No. Decomposers in an ecosystem are generally organisms like bacteria and fungi: they feed on or absorb dead tissue and waste products, and they also break it down so that other creatures can benefit from it. Most science textbooks consider mackerel "consumers"-- they are scavengers that eat other sea animals (like jellyfish and shrimp).
yes
mackerels are carnivores
A shoal of mackerels
There are not many differences between female jack mackerels and male mackerels. However, the female jack mackerels are able to lay eggs and reproduce.
a shark
Mackerel or mackerels
mackerels are carnivores
Mackerels are saltwater fish. Tadpoles live in freshwater. Meaning a mackerel wouldn't have much chance of eating tadpoles.
A shoal of mackerels
Spotted Dolphins Spotted Dolphins
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 carnivores
mackerels are carnivores