Mass fish deaths at the Waterfront are causing problems - why whales are partly to blame
- Residents of the V&A Waterfront and the surrounding Cape Town foreshore are gagging their way through a fishy stink thanks to thousands of tiny, dead fish.
- A school of mackerel chased into the harbour by a pair of Humpback whales, as well as higher than normal volumes of mullet breeding in the bay caused a ‘system overload’, resulting in them using up all the oxygen in the bay.
- The V&A says it has been doing everything it can to reduce the fishy odour, from increasing the frequency of flushing fresh water into the canals to sending out staff to sweep up the dead fish.
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Thousands of tiny, dead fish are floating around the V&A Waterfront and the surrounding Cape Town foreshore, which - apart from the stench - are causing all kinds of problems.
Fields of Cape horse mackerel, colloquially known as maasbanker, and mullet are floating among the expensive yachts and man-made seal islands throughout the V&A’s canals. The smell has been so bad that a guest at the luxurious Cape Grace Hotel left because of it, reported Cape Talk Radio.
The deaths were caused when a school of mackerel were chased into the harbour by a pair of Humpback whales. In addition, there have been higher-than-normal volumes of mullet breeding in the bay. The combined effect was overpopulation and death.
“Every year we have mullets breeding in the basin, and this year the number was quite high. We also saw a large school of mackerel entering the harbour, and the high volume of fish obviously impacted on the levels of oxygen in the water, causing the fish to die,” said Donald Kau, V&A Waterfront head of public relations.
The V&A says it has been doing everything it can to reduce the fishy odour, from increasing the frequency of flushing fresh water into the canals to sending out staff to sweep up the dead fish.
“When it happens, we mitigate it by opening the locks to bring the fresh water in from the canals. Currently, that is being done about six times a day to flush out the water. In effect, you have got a system overload in the harbour,” said Kau.
Once the fish are caught in the basin it is only a matter of time before they die out because they use up all the oxygen in the water.
"Fish move into the area. They use a lot of oxygen. The plankton starts dying. That causes more oxygen to be used. Then the little fish (which actually use more oxygen than the bigger ones) run out of oxygen and die. That decomposition causes even more oxygen depletion, and so on, and so forth," said Renee Leeuwner, Media Executive at the Two Oceans Aquarium.
Masking up and stomaching the stench isn't the only concern for the Two Oceans Aquarium, which is also a resident at the V&A.
Along with the foul smell , the dead fish decompose and increase ammonia levels in the water. This is a big problem for the aquarium that gets its water for its exhibits straight from the marina. They have now had to shut off that water supply and run on a closed system because of the water quality.
“We check the water on a daily basis as we actually get a lot of our water from the basin area. The dissolved O2 went from 60% to 22% overnight, but is sitting at just over 1% this morning,” said Renee Leeuwner, Media Executive at the Two Oceans Aquarium.
Humpback #whales in #CapeTown harbour. Going on all the fish and bird action in the harbour at the moment, possibly feeding. Hope they‘ll be fine and that @TransnetNPA is warning vessels. In 2019 a whale was cut in half by a ship prop in the harbour. @VandAWaterfront pic.twitter.com/LFKp7NNwVP— Seafari (@SeafariApp) March 22, 2021
As the problem persists and continues to be a nuisance for humans, there are some creatures that are having a blast. Thanks to all the fish, the V&A says it has seen increased activity of seals and sea birds - even a Humpback whale has been attracted to the free seafood buffet.
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