There's more of a risk of them trying to eat a silvery fish that may seem small enough to the wolf, this is due to the reflection of surrounding light the silver scales cause. Basically making it more tempting by catching the wolfs eye and most of the time when it reflects the silver fish is swimming therefore triggering a predatory instinct. It's really just more temptation with silver fish. But that's it, they'd still go after a fish they think they can eat if they're hungry. Just a predatory attack, not a territorial one. A fish to large to eat, won't be preyed upon if it's obvious, if hey look possible to eat to the wolf he'll try. And as stated aggression goes off of the specimen but typically wolves aren't as bad as they're made out to be