@ibstubro In fish with livers, all the beneficial oil is in the liver. It’s very good for you and the Scandinavians make a paste of it. In Sweden, roe and cod liver is sold in toothpaste tubes and spread on knäckebröd, or bread crisps. It’s a staple at either breakfast or lunch.
Conversely, fish without livers—such as Salmon, mackerel, mullet, trout and many others—are known as “oily fish” because the beneficial oils reside in the meat itself. This is why they are considered healthier to eat than non-oily fish and are now more expensive. Because they were oilier and tasted “fishier,” they were less desirable just a generation ago. Except for salmon and trout, of course. But mullet and mackerel are good examples of formerly cheap, oily fish. They are great for smoking.
In the States, they used to throw the liver away, but in recent years they harvest them for their oils and sell it in caps at the drugstore. You don’t see a lot of it in natural form, as fish liver pate’ like you do in Scandinavia and other northern European countries.