Couple of years ago I caught close to 4lb whitefish in Shuswap river. It was a mid spring, time of salmon eggs already hatched in to alevins. When I was unhooking this whitefish and gently held her in mid section, she puked out about 25 of this little salmons, some still alive and wiggling. This fish was absolutely gorged with the fry. They also feed on salmon eggs all winter. It is more like a sanitary function, as these are dislodged and spoiled old eggs. In winter time flesh of these fish reeks of spoiled eggs and rotten flesh ans not appealing.
Not many people target them and even less retain them, however it is a tasty fish when fresh. Superb smoked.