What's the most amount of fish you've ever seen in one place?

In Alaska, we saw a salmon run, we were a little late in the season, so many had spawned and already died, but it was an amazing experience. I need to look for my photos. here are 2 examples

last night in my dream i saw a huge harvest being made from a swimming pool

Thousands of salmon running up rivers several times.

Scuba diving in the Red Sea.

The aquarium in NOLA

There's a lake in northern iowa that used to have swarms of bullhead (mini catfish), until a fish appeared that was considered invasive in the early 90's. They poisoned the lake and all the fish died, it has never recovered.