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Adventure Australia Review

White sharks are great

Last night Alex and I went to a brilliant talk about great white sharks at Melbourne Aquarium.

The talk was part of Melbourne Aquarium’s Marine Discovery Lecture Series 2013, and was given by Barry Bruce, marine researcher at the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Bruce
Bruce

The backdrop to the talk was Melbourne Aquarium’s 2.2 million litre Oceanarium – so every time Bruce mentioned sharks, a real life one was right there behind him (albeit a grey nurse or blacktip reef shark, rather than a great white!)

Barry Bruce is an expert when it comes to tagging white sharks, and is known as the Aussie authority on these sharks, no less. Not only that, but the great white shark in Finding Nemo was actually named after him! If that isn’t a claim to fame, I don’t know what is.

Bruce started his talk by saying that despite over 20 years of research, there is still much that is not known about these creatures. He added that he and his scientific colleagues prefer to call them ‘white sharks’ rather than ‘great white sharks’ because they are really no greater than any other shark!

He also mentioned that the media is responsible for the common image of white sharks (below) – launching out of the water looking scary and murderous – and urged us not to believe everything we read (as this news story proves).

Great white shark
Great white shark – as perpetuated by the media

Bruce went on to cover some facts that are known about white sharks, for example:

  1. They can grow to at least 6 metres (2000-3000kg)
  2. They possibly live for 50-60 years (although this isn’t known for sure – it might be longer)
  3. Females don’t mature until they are 5 metres
  4. They are warm-bodied (25-27 degrees) – so are more like mammals
  5. They produce few young and there is no parental care
  6. They eat fish and other sharks/rays when young (< 3 metres)
  7. They do not live at seal colonies – most of their time is spent elsewhere
  8. Some may not feed on seals at all.

The majority of the talk then focussed on understanding movement patterns – the first step in answering questions about whether numbers are going up or down – and that is where tagging comes in. In the words of Jennifer Aniston in a shampoo advert, here comes the science bit…

Acoustic tag
Acoustic tag

The main types of tagging Bruce and his team use are:

  • Acoustic tagging – a unique code is sent to a receiver whenever a tagged shark swims past;
  • Satellite tagging – the tagged shark links to a satellite whenever it comes to the surface (as long as a satellite is in range).

The first white shark ever tagged was in Victoria, and Bruce’s three tagging areas are the Neptune Islands (SA), Corner Inlet (VIC) and Port Stephens (NSW). From his team’s research he has been able to tell that white sharks travel large coastal distances and to tropical waters (eg Ningaloo and the Great Barrier Reef). It has even been known for a shark to travel from South Africa all the way to Ningaloo! The open ocean is an important habitat for white sharks, and some have been known to spend up to 2 years in open ocean before returning to land.

Bruce also discovered that, on the whole, a shark tagged in South Australia stays south and west, whereas a shark tagged in eastern Australia stays east. This means there are two distinct populations that don’t seem to cross the Bass Straight (the water between Tasmania and Victoria) – and they need to be looked at separately.

At the moment more is known about the eastern population of white sharks, and Port Stephens has emerged as a particularly interesting area. It’s hugely popular for swimmers, surfers and divers, but it’s also here that white sharks are often found in the surf zone just off the beach (compared to further north or south, where the sharks tend to stay away from the shore). So Bruce and his team locate juveniles here for tagging.

Juvenile great white shark
Juvenile great white shark

Port Stephens is known as a ‘nursery area’ for white sharks – mostly the sharks are 2 years old. (It is not a breeding area, as there are no new-borns – which also means there are no big adults around either!) Corner Inlet is another nursery area, and sharks have been tracked moving directly and rapidly between the two nursery areas.

Hawks Nest Surf Club in Port Stephens closed the beach 44 times one summer due to white sharks swimming between the flags. In fact if you type ‘Hawks Nest NSW’ into Google Earth and zoom in, you can see a white shark close to the shore – with a load of people just a little further up the beach.

But while white sharks meet people at these beaches every day, there has never been an attack there. So the answer to the question ‘what normally happens when sharks and people meet?’ is just ‘nothing’.

It was then time for some questions from the audience, and someone asked what Bruce thought about culling. This is a very topical issue, given there have been a handful of attacks in Australia recently, and many mentions of shark culling in the media as a result. Bruce responded that there have been very few cases when the shark responsible for an attack has been caught – so that sort of approach is just a waste of time and resources. He also said that there is no evidence that a shark that has bitten once will bite again. And the Port Stephens situation proves that more sharks does not mean more attacks. Given the audience was made up of shark enthusiasts, I think we were all please to hear from Australia’s authority on white sharks that culling is not the answer.

I then plucked up the courage to ask a question about cage diving. I’ve always wanted to do it, but was worried about whether it’s the right thing to do for the shark. And does chumming make sharks associate people with food? Bruce answered that cage diving is highly regulated in Australia. It takes place in the Neptune Islands, and there are always two days per week with no dives – which is for the benefit of the sharks, not the safety of the people. He mentioned that sharks sometimes stick around for a bit longer than usual at cage diving sites, but there is no evidence that cage diving leads the shark to associate people with food. In fact there’s so much going on, what with the noise from the boat and the smells, that the diver in the middle of it all is really no big deal. Plus there’s not much reward for the shark – they might get a bit of tuna off the tether, but mostly it’s berley (chum) to attract them, rather than real food.

After a couple more questions the talk came to an end. I left the aquarium feeling inspired and still can’t believe I had the opportunity to hear about these sharks from the country’s top white shark researcher. There is one thing I disagree with Bruce about though – to me they will always be great white sharks.