Just about every predatory fish in the sea.
Any fish that can fit it into their mouth and swallow it, will probably eat it. That's the way things are with most fish. Fish should only be kept with other fish of the same or similar size.
Mackerel are a cannabalistic species of fish and they only eat each other.
Humans can indeed eat mackerels
Seals are a lot bigger than mackerels. It is far more likely for a seal to eat a mackerel than the other way around.
Mackerels are saltwater fish. Tadpoles live in freshwater. Meaning a mackerel wouldn't have much chance of eating tadpoles.
mackerels are carnivores
A shoal of mackerels
It depends on what type of shark I guess. I know for a fact that guitarfish (aka shovelnose shark) eat Mackerel
There are not many differences between female jack mackerels and male mackerels. However, the female jack mackerels are able to lay eggs and reproduce.
Yellow tail snappers will eat rolled up oats and Yellow tail flounders will eat Crustaceans, amphipods and, polychaete worms
a shark
mackerels are carnivores
Mackerel or mackerels
Spotted Dolphins Spotted Dolphins
A shoal of mackerels