The fossil tooth fairy was smiling upon me today. After a snorkel we headed to bayside Melbourne to search for fossils. Soon after, I turned a rock, and found the tooth of a 5-6 million year old Carchardon hastias, or ‘giant great white shark.’ A first for me, and very exciting. It was also a timely find. I’ve been reviewing the role and history of sharks in bayside Melbourne as well as looking at the role of aquatic predators in ecosystemsHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More. It was partly the subject of my last blog. What is the value of sharks then? In the spirit of Dickens, let’s take a look at what story the ghosts of sharks of past, present and future, can tell us about their importance to humanity.
The ghost of sharks past
This fossil find or ‘ghost of sharks past’ was a timely reminder to me. It revealed the importance these creatures played in the evolution of planet Earth. This 5-7m long animal was feasting on marine mammals millions of years before humans (Hominins) had evolved. Sharks evolved about 250 million years ago and helped stabilise our climate from 20-30 million years ago. Everything we depend on today, was built on millions of years of their impact on oceans.
Every shark produced 20,000-40,000 teeth. They are one of the commonest and most notable fossils. An indication of just how profoundly important sharks have been to our oceans.
The ghost of sharks present
As for the ghost of sharks present, that’s another story. There are two notable shark species still present in southeast Australia that used to be abundant in bayside Melbourne. At the turn of the century, Grey Nurse Sharks were once common, as revealed by memoirs in Museum Victoria and the collections.
Safety Beach was even an important spawning ground and renamed, in an attempt to lure tourists. Grey Nurse Sharks, dubbed ‘labradors of the sea’, are enormously popular among divers and snorkelers. But they were practically wiped out nationally by spearfishing competitions in the mid-20th century. This was pointed out by Valerie Taylor in recent documentaries. Shark-killing competitions even exist to this day in the form of ‘sports’ sponsored by name-brands in Australia.
Elsewhere in Victoria, Wobbegongs, or carpet-sharks can be seen along the Bass Coast. Here they are also, sadly, a popular target for spear fishers. If nothing is done soon they may go the same way as grey nurse sharks and disappear from our coasts forever. Wobbengongs used to be found in bayside Melbourne too.
The ghost of sharks future
If we don’t accept the value of sharks and replenish their numbers locally, we face a future of uncertainty. Without sharks imbalances are already being felt across the world. Even local fishing will become a thing of the past. Then climate will not be able to be regulated either. This hasn’t stopped the fishing lobby in NSW from stopping any attempts to reintroduce them though. The fear is that it will mean tighter regulation of fishing rights. And perhaps there is a point to this: that our legislation needs to be more inclusive. But we don’t have time for petty politics.
There is no single mechanism that explains the value of sharks, as this study by Hammerschlag et al 2019 illustrates. The study shows how all aquatic predators are essential. But ‘top-down’ dynamics exist throughout the food chainA single thread in a food web illustrating the chain of animals that eat each other. At the base of the food chain are small high-energy (fast metabolism) animals and at the other end large low metabolism animals. An example would be whales eating krill that eat plankton that eat algae. Or lions that eat gazelles that eat grass. More and the mechanisms are complex and varied. Sharks play a significant role in holding things together.
Humanity has no future without them.
