I would not bet my money on it. In some areas fishes can score higher than many other vertebrates for sure, including big apes

Anybody keeping an aquarium knows that many fishes are surprisingly smart. Specially predatory fishes. They have a good long term memory and can recognize individual caretaker humans.

The brain/bodyweight ratio of some species is bigger than humans. This mean that they have a bigger brain that most birds, lizards and rodents of the same size. Sharks are pretty clever for example.