island's Steenbok Channel shoreline?

In early 2011, when the Steenbok Channel was clothed in a luxuriant and healthy eelgrass bed, Richard Barnes investigated its invertebrate fauna at a series of nine points (at Kingfisher Creek near its junction with the Ashmead Channel, at its head near the Armstrong Causeway, and at a point halfway between the two, adjacent to the Reserve's Indigenous Garden; and at three points down the shore at each of those three sites - low water neap, mean low water, and low water spring).  Early this year, he sampled those same nine points again but in 2018 in areas of bare mud left after loss of the seagrass.  This was a race against time before the bare mud itself disappeared under...

Read More

Progress on identification of the Moonshine baitworm in Knysna Estuary

Progress on identification of the Moonshine baitworm in Knysna Estuary

The Moonshine worm, a popular bait worm that can be found almost anywhere in the Knysna Estuary, now most likely seems to be an alien species. Our work started owing to a rise in popularity in use of the Moonshine worm as bait among local fishermen. Further investigation showed that these worms were not found within the Knysna Estuary during the 1950’s and 90’s, during extensive ecological surveys. This provides strong circumstantial evidence that these worms moved into the Knysna Estuary some time during the last two decades. The question that arose was whether the worms moved in from another local area, such as a nearby estuary or the ocean floor, or whether it was brought here from elsewhere. (more…)

Read More

Water quality monitoring in the Knysna estuary

KEMP Knysna Basin Project

The winter of 2017 was somewhat drawn out, cold and occasionally wet which fortunately did not interfere with the necessary sampling of the estuary water column in the vicinity of Thesen Jetty.  At this site KEMP, a part of the overall Knysna Basin Project had set up a Hach Ott multiparameter sonde well below the surface at low water and delivered real time changes in dissolved oxygen acidity (pH), water levels, and measured chla fluorometrically (digitally). (more…)

Read More

Sea Star Sundays

The Spiny sea star Marthasterias glacialis

The Spiny sea star Marthasterias glacialis is widely distributed. However, the South African Marthasterias population has been reclassified as Marthasterias africana. These critters were easy to spot with their vibrant orange and purple colourings and their arms covered in small spines. The spread of M. africana within The Knysna Estuary is suspected to be because of the invasive mussel species Mytilus galloprovincialis, as it is the sea star’s main source of food. (more…)

Read More

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…)

Read More

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…)

Read More

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...

Read More