RiverWise

The monthly newsletter of the Lower Breede River Conservancy Trust.


Issue 1 ~ April 2018.

Turtle Talk

by Tasmyn Taylor

Did you know that there are 5 different species of Turtle that occupy South Africa’s waters? Neither did I until Two Oceans was kind enough to make a stop in Witsand and take the time to present a talk to the Conservancy and members of the public on what to do when they find a turtle hatchling. Luckily they did, because soon after, there were various reports of hatchlings to be found on the beach and two were brought in to the LBRCT offices. Meet Nina (picture below).

A photo of a small sea turtle.
Nina: Before.
A photo of a small sea turtle.
Nina: After.

Nina is a Loggerhead Turtle hatchling that washed up on the beach near Blokke in Witsand. She was found on the beach, thought to be dead, until two good Samaritans, Charlie Luis and Nicolene van Zyl picked her up and realized she was alive. LBRCT arranged for Nina to be taken to Two Oceans Aquarium in Cape Town where she is receiving all the love and care in the world to grow big enough to be released back into the wild. She will remain at Two Oceans being cared for and fed for the next 9 – 12 months. As you can see in the before picture, Nina was given to us covered in parasites called Goose Barnacles. Goose Barnacles attach to floating objects by a long and tough, fleshy stalk. They occur in dense colonies on ships or floating objects. They attached to Nina because hatchlings float in the water, using the different currents to travel the seas.

On Sunday, 29th April the LBRCT was called out to a turtle stranded on the beach near the NSRI station. To our surprise, it was a lot bigger than we anticipated... but WHAT and experience! Meet Mark. Mark is a Loggerhead Turtle that measured just over a meter long and weighed 70 KG. Loggerheads can weigh up to 150 KG and live to be 60 years old. For reasons still unknown, he washed up. The LBRCT, with assistance from the rescuers, Sharon and family, along with the NSRI loaded him onto the bakkie and off to Two Oceans he went!

A photo of Mark the sea turtle and his rescuers.
Mark with his rescuers.
A photo of Mark the sea turtle.
Exhausted but holding on.

He is safely recovering thanks to all our efforts. We would also like to thank Mr Gary Taylor for the fuel sponsorship to get Mark to Two Oceans. It was greatly appreciated. Nina and Mark are both a part of Witsand’s success stories that are worth reading about and spreading the news. Thank you, Charlie and Nicolene for helping Nina, Sharon, Mark, NSRI and Gary for helping Mark. Because of this, they are now both able to contribute to the struggling turtle numbers.

Save a life because every life counts.


Water Hyacinth

by Tasmyn Taylor

What is Water Hyacinth?

A colour illustration of Eichhornia crassipes.

Water hyacinth (Eichhornia crassipes) is a free-floating perennial aquatic plant (or hydrophyte) native to tropical and sub-tropical South America. With broad, thick, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as 1 meter in height. The leaves are 10–20 cm across, and float above the water surface.

What are the effects on natural systems?

As hyacinths cover the water’s surface, they restrict life-sustaining sunlight that submerged native plants need to grow. Eventually the shaded underwater plants die and decay. They decaying process depletes the amount of dissolved oxygen in the water. As the oxygen level declines, fish such as bass, perch, and bream, seek new habitat areas, leaving fish such as catfish, carp and gar, all of which can tolerate lower oxygen levels than the more desirable fish. Once oxygen levels become so low that even these less desirable fish cannot survive, the waters below water hyacinth masses become devoid of most life.

What is the growth rate?

Water hyacinths reproduce very effectively by two vegetative methods.

They can make new plants by the process of fragmentation or breaking into smaller pieces. Fragmentation can be caused by the churning propellers of motor boats, the thrashing of swimming animals and grazing by animals. They can also reproduce by forming plantlets at the end of a shoot that grows from the base of the stems. This method of reproduction is very effective at making many new plantlets in a relatively short time.

What control methods are there?

Water hyacinth can be controlled in three ways:

  • Chemical, mechanical and biological.
  • Use only registered herbicides for chemical control.
  • Biocontrol agents are available for Water hyacinth. Two beetles/bruchids: Neochetina eichhorniae & N. bruchi.

Summary:

  • NEMBA – Category 1b
  • CARA Category 1
  • There are mechanical, chemical and biological control methods currently being used.
  • Problem: dense mats completely cover the water surface altering the chemical composition of the water.

Water quality data - April 2018

by Tasmyn Taylor

On the horizontal axis stands the names and site number of the locations along the Breede River Estuary at which a manual probe operated by the LBRCT, measured the waters salinity, temperature and turbidity. On the vertical axis, stands the values measuring the salinity, temperature and turbidity.

Water quality run - 16 April 2018

A chart of the water quality data for 16 April 2018.
DateSiteSite NameSalinity (PSU)Temperature (⁰C)Turbidity (m)
16/04/20181Gov. Slip23.8191.9
16/04/20182Hotel23.5202.4
16/04/20183Mudlark23.9202.7
16/04/20184Goudmyn21.7202
16/04/20185Karoolskraal23.1201.6
16/04/20186Powerlines21.7191.3
16/04/2018713km from mouth19.8201
16/04/20188White House17.7210.9
16/04/2018917km from mouth16.520.50.6
16/04/201810Bobbejaanskrans14.6210.5
16/04/201812Bush Pub 1220.50.7
16/04/201814Riverine 8.8211
16/04/201819Dave Taylor0.0520.50.6
16/04/201821Pont 0.0420.50.4

Water quality run - 30 April 2018

A chart of the water quality data for 30 April 2018.
DateSiteSite NameSalinity (PSU)Temperature (⁰C)Turbidity (m)
30/04/20181Gov. Slip23.4182.4
30/04/20182Hotel23.3182.8
30/04/20183Mudlark23.3182.7
30/04/20184Goudmyn22.7181.9
30/04/20185Karoolskraal21.5171.4
30/04/20186Powerlines20.5171.1
30/04/2018713km from mouth19.1171
30/04/20188White House17.5180.9
30/04/2018917km from mouth16.2180.7
30/04/201810Bobbejaanskrans14.1180.5
30/04/201812Bush Pub 11.8180.8
30/04/201814Riverine 9.5180.8
30/04/201819Dave Taylor3.17180.5
30/04/201821Pont 1.4180.2

The salinity readings slowly decrease as you move from the river mouth towards the Pont. Salinity is measured by PSU (Practical Salinity Unit) where the probe emits an electrical current between two metal plates in the water sample and measures the strength of the flowing current. The more dissolved salt in the water, the stronger the current flow and the higher the electrical conductivity. For this reason, due to the lack of salt water present in the upper reaches, the salinity decreases. The temperature remains at a steady value throughout the estuary between 17 and 18 degrees Celsius and the turbidity is measured using a secci disk which helps determine the clarity of the water. As you move up river, the water becomes darker due to the presence of freshwater, decreasing the depth of how deep you can see into the water. At the river mouth, the clarity of the water can be up to two and a half meters but if you move up stream towards the Pont, it becomes less that half a meter.


Species of the Month: Verreaux’s Eagle

by Tasmyn Taylor

A photo of a Verreaux's eagle perched on a rock.
Photo courtesy of the The Endangered Wildlife Trust.

The Verreaux’s Eagle (Aquila verreauxii), also known in South Africa as the Black Eagle or Witkruisarend, is a large bird of prey with highly specialised senses. These eagles’ distribution revolves around their prey, which consists of Rock Hyraxes (Dassies) that live in mountainous terrain along with small mammals, birds and reptiles. Its widespread throughout Africa and occurs as far south as South Africa as well as, as far north as Eritrea. Once upon a time this eagle was affected by human populations but due to the efforts of conservationists, the impact humans have on their populations have reduced along their numbers to stabilize.

When perched or at rest, the adult Verreaux’s Eagle are entirely black in appearance except for the “V” shape above the wings on the eagles back. To differ between sexes can be challenging but when two individuals are paired, the female will be larger than the male.

Smart strategies

The pair is often seen flyting together and they are most likely to hunt in a pair as well. One individual will distract a prey while the other one strikes. Verreaux’s eagles prefer to eat where they feel safe, most likely their nests which are built on cliff faces to minimise predation on their chicks.

Poorer without Me

Verreaux’s Eagles are the top predators in the ecosystem, especially the Breede ecosystem, another competitor would be the Fish Eagle but due to the difference in size and food items, the two species do not compete. In the Breede ecosystem, they play an important role in maintaining the health of the ecosystem. For example, by hunting Hyrax, the eagle decreases the competition between Hyrax’s and crops belonging to the neighbouring farmers. The less destruction done to the crops, the more the farmers have for feed for their livestock.

People and I

This species biggest threat is poisoning and hunting which coincide with livestock farms. Poisoning in a non-specific species method of removing predators meaning poison causes a great and harmful impact on the species which keep the ecosystem in check and maintain a natural balance. In areas where Hyraxes have been hunted for their fur and as a source of food, the Verreaux Eagle’s populations have declined due to the declining prey population. Other possible threats they might face include an overlap in habitat between natural habitats and farmlands. The LBRCT has decided to name this eagle The Species of the Month because it was sighted in the beginning of March while doing a boat patrol and nowhere in the Bird Monitoring data has a sighting been recorded.

An illustration highlighting distinctive features of the Verreaux's eagle.
Image courtesy of the Wikimedia Commons.

Thank you for reading

We hope you enjoyed this months' issue. Should you have any feedback, questions, or matters you would like us to cover in a future issue, please do not hesitate to write to us at news@breede-river.org.

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