I visited the Seattle Aquarium yesterday and passed thru the underwater tank at feeding time. For those of you who have never been there, they have a huge underwater viewing area into a tank filled with many different types of Puget Sound fish - lots of salmon, halibut, rock cod, sturgeon, etc. At 1:30pm everyday, a couple divers jump into the tank with bags of dead herring, shrimp and squid. They disperse the food into the water and the fish go crazy...

It was facsinating to watch the salmon feed. They would only eat if they were swimming up thru the cloud of food. They didn't eat on the way down nor did they eat when they were swimming horizontally. They would swoop up thru the food, turn away from the food, dive down and swoop up again. Even if a piece of food was right in front of them, they wouldn't eat it unless they were swimming up (vertically).

Does this mean that they rely more on sight than smell or sound?

It certainly supports the notion that the feeding salmon will be under a bait ball.