Pollock is the preferred fish of many restaurants, taquerias and fast food chains. Pollock is the fish that makes the pervasive fish paste that is used to make seafood analogs, the artificial shellfish products that look and taste very much like the real thing, but cost a lot less.
As far as the nutritional value of pollock, like salmon, tuna and cod, it is a good source of lean protein and low in saturated fat. All of these fish are also a good source of vitamin B12, phosphorous, and selenium.
Salmon is the highest in omega 3 fat, which is one of the best reasons for eating fish. But it is also important to consider how the fish is prepared, because if it is deep fried, it is high in fat and not a very healthy choice as compared to baking or grilling. And remember that canned tuna is usually high in sodium.
Pollock is as healthy a fish choice as cod and tuna except it is often served fried, which would negate the benefit of eating fish as your protein choice. And Alaska Pollock, not deep fried, is the better value whitefish.