RiverWise
Issue 24 ~ July 2020
The monthly newsletter of the Lower Breede River Conservancy Trust
In this issue
This issue covers our activities for July 2020. We start off with the highlights of what we have been up during the month. For the species focus we take a look at the Mudprawn, one of the most common macroinvertebrates in South African estuaries. We end off with a summary of our bird count data for the month.
What we have been up to
Penguin Rescue
On Friday morning the 3rd of July, concerned residents saw a penguin on the main beach and immediately informed the LBRCT office. Thank you to Erna Smith for informing us - he was named Waldo by his rescuers. We collected Waldo and arranged with African Penguin and Seabird Sanctuary for a pick up in Heidelberg so that he could undergo a complete check-up.
Ten days later we got some feedback that he is doing well. He still sleeps in the hospital in the evenings but is let out during the day for some playtime.
Red-Knobbed Coot rescue and release
Over the weekend of the 18th of July, a Red-knobbed Coot was found on the beach in Witsand. He was weak and brought in by concerned residents. This freshwater species was clearly lost. After spending the night under observation and getting fluits the Coot's health improved and he was released at the Pont. Thank you to Eldry Hill for bringing him in.
Shark appreciation month
July was shark appreciation month here at the LBRCT, as the 14th of July was recognised as Shark Awareness Day. Due to the importance of this day on the environmental calendar we highlighted some of the endemic shark species found along the south African coastline throughout the month on our social media pages. Be sure to follow us if you don't already.
Second peguin rescue for July
On Saturday the 25th of July, we received a report of another penguin on the beach. He was collected and transported to African Penguin and Seabird Sanctuary - APSS for a full check up. A big thank you to Owen and Helen Jarman from Barry's Holiday Accommodation that offered to transport him. We will follow up on his progress in a couple of days.
Species of the month:
Mudprawn
Upogebia Africana
The mudprawn Upogebia Africana is one of the most common macroinvertebrates in South African estuaries and is therefore one of the main bait species exploited in these systems. A southern African endemic, this bottom-dwelling invertebrate is found from Lamberts Bay (West Coast) to Maputo (Mozambique). Within its distribution, mudprawns are only found in those estuaries that are always or mostly connected to the sea.
Mudprawns live in sediment by burrowing into it and forming a U-shaped burrow that is excavated and maintained continuously. A certain sediment type is required to stop the burrow collapsing, with a finer sediment with a high mud content or mud and sand mix needed. Due to the extensive mudbanks present along the Breede River Estuary, this species is a popular bait for the fishermen in the area.
An important part of the food chain, mudprawns are preyed upon by fish as well as a variety of birds including waders that feed on the exposed mudflats. Common Terns, Grey Plovers, Whimbrels and Kelp Gulls can have their diet dominated by udprawns. A study in the Knysna estuary showed over 80% of mudprawns that are disturbed from their burrows were eaten by birds.
Mudprawns are important filter feeders in an estuarine ecosystem. Any over-exploitation and disturbance could have a knock-on effect on other components of these estuarine systems. Disturbance and compaction of the sediment (mud) from bait collection can have a greater effect on mudprawns than the harvesting itself. These disturbances associated with bait removal can potentially result in changes in the infaunal (aquatic organisms that live in a surface specially soft sediments (mud) in of a body of water) community composition. Studies have shown that illegal bait collecting methods such as digging with a garden spade or fork can negatively impact an area for up to 18 months.
The mudprawn has a complex life-history which requires the larvae to spend part of its lifecycle in the marine environment. Two breeding seasons occur between July and October, and December to March. Female mudprawns carry eggs underneath her abdomen, which is often called “in berry”, for up to a month before they hatch. The larvae are released into the water and move out to sea where they go through three developmental stages before the past-larvae recruit back into the estuary. They can live for an estimated 3-4 years.
Current regulations state that 50 mudprawn can be taken per person per day and can only be collected by hand, suction pump or inverted tin.
In the data
Monthly routine monitoring
July bird counts
After several months off the water due to COVID-19 lockdown, we managed to get a bird count in. The weather was chilly with thick fog, but we managed to see over 400 birds and 28 species. There was a pleasant surprise when we found a single Bar-Tailed Godwit. These palearctic migrants are usually present in South Africa from October to April. Some birds overwinter in South Africa so it was nice to see one bird liked the Breede so much it decided to stay. Low numbers of the usual overwintering migrants were also seen: Grey Plover, Common Greenshank and Whimbrel.
The most abundant birds seen were: Yellow-billed Ducks (138 birds), followed by Egyptian Geese (74 birds) and African Sacred Ibis (35 birds).
July 2020
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.