#006 Crouching Urchin, Hidden Wobbegong

Have you ever heard the fate of the US Cities Service Boston?

May 16th, 1943. Guns up and down the Illawarra coast were trained on the ocean. Rumour of Japanese submarines abounded, and a convoy of American ships patrolled the coast, ready for a fight.

The ships strayed too close to land. At dawn the US Cities Service Boston ran aground in rough seas, trapping her 62 crew aboard. In such stormy seas, trying to swim to the rocky coast was suicide.

As word went up from nearby Shellharbour that the ship was sinking, the 6 Machine Gun Battery camped at Kembla Grange was called in for the rescue. Australian soldiers worked through the day with ropes to bring the Americans bruised but alive back to shore.

But the sea, not sated with the ship in her belly, threw a wave that dragged ten soldiers, Australian and American, back into the brine. Six made it; four didn’t, and those four Australians lie with the Cities Service Boston in the bed of what is now Bass Point Reserve.

And while the US Cities Service Boston is the most notorious shipwreck, it is by no means the only.

But the shipwreck was not the start of Bass Point’s history. The Eloueran Aboriginals have occupied the reserve for the past 20 000 years. Archaeological finds from the reserve include middens, a sacred burial ground, and rare signs of established occupation. And while the US Cities Service Boston is the most notorious shipwreck, it is by no means the only.


Leaving the Shellharbour dive shop early on Sunday morning, we hammer along the dirt road to Bass Point in the battered shop truck.

Bushland fringes the road, cut with windows overlooking brilliant sparkling ocean. We suit up in our dive gear admiring the smoky panorama of the northern headlands, Windang Island, the Port Kembla Steelworks, and blue expanse of the South Pacific Ocean.

On any given weekend the reserve will be alive with divers, fishermen and snorkelers. Diving schools frequent the area and at times there are 50 divers in the water. The popular entry points are the Gravel Loader if you want to see Grey Nurse Sharks, and the Gutter for everything else.

The Gutter drops us 3 – 6 m from surface to seabed depending on the tide, and gives instant access a verdant underwater world. The Nursery, Blue Devil Cave and Sponge Garden are all accessed from here.

It is all spectacular. The underwater world exists in a realm unto itself. Once your head is below the water, you are swept away to another life.

The first thing I notice as cool rushes over me is the opacity of the water. On the surface I could see a dozen kilometres to the bow of the ocean disappearing behind the curvature of the Earth. In the water, on an average day, we can see maybe 10 to 15 metres. When cold water is pushing up from the south, visibility can drop to less than 5 metres. Light dims away quickly, plunging me from bright morning to early evening. Everything is magnified. A Maori Wrasse glides by and I reached out and touch it with a giant white finger. My hand looks like my father’s. All around me are the neon yellows and electric purples of other divers’ fins and suits. I look for the solid yellow fins of my diving buddy. I run my fingers around the edge of my hood, and cool water rushes down my neck. My buddy gives a signal: we’re moving forward.


Fishes shoal around us. Most are young, wrasses, Stripeys and others too young to recognise. Beneath us are bare rocks and dwarf fronds of brown algae. We push into deeper water, the fishes growing larger and the walls of the Gutter opening onto the boulder-strewn landscape of the ocean.

At 10 metres, I spy a pair of juvenile cuttlefishes changing colour with sunlight filtering down from the surface. The algal fans beneath the cuttlefish are iridescent, flashing from pale blue to brown to ultramarine. Two spots on the cuttlefishes’ backs flare white in rhythm with the dappled light. Their smooth bodies, parallel with the seabed, show waves of brown and blue. Their disguise is so flawless that I am almost on top of them by time I notice them. I reach out and stroke one gently on the back. Its whole body flares white, then blue, and it returns to mimicking the flickering light.

The cuttlefish aren’t the only critters I’ve spotted at the last moment: many times I’ve gone to place my hand on a rock only to glimpse the black needles of a Long-Spined Urchin. Peering down into the gap in the rock, I see half dozen urchins. Their black spines shimmer purple and green. At night this horde will creep from between the rocks and feed on the kelp abundant in the warm, shallow water.

Why is the Long-Spined Urchin such a problem?

#091 Long-Spined Urchin (Centrostephanus rodgersii)

Long-Spined Urchins may be too good at what they do. Not only do they eat the kelp, they also scrape the microalgae from the surface of rocks, creating areas known as “urchin barrens” where nothing else can grow. A large enough group of these urchins will bulldoze a seabed, driving out rock lobsters, abalones, fishes and everything else dependant on the algae for life. Like the plants of the rainforest, algae is the basis of the ocean food chain. Remove it and everything above it has to leave too. The urchins have become so prolific in recent years that they now pose a major threat to fisheries in NSW and Tasmania.

Yet why is it the Long-Spined Urchin such a problem? It’s native, and it used to be that natural predators such as the Spiny Lobster kept its numbers in check.

It turns out that the Long-Spined Urchin is particularly good at adapting to climate change. Warmer, more acidic oceans do not have as great an impact on these urchins as they do on other marine animals. These warmer waters are shifted on the major ocean currents, and carrying Long-Spined Urchins to places they have never been before. Because the urchins were not previously found here, there are few local animals willing to eat them. The urchins are able to take advantage of untapped seabeds and limitless opportunities for growth, becoming a major pest.

In NSW, where the Black-Spined Urchin was always found, overfishing for species like the Spiny Lobster has removed its natural predators. As in Tasmania, the eastern coast of Australia is now facing an expanding population of urchins with nothing to keep them in check.

This must be a real headache for the fishing industry. Urchins can be harvested for their roe (eggs) but as you may imagine, removing eggs from urchins is a time-exhaustive process met with a limited market. The far more valuable trade is in the lobsters and abalones that the urchins drive out. Lobsters alone are worth $369 million a year to Australia, and abalones worth another $173 million. When we think of overfishing, we think of fishes like tuna and sturgeon. Yet here is a case in which the removal of a humble crab could lead to the collapse of an entire ecosystem and the fishing industry dependant on it.

There are animals in the ocean that we never think can be impacted by fishing.

Another master of disguise.

There are animals in the ocean that we never think can be impacted by fishing. These apex predators seem above all that, immune to hooks and lines, and they hardly seem palatable. I’m talking about sharks.

However, researching wobbegong sharks, that’s exactly what I found. The Banded Wobbegong, one of the larger sharks in these waters, is commonly hooked through the belly. Sometimes the animals are killed (and fished intentionally, sold as boneless fillet or flake), but other times the hooked animal is released back into the water.

This sounds like a happy ending where the Banded Wobbegong gets to live again another day. But in truth released sharks are often badly injured and will die as a result of being hooked. J-hooks tear the shark’s stomach and liver, injuries from which it has little chance of recovery. The use of circular hooks has reduced mortality of captured sharks, but have yet to be instated as mandatory in NSW.

#104 Banded Wobbegong (Orectolobus halei)

Banded Wobbegongs are well-liked by divers. They are a type of carpet shark, called so because they lie in wait on the seabed. A Banded Wobbegong can grow to 2.5 m, with reports up to 3 m, and they live to a depth of 195 m. The name “wobbegong” is of Aboriginal origin, meaning “shaggy beard” in reference to the weed-like whiskers around the shark’s face.

These weeds are an essential part of the Banded Wobbegong’s camouflage. It becomes invisible on the seabed, resting throughout the day. When divers approach, the Banded Wobbegong waits patiently for them to leave. Bullseyes, Blue Devils and other fishes swim by and the Banded Wobbegong does not flick a whisker.

The use of circular hooks has reduced mortality of captured sharks, but have yet to be instated as mandatory in NSW.

It is only when the shark is hungry that it attacks (this is a lie. A diver leaning on a wobbegong for a photo received a nasty bite on his leg. Touch them and they get bitey.) A fish passes overhead. The wobbegong launches itself from the seabed, inhaling the fish into its wide mouth. Its small sharp teeth prevent prey from swimming out. With a gulp, the shark swallows, and drifts back to the ocean floor.


Hiding in crevices and ambushing dinner is all very well. Yet some animals are so deft at camouflage that they hide in plain sight.

The Yellow Umbrella Snail is one of these. The charismatic yellow of this Notaspidea (meaning “back shield”) is anything but clandestine. They are found high up on sponge-encrusted reefs. So how does anyone miss them?

#029 Yellow Umbrella Snail (Tylodina corticalis)

Well, the Yellow Umbrella Snail is the same shade of yellow as the inside of its favourite sponge. All species in the genus Tylodina, all over the world, feast on species of the same genus of sponge, Pseudoceratina. Set against the yellow background of the masticated sponge, the Yellow Umbrella Snail becomes virtually invisible.

At 20m, a Yellow Umbrella Snail munches on its favourite sponge.

There’s also the small matter that probably nothing wants to eat the Yellow Umbrella. Pseudoceratina sponges have been the subject of extensive research into cures for breast cancer, owed to their chemical weaponry. These sponges produce rare alkaloids that are antimicrobial, antifungal, cytotoxic and antimalarial, and anti-anything else living inside you. The sponges themselves are so toxic that they have no natural predators outside the Tylodina snails and a few Aplysian nudibranchs, themselves highly toxic.

The question is how do Yellow Umbrellas eat these sponges without being poisoned? It turns out that Tylodina snails can modify the chemicals produced by the sponge and cherry-pick which are best used for their own defence. That charming Yellow Umbrella Snail is actually building a chemical armoury in its body.

That’s something to munch on the next time you see a charmingly coloured mollusc.


Next time you’re looking out across the white-capped waves, or even just have fish for dinner, consider the story of what you’re looking at. Wobbegong meat is sold as flake – commonly battered and not at all highly valued. If rock lobsters were sustainably farmed, fisheries would not be facing hordes of urchins which destroy the habitats for those lobsters, abalones and fishes.

Like everything, there’s an app to check if your fish has been sustainably farmed. It was published by the Australian Marine Conservation Society and you can find it right here. http://www.sustainableseafood.org.au/

And then, because we all like a guilt-free trip to the beach, come and join Salty, Keen and I this Saturday the 13th of March on our second voyage to Windang Island. I’ve wrangled a portable BBQ and some chalk and we’re going to have a merry old time counting species on the intertidal. There will even be a prize for whomever finds the biggest Zebra Snail.

See you there!



Watch the Banded Wobbegong’s ambush technique: http://www.abc.net.au/science/articles/2013/07/31/3811486.htm

A chilling look at sea urchin barrens: http://www.abc.net.au/science/articles/2013/07/31/3811486.htm

More on the sea sponges, Pseudoceratina spp.: http://www.telegraph.co.uk/news/health/news/11203823/Sea-sponge-drug-could-boost-breast-cancer-survival.html