Interesting thread and I would love to hear more opinions about it..
Like ballin said, there may not be many scientists/biologists in this section, but opinions are always worth reading.
I would assume they are intelligent fish because of their skittishness. They make an escape whenever they feel they are in danger. IME, they know when they are the predators, and know when they are being preyed upon.
Their hunting methods, fleeing methods, and over all survival instinct makes me assume they are an intelligent fish.
Are there fish out there have have greater intelligence? Yes.
Are they the dumbest? No.