I'm no expert, but my husband fishes, and always eats the liver and heart raw, right away, and the eggs if there are any...I've been lucky enough to taste these organs right away, and compared to other offal, they have a very mild flavor...barely there...but I get a zing of energy afterwards that tells me my body likes what I've just fed it!

I ate a salmon heart last month. Taste was a little bitter, but okay. I was making fermented raw salmon at the time, so I added the heart to the ferment. Within a month the ferment was ready to eat. The heart's texture was crumbly or mealy on the inside, with a thin rubbery outer skin. The entire heart was small, about an inch wide. It's not a taste for the squeemish - I like salmon eggs much better.

FWIW, monkfish liver is a Japanese delicacy of sorts, and the one time I had it I found it to be delicious. The preparation was not unlike that of a goose liver pate.

I remember reading (Nourishing Traditions, I think) that real, fermented fish sauce retains the nutrients of the "best parts" of the fish.. eg the liver and thyroid. Red Boat makes a quality fish sauce.

I've been ordering canned cod livers from Amazon. I just throw them on a salad. Not great, but not bad either, basic canned fishy flavor and kind of a creamy texture. I bet they'd be good smeared on a cracker like pate.

I haven't tried other fish organs, but I did accidentally buy a whole salmon full of eggs once, and it was a delightful treat (but a little does go a long way).