Rendered beef fat can be used in a lot of ways. You can use it in place of oil in a lot of recipes, but finding out which ones you like will take some experimenting. Around our house, I use rendered fat from beef or bacon in place of oil when sautéing, for example with onions and peppers, garlic or mushrooms. I've also used it to add some kick to gravies.
You could use it to pop popcorn, which I've heard is delicious but unfortunately have never tried.
I've had pasties made with beef fat, and they were delicious. Mashed potatoes as well.
As far as fat ratio goes, it's better than butter, but not as good as other fats. Beef fat has a high smoke point and is suitable for frying.
The table below is based off of 1 tablespoon. Ratio means saturated to unsaturated. Smoke point can vary depending on a lot of factors (olive oil can range from 300 when unrefined, to 375-450 when refined depending on quality) but the table below should be a good guide. For the oils, I took the refined numbers.
sat mono poly ratio smoke
Canola Oil 0.9 8.2 4.1 1:12 470°F
Olive Oil 1.8 10.0 1.2 2:11 450°F
Chicken Fat 3.8 5.7 2.6 1:2 375°F
Duck Fat 4.3 6.3 1.7 1:2 375°F
Lard (pork fat) 5.0 5.8 1.4 5:7 365°F
Beef Tallow 6.4 5.4 0.5 1:1 400°F
Butter 7.2 3.3 0.5 7:4 350°F
(fat source) (smoke point source)
A lot of people mix it into their dog's food, or use it to feed birds.
Seach for tallow if you want to find recipes that specifically use it.
I've had Salmon Trout. They are a pink fleshed trout, that mimics the flavour of Salmon somewhat.
My favourite preparation is to do it as a Yerevan Trout. Essentially Roast the fish filets, prepare the sauce - Lemon, Butter, Capers, Artichokes, and any pan juice you can get. Serve beside your favourite rice.
Best Answer
Salmon or Tuna will make a very strong flavoured stock and will have lots of oil that coat your tongue. Not what you're looking for if you want a light brightly flavoured fish sauce.
In a traditional French kitchen you want generic stocks (fish/brown/chicken/veal) that are able to be used for a wide range of sauces/dishes so having a salmon stock around doesn't meet that criteria.
That said, I worked at a restaurant that made fish stock from salmon bones all the time as it was mainly used in a house specialty, a very robust West Coast spin on Bouillabaisse. Any true Frechman would have turned his back on us in disgust for doing what we did but damn it, it tasted great and the customers loved it! For any other fish sauces we used the traditional white fish bones.
FYI...Japanese dishes use Bonito flakes (tuna) liberally to make dashi(sp?) which is a fish flavoured broth for miso soup as well as other items.
So basically what I'm saying is if a fatty fish stock gets the job done for you and you're happy with it then go for it. Just remember that if you're trying to make a classic recipe then using a non-traditional ingredient will mess it up.