Sharks having a whale of a time?

5% = ~400

10% = ~800

And if only a quarter of the whale deaths occur where east-coast whites can exploit them, 5% of that resource could still represent something like 100 additional large-shark-years of food.

These are not estimates of how many extra sharks there actually are. They show the scale of the potential additional carrying capacity.

There's another important point.

The whales aren't simply recycling food already present off NSW.

They feed principally in Antarctic waters, accumulate vast energy reserves, then carry that energy thousands of kilometres north while largely fasting.

So every year tens of thousands of humpbacks effectively import Antarctic biological energy into the east Australian coastal ecosystem.

It would be surprising if adding an energy flow on that scale had no ecological consequences.

And we already know great whites exploit it. Scientists have documented whites aggregating around and feeding on whale carcasses off NSW.

But whales probably aren't the original reason for the seasonal movement of sharks.

The east coast already has a moving winter food chain. Sea mullet form huge schools and migrate north. Australian salmon move and aggregate seasonally. Tailor migrate as well. Those fish are themselves important prey for white sharks.