What is a fishes prey?
While Giant pandas are classified as carnivores, they feed primarily on bamboo. However, they DO also eat small mammals and fishes. it is estimated that 99% of the Giant panda's diet consists of bamboo, but they must predate on the small mammals and fishes that they eat. So the answer is yes, they are a predator for a prey, occasionally.
Why was the development of two sets of paired limbs in fishes important to the evolutionary development of all vertebrates?
In order to catch the prey they need to feed themselves, squids use their tentacles, because they have a suction and hook that captures the prey, which usually are small crabs, shrimps and small fishes. While they have a tight grip on the small animal, they use their sharp tongue to extract the contents of the prey's body.
Narwhals would get along with whatever fish might not count as one of their predators or as one of their prey. They tend to follow a specialized diet. The fish that they're known to prey on include Arctic and polar cod, Gonatus squid, Greenland halibut, and shrimp. But they also are known to prey on capelin and wolffish. So the preceding fishes have the appeal of a meal, not of companionship.
Viperfish has wide mouth with fang like teeth. The fangs are too large to fit inside their mouth. They catch prey by swimming in high speed and thus impaling their prey with their fangs. The fangs act like spears. Viperfish can swallow large fishes because their jaws can expand and they have large stomach.