The monthly newsletter of the Lower Breede River Conservancy Trust
The Southern Right Whale
During wintertime, people tend to think the coastline gets a bit dull with activity because nature tends to slow down, but one spectacle that comes around is the sightings of all the different whale species that travel the coastline.
One very common traveller seen along the coast is the Southern right whale. They are often seen in St Sebastian Bay, Witsand, “the” nursery of the whales in South Africa.
Southern right whales belong to the Cetacea family, which includes all whales, dolphins and porpoises. These whales do have teeth, well more bristles then teeth, because they fall under baleen whales. The Southern right whale makes up one of three species within the right whale family and all three species are endangered.
Physical characteristics and appearance
As they reach maturity, they can grow to be up to 18 meters in length and weigh up to 80 tons with their head comprising of a quarter of the whole body. Interestingly, the Southern right whale lacks a dorsal fin. With a lifespan of up to 100 years the southern right whale is one of the longest living species of Cetacea.
When it comes to dentation these marine mammals (as with all baleen whales) lack the presence of teeth but are equipped with baleen plates that have bristles attached to them which allow these whales to filter their prey from the water as they swim through the ocean. The primary diet of Southern right whales consists of copepods, krill, mysids and plankton among other tiny crustaceans. These whales are skimmers and can be seen swimming at or near the surface of the water when hunting for food. On occasion they will also dive into deep waters as well in search of prey. They hunt their prey by swimming with their mouth open and trapping their prey in their baleen bristles while also filtering water out of their mouth.
Due to their thick layer of blubber the Southern right whale never crosses over the equator into the northern hemisphere because their body is unable to handle the extreme heat.
Social structure and communication
Southern Right Whales are a fairly active species that can be seen breaching and performing in the sea. They are very social animals amongst themselves and with other species. It’s this playful nature that creates the curiosity with vessels and boats to observe the people and boats. When interacting with humans or other animals these marine mammals appear to be thoughtful and aware of their large size and strength, which limits their activity and behaviour when around humans. This just insures no harm comes to the smaller marine animals, boats and people.
When it comes to impressing the ladies, these whales do not typically fight with one another or show any signs of jealousy when it comes to mating but rather act as gentlemen. These whales are polygamous where one male whale can have up to seven female partners.
The total population is estimated to be around 10,000. Since hunting ceased, stocks are estimated to have grown by 7% a year. It appears that the South American, South African and Australasian groups intermix very little if at all, because maternal fidelity to feeding and calving habitats is very strong. The mother also passes these choices to her calves.
These whales have been known to face many threats as they live in the open sea. Threats may include being hit by passing ships or large vessels in highly commercial areas, potential health hazards from chemical and plastic pollution which can affect their food supply or harm the whale directly, aquatic constructions such as sewage plants, aquatic mining and ocean-based oil refineries that can negatively impact the whale’s ecosystem and environment and numerous other issues from agricultural changes to global warming.
May water quality
The salinity was highest at Gov. slip and Breede River Lodge which is to be expected as these sites are closest to the mouth and the marine influence. The salinity at Powerlines was 31.1 PSU which is still very saline and just below that of seawater. The greatest drop in salinity between sites occurred between Bobbejaanskrans and Ronnies. The salinity near the pont at Malgas was almost freshwater.
As the rainy season approaches, the salinity will decrease further with more freshwater entering the estuary.
May bird count
We were lucky enough to count 33 species and a total of 680 birds. The most commonly found bird were yellow-billed ducks (288 birds), followed by Egyptian Geese (87) and Kelp Gulls (52 birds).
Some interesting birds recorded was a single Grey-headed Gull and Pied Kingfisher as well as Black-winged Stilts and a Three-banded Plover. A couple of migrant species were still recorded: Whimbrel and Grey Plover. Some birds of these two species stay in South Africa over winter and don’t migrate with other birds.
May marine debris
Over 1100 pieces of litter were picked up between Blokke and the Tidal Pool, with the biggest culprit being tiny plastic pieces. Over 64% of the litter picked up fell into this category. Fishing related litter was the next most abundant litter type with 11% of all litter collected. Plastic bottles accounted for 3.7% of all litter collected. We also found a dirty diaper, shoes, tinfoil and cigarette lighters on the beach. Nurdles are still a problem on our beaches with 39 found on this small section of beach.
A total of 356 pieces of litter were recorded at the Oysterbeds survey site. The most abundant litter found was fishing line (116 meters) which accounted for 32.6% of all litter found. The next most abundant litter were beer bottle pieces. Nearly 20% of the litter found on the survey was glass pieces. Smoking related litter which includes cigarette butts and cigarette packaging accounted for over 10% of the litter found. Many plastic bags are still being found.
Witsand main Beach produced the most litter picked up during May. A total of 1660 pieces of litter were recorded. The most abundant type of litter recorded was plastic pieces which accounted for 54% of all litter found. Worryingly, we are still finding nurdles on our local beaches with 399 recorded on this stretch of beach. Other important litter found were 54 plastic bottle caps (3.2%), 49 plastic lids (3%), 31 food wrappers (1.9%) and plastic packaging. Other odd items that were found were three flip flops, a shoe, a beach towel and two clothes hangers.
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 email@example.com.