I am only a tiny fish

Big fish eat small fish - says the proverb.

I am only a tiny fish - and the world out there is full of hungry predators.

I personally exist at the bottom of the food-chain.
The bigger fish come in different shapes and sizes - you have huge fish, not-so-huge fish, medium-sized fish and small-medium fish.
Their size - most of the time - gives you an idea of how hungry the fish are.

The bigger fish are not that keen on feeding on the little'uns (like me and you) - for what is the point, what is the 'victory' in eating something that small and insignificant?

The medium and small-medium fish I am worried about. They just itch to become big fish; to become big fish they need to eat (me and you). And they eat, eat, eat - sometimes they even eat fish their own size; yes, they eat their competition.

There is one issue though: you end up with lots and lots of big fish and not so many small fish ('cause me and you have already been eaten, remember?). So the food-chain is getting significantly smaller.
I wonder what happens when there's only one link left in that chain?