I've listened to Bach for this before especially harpsichord concertos (Gould on piano is good) because of the rhythm but can take a while to get used to. Generally I don't listen to classical musics for gym anymore
I love it but so much salmon is farmed and I'm not sure about it...and the cheapest wild salmon like sockeye isn't really suited to it or especially tasty
my favorite fish all-time is gelatinous fish like turbot, but not so easy to find; I also like sardines, smelts, anchovies...but all depends what you can eat most easily. I find very difficult to eat much bland food lately so I forget to eat