Where did all the Cow sharks go?

Cow sharks (Notorynchus cepedianus) were once frequently spotted in the waters around Millers Point. Between the inner and outer kelp forests in a clearing, infamously called ‘Shark Alley’. Divers would be surrounded by up to 10 + cow sharks at any one time pre 2014/15. However, in recent years, sightings of these sharks at this dive spot have all but disappeared, with maybe 1 sighting a year if you’re lucky…

So this begs the questions, where did all the cow sharks go and why?

Well, there are a few reasons why this may be the case:

1. Changes in the Ecosystem: Cow sharks are sensitive to environmental changes, with increasing climate shift and the knock-on effects on the entire ocean this may be effecting prey quantity and quality for large apex predator, meaning they need to look further afield for their dinner.
2. Overfishing and Declining Fish Populations: We are all pretty aware by now of the global overfishing issues and a decline in almost all fish populations. Especially small bait fish such as sardine, mackerel, pilchards etc. This is also an issue locally in South Africa, and is starting to have detrimental effect throughout the food chain as trophic levels collapse due to a shortage of the primary foundations of the trophic pyramid. Although these fish aren’t the main food source for cowsharks, their prey like larger fish and smaller sharks, seals and penguins need them to survive.
3. Increased Human Activity: With growing tourism, fishing, and diving activities in areas like Millers Point, sharks may have been displaced by disturbances or changes in their environment caused by human interaction. Although these sharks seem very relaxed and unphased by humans by the most part, the persistent presence of boats, divers, and fishermen could impact their behaviour and make the area less attractive to the sharks to stick around.
4. Shark Behaviour and Killer Whale Attack: Sharks, like many other marine species, often change their behaviour or migration patterns based on seasonal factors, environmental cues, or even social structures. In 2015 we had an unusual case of two Killer whales (Port & Starboard) who started frequenting the area. Over the following months we saw a number of white sharks wash up between False Bay and Mossel Bay along the south coast of South Africa. There we also 9 cowsharks killed by the infamous pair. This event made the white sharks disappear from False Bay overnight, and…. They never returned. At least not in the aggregating numbers in which they used to. The cowsharks also disappeared and laid low for a long time. However, some months later the shark cage boats reported cowsharks coming to the boats at Seal Island. This was very rare in the past as the white sharks were the dominating species and out competed smaller sharks in the area. But… now there were no white sharks. This is a great example of trophic shifts and competitive habitat adaptation. When one species is no longer dominating a favourable habitat, other species can now ove in to exploit the resource…in this case, seals.

While sightings of Cow Sharks at Millers Point may be less frequent now, we have seen them frequently in and around the False Bay Yacht Club marina. They seem to enjoy the protection and shelter of the navy wall which have large holes in where they like to slowly cruise in and out of. More often they are spotted on Impact Divers night dives. We have on rare occasion seen the swimming around the public jetty in the late afternoon passing fishing rods bait.

Monitoring and studying these changes in large shark species habitat can help marine biologists better understand the shifting patterns of these fascinating creatures and what needs to be done to protect their habitats. We can better understand their behaviour and habitat niche needs.

Cow Sharks are not typically aggressive towards humans. I’ve never seen anything aggressive from them towards a human in my time diving with them. They are fascinating prehistoric creatures and play an important role in the local marine ecosystem. So, if you’re wondering where the cowharks went and interesting in diving or exploring in the area, get in touch with Cape RADD or Impact Divers to book a shark dive.