Squids, as I may have mentioned before, are the snacks of the sea. Everyone who can eat them, does. Whales. Sharks. Birds. Other squids. They're swimming tubes of protein with no scales or bones to get in the way, and they're highly abundant. If you're any kind of marine predator, squids are the perfect prey.

But one has to wonder: if squids fuel everything from albacore to albatross, what fuels the squids? Sure, they'll eat each other, but the ouroboros model doesn't really work that well for ecology.

Squid cannot live by squid alone.

Every species of squid, of course, has its own solution to the problem of what to eat. For example, one of the most abundant large squid species, the Humboldt, makes up the bulk of its diet by devouring staggering quantities of a kind of fish that most seafood connoisseurs have never tasted.

Well, technically it's two kinds of fish: lanternfish and lightfish.

As you may have been able to guess from the names, both kinds of fish are shiny (okay, fine, bioluminescent). They're even shiny in similar ways: they have rows of light-producing photophores on their bellies.

And they're small: lanternfish and lightfish rarely grow larger than a few inches in length.

Daww! Big eyes endear deep-sea fishes just as well as Bambi.

The most striking feature of these little guys, though, is their sheer biomass. Lanternfish, or myctophids, are so thick in the ocean that, when they start their daily migration towards the surface, it actually seems like the seafloor is rising. No joke. Wikipedia gives an "estimated global biomass of 550 - 660 million metric tonnes, several times the entire* world fisheries catch."

Emphasis mine, because, WOW, people. Just wow.

Of course, much of that biomass is contributing indirectly to the world fisheries catch, as squid (and other creatures) are happily devouring myctophids and then being caught and happily devoured by people.

And what about lightfish? Well, let's consider just one genus--Vinciguerria--that favored prey of Humboldt squid that I mentioned a couple of days ago:
Vinciguerria is thought — with the possible exception of Cyclothone — to be the most abundant genus of vertebrates.
Got that? The MOST ABUNDANT GENUS OF VERTEBRATES. There are piles and piles of these little fish out there in the sea.

And that is at least one reason why there are also piles and piles of squid. 

* My friend Annie pointed out that this should be specified as the entire ANNUAL world fisheries catch. Yes indeed.