Astacopsis gouldi

Way, way back in time, the world was covered in massive forests and primitive plants.

Rock and fossil experts (paleontologists) call it the Paleozoic — Mesozoic era, and it was a time of dramatic climatic shifts, massive glaciation events and following global-scale melts.

About then, the scientists think, some fish slithered out of the sea — slow but greedy fish looking for new territory and new things to eat. They hunted seashores for small edible things, and grew scales to protect themselves from predators in the shallow water. They developed pincers to grab food with. They thrived, they mutated. They became lobsters.

The lobsters became numerous; like mini, sea-based dinosaurs. They weren’t pretty, but they were effective eaters and breeders. And there were millions of them; life got a bit crowded on the borders of the sea. Some decided to travel, and headed away from the seashores, up the rivers into the hills.

Life was less crowded there and riverbank forests were home to plenty of protein-rich creepy-crawlies that helped them to grow big and live long.

Over the hundreds and hundreds of centuries since then, some of those migratory lobsters turned into fully-acclimatised, freshwater-loving crayfish, and colonised rivers way up in the hills.

They thrived in the cool, fresh, clean river waters and spread worldwide — but slowly, insidiously, the signs of an impending crayfish cataclysm were starting to show.

The freshwater crayfish were slow-moving and slow-growing, and despite having those armour plated shells they offered easy-access snacks to plenty of newly evolving fast, strong carnivores which were spreading rapidly on land — but could reach easily into rivers. Freshwater crayfish numbers started to shrink.

In the centuries that followed, this also meant that pioneer homo sapiens bush-whackers found them easy to catch and eat too. Simply walk up a creek, kick a few small rocks around and hey — there’s dinner! Tough times got tougher for river crayfish — they tasted too good and were too easily caught.

Over the centuries their numbers have dropped and dropped thanks to predators on both four legs and two. Today, they have been hunted to near-extinction across the world. There are remote pockets of riverine bushland where they survive, but only in very limited numbers.

In fact almost a third of the world’s freshwater crayfish species are on endangered Red Lists, and catching them is illegal in most places. People who do can be whacked fines of thousands of dollars. They are damn special, and damn rare.

But in some places, tucked away where humans and other predators find it hard to get to, there are still tiny, struggling colonies of freshwater crayfish — one of which is the Astacopsis gouldi, the largest non-marine invertebrate in the world. It is a monster of a creature, and can grow to a metre long and weigh over 6kg. If it lives long enough that is. In it’s native habitat (only in a tiny watershed of rivers that feed into the Bass Strait in Australia) it is numbered in the thousands today. A whole race is almost extinct.

And guess what, yesterday, out hiking up in the hills behind Deloraine with my friend Roland, he suddenly stopped and said — “hey what’s that?” and pointed to what I recognised as a medium-sized duck-billed platypus slowly traversing a small creek. That’s quite an unusual sighting, but platypi aren’t that rare in Tasmanian rivers, to be honest.

But the thing was, it wasn’t a platypus.

It was a half-metre Astacopsis, crawling slowly, slowly, feelers waving in front of its face as it inched along a creek bed right next to where we were slogging through the dripping, rain soaked bush.

Just like it would have done 300 million years ago. Right here in Tassie, on our doorstep.

Up in the foothills of the Western Tiers, the freshwater crayfish is still surviving, and we saw one. It made me feel very young, and very lucky to have met it.

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