RiverWise
Issue 25 ~ Aug 2020
The monthly newsletter of the Lower Breede River Conservancy Trust
Have you renewed your
boat licence yet?
Annual Municipal Boat licences are due for renewal every year from 1 July and valid until 30 June the following year.
Just a reminder of our outlets available for boat licence sales for 2020/2021
MALGAS OUTLET:
Living the Breede
Phone: 067 162 9081 or 082 324 2757
Open: Mon-Sun from 08h00 - 17h00
RIVERINE OUTLET:
Breede Riverine Estate
Phone: 028 542 1345
Open: 09h00 – 17h00
WITSAND OUTLETS:
Lower Breede River Conservancy Office
Sands Supermarket
Nella's se Winkel
SWELLENDAM OUTLET:
Heyneman Yamaha
Phone: 028 514 2010
Open: 8h00 – 17h00
ONLINE LICENCES:
Buy your boat licence online and arrange to pick up your disk at Living the Breede (Malgas) or LBRCT office (Witsand)
https://breede-river.org/licences/
Contact our office if you have any questions regarding the boat licences - 028 537 1296 / info@breede-river.com
What we have been up to
In this issue
This issue covers our activities for August 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 Bloodworm, an estuarine dependant bait species. We end off with a summary of our bird count and water quality data for the month.
Marking hazzard areas in the river
Over the weekend of the 1st of August, our rangers marked some submerged tree stumps with red drums as a safety precaution. This picture was taken at Lemoentuin. Please drive with caution on the river.
Monitoring Projects
During the week of the 17th, we conducted our monthly bird count and water quality run on the Breede River. Between the cold fronts, the weather played along for us to get the work done.
Southern Right Whales
During the month of August we looked at the Souther Right Whale, and the uniqueness of this species on our social media pages. At the begining of the month we started to notice more of them in the bay.
Just a friendly reminder to be aware of the minimum distance for non-permitted boat-based whale watching. For drone footage and boats its at least 300m from the whales. If you ever see a boat or drone approach closer than 300m, please contact the Department of Environment Forestry and Fisheries on (021) 819 5156.
- Species of the month:
Bloodworm
Arenicola loveni
Bloodworm are an estuarine dependant bait species, extensively used by saltwater anglers. Preserving healthy stocks is an important component of estuarine ecology, and at the same time encouraging the maximum exploitation of our local stocks. Currently there is a bag limit of 5 worms per day per angler.
They are found from Saldanha Bay up to northern KwaZulu-Natal in estuaries, lagoons and sandy beaches. The presence of their L shaped burrows are marked by a funnel shaped (head shaft) depression at one end and a pile of faecal sand (tail end) at the other. The depth of head shaft of mature specimens are usually in excess of 75 cm.
The head shafts serves as both a food filter and oxygen delivery mechanisms. Organic material and oxygenated water are pushed down the head shaft by currents. The bloodworm “gardens” with this organic matter around its head, allowing micro-organisms to flourish in the irrigated garden, essentially farming these micro-organisms for nutrition.
Dissolved oxygen is very important to bloodworms, and they have a mechanism of trapping our bubbles in their burrows when deoxygenated water levels increase, and closing the head funnel, avoiding harmful water from circulating in their burrow. This is especially evident in the Breede after a flood, where surface signs of burrows reduce dramatically. Juvenile bloodworms will die within 3 hours in 100% fresh water, and within 30 hours in 50% sea-water, making them quite sensitive to changes in salinity. In the Heuningnes River Estuary, after years of drought and closure of the mouth, the local population became extinct.
Bloodworms can grow to a mass of 150 grams and 80 cm in length, living for up to 4 years, with the oldest recorded being 7 years. The last proper population study on bloodworm in the Breede was performed by CM Gaigher in 1979 for his masters thesis, where it was found on average one would find 0.75 worms per square meter.
From the same study it was also revealed that most bloodworms start their larval life cycle on the Infanta side of the river, and migrate to the central sand island as they mature. It was also established that they grow slower in winter months, which is problematic conservation wise as they are targeted during the summer holiday months when they mature faster. That bag limit of 5 worms per day is to prevent wastage. As civilians we can band together to educate and discourage exploitative behaviour.
References: Gaigher CM. 1979. Aspects of the population dynamics and ecology of the bloodworm (Arenicola loveni Kinberg). MSc thesis. University of Cape Town
In the data
Monthly routine monitoring
August bird counts
A chilly start to the morning’s waterbird count along the Breede River Estuary, we saw a total 351 birds which accounted for 27 different species. The five most abundant species during this trip accounted for 63% of all birds seen. These five species are: Southern Red Bishop (92 birds), African Sacred Ibis (45 birds), Yellow-billed Duck (36 birds), Egyptian Goose (28 birds) and Reed Cormorant (20 Birds). Most birds were seen in Zone 1, with 154 birds, which stretches from the Breede River Estuary Mouth to Powerlines some 9km upstream. A variety of habitats are found in this zone, and these include beaches, sand banks, rocky shores and extensive mudflats. The area between Powerlines and Bobbejaans (Zone 2) recorded the second highest number of birds (86). Within these zones, a finer scale look shows Groenpunt to Powerlines (100 birds) and Powerlines to White House (69) as the two areas preferred by birds. Similar trends were shown in the areas with the highest species count, with Zone 1 (21 species) recording the most species followed by Zone 2 (19 species). Overall, 21 of the 27 species seen were found between Groenpunt and the White House. This is an impressive 77.7%.
Many of the species seen during this survey showed a preference for different areas. Southern Red Bishops were predominantly found between the Boat House (28 km upriver) and Clive Tandy (34km upriver) in the extensive reed beds, which is their habitat for the breeding season. African Sacred Ibis were most abundant between (Groenpunt to Powerlines) as they favour marshy wetlands and mudflats.
African Darters which are freshwater associated species and are rarely found in estuaries and prefer lakes, dams and slow-moving rivers, were recorded between Oysterbeds and Groenpunt. This species is usually found further upstream during waterbird counts. The shift further downstream during this survey could be the result of freshwater input into the system which resulted in the low salinities being recorded near the mouth.
August water quality
The surface and estuarine bed salinity values showed similar trends this month with highest salinities near the mouth and freshwater conditions further upstream. Due to the high rainfall experienced prior to the survey on 19 August, the marine influence on the system was limited. The sites near the mouth, Gov. slip and the Breede River Lodge, recorded peak salinities during the study. The surface salinity for these sites (6.86 and 4.88 respectively) was lower than those at maximum depth (6.95 and 6.1 respectively) due to higher salinity water being more dense than freshwater.
From Mudlark up towards the pont, the surface water was fresh, but salinities still increasing with depth. The bottom salinities at Mudlark (4.8) and Goudmyn (3.5) recorded brackish conditions. The salinity was constistant throughout the water column at each site, with no change in salinity from the surface to the estuarine bed between White House and the Point.
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.