Read on Twitter
Lots of criticism of Seaspiracy, but here’s an overlooked fact: the film asserts that the “world’s most expensive fish” is the bluefin tuna. Nope. It’s the American eel. I’ll explain in this short thread. 
It’s true that bluefin tuna can sell for colossal amounts. One sold for $3M+ once. But that’s not typical. That’s $5K/pound. They’re more likely to sell for $40 or $50 per pound. (That’s WAY more than most fish/seafood. Scallops, a money species, go for about $11 at the docks.)
So, tuna are a big money species. But, AFAIK from covering the industry, no species even comes close to the baby eel, which is called an elver. They often go for $2K/pound a year in a normal year.
Now, why the heck is that? Because baby eels are critical as seed stock for the aquaculture industry in Asia. They need baby eels to raise to maturity for use as unagi and kabayaki.
In the early 2010s, international sources of elvers collapsed. The American fishery exploded in value to fill that gap. And the US elver fishery (which takes baby American eels) is TINY. It’s based almost exclusively in Maine and limited to less than 10K pounds per year.
So, the Asian aquaculture industry really needs elvers. The US has elvers, but a limited supply. The demand side has inflated the value to the point where in a typical year baby eels are basically gold. Not uncommon to be worth 40X a bluefin at the docks.
(Last year this was all upended by the pandemic, in part because the elver fishing season starts in March.) https://apnews.com/article/91bfcac1081152076fd5a322c017a837
If you’re intrigued by all this weirdness, here’s more. If you’ve ever had eel at a sushi restaurant in the US, it’s entirely possible it was caught in a Maine river and essentially traveled the world twice to become your dinner. https://www.pressherald.com/2017/08/07/baby-eels-are-being-poached-operation-broken-glass-is-the-response/
PS - This is also significant! https://twitter.com/conathan/status/1380985059973472257
This is a good fact-check of the aspects of the film that do not involve the complex economics of eels/tuna. https://www.bbc.com/news/56660823
